###############################################################################
#
# Chart - A class for writing the Excel XLSX Worksheet file.
#
# SPDX-License-Identifier: BSD-2-Clause
#
# Copyright (c) 2013-2025, John McNamara, jmcnamara@cpan.org
#

import copy
import re
from warnings import warn

from . import xmlwriter
from .shape import Shape
from .utility import (
    _datetime_to_excel_datetime,
    _get_rgb_color,
    _supported_datetime,
    quote_sheetname,
    xl_range_formula,
    xl_rowcol_to_cell,
)


class Chart(xmlwriter.XMLwriter):
    """
    A class for writing the Excel XLSX Chart file.


    """

    ###########################################################################
    #
    # Public API.
    #
    ###########################################################################

    def __init__(self):
        """
        Constructor.

        """

        super().__init__()

        self.subtype = None
        self.sheet_type = 0x0200
        self.orientation = 0x0
        self.series = []
        self.embedded = 0
        self.id = -1
        self.series_index = 0
        self.style_id = 2
        self.axis_ids = []
        self.axis2_ids = []
        self.cat_has_num_fmt = 0
        self.requires_category = False
        self.legend = {}
        self.cat_axis_position = "b"
        self.val_axis_position = "l"
        self.formula_ids = {}
        self.formula_data = []
        self.horiz_cat_axis = 0
        self.horiz_val_axis = 1
        self.protection = 0
        self.chartarea = {}
        self.plotarea = {}
        self.x_axis = {}
        self.y_axis = {}
        self.y2_axis = {}
        self.x2_axis = {}
        self.chart_name = ""
        self.show_blanks = "gap"
        self.show_na_as_empty = False
        self.show_hidden = False
        self.show_crosses = True
        self.width = 480
        self.height = 288
        self.x_scale = 1
        self.y_scale = 1
        self.x_offset = 0
        self.y_offset = 0
        self.table = None
        self.cross_between = "between"
        self.default_marker = None
        self.series_gap_1 = None
        self.series_gap_2 = None
        self.series_overlap_1 = None
        self.series_overlap_2 = None
        self.drop_lines = None
        self.hi_low_lines = None
        self.up_down_bars = None
        self.smooth_allowed = False
        self.title_font = None
        self.title_name = None
        self.title_formula = None
        self.title_data_id = None
        self.title_layout = None
        self.title_overlay = None
        self.title_none = False
        self.date_category = False
        self.date_1904 = False
        self.remove_timezone = False
        self.label_positions = {}
        self.label_position_default = ""
        self.already_inserted = False
        self.combined = None
        self.is_secondary = False
        self.warn_sheetname = True
        self._set_default_properties()
        self.fill = {}

    def add_series(self, options=None):
        """
        Add a data series to a chart.

        Args:
            options:  A dictionary of chart series options.

        Returns:
            Nothing.

        """
        # Add a series and it's properties to a chart.
        if options is None:
            options = {}

        # Check that the required input has been specified.
        if "values" not in options:
            warn("Must specify 'values' in add_series()")
            return

        if self.requires_category and "categories" not in options:
            warn("Must specify 'categories' in add_series() for this chart type")
            return

        if len(self.series) == 255:
            warn(
                "The maximum number of series that can be added to an "
                "Excel Chart is 255"
            )
            return

        # Convert list into a formula string.
        values = self._list_to_formula(options.get("values"))
        categories = self._list_to_formula(options.get("categories"))

        # Switch name and name_formula parameters if required.
        name, name_formula = self._process_names(
            options.get("name"), options.get("name_formula")
        )

        # Get an id for the data equivalent to the range formula.
        cat_id = self._get_data_id(categories, options.get("categories_data"))
        val_id = self._get_data_id(values, options.get("values_data"))
        name_id = self._get_data_id(name_formula, options.get("name_data"))

        # Set the line properties for the series.
        line = Shape._get_line_properties(options.get("line"))

        # Allow 'border' as a synonym for 'line' in bar/column style charts.
        if options.get("border"):
            line = Shape._get_line_properties(options["border"])

        # Set the fill properties for the series.
        fill = Shape._get_fill_properties(options.get("fill"))

        # Set the pattern fill properties for the series.
        pattern = Shape._get_pattern_properties(options.get("pattern"))

        # Set the gradient fill properties for the series.
        gradient = Shape._get_gradient_properties(options.get("gradient"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        # Set the marker properties for the series.
        marker = self._get_marker_properties(options.get("marker"))

        # Set the trendline properties for the series.
        trendline = self._get_trendline_properties(options.get("trendline"))

        # Set the line smooth property for the series.
        smooth = options.get("smooth")

        # Set the error bars properties for the series.
        y_error_bars = self._get_error_bars_props(options.get("y_error_bars"))
        x_error_bars = self._get_error_bars_props(options.get("x_error_bars"))

        error_bars = {"x_error_bars": x_error_bars, "y_error_bars": y_error_bars}

        # Set the point properties for the series.
        points = self._get_points_properties(options.get("points"))

        # Set the labels properties for the series.
        labels = self._get_labels_properties(options.get("data_labels"))

        # Set the "invert if negative" fill property.
        invert_if_neg = options.get("invert_if_negative", False)
        inverted_color = options.get("invert_if_negative_color", False)

        # Set the secondary axis properties.
        x2_axis = options.get("x2_axis")
        y2_axis = options.get("y2_axis")

        # Store secondary status for combined charts.
        if x2_axis or y2_axis:
            self.is_secondary = True

        # Set the gap for Bar/Column charts.
        if options.get("gap") is not None:
            if y2_axis:
                self.series_gap_2 = options["gap"]
            else:
                self.series_gap_1 = options["gap"]

        # Set the overlap for Bar/Column charts.
        if options.get("overlap"):
            if y2_axis:
                self.series_overlap_2 = options["overlap"]
            else:
                self.series_overlap_1 = options["overlap"]

        # Add the user supplied data to the internal structures.
        series = {
            "values": values,
            "categories": categories,
            "name": name,
            "name_formula": name_formula,
            "name_id": name_id,
            "val_data_id": val_id,
            "cat_data_id": cat_id,
            "line": line,
            "fill": fill,
            "pattern": pattern,
            "gradient": gradient,
            "marker": marker,
            "trendline": trendline,
            "labels": labels,
            "invert_if_neg": invert_if_neg,
            "inverted_color": inverted_color,
            "x2_axis": x2_axis,
            "y2_axis": y2_axis,
            "points": points,
            "error_bars": error_bars,
            "smooth": smooth,
        }

        self.series.append(series)

    def set_x_axis(self, options):
        """
        Set the chart X axis options.

        Args:
            options:  A dictionary of axis options.

        Returns:
            Nothing.

        """
        axis = self._convert_axis_args(self.x_axis, options)

        self.x_axis = axis

    def set_y_axis(self, options):
        """
        Set the chart Y axis options.

        Args:
            options: A dictionary of axis options.

        Returns:
            Nothing.

        """
        axis = self._convert_axis_args(self.y_axis, options)

        self.y_axis = axis

    def set_x2_axis(self, options):
        """
        Set the chart secondary X axis options.

        Args:
            options: A dictionary of axis options.

        Returns:
            Nothing.

        """
        axis = self._convert_axis_args(self.x2_axis, options)

        self.x2_axis = axis

    def set_y2_axis(self, options):
        """
        Set the chart secondary Y axis options.

        Args:
            options: A dictionary of axis options.

        Returns:
            Nothing.

        """
        axis = self._convert_axis_args(self.y2_axis, options)

        self.y2_axis = axis

    def set_title(self, options=None):
        """
        Set the chart title options.

        Args:
            options: A dictionary of chart title options.

        Returns:
            Nothing.

        """
        if options is None:
            options = {}

        name, name_formula = self._process_names(
            options.get("name"), options.get("name_formula")
        )

        data_id = self._get_data_id(name_formula, options.get("data"))

        self.title_name = name
        self.title_formula = name_formula
        self.title_data_id = data_id

        # Set the font properties if present.
        self.title_font = self._convert_font_args(options.get("name_font"))

        # Set the axis name layout.
        self.title_layout = self._get_layout_properties(options.get("layout"), True)
        # Set the title overlay option.
        self.title_overlay = options.get("overlay")

        # Set the automatic title option.
        self.title_none = options.get("none")

    def set_legend(self, options):
        """
        Set the chart legend options.

        Args:
            options: A dictionary of chart legend options.

        Returns:
            Nothing.
        """
        # Convert the user defined properties to internal properties.
        self.legend = self._get_legend_properties(options)

    def set_plotarea(self, options):
        """
        Set the chart plot area options.

        Args:
            options: A dictionary of chart plot area options.

        Returns:
            Nothing.
        """
        # Convert the user defined properties to internal properties.
        self.plotarea = self._get_area_properties(options)

    def set_chartarea(self, options):
        """
        Set the chart area options.

        Args:
            options: A dictionary of chart area options.

        Returns:
            Nothing.
        """
        # Convert the user defined properties to internal properties.
        self.chartarea = self._get_area_properties(options)

    def set_style(self, style_id):
        """
        Set the chart style type.

        Args:
            style_id: An int representing the chart style.

        Returns:
            Nothing.
        """
        # Set one of the 48 built-in Excel chart styles. The default is 2.
        if style_id is None:
            style_id = 2

        if style_id < 1 or style_id > 48:
            style_id = 2

        self.style_id = style_id

    def show_blanks_as(self, option):
        """
        Set the option for displaying blank data in a chart.

        Args:
            option: A string representing the display option.

        Returns:
            Nothing.
        """
        if not option:
            return

        valid_options = {
            "gap": 1,
            "zero": 1,
            "span": 1,
        }

        if option not in valid_options:
            warn(f"Unknown show_blanks_as() option '{option}'")
            return

        self.show_blanks = option

    def show_na_as_empty_cell(self):
        """
        Display ``#N/A`` on charts as blank/empty cells.

        Args:
            None.

        Returns:
            Nothing.
        """
        self.show_na_as_empty = True

    def show_hidden_data(self):
        """
        Display data on charts from hidden rows or columns.

        Args:
            None.

        Returns:
            Nothing.
        """
        self.show_hidden = True

    def set_size(self, options=None):
        """
        Set size or scale of the chart.

        Args:
            options: A dictionary of chart size options.

        Returns:
            Nothing.
        """
        if options is None:
            options = {}

        # Set dimensions or scale for the chart.
        self.width = options.get("width", self.width)
        self.height = options.get("height", self.height)
        self.x_scale = options.get("x_scale", 1)
        self.y_scale = options.get("y_scale", 1)
        self.x_offset = options.get("x_offset", 0)
        self.y_offset = options.get("y_offset", 0)

    def set_table(self, options=None):
        """
        Set properties for an axis data table.

        Args:
            options: A dictionary of axis table options.

        Returns:
            Nothing.

        """
        if options is None:
            options = {}

        table = {}

        table["horizontal"] = options.get("horizontal", 1)
        table["vertical"] = options.get("vertical", 1)
        table["outline"] = options.get("outline", 1)
        table["show_keys"] = options.get("show_keys", 0)
        table["font"] = self._convert_font_args(options.get("font"))

        self.table = table

    def set_up_down_bars(self, options=None):
        """
        Set properties for the chart up-down bars.

        Args:
            options: A dictionary of options.

        Returns:
            Nothing.

        """
        if options is None:
            options = {}

        # Defaults.
        up_line = None
        up_fill = None
        down_line = None
        down_fill = None

        # Set properties for 'up' bar.
        if options.get("up"):
            if "border" in options["up"]:
                # Map border to line.
                up_line = Shape._get_line_properties(options["up"]["border"])

            if "line" in options["up"]:
                up_line = Shape._get_line_properties(options["up"]["line"])

            if "fill" in options["up"]:
                up_fill = Shape._get_fill_properties(options["up"]["fill"])

        # Set properties for 'down' bar.
        if options.get("down"):
            if "border" in options["down"]:
                # Map border to line.
                down_line = Shape._get_line_properties(options["down"]["border"])

            if "line" in options["down"]:
                down_line = Shape._get_line_properties(options["down"]["line"])

            if "fill" in options["down"]:
                down_fill = Shape._get_fill_properties(options["down"]["fill"])

        self.up_down_bars = {
            "up": {
                "line": up_line,
                "fill": up_fill,
            },
            "down": {
                "line": down_line,
                "fill": down_fill,
            },
        }

    def set_drop_lines(self, options=None):
        """
        Set properties for the chart drop lines.

        Args:
            options: A dictionary of options.

        Returns:
            Nothing.

        """
        if options is None:
            options = {}

        line = Shape._get_line_properties(options.get("line"))
        fill = Shape._get_fill_properties(options.get("fill"))

        # Set the pattern fill properties for the series.
        pattern = Shape._get_pattern_properties(options.get("pattern"))

        # Set the gradient fill properties for the series.
        gradient = Shape._get_gradient_properties(options.get("gradient"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        self.drop_lines = {
            "line": line,
            "fill": fill,
            "pattern": pattern,
            "gradient": gradient,
        }

    def set_high_low_lines(self, options=None):
        """
        Set properties for the chart high-low lines.

        Args:
            options: A dictionary of options.

        Returns:
            Nothing.

        """
        if options is None:
            options = {}

        line = Shape._get_line_properties(options.get("line"))
        fill = Shape._get_fill_properties(options.get("fill"))

        # Set the pattern fill properties for the series.
        pattern = Shape._get_pattern_properties(options.get("pattern"))

        # Set the gradient fill properties for the series.
        gradient = Shape._get_gradient_properties(options.get("gradient"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        self.hi_low_lines = {
            "line": line,
            "fill": fill,
            "pattern": pattern,
            "gradient": gradient,
        }

    def combine(self, chart=None):
        """
        Create a combination chart with a secondary chart.

        Args:
            chart: The secondary chart to combine with the primary chart.

        Returns:
            Nothing.

        """
        if chart is None:
            return

        self.combined = chart

    ###########################################################################
    #
    # Private API.
    #
    ###########################################################################

    def _assemble_xml_file(self):
        # Assemble and write the XML file.

        # Write the XML declaration.
        self._xml_declaration()

        # Write the c:chartSpace element.
        self._write_chart_space()

        # Write the c:lang element.
        self._write_lang()

        # Write the c:style element.
        self._write_style()

        # Write the c:protection element.
        self._write_protection()

        # Write the c:chart element.
        self._write_chart()

        # Write the c:spPr element for the chartarea formatting.
        self._write_sp_pr(self.chartarea)

        # Write the c:printSettings element.
        if self.embedded:
            self._write_print_settings()

        # Close the worksheet tag.
        self._xml_end_tag("c:chartSpace")
        # Close the file.
        self._xml_close()

    def _convert_axis_args(self, axis, user_options):
        # Convert user defined axis values into private hash values.
        options = axis["defaults"].copy()
        options.update(user_options)

        name, name_formula = self._process_names(
            options.get("name"), options.get("name_formula")
        )

        data_id = self._get_data_id(name_formula, options.get("data"))

        axis = {
            "defaults": axis["defaults"],
            "name": name,
            "formula": name_formula,
            "data_id": data_id,
            "reverse": options.get("reverse"),
            "min": options.get("min"),
            "max": options.get("max"),
            "minor_unit": options.get("minor_unit"),
            "major_unit": options.get("major_unit"),
            "minor_unit_type": options.get("minor_unit_type"),
            "major_unit_type": options.get("major_unit_type"),
            "display_units": options.get("display_units"),
            "log_base": options.get("log_base"),
            "crossing": options.get("crossing"),
            "position_axis": options.get("position_axis"),
            "position": options.get("position"),
            "label_position": options.get("label_position"),
            "label_align": options.get("label_align"),
            "num_format": options.get("num_format"),
            "num_format_linked": options.get("num_format_linked"),
            "interval_unit": options.get("interval_unit"),
            "interval_tick": options.get("interval_tick"),
            "text_axis": False,
        }

        axis["visible"] = options.get("visible", True)

        # Convert the display units.
        axis["display_units"] = self._get_display_units(axis["display_units"])
        axis["display_units_visible"] = options.get("display_units_visible", True)

        # Map major_gridlines properties.
        if options.get("major_gridlines") and options["major_gridlines"]["visible"]:
            axis["major_gridlines"] = self._get_gridline_properties(
                options["major_gridlines"]
            )

        # Map minor_gridlines properties.
        if options.get("minor_gridlines") and options["minor_gridlines"]["visible"]:
            axis["minor_gridlines"] = self._get_gridline_properties(
                options["minor_gridlines"]
            )

        # Only use the first letter of bottom, top, left or right.
        if axis.get("position"):
            axis["position"] = axis["position"].lower()[0]

        # Set the position for a category axis on or between the tick marks.
        if axis.get("position_axis"):
            if axis["position_axis"] == "on_tick":
                axis["position_axis"] = "midCat"
            elif axis["position_axis"] == "between":
                # Doesn't need to be modified.
                pass
            else:
                # Otherwise use the default value.
                axis["position_axis"] = None

        # Set the category axis as a date axis.
        if options.get("date_axis"):
            self.date_category = True

        # Set the category axis as a text axis.
        if options.get("text_axis"):
            self.date_category = False
            axis["text_axis"] = True

        # Convert datetime args if required.
        if axis.get("min") and _supported_datetime(axis["min"]):
            axis["min"] = _datetime_to_excel_datetime(
                axis["min"], self.date_1904, self.remove_timezone
            )
        if axis.get("max") and _supported_datetime(axis["max"]):
            axis["max"] = _datetime_to_excel_datetime(
                axis["max"], self.date_1904, self.remove_timezone
            )
        if axis.get("crossing") and _supported_datetime(axis["crossing"]):
            axis["crossing"] = _datetime_to_excel_datetime(
                axis["crossing"], self.date_1904, self.remove_timezone
            )

        # Set the font properties if present.
        axis["num_font"] = self._convert_font_args(options.get("num_font"))
        axis["name_font"] = self._convert_font_args(options.get("name_font"))

        # Set the axis name layout.
        axis["name_layout"] = self._get_layout_properties(
            options.get("name_layout"), True
        )

        # Set the line properties for the axis.
        axis["line"] = Shape._get_line_properties(options.get("line"))

        # Set the fill properties for the axis.
        axis["fill"] = Shape._get_fill_properties(options.get("fill"))

        # Set the pattern fill properties for the series.
        axis["pattern"] = Shape._get_pattern_properties(options.get("pattern"))

        # Set the gradient fill properties for the series.
        axis["gradient"] = Shape._get_gradient_properties(options.get("gradient"))

        # Pattern fill overrides solid fill.
        if axis.get("pattern"):
            axis["fill"] = None

        # Gradient fill overrides the solid and pattern fill.
        if axis.get("gradient"):
            axis["pattern"] = None
            axis["fill"] = None

        # Set the tick marker types.
        axis["minor_tick_mark"] = self._get_tick_type(options.get("minor_tick_mark"))
        axis["major_tick_mark"] = self._get_tick_type(options.get("major_tick_mark"))

        return axis

    def _convert_font_args(self, options):
        # Convert user defined font values into private dict values.
        if not options:
            return {}

        font = {
            "name": options.get("name"),
            "color": options.get("color"),
            "size": options.get("size"),
            "bold": options.get("bold"),
            "italic": options.get("italic"),
            "underline": options.get("underline"),
            "pitch_family": options.get("pitch_family"),
            "charset": options.get("charset"),
            "baseline": options.get("baseline", 0),
            "rotation": options.get("rotation"),
        }

        # Convert font size units.
        if font["size"]:
            font["size"] = int(font["size"] * 100)

        # Convert rotation into 60,000ths of a degree.
        if font["rotation"]:
            font["rotation"] = 60000 * int(font["rotation"])

        return font

    def _list_to_formula(self, data):
        # Convert and list of row col values to a range formula.

        # If it isn't an array ref it is probably a formula already.
        if not isinstance(data, list):
            # Check for unquoted sheetnames.
            if data and " " in data and "'" not in data and self.warn_sheetname:
                warn(
                    f"Sheetname in '{data}' contains spaces but isn't quoted. "
                    f"This may cause an error in Excel."
                )
            return data

        formula = xl_range_formula(*data)

        return formula

    def _process_names(self, name, name_formula):
        # Switch name and name_formula parameters if required.

        if name is not None:
            if isinstance(name, list):
                # Convert a list of values into a name formula.
                cell = xl_rowcol_to_cell(name[1], name[2], True, True)
                name_formula = quote_sheetname(name[0]) + "!" + cell
                name = ""
            elif re.match(r"^=?[^!]+!\$?[A-Z]+\$?\d+", name):
                # Name looks like a formula, use it to set name_formula.
                name_formula = name
                name = ""

        return name, name_formula

    def _get_data_type(self, data):
        # Find the overall type of the data associated with a series.

        # Check for no data in the series.
        if data is None or len(data) == 0:
            return "none"

        if isinstance(data[0], list):
            return "multi_str"

        # Determine if data is numeric or strings.
        for token in data:
            if token is None:
                continue

            # Check for strings that would evaluate to float like
            # '1.1_1' of ' 1'.
            if isinstance(token, str) and re.search("[_ ]", token):
                # Assume entire data series is string data.
                return "str"

            try:
                float(token)
            except ValueError:
                # Not a number. Assume entire data series is string data.
                return "str"

        # The series data was all numeric.
        return "num"

    def _get_data_id(self, formula, data):
        # Assign an id to a each unique series formula or title/axis formula.
        # Repeated formulas such as for categories get the same id. If the
        # series or title has user specified data associated with it then
        # that is also stored. This data is used to populate cached Excel
        # data when creating a chart. If there is no user defined data then
        # it will be populated by the parent Workbook._add_chart_data().

        # Ignore series without a range formula.
        if not formula:
            return None

        # Strip the leading '=' from the formula.
        if formula.startswith("="):
            formula = formula.lstrip("=")

        # Store the data id in a hash keyed by the formula and store the data
        # in a separate array with the same id.
        if formula not in self.formula_ids:
            # Haven't seen this formula before.
            formula_id = len(self.formula_data)

            self.formula_data.append(data)
            self.formula_ids[formula] = formula_id
        else:
            # Formula already seen. Return existing id.
            formula_id = self.formula_ids[formula]

            # Store user defined data if it isn't already there.
            if self.formula_data[formula_id] is None:
                self.formula_data[formula_id] = data

        return formula_id

    def _get_marker_properties(self, marker):
        # Convert user marker properties to the structure required internally.

        if not marker:
            return None

        # Copy the user defined properties since they will be modified.
        marker = copy.deepcopy(marker)

        types = {
            "automatic": "automatic",
            "none": "none",
            "square": "square",
            "diamond": "diamond",
            "triangle": "triangle",
            "x": "x",
            "star": "star",
            "dot": "dot",
            "short_dash": "dot",
            "dash": "dash",
            "long_dash": "dash",
            "circle": "circle",
            "plus": "plus",
            "picture": "picture",
        }

        # Check for valid types.
        marker_type = marker.get("type")

        if marker_type is not None:
            if marker_type in types:
                marker["type"] = types[marker_type]
            else:
                warn(f"Unknown marker type '{marker_type}")
                return None

        # Set the line properties for the marker.
        line = Shape._get_line_properties(marker.get("line"))

        # Allow 'border' as a synonym for 'line'.
        if "border" in marker:
            line = Shape._get_line_properties(marker["border"])

        # Set the fill properties for the marker.
        fill = Shape._get_fill_properties(marker.get("fill"))

        # Set the pattern fill properties for the series.
        pattern = Shape._get_pattern_properties(marker.get("pattern"))

        # Set the gradient fill properties for the series.
        gradient = Shape._get_gradient_properties(marker.get("gradient"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        marker["line"] = line
        marker["fill"] = fill
        marker["pattern"] = pattern
        marker["gradient"] = gradient

        return marker

    def _get_trendline_properties(self, trendline):
        # Convert user trendline properties to structure required internally.

        if not trendline:
            return None

        # Copy the user defined properties since they will be modified.
        trendline = copy.deepcopy(trendline)

        types = {
            "exponential": "exp",
            "linear": "linear",
            "log": "log",
            "moving_average": "movingAvg",
            "polynomial": "poly",
            "power": "power",
        }

        # Check the trendline type.
        trend_type = trendline.get("type")

        if trend_type in types:
            trendline["type"] = types[trend_type]
        else:
            warn(f"Unknown trendline type '{trend_type}'")
            return None

        # Set the line properties for the trendline.
        line = Shape._get_line_properties(trendline.get("line"))

        # Allow 'border' as a synonym for 'line'.
        if "border" in trendline:
            line = Shape._get_line_properties(trendline["border"])

        # Set the fill properties for the trendline.
        fill = Shape._get_fill_properties(trendline.get("fill"))

        # Set the pattern fill properties for the trendline.
        pattern = Shape._get_pattern_properties(trendline.get("pattern"))

        # Set the gradient fill properties for the trendline.
        gradient = Shape._get_gradient_properties(trendline.get("gradient"))

        # Set the format properties for the trendline label.
        label = self._get_trendline_label_properties(trendline.get("label"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        trendline["line"] = line
        trendline["fill"] = fill
        trendline["pattern"] = pattern
        trendline["gradient"] = gradient
        trendline["label"] = label

        return trendline

    def _get_trendline_label_properties(self, label):
        # Convert user trendline properties to structure required internally.

        if not label:
            return {}

        # Copy the user defined properties since they will be modified.
        label = copy.deepcopy(label)

        # Set the font properties if present.
        font = self._convert_font_args(label.get("font"))

        # Set the line properties for the label.
        line = Shape._get_line_properties(label.get("line"))

        # Allow 'border' as a synonym for 'line'.
        if "border" in label:
            line = Shape._get_line_properties(label["border"])

        # Set the fill properties for the label.
        fill = Shape._get_fill_properties(label.get("fill"))

        # Set the pattern fill properties for the label.
        pattern = Shape._get_pattern_properties(label.get("pattern"))

        # Set the gradient fill properties for the label.
        gradient = Shape._get_gradient_properties(label.get("gradient"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        label["font"] = font
        label["line"] = line
        label["fill"] = fill
        label["pattern"] = pattern
        label["gradient"] = gradient

        return label

    def _get_error_bars_props(self, options):
        # Convert user error bars properties to structure required internally.
        if not options:
            return {}

        # Default values.
        error_bars = {"type": "fixedVal", "value": 1, "endcap": 1, "direction": "both"}

        types = {
            "fixed": "fixedVal",
            "percentage": "percentage",
            "standard_deviation": "stdDev",
            "standard_error": "stdErr",
            "custom": "cust",
        }

        # Check the error bars type.
        error_type = options["type"]

        if error_type in types:
            error_bars["type"] = types[error_type]
        else:
            warn(f"Unknown error bars type '{error_type}")
            return {}

        # Set the value for error types that require it.
        if "value" in options:
            error_bars["value"] = options["value"]

        # Set the end-cap style.
        if "end_style" in options:
            error_bars["endcap"] = options["end_style"]

        # Set the error bar direction.
        if "direction" in options:
            if options["direction"] == "minus":
                error_bars["direction"] = "minus"
            elif options["direction"] == "plus":
                error_bars["direction"] = "plus"
            else:
                # Default to 'both'.
                pass

        # Set any custom values.
        error_bars["plus_values"] = options.get("plus_values")
        error_bars["minus_values"] = options.get("minus_values")
        error_bars["plus_data"] = options.get("plus_data")
        error_bars["minus_data"] = options.get("minus_data")

        # Set the line properties for the error bars.
        error_bars["line"] = Shape._get_line_properties(options.get("line"))

        return error_bars

    def _get_gridline_properties(self, options):
        # Convert user gridline properties to structure required internally.

        # Set the visible property for the gridline.
        gridline = {"visible": options.get("visible")}

        # Set the line properties for the gridline.
        gridline["line"] = Shape._get_line_properties(options.get("line"))

        return gridline

    def _get_labels_properties(self, labels):
        # Convert user labels properties to the structure required internally.

        if not labels:
            return None

        # Copy the user defined properties since they will be modified.
        labels = copy.deepcopy(labels)

        # Map user defined label positions to Excel positions.
        position = labels.get("position")

        if position:
            if position in self.label_positions:
                if position == self.label_position_default:
                    labels["position"] = None
                else:
                    labels["position"] = self.label_positions[position]
            else:
                warn(f"Unsupported label position '{position}' for this chart type")
                return None

        # Map the user defined label separator to the Excel separator.
        separator = labels.get("separator")
        separators = {
            ",": ", ",
            ";": "; ",
            ".": ". ",
            "\n": "\n",
            " ": " ",
        }

        if separator:
            if separator in separators:
                labels["separator"] = separators[separator]
            else:
                warn("Unsupported label separator")
                return None

        # Set the font properties if present.
        labels["font"] = self._convert_font_args(labels.get("font"))

        # Set the line properties for the labels.
        line = Shape._get_line_properties(labels.get("line"))

        # Allow 'border' as a synonym for 'line'.
        if "border" in labels:
            line = Shape._get_line_properties(labels["border"])

        # Set the fill properties for the labels.
        fill = Shape._get_fill_properties(labels.get("fill"))

        # Set the pattern fill properties for the labels.
        pattern = Shape._get_pattern_properties(labels.get("pattern"))

        # Set the gradient fill properties for the labels.
        gradient = Shape._get_gradient_properties(labels.get("gradient"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        labels["line"] = line
        labels["fill"] = fill
        labels["pattern"] = pattern
        labels["gradient"] = gradient

        if labels.get("custom"):
            for label in labels["custom"]:
                if label is None:
                    continue

                value = label.get("value")
                if value and re.match(r"^=?[^!]+!\$?[A-Z]+\$?\d+", str(value)):
                    label["formula"] = value

                formula = label.get("formula")
                if formula and formula.startswith("="):
                    label["formula"] = formula.lstrip("=")

                data_id = self._get_data_id(formula, label.get("data"))
                label["data_id"] = data_id

                label["font"] = self._convert_font_args(label.get("font"))

                # Set the line properties for the label.
                line = Shape._get_line_properties(label.get("line"))

                # Allow 'border' as a synonym for 'line'.
                if "border" in label:
                    line = Shape._get_line_properties(label["border"])

                # Set the fill properties for the label.
                fill = Shape._get_fill_properties(label.get("fill"))

                # Set the pattern fill properties for the label.
                pattern = Shape._get_pattern_properties(label.get("pattern"))

                # Set the gradient fill properties for the label.
                gradient = Shape._get_gradient_properties(label.get("gradient"))

                # Pattern fill overrides solid fill.
                if pattern:
                    self.fill = None

                # Gradient fill overrides the solid and pattern fill.
                if gradient:
                    pattern = None
                    fill = None

                label["line"] = line
                label["fill"] = fill
                label["pattern"] = pattern
                label["gradient"] = gradient

        return labels

    def _get_area_properties(self, options):
        # Convert user area properties to the structure required internally.
        area = {}

        # Set the line properties for the chartarea.
        line = Shape._get_line_properties(options.get("line"))

        # Allow 'border' as a synonym for 'line'.
        if options.get("border"):
            line = Shape._get_line_properties(options["border"])

        # Set the fill properties for the chartarea.
        fill = Shape._get_fill_properties(options.get("fill"))

        # Set the pattern fill properties for the series.
        pattern = Shape._get_pattern_properties(options.get("pattern"))

        # Set the gradient fill properties for the series.
        gradient = Shape._get_gradient_properties(options.get("gradient"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        # Set the plotarea layout.
        layout = self._get_layout_properties(options.get("layout"), False)

        area["line"] = line
        area["fill"] = fill
        area["pattern"] = pattern
        area["layout"] = layout
        area["gradient"] = gradient

        return area

    def _get_legend_properties(self, options=None):
        # Convert user legend properties to the structure required internally.
        legend = {}

        if options is None:
            options = {}

        legend["position"] = options.get("position", "right")
        legend["delete_series"] = options.get("delete_series")
        legend["font"] = self._convert_font_args(options.get("font"))
        legend["layout"] = self._get_layout_properties(options.get("layout"), False)

        # Turn off the legend.
        if options.get("none"):
            legend["position"] = "none"

        # Set the line properties for the legend.
        line = Shape._get_line_properties(options.get("line"))

        # Allow 'border' as a synonym for 'line'.
        if options.get("border"):
            line = Shape._get_line_properties(options["border"])

        # Set the fill properties for the legend.
        fill = Shape._get_fill_properties(options.get("fill"))

        # Set the pattern fill properties for the series.
        pattern = Shape._get_pattern_properties(options.get("pattern"))

        # Set the gradient fill properties for the series.
        gradient = Shape._get_gradient_properties(options.get("gradient"))

        # Pattern fill overrides solid fill.
        if pattern:
            self.fill = None

        # Gradient fill overrides the solid and pattern fill.
        if gradient:
            pattern = None
            fill = None

        # Set the legend layout.
        layout = self._get_layout_properties(options.get("layout"), False)

        legend["line"] = line
        legend["fill"] = fill
        legend["pattern"] = pattern
        legend["layout"] = layout
        legend["gradient"] = gradient

        return legend

    def _get_layout_properties(self, args, is_text):
        # Convert user defined layout properties to format used internally.
        layout = {}

        if not args:
            return {}

        if is_text:
            properties = ("x", "y")
        else:
            properties = ("x", "y", "width", "height")

        # Check for valid properties.
        for key in args.keys():
            if key not in properties:
                warn(f"Property '{key}' not supported in layout options")
                return {}

        # Set the layout properties.
        for prop in properties:
            if prop not in args.keys():
                warn(f"Property '{prop}' must be specified in layout options")
                return {}

            value = args[prop]

            try:
                float(value)
            except ValueError:
                warn(f"Property '{prop}' value '{value}' must be numeric in layout")
                return {}

            if value < 0 or value > 1:
                warn(
                    f"Property '{prop}' value '{value}' must be in range "
                    f"0 < x <= 1 in layout options"
                )
                return {}

            # Convert to the format used by Excel for easier testing
            layout[prop] = f"{value:.17g}"

        return layout

    def _get_points_properties(self, user_points):
        # Convert user points properties to structure required internally.
        points = []

        if not user_points:
            return []

        for user_point in user_points:
            point = {}

            if user_point is not None:
                # Set the line properties for the point.
                line = Shape._get_line_properties(user_point.get("line"))

                # Allow 'border' as a synonym for 'line'.
                if "border" in user_point:
                    line = Shape._get_line_properties(user_point["border"])

                # Set the fill properties for the chartarea.
                fill = Shape._get_fill_properties(user_point.get("fill"))

                # Set the pattern fill properties for the series.
                pattern = Shape._get_pattern_properties(user_point.get("pattern"))

                # Set the gradient fill properties for the series.
                gradient = Shape._get_gradient_properties(user_point.get("gradient"))

                # Pattern fill overrides solid fill.
                if pattern:
                    self.fill = None

                # Gradient fill overrides the solid and pattern fill.
                if gradient:
                    pattern = None
                    fill = None

                point["line"] = line
                point["fill"] = fill
                point["pattern"] = pattern
                point["gradient"] = gradient

            points.append(point)

        return points

    def _has_fill_formatting(self, element):
        # Check if a chart element has line, fill or gradient formatting.
        has_fill = False
        has_line = False
        has_pattern = element.get("pattern")
        has_gradient = element.get("gradient")

        if element.get("fill") and element["fill"]["defined"]:
            has_fill = True

        if element.get("line") and element["line"]["defined"]:
            has_line = True

        return has_fill or has_line or has_pattern or has_gradient

    def _get_display_units(self, display_units):
        # Convert user defined display units to internal units.
        if not display_units:
            return None

        types = {
            "hundreds": "hundreds",
            "thousands": "thousands",
            "ten_thousands": "tenThousands",
            "hundred_thousands": "hundredThousands",
            "millions": "millions",
            "ten_millions": "tenMillions",
            "hundred_millions": "hundredMillions",
            "billions": "billions",
            "trillions": "trillions",
        }

        if display_units in types:
            display_units = types[display_units]
        else:
            warn(f"Unknown display_units type '{display_units}'")
            return None

        return display_units

    def _get_tick_type(self, tick_type):
        # Convert user defined display units to internal units.
        if not tick_type:
            return None

        types = {
            "outside": "out",
            "inside": "in",
            "none": "none",
            "cross": "cross",
        }

        if tick_type in types:
            tick_type = types[tick_type]
        else:
            warn(f"Unknown tick_type '{tick_type}'")
            return None

        return tick_type

    def _get_primary_axes_series(self):
        # Returns series which use the primary axes.
        primary_axes_series = []

        for series in self.series:
            if not series["y2_axis"]:
                primary_axes_series.append(series)

        return primary_axes_series

    def _get_secondary_axes_series(self):
        # Returns series which use the secondary axes.
        secondary_axes_series = []

        for series in self.series:
            if series["y2_axis"]:
                secondary_axes_series.append(series)

        return secondary_axes_series

    def _add_axis_ids(self, args):
        # Add unique ids for primary or secondary axes
        chart_id = 5001 + int(self.id)
        axis_count = 1 + len(self.axis2_ids) + len(self.axis_ids)

        id1 = f"{chart_id:04d}{axis_count:04d}"
        id2 = f"{chart_id:04d}{axis_count + 1:04d}"

        if args["primary_axes"]:
            self.axis_ids.append(id1)
            self.axis_ids.append(id2)

        if not args["primary_axes"]:
            self.axis2_ids.append(id1)
            self.axis2_ids.append(id2)

    def _set_default_properties(self):
        # Setup the default properties for a chart.

        self.x_axis["defaults"] = {
            "num_format": "General",
            "major_gridlines": {"visible": 0},
        }

        self.y_axis["defaults"] = {
            "num_format": "General",
            "major_gridlines": {"visible": 1},
        }

        self.x2_axis["defaults"] = {
            "num_format": "General",
            "label_position": "none",
            "crossing": "max",
            "visible": 0,
        }

        self.y2_axis["defaults"] = {
            "num_format": "General",
            "major_gridlines": {"visible": 0},
            "position": "right",
            "visible": 1,
        }

        self.set_x_axis({})
        self.set_y_axis({})

        self.set_x2_axis({})
        self.set_y2_axis({})

    ###########################################################################
    #
    # XML methods.
    #
    ###########################################################################

    def _write_chart_space(self):
        # Write the <c:chartSpace> element.
        schema = "http://schemas.openxmlformats.org/"
        xmlns_c = schema + "drawingml/2006/chart"
        xmlns_a = schema + "drawingml/2006/main"
        xmlns_r = schema + "officeDocument/2006/relationships"

        attributes = [
            ("xmlns:c", xmlns_c),
            ("xmlns:a", xmlns_a),
            ("xmlns:r", xmlns_r),
        ]

        self._xml_start_tag("c:chartSpace", attributes)

    def _write_lang(self):
        # Write the <c:lang> element.
        val = "en-US"

        attributes = [("val", val)]

        self._xml_empty_tag("c:lang", attributes)

    def _write_style(self):
        # Write the <c:style> element.
        style_id = self.style_id

        # Don't write an element for the default style, 2.
        if style_id == 2:
            return

        attributes = [("val", style_id)]

        self._xml_empty_tag("c:style", attributes)

    def _write_chart(self):
        # Write the <c:chart> element.
        self._xml_start_tag("c:chart")

        if self.title_none:
            # Turn off the title.
            self._write_c_auto_title_deleted()
        else:
            # Write the chart title elements.
            if self.title_formula is not None:
                self._write_title_formula(
                    self.title_formula,
                    self.title_data_id,
                    None,
                    self.title_font,
                    self.title_layout,
                    self.title_overlay,
                )
            elif self.title_name is not None:
                self._write_title_rich(
                    self.title_name,
                    None,
                    self.title_font,
                    self.title_layout,
                    self.title_overlay,
                )

        # Write the c:plotArea element.
        self._write_plot_area()

        # Write the c:legend element.
        self._write_legend()

        # Write the c:plotVisOnly element.
        self._write_plot_vis_only()

        # Write the c:dispBlanksAs element.
        self._write_disp_blanks_as()

        # Write the c:extLst element.
        if self.show_na_as_empty:
            self._write_c_ext_lst_display_na()

        self._xml_end_tag("c:chart")

    def _write_disp_blanks_as(self):
        # Write the <c:dispBlanksAs> element.
        val = self.show_blanks

        # Ignore the default value.
        if val == "gap":
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:dispBlanksAs", attributes)

    def _write_plot_area(self):
        # Write the <c:plotArea> element.
        self._xml_start_tag("c:plotArea")

        # Write the c:layout element.
        self._write_layout(self.plotarea.get("layout"), "plot")

        # Write  subclass chart type elements for primary and secondary axes.
        self._write_chart_type({"primary_axes": True})
        self._write_chart_type({"primary_axes": False})

        # Configure a combined chart if present.
        second_chart = self.combined
        if second_chart:
            # Secondary axis has unique id otherwise use same as primary.
            if second_chart.is_secondary:
                second_chart.id = 1000 + self.id
            else:
                second_chart.id = self.id

            # Share the same filehandle for writing.
            second_chart.fh = self.fh

            # Share series index with primary chart.
            second_chart.series_index = self.series_index

            # Write the subclass chart type elements for combined chart.
            second_chart._write_chart_type({"primary_axes": True})
            second_chart._write_chart_type({"primary_axes": False})

        # Write the category and value elements for the primary axes.
        args = {"x_axis": self.x_axis, "y_axis": self.y_axis, "axis_ids": self.axis_ids}

        if self.date_category:
            self._write_date_axis(args)
        else:
            self._write_cat_axis(args)

        self._write_val_axis(args)

        # Write the category and value elements for the secondary axes.
        args = {
            "x_axis": self.x2_axis,
            "y_axis": self.y2_axis,
            "axis_ids": self.axis2_ids,
        }

        self._write_val_axis(args)

        # Write the secondary axis for the secondary chart.
        if second_chart and second_chart.is_secondary:
            args = {
                "x_axis": second_chart.x2_axis,
                "y_axis": second_chart.y2_axis,
                "axis_ids": second_chart.axis2_ids,
            }

            second_chart._write_val_axis(args)

        if self.date_category:
            self._write_date_axis(args)
        else:
            self._write_cat_axis(args)

        # Write the c:dTable element.
        self._write_d_table()

        # Write the c:spPr element for the plotarea formatting.
        self._write_sp_pr(self.plotarea)

        self._xml_end_tag("c:plotArea")

    def _write_layout(self, layout, layout_type):
        # Write the <c:layout> element.

        if not layout:
            # Automatic layout.
            self._xml_empty_tag("c:layout")
        else:
            # User defined manual layout.
            self._xml_start_tag("c:layout")
            self._write_manual_layout(layout, layout_type)
            self._xml_end_tag("c:layout")

    def _write_manual_layout(self, layout, layout_type):
        # Write the <c:manualLayout> element.
        self._xml_start_tag("c:manualLayout")

        # Plotarea has a layoutTarget element.
        if layout_type == "plot":
            self._xml_empty_tag("c:layoutTarget", [("val", "inner")])

        # Set the x, y positions.
        self._xml_empty_tag("c:xMode", [("val", "edge")])
        self._xml_empty_tag("c:yMode", [("val", "edge")])
        self._xml_empty_tag("c:x", [("val", layout["x"])])
        self._xml_empty_tag("c:y", [("val", layout["y"])])

        # For plotarea and legend set the width and height.
        if layout_type != "text":
            self._xml_empty_tag("c:w", [("val", layout["width"])])
            self._xml_empty_tag("c:h", [("val", layout["height"])])

        self._xml_end_tag("c:manualLayout")

    def _write_chart_type(self, args):
        # pylint: disable=unused-argument
        # Write the chart type element. This method should be overridden
        # by the subclasses.
        return

    def _write_grouping(self, val):
        # Write the <c:grouping> element.
        attributes = [("val", val)]

        self._xml_empty_tag("c:grouping", attributes)

    def _write_series(self, series):
        # Write the series elements.
        self._write_ser(series)

    def _write_ser(self, series):
        # Write the <c:ser> element.
        index = self.series_index
        self.series_index += 1

        self._xml_start_tag("c:ser")

        # Write the c:idx element.
        self._write_idx(index)

        # Write the c:order element.
        self._write_order(index)

        # Write the series name.
        self._write_series_name(series)

        # Write the c:spPr element.
        self._write_sp_pr(series)

        # Write the c:marker element.
        self._write_marker(series["marker"])

        # Write the c:invertIfNegative element.
        self._write_c_invert_if_negative(series["invert_if_neg"])

        # Write the c:dPt element.
        self._write_d_pt(series["points"])

        # Write the c:dLbls element.
        self._write_d_lbls(series["labels"])

        # Write the c:trendline element.
        self._write_trendline(series["trendline"])

        # Write the c:errBars element.
        self._write_error_bars(series["error_bars"])

        # Write the c:cat element.
        self._write_cat(series)

        # Write the c:val element.
        self._write_val(series)

        # Write the c:smooth element.
        if self.smooth_allowed:
            self._write_c_smooth(series["smooth"])

        # Write the c:extLst element.
        if series.get("inverted_color"):
            self._write_c_ext_lst_inverted_color(series["inverted_color"])

        self._xml_end_tag("c:ser")

    def _write_c_ext_lst_inverted_color(self, color):
        # Write the <c:extLst> element for the inverted fill color.

        uri = "{6F2FDCE9-48DA-4B69-8628-5D25D57E5C99}"
        xmlns_c_14 = "http://schemas.microsoft.com/office/drawing/2007/8/2/chart"

        attributes1 = [
            ("uri", uri),
            ("xmlns:c14", xmlns_c_14),
        ]

        attributes2 = [("xmlns:c14", xmlns_c_14)]

        self._xml_start_tag("c:extLst")
        self._xml_start_tag("c:ext", attributes1)
        self._xml_start_tag("c14:invertSolidFillFmt")
        self._xml_start_tag("c14:spPr", attributes2)

        self._write_a_solid_fill({"color": color})

        self._xml_end_tag("c14:spPr")
        self._xml_end_tag("c14:invertSolidFillFmt")
        self._xml_end_tag("c:ext")
        self._xml_end_tag("c:extLst")

    def _write_c_ext_lst_display_na(self):
        # Write the <c:extLst> element for the display NA as empty cell option.

        uri = "{56B9EC1D-385E-4148-901F-78D8002777C0}"
        xmlns_c_16 = "http://schemas.microsoft.com/office/drawing/2017/03/chart"

        attributes1 = [
            ("uri", uri),
            ("xmlns:c16r3", xmlns_c_16),
        ]

        attributes2 = [("val", 1)]

        self._xml_start_tag("c:extLst")
        self._xml_start_tag("c:ext", attributes1)
        self._xml_start_tag("c16r3:dataDisplayOptions16")
        self._xml_empty_tag("c16r3:dispNaAsBlank", attributes2)
        self._xml_end_tag("c16r3:dataDisplayOptions16")
        self._xml_end_tag("c:ext")
        self._xml_end_tag("c:extLst")

    def _write_idx(self, val):
        # Write the <c:idx> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:idx", attributes)

    def _write_order(self, val):
        # Write the <c:order> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:order", attributes)

    def _write_series_name(self, series):
        # Write the series name.

        if series["name_formula"] is not None:
            self._write_tx_formula(series["name_formula"], series["name_id"])
        elif series["name"] is not None:
            self._write_tx_value(series["name"])

    def _write_c_smooth(self, smooth):
        # Write the <c:smooth> element.

        if smooth:
            self._xml_empty_tag("c:smooth", [("val", "1")])

    def _write_cat(self, series):
        # Write the <c:cat> element.
        formula = series["categories"]
        data_id = series["cat_data_id"]
        data = None

        if data_id is not None:
            data = self.formula_data[data_id]

        # Ignore <c:cat> elements for charts without category values.
        if not formula:
            return

        self._xml_start_tag("c:cat")

        # Check the type of cached data.
        cat_type = self._get_data_type(data)

        if cat_type == "str":
            self.cat_has_num_fmt = 0
            # Write the c:numRef element.
            self._write_str_ref(formula, data, cat_type)

        elif cat_type == "multi_str":
            self.cat_has_num_fmt = 0
            # Write the c:numRef element.
            self._write_multi_lvl_str_ref(formula, data)

        else:
            self.cat_has_num_fmt = 1
            # Write the c:numRef element.
            self._write_num_ref(formula, data, cat_type)

        self._xml_end_tag("c:cat")

    def _write_val(self, series):
        # Write the <c:val> element.
        formula = series["values"]
        data_id = series["val_data_id"]
        data = self.formula_data[data_id]

        self._xml_start_tag("c:val")

        # Unlike Cat axes data should only be numeric.
        # Write the c:numRef element.
        self._write_num_ref(formula, data, "num")

        self._xml_end_tag("c:val")

    def _write_num_ref(self, formula, data, ref_type):
        # Write the <c:numRef> element.
        self._xml_start_tag("c:numRef")

        # Write the c:f element.
        self._write_series_formula(formula)

        if ref_type == "num":
            # Write the c:numCache element.
            self._write_num_cache(data)
        elif ref_type == "str":
            # Write the c:strCache element.
            self._write_str_cache(data)

        self._xml_end_tag("c:numRef")

    def _write_str_ref(self, formula, data, ref_type):
        # Write the <c:strRef> element.

        self._xml_start_tag("c:strRef")

        # Write the c:f element.
        self._write_series_formula(formula)

        if ref_type == "num":
            # Write the c:numCache element.
            self._write_num_cache(data)
        elif ref_type == "str":
            # Write the c:strCache element.
            self._write_str_cache(data)

        self._xml_end_tag("c:strRef")

    def _write_multi_lvl_str_ref(self, formula, data):
        # Write the <c:multiLvlStrRef> element.

        if not data:
            return

        self._xml_start_tag("c:multiLvlStrRef")

        # Write the c:f element.
        self._write_series_formula(formula)

        self._xml_start_tag("c:multiLvlStrCache")

        # Write the c:ptCount element.
        count = len(data[-1])
        self._write_pt_count(count)

        for cat_data in reversed(data):
            self._xml_start_tag("c:lvl")

            for i, point in enumerate(cat_data):
                # Write the c:pt element.
                self._write_pt(i, point)

            self._xml_end_tag("c:lvl")

        self._xml_end_tag("c:multiLvlStrCache")
        self._xml_end_tag("c:multiLvlStrRef")

    def _write_series_formula(self, formula):
        # Write the <c:f> element.

        # Strip the leading '=' from the formula.
        if formula.startswith("="):
            formula = formula.lstrip("=")

        self._xml_data_element("c:f", formula)

    def _write_axis_ids(self, args):
        # Write the <c:axId> elements for the primary or secondary axes.

        # Generate the axis ids.
        self._add_axis_ids(args)

        if args["primary_axes"]:
            # Write the axis ids for the primary axes.
            self._write_axis_id(self.axis_ids[0])
            self._write_axis_id(self.axis_ids[1])
        else:
            # Write the axis ids for the secondary axes.
            self._write_axis_id(self.axis2_ids[0])
            self._write_axis_id(self.axis2_ids[1])

    def _write_axis_id(self, val):
        # Write the <c:axId> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:axId", attributes)

    def _write_cat_axis(self, args):
        # Write the <c:catAx> element. Usually the X axis.
        x_axis = args["x_axis"]
        y_axis = args["y_axis"]
        axis_ids = args["axis_ids"]

        # If there are no axis_ids then we don't need to write this element.
        if axis_ids is None or not axis_ids:
            return

        position = self.cat_axis_position
        is_y_axis = self.horiz_cat_axis

        # Overwrite the default axis position with a user supplied value.
        if x_axis.get("position"):
            position = x_axis["position"]

        self._xml_start_tag("c:catAx")

        self._write_axis_id(axis_ids[0])

        # Write the c:scaling element.
        self._write_scaling(x_axis.get("reverse"), None, None, None)

        if not x_axis.get("visible"):
            self._write_delete(1)

        # Write the c:axPos element.
        self._write_axis_pos(position, y_axis.get("reverse"))

        # Write the c:majorGridlines element.
        self._write_major_gridlines(x_axis.get("major_gridlines"))

        # Write the c:minorGridlines element.
        self._write_minor_gridlines(x_axis.get("minor_gridlines"))

        # Write the axis title elements.
        if x_axis["formula"] is not None:
            self._write_title_formula(
                x_axis["formula"],
                x_axis["data_id"],
                is_y_axis,
                x_axis["name_font"],
                x_axis["name_layout"],
            )
        elif x_axis["name"] is not None:
            self._write_title_rich(
                x_axis["name"], is_y_axis, x_axis["name_font"], x_axis["name_layout"]
            )

        # Write the c:numFmt element.
        self._write_cat_number_format(x_axis)

        # Write the c:majorTickMark element.
        self._write_major_tick_mark(x_axis.get("major_tick_mark"))

        # Write the c:minorTickMark element.
        self._write_minor_tick_mark(x_axis.get("minor_tick_mark"))

        # Write the c:tickLblPos element.
        self._write_tick_label_pos(x_axis.get("label_position"))

        # Write the c:spPr element for the axis line.
        self._write_sp_pr(x_axis)

        # Write the axis font elements.
        self._write_axis_font(x_axis.get("num_font"))

        # Write the c:crossAx element.
        self._write_cross_axis(axis_ids[1])

        if self.show_crosses or x_axis.get("visible"):
            # Note, the category crossing comes from the value axis.
            if (
                y_axis.get("crossing") is None
                or y_axis.get("crossing") == "max"
                or y_axis["crossing"] == "min"
            ):
                # Write the c:crosses element.
                self._write_crosses(y_axis.get("crossing"))
            else:
                # Write the c:crossesAt element.
                self._write_c_crosses_at(y_axis.get("crossing"))

        # Write the c:auto element.
        if not x_axis.get("text_axis"):
            self._write_auto(1)

        # Write the c:labelAlign element.
        self._write_label_align(x_axis.get("label_align"))

        # Write the c:labelOffset element.
        self._write_label_offset(100)

        # Write the c:tickLblSkip element.
        self._write_c_tick_lbl_skip(x_axis.get("interval_unit"))

        # Write the c:tickMarkSkip element.
        self._write_c_tick_mark_skip(x_axis.get("interval_tick"))

        self._xml_end_tag("c:catAx")

    def _write_val_axis(self, args):
        # Write the <c:valAx> element. Usually the Y axis.
        x_axis = args["x_axis"]
        y_axis = args["y_axis"]
        axis_ids = args["axis_ids"]
        position = args.get("position", self.val_axis_position)
        is_y_axis = self.horiz_val_axis

        # If there are no axis_ids then we don't need to write this element.
        if axis_ids is None or not axis_ids:
            return

        # Overwrite the default axis position with a user supplied value.
        position = y_axis.get("position") or position

        self._xml_start_tag("c:valAx")

        self._write_axis_id(axis_ids[1])

        # Write the c:scaling element.
        self._write_scaling(
            y_axis.get("reverse"),
            y_axis.get("min"),
            y_axis.get("max"),
            y_axis.get("log_base"),
        )

        if not y_axis.get("visible"):
            self._write_delete(1)

        # Write the c:axPos element.
        self._write_axis_pos(position, x_axis.get("reverse"))

        # Write the c:majorGridlines element.
        self._write_major_gridlines(y_axis.get("major_gridlines"))

        # Write the c:minorGridlines element.
        self._write_minor_gridlines(y_axis.get("minor_gridlines"))

        # Write the axis title elements.
        if y_axis["formula"] is not None:
            self._write_title_formula(
                y_axis["formula"],
                y_axis["data_id"],
                is_y_axis,
                y_axis["name_font"],
                y_axis["name_layout"],
            )
        elif y_axis["name"] is not None:
            self._write_title_rich(
                y_axis["name"],
                is_y_axis,
                y_axis.get("name_font"),
                y_axis.get("name_layout"),
            )

        # Write the c:numberFormat element.
        self._write_number_format(y_axis)

        # Write the c:majorTickMark element.
        self._write_major_tick_mark(y_axis.get("major_tick_mark"))

        # Write the c:minorTickMark element.
        self._write_minor_tick_mark(y_axis.get("minor_tick_mark"))

        # Write the c:tickLblPos element.
        self._write_tick_label_pos(y_axis.get("label_position"))

        # Write the c:spPr element for the axis line.
        self._write_sp_pr(y_axis)

        # Write the axis font elements.
        self._write_axis_font(y_axis.get("num_font"))

        # Write the c:crossAx element.
        self._write_cross_axis(axis_ids[0])

        # Note, the category crossing comes from the value axis.
        if (
            x_axis.get("crossing") is None
            or x_axis["crossing"] == "max"
            or x_axis["crossing"] == "min"
        ):
            # Write the c:crosses element.
            self._write_crosses(x_axis.get("crossing"))
        else:
            # Write the c:crossesAt element.
            self._write_c_crosses_at(x_axis.get("crossing"))

        # Write the c:crossBetween element.
        self._write_cross_between(x_axis.get("position_axis"))

        # Write the c:majorUnit element.
        self._write_c_major_unit(y_axis.get("major_unit"))

        # Write the c:minorUnit element.
        self._write_c_minor_unit(y_axis.get("minor_unit"))

        # Write the c:dispUnits element.
        self._write_disp_units(
            y_axis.get("display_units"), y_axis.get("display_units_visible")
        )

        self._xml_end_tag("c:valAx")

    def _write_cat_val_axis(self, args):
        # Write the <c:valAx> element. This is for the second valAx
        # in scatter plots. Usually the X axis.
        x_axis = args["x_axis"]
        y_axis = args["y_axis"]
        axis_ids = args["axis_ids"]
        position = args["position"] or self.val_axis_position
        is_y_axis = self.horiz_val_axis

        # If there are no axis_ids then we don't need to write this element.
        if axis_ids is None or not axis_ids:
            return

        # Overwrite the default axis position with a user supplied value.
        position = x_axis.get("position") or position

        self._xml_start_tag("c:valAx")

        self._write_axis_id(axis_ids[0])

        # Write the c:scaling element.
        self._write_scaling(
            x_axis.get("reverse"),
            x_axis.get("min"),
            x_axis.get("max"),
            x_axis.get("log_base"),
        )

        if not x_axis.get("visible"):
            self._write_delete(1)

        # Write the c:axPos element.
        self._write_axis_pos(position, y_axis.get("reverse"))

        # Write the c:majorGridlines element.
        self._write_major_gridlines(x_axis.get("major_gridlines"))

        # Write the c:minorGridlines element.
        self._write_minor_gridlines(x_axis.get("minor_gridlines"))

        # Write the axis title elements.
        if x_axis["formula"] is not None:
            self._write_title_formula(
                x_axis["formula"],
                x_axis["data_id"],
                is_y_axis,
                x_axis["name_font"],
                x_axis["name_layout"],
            )
        elif x_axis["name"] is not None:
            self._write_title_rich(
                x_axis["name"], is_y_axis, x_axis["name_font"], x_axis["name_layout"]
            )

        # Write the c:numberFormat element.
        self._write_number_format(x_axis)

        # Write the c:majorTickMark element.
        self._write_major_tick_mark(x_axis.get("major_tick_mark"))

        # Write the c:minorTickMark element.
        self._write_minor_tick_mark(x_axis.get("minor_tick_mark"))

        # Write the c:tickLblPos element.
        self._write_tick_label_pos(x_axis.get("label_position"))

        # Write the c:spPr element for the axis line.
        self._write_sp_pr(x_axis)

        # Write the axis font elements.
        self._write_axis_font(x_axis.get("num_font"))

        # Write the c:crossAx element.
        self._write_cross_axis(axis_ids[1])

        # Note, the category crossing comes from the value axis.
        if (
            y_axis.get("crossing") is None
            or y_axis["crossing"] == "max"
            or y_axis["crossing"] == "min"
        ):
            # Write the c:crosses element.
            self._write_crosses(y_axis.get("crossing"))
        else:
            # Write the c:crossesAt element.
            self._write_c_crosses_at(y_axis.get("crossing"))

        # Write the c:crossBetween element.
        self._write_cross_between(y_axis.get("position_axis"))

        # Write the c:majorUnit element.
        self._write_c_major_unit(x_axis.get("major_unit"))

        # Write the c:minorUnit element.
        self._write_c_minor_unit(x_axis.get("minor_unit"))

        # Write the c:dispUnits element.
        self._write_disp_units(
            x_axis.get("display_units"), x_axis.get("display_units_visible")
        )

        self._xml_end_tag("c:valAx")

    def _write_date_axis(self, args):
        # Write the <c:dateAx> element. Usually the X axis.
        x_axis = args["x_axis"]
        y_axis = args["y_axis"]
        axis_ids = args["axis_ids"]

        # If there are no axis_ids then we don't need to write this element.
        if axis_ids is None or not axis_ids:
            return

        position = self.cat_axis_position

        # Overwrite the default axis position with a user supplied value.
        position = x_axis.get("position") or position

        self._xml_start_tag("c:dateAx")

        self._write_axis_id(axis_ids[0])

        # Write the c:scaling element.
        self._write_scaling(
            x_axis.get("reverse"),
            x_axis.get("min"),
            x_axis.get("max"),
            x_axis.get("log_base"),
        )

        if not x_axis.get("visible"):
            self._write_delete(1)

        # Write the c:axPos element.
        self._write_axis_pos(position, y_axis.get("reverse"))

        # Write the c:majorGridlines element.
        self._write_major_gridlines(x_axis.get("major_gridlines"))

        # Write the c:minorGridlines element.
        self._write_minor_gridlines(x_axis.get("minor_gridlines"))

        # Write the axis title elements.
        if x_axis["formula"] is not None:
            self._write_title_formula(
                x_axis["formula"],
                x_axis["data_id"],
                None,
                x_axis["name_font"],
                x_axis["name_layout"],
            )
        elif x_axis["name"] is not None:
            self._write_title_rich(
                x_axis["name"], None, x_axis["name_font"], x_axis["name_layout"]
            )

        # Write the c:numFmt element.
        self._write_number_format(x_axis)

        # Write the c:majorTickMark element.
        self._write_major_tick_mark(x_axis.get("major_tick_mark"))

        # Write the c:minorTickMark element.
        self._write_minor_tick_mark(x_axis.get("minor_tick_mark"))

        # Write the c:tickLblPos element.
        self._write_tick_label_pos(x_axis.get("label_position"))

        # Write the c:spPr element for the axis line.
        self._write_sp_pr(x_axis)

        # Write the axis font elements.
        self._write_axis_font(x_axis.get("num_font"))

        # Write the c:crossAx element.
        self._write_cross_axis(axis_ids[1])

        if self.show_crosses or x_axis.get("visible"):
            # Note, the category crossing comes from the value axis.
            if (
                y_axis.get("crossing") is None
                or y_axis.get("crossing") == "max"
                or y_axis["crossing"] == "min"
            ):
                # Write the c:crosses element.
                self._write_crosses(y_axis.get("crossing"))
            else:
                # Write the c:crossesAt element.
                self._write_c_crosses_at(y_axis.get("crossing"))

        # Write the c:auto element.
        self._write_auto(1)

        # Write the c:labelOffset element.
        self._write_label_offset(100)

        # Write the c:tickLblSkip element.
        self._write_c_tick_lbl_skip(x_axis.get("interval_unit"))

        # Write the c:tickMarkSkip element.
        self._write_c_tick_mark_skip(x_axis.get("interval_tick"))

        # Write the c:majorUnit element.
        self._write_c_major_unit(x_axis.get("major_unit"))

        # Write the c:majorTimeUnit element.
        if x_axis.get("major_unit"):
            self._write_c_major_time_unit(x_axis["major_unit_type"])

        # Write the c:minorUnit element.
        self._write_c_minor_unit(x_axis.get("minor_unit"))

        # Write the c:minorTimeUnit element.
        if x_axis.get("minor_unit"):
            self._write_c_minor_time_unit(x_axis["minor_unit_type"])

        self._xml_end_tag("c:dateAx")

    def _write_scaling(self, reverse, min_val, max_val, log_base):
        # Write the <c:scaling> element.

        self._xml_start_tag("c:scaling")

        # Write the c:logBase element.
        self._write_c_log_base(log_base)

        # Write the c:orientation element.
        self._write_orientation(reverse)

        # Write the c:max element.
        self._write_c_max(max_val)

        # Write the c:min element.
        self._write_c_min(min_val)

        self._xml_end_tag("c:scaling")

    def _write_c_log_base(self, val):
        # Write the <c:logBase> element.

        if not val:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:logBase", attributes)

    def _write_orientation(self, reverse):
        # Write the <c:orientation> element.
        val = "minMax"

        if reverse:
            val = "maxMin"

        attributes = [("val", val)]

        self._xml_empty_tag("c:orientation", attributes)

    def _write_c_max(self, max_val):
        # Write the <c:max> element.

        if max_val is None:
            return

        attributes = [("val", max_val)]

        self._xml_empty_tag("c:max", attributes)

    def _write_c_min(self, min_val):
        # Write the <c:min> element.

        if min_val is None:
            return

        attributes = [("val", min_val)]

        self._xml_empty_tag("c:min", attributes)

    def _write_axis_pos(self, val, reverse):
        # Write the <c:axPos> element.

        if reverse:
            if val == "l":
                val = "r"
            if val == "b":
                val = "t"

        attributes = [("val", val)]

        self._xml_empty_tag("c:axPos", attributes)

    def _write_number_format(self, axis):
        # Write the <c:numberFormat> element. Note: It is assumed that if
        # a user defined number format is supplied (i.e., non-default) then
        # the sourceLinked attribute is 0.
        # The user can override this if required.
        format_code = axis.get("num_format")
        source_linked = 1

        # Check if a user defined number format has been set.
        if format_code is not None and format_code != axis["defaults"]["num_format"]:
            source_linked = 0

        # User override of sourceLinked.
        if axis.get("num_format_linked"):
            source_linked = 1

        attributes = [
            ("formatCode", format_code),
            ("sourceLinked", source_linked),
        ]

        self._xml_empty_tag("c:numFmt", attributes)

    def _write_cat_number_format(self, axis):
        # Write the <c:numFmt> element. Special case handler for category
        # axes which don't always have a number format.
        format_code = axis.get("num_format")
        source_linked = 1
        default_format = 1

        # Check if a user defined number format has been set.
        if format_code is not None and format_code != axis["defaults"]["num_format"]:
            source_linked = 0
            default_format = 0

        # User override of sourceLinked.
        if axis.get("num_format_linked"):
            source_linked = 1

        # Skip if cat doesn't have a num format (unless it is non-default).
        if not self.cat_has_num_fmt and default_format:
            return

        attributes = [
            ("formatCode", format_code),
            ("sourceLinked", source_linked),
        ]

        self._xml_empty_tag("c:numFmt", attributes)

    def _write_data_label_number_format(self, format_code):
        # Write the <c:numberFormat> element for data labels.
        source_linked = 0

        attributes = [
            ("formatCode", format_code),
            ("sourceLinked", source_linked),
        ]

        self._xml_empty_tag("c:numFmt", attributes)

    def _write_major_tick_mark(self, val):
        # Write the <c:majorTickMark> element.

        if not val:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:majorTickMark", attributes)

    def _write_minor_tick_mark(self, val):
        # Write the <c:minorTickMark> element.

        if not val:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:minorTickMark", attributes)

    def _write_tick_label_pos(self, val=None):
        # Write the <c:tickLblPos> element.
        if val is None or val == "next_to":
            val = "nextTo"

        attributes = [("val", val)]

        self._xml_empty_tag("c:tickLblPos", attributes)

    def _write_cross_axis(self, val):
        # Write the <c:crossAx> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:crossAx", attributes)

    def _write_crosses(self, val=None):
        # Write the <c:crosses> element.
        if val is None:
            val = "autoZero"

        attributes = [("val", val)]

        self._xml_empty_tag("c:crosses", attributes)

    def _write_c_crosses_at(self, val):
        # Write the <c:crossesAt> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:crossesAt", attributes)

    def _write_auto(self, val):
        # Write the <c:auto> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:auto", attributes)

    def _write_label_align(self, val=None):
        # Write the <c:labelAlign> element.

        if val is None:
            val = "ctr"

        if val == "right":
            val = "r"

        if val == "left":
            val = "l"

        attributes = [("val", val)]

        self._xml_empty_tag("c:lblAlgn", attributes)

    def _write_label_offset(self, val):
        # Write the <c:labelOffset> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:lblOffset", attributes)

    def _write_c_tick_lbl_skip(self, val):
        # Write the <c:tickLblSkip> element.
        if val is None:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:tickLblSkip", attributes)

    def _write_c_tick_mark_skip(self, val):
        # Write the <c:tickMarkSkip> element.
        if val is None:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:tickMarkSkip", attributes)

    def _write_major_gridlines(self, gridlines):
        # Write the <c:majorGridlines> element.

        if not gridlines:
            return

        if not gridlines["visible"]:
            return

        if gridlines["line"]["defined"]:
            self._xml_start_tag("c:majorGridlines")

            # Write the c:spPr element.
            self._write_sp_pr(gridlines)

            self._xml_end_tag("c:majorGridlines")
        else:
            self._xml_empty_tag("c:majorGridlines")

    def _write_minor_gridlines(self, gridlines):
        # Write the <c:minorGridlines> element.

        if not gridlines:
            return

        if not gridlines["visible"]:
            return

        if gridlines["line"]["defined"]:
            self._xml_start_tag("c:minorGridlines")

            # Write the c:spPr element.
            self._write_sp_pr(gridlines)

            self._xml_end_tag("c:minorGridlines")
        else:
            self._xml_empty_tag("c:minorGridlines")

    def _write_cross_between(self, val):
        # Write the <c:crossBetween> element.
        if val is None:
            val = self.cross_between

        attributes = [("val", val)]

        self._xml_empty_tag("c:crossBetween", attributes)

    def _write_c_major_unit(self, val):
        # Write the <c:majorUnit> element.

        if not val:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:majorUnit", attributes)

    def _write_c_minor_unit(self, val):
        # Write the <c:minorUnit> element.

        if not val:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:minorUnit", attributes)

    def _write_c_major_time_unit(self, val=None):
        # Write the <c:majorTimeUnit> element.
        if val is None:
            val = "days"

        attributes = [("val", val)]

        self._xml_empty_tag("c:majorTimeUnit", attributes)

    def _write_c_minor_time_unit(self, val=None):
        # Write the <c:minorTimeUnit> element.
        if val is None:
            val = "days"

        attributes = [("val", val)]

        self._xml_empty_tag("c:minorTimeUnit", attributes)

    def _write_legend(self):
        # Write the <c:legend> element.
        legend = self.legend
        position = legend.get("position", "right")
        font = legend.get("font")
        delete_series = []
        overlay = 0

        if legend.get("delete_series") and isinstance(legend["delete_series"], list):
            delete_series = legend["delete_series"]

        if position.startswith("overlay_"):
            position = position.replace("overlay_", "")
            overlay = 1

        allowed = {
            "right": "r",
            "left": "l",
            "top": "t",
            "bottom": "b",
            "top_right": "tr",
        }

        if position == "none":
            return

        if position not in allowed:
            return

        position = allowed[position]

        self._xml_start_tag("c:legend")

        # Write the c:legendPos element.
        self._write_legend_pos(position)

        # Remove series labels from the legend.
        for index in delete_series:
            # Write the c:legendEntry element.
            self._write_legend_entry(index)

        # Write the c:layout element.
        self._write_layout(legend.get("layout"), "legend")

        # Write the c:overlay element.
        if overlay:
            self._write_overlay()

        if font:
            self._write_tx_pr(font)

        # Write the c:spPr element.
        self._write_sp_pr(legend)

        self._xml_end_tag("c:legend")

    def _write_legend_pos(self, val):
        # Write the <c:legendPos> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:legendPos", attributes)

    def _write_legend_entry(self, index):
        # Write the <c:legendEntry> element.

        self._xml_start_tag("c:legendEntry")

        # Write the c:idx element.
        self._write_idx(index)

        # Write the c:delete element.
        self._write_delete(1)

        self._xml_end_tag("c:legendEntry")

    def _write_overlay(self):
        # Write the <c:overlay> element.
        val = 1

        attributes = [("val", val)]

        self._xml_empty_tag("c:overlay", attributes)

    def _write_plot_vis_only(self):
        # Write the <c:plotVisOnly> element.
        val = 1

        # Ignore this element if we are plotting hidden data.
        if self.show_hidden:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:plotVisOnly", attributes)

    def _write_print_settings(self):
        # Write the <c:printSettings> element.
        self._xml_start_tag("c:printSettings")

        # Write the c:headerFooter element.
        self._write_header_footer()

        # Write the c:pageMargins element.
        self._write_page_margins()

        # Write the c:pageSetup element.
        self._write_page_setup()

        self._xml_end_tag("c:printSettings")

    def _write_header_footer(self):
        # Write the <c:headerFooter> element.
        self._xml_empty_tag("c:headerFooter")

    def _write_page_margins(self):
        # Write the <c:pageMargins> element.
        bottom = 0.75
        left = 0.7
        right = 0.7
        top = 0.75
        header = 0.3
        footer = 0.3

        attributes = [
            ("b", bottom),
            ("l", left),
            ("r", right),
            ("t", top),
            ("header", header),
            ("footer", footer),
        ]

        self._xml_empty_tag("c:pageMargins", attributes)

    def _write_page_setup(self):
        # Write the <c:pageSetup> element.
        self._xml_empty_tag("c:pageSetup")

    def _write_c_auto_title_deleted(self):
        # Write the <c:autoTitleDeleted> element.
        self._xml_empty_tag("c:autoTitleDeleted", [("val", 1)])

    def _write_title_rich(self, title, is_y_axis, font, layout, overlay=False):
        # Write the <c:title> element for a rich string.

        self._xml_start_tag("c:title")

        # Write the c:tx element.
        self._write_tx_rich(title, is_y_axis, font)

        # Write the c:layout element.
        self._write_layout(layout, "text")

        # Write the c:overlay element.
        if overlay:
            self._write_overlay()

        self._xml_end_tag("c:title")

    def _write_title_formula(
        self, title, data_id, is_y_axis, font, layout, overlay=False
    ):
        # Write the <c:title> element for a rich string.

        self._xml_start_tag("c:title")

        # Write the c:tx element.
        self._write_tx_formula(title, data_id)

        # Write the c:layout element.
        self._write_layout(layout, "text")

        # Write the c:overlay element.
        if overlay:
            self._write_overlay()

        # Write the c:txPr element.
        self._write_tx_pr(font, is_y_axis)

        self._xml_end_tag("c:title")

    def _write_tx_rich(self, title, is_y_axis, font):
        # Write the <c:tx> element.

        self._xml_start_tag("c:tx")

        # Write the c:rich element.
        self._write_rich(title, font, is_y_axis, ignore_rich_pr=False)

        self._xml_end_tag("c:tx")

    def _write_tx_value(self, title):
        # Write the <c:tx> element with a value such as for series names.

        self._xml_start_tag("c:tx")

        # Write the c:v element.
        self._write_v(title)

        self._xml_end_tag("c:tx")

    def _write_tx_formula(self, title, data_id):
        # Write the <c:tx> element.
        data = None

        if data_id is not None:
            data = self.formula_data[data_id]

        self._xml_start_tag("c:tx")

        # Write the c:strRef element.
        self._write_str_ref(title, data, "str")

        self._xml_end_tag("c:tx")

    def _write_rich(self, title, font, is_y_axis, ignore_rich_pr):
        # Write the <c:rich> element.

        if font and font.get("rotation") is not None:
            rotation = font["rotation"]
        else:
            rotation = None

        self._xml_start_tag("c:rich")

        # Write the a:bodyPr element.
        self._write_a_body_pr(rotation, is_y_axis)

        # Write the a:lstStyle element.
        self._write_a_lst_style()

        # Write the a:p element.
        self._write_a_p_rich(title, font, ignore_rich_pr)

        self._xml_end_tag("c:rich")

    def _write_a_body_pr(self, rotation, is_y_axis):
        # Write the <a:bodyPr> element.
        attributes = []

        if rotation is None and is_y_axis:
            rotation = -5400000

        if rotation is not None:
            if rotation == 16200000:
                # 270 deg/stacked angle.
                attributes.append(("rot", 0))
                attributes.append(("vert", "wordArtVert"))
            elif rotation == 16260000:
                # 271 deg/East Asian vertical.
                attributes.append(("rot", 0))
                attributes.append(("vert", "eaVert"))
            else:
                attributes.append(("rot", rotation))
                attributes.append(("vert", "horz"))

        self._xml_empty_tag("a:bodyPr", attributes)

    def _write_a_lst_style(self):
        # Write the <a:lstStyle> element.
        self._xml_empty_tag("a:lstStyle")

    def _write_a_p_rich(self, title, font, ignore_rich_pr):
        # Write the <a:p> element for rich string titles.

        self._xml_start_tag("a:p")

        # Write the a:pPr element.
        if not ignore_rich_pr:
            self._write_a_p_pr_rich(font)

        # Write the a:r element.
        self._write_a_r(title, font)

        self._xml_end_tag("a:p")

    def _write_a_p_formula(self, font):
        # Write the <a:p> element for formula titles.

        self._xml_start_tag("a:p")

        # Write the a:pPr element.
        self._write_a_p_pr_rich(font)

        # Write the a:endParaRPr element.
        self._write_a_end_para_rpr()

        self._xml_end_tag("a:p")

    def _write_a_p_pr_rich(self, font):
        # Write the <a:pPr> element for rich string titles.

        self._xml_start_tag("a:pPr")

        # Write the a:defRPr element.
        self._write_a_def_rpr(font)

        self._xml_end_tag("a:pPr")

    def _write_a_def_rpr(self, font):
        # Write the <a:defRPr> element.
        has_color = 0

        style_attributes = Shape._get_font_style_attributes(font)
        latin_attributes = Shape._get_font_latin_attributes(font)

        if font and font.get("color") is not None:
            has_color = 1

        if latin_attributes or has_color:
            self._xml_start_tag("a:defRPr", style_attributes)

            if has_color:
                self._write_a_solid_fill({"color": font["color"]})

            if latin_attributes:
                self._write_a_latin(latin_attributes)

            self._xml_end_tag("a:defRPr")
        else:
            self._xml_empty_tag("a:defRPr", style_attributes)

    def _write_a_end_para_rpr(self):
        # Write the <a:endParaRPr> element.
        lang = "en-US"

        attributes = [("lang", lang)]

        self._xml_empty_tag("a:endParaRPr", attributes)

    def _write_a_r(self, title, font):
        # Write the <a:r> element.

        self._xml_start_tag("a:r")

        # Write the a:rPr element.
        self._write_a_r_pr(font)

        # Write the a:t element.
        self._write_a_t(title)

        self._xml_end_tag("a:r")

    def _write_a_r_pr(self, font):
        # Write the <a:rPr> element.
        has_color = 0
        lang = "en-US"

        style_attributes = Shape._get_font_style_attributes(font)
        latin_attributes = Shape._get_font_latin_attributes(font)

        if font and font["color"] is not None:
            has_color = 1

        # Add the lang type to the attributes.
        style_attributes.insert(0, ("lang", lang))

        if latin_attributes or has_color:
            self._xml_start_tag("a:rPr", style_attributes)

            if has_color:
                self._write_a_solid_fill({"color": font["color"]})

            if latin_attributes:
                self._write_a_latin(latin_attributes)

            self._xml_end_tag("a:rPr")
        else:
            self._xml_empty_tag("a:rPr", style_attributes)

    def _write_a_t(self, title):
        # Write the <a:t> element.

        self._xml_data_element("a:t", title)

    def _write_tx_pr(self, font, is_y_axis=False):
        # Write the <c:txPr> element.

        if font and font.get("rotation") is not None:
            rotation = font["rotation"]
        else:
            rotation = None

        self._xml_start_tag("c:txPr")

        # Write the a:bodyPr element.
        self._write_a_body_pr(rotation, is_y_axis)

        # Write the a:lstStyle element.
        self._write_a_lst_style()

        # Write the a:p element.
        self._write_a_p_formula(font)

        self._xml_end_tag("c:txPr")

    def _write_marker(self, marker):
        # Write the <c:marker> element.
        if marker is None:
            marker = self.default_marker

        if not marker:
            return

        if marker["type"] == "automatic":
            return

        self._xml_start_tag("c:marker")

        # Write the c:symbol element.
        self._write_symbol(marker["type"])

        # Write the c:size element.
        if marker.get("size"):
            self._write_marker_size(marker["size"])

        # Write the c:spPr element.
        self._write_sp_pr(marker)

        self._xml_end_tag("c:marker")

    def _write_marker_size(self, val):
        # Write the <c:size> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:size", attributes)

    def _write_symbol(self, val):
        # Write the <c:symbol> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:symbol", attributes)

    def _write_sp_pr(self, series):
        # Write the <c:spPr> element.

        if not self._has_fill_formatting(series):
            return

        self._xml_start_tag("c:spPr")

        # Write the fill elements for solid charts such as pie and bar.
        if series.get("fill") and series["fill"]["defined"]:
            if "none" in series["fill"]:
                # Write the a:noFill element.
                self._write_a_no_fill()
            else:
                # Write the a:solidFill element.
                self._write_a_solid_fill(series["fill"])

        if series.get("pattern"):
            # Write the a:gradFill element.
            self._write_a_patt_fill(series["pattern"])

        if series.get("gradient"):
            # Write the a:gradFill element.
            self._write_a_grad_fill(series["gradient"])

        # Write the a:ln element.
        if series.get("line") and series["line"]["defined"]:
            self._write_a_ln(series["line"])

        self._xml_end_tag("c:spPr")

    def _write_a_ln(self, line):
        # Write the <a:ln> element.
        attributes = []

        # Add the line width as an attribute.
        width = line.get("width")

        if width is not None:
            # Round width to nearest 0.25, like Excel.
            width = int((width + 0.125) * 4) / 4.0

            # Convert to internal units.
            width = int(0.5 + (12700 * width))

            attributes = [("w", width)]

        if line.get("none") or line.get("color") or line.get("dash_type"):
            self._xml_start_tag("a:ln", attributes)

            # Write the line fill.
            if "none" in line:
                # Write the a:noFill element.
                self._write_a_no_fill()
            elif "color" in line:
                # Write the a:solidFill element.
                self._write_a_solid_fill(line)

            # Write the line/dash type.
            line_type = line.get("dash_type")
            if line_type:
                # Write the a:prstDash element.
                self._write_a_prst_dash(line_type)

            self._xml_end_tag("a:ln")
        else:
            self._xml_empty_tag("a:ln", attributes)

    def _write_a_no_fill(self):
        # Write the <a:noFill> element.
        self._xml_empty_tag("a:noFill")

    def _write_a_solid_fill(self, fill):
        # Write the <a:solidFill> element.

        self._xml_start_tag("a:solidFill")

        if "color" in fill:
            color = _get_rgb_color(fill["color"])
            transparency = fill.get("transparency")
            # Write the a:srgbClr element.
            self._write_a_srgb_clr(color, transparency)

        self._xml_end_tag("a:solidFill")

    def _write_a_srgb_clr(self, val, transparency=None):
        # Write the <a:srgbClr> element.
        attributes = [("val", val)]

        if transparency:
            self._xml_start_tag("a:srgbClr", attributes)

            # Write the a:alpha element.
            self._write_a_alpha(transparency)

            self._xml_end_tag("a:srgbClr")
        else:
            self._xml_empty_tag("a:srgbClr", attributes)

    def _write_a_alpha(self, val):
        # Write the <a:alpha> element.

        val = int((100 - int(val)) * 1000)

        attributes = [("val", val)]

        self._xml_empty_tag("a:alpha", attributes)

    def _write_a_prst_dash(self, val):
        # Write the <a:prstDash> element.

        attributes = [("val", val)]

        self._xml_empty_tag("a:prstDash", attributes)

    def _write_trendline(self, trendline):
        # Write the <c:trendline> element.

        if not trendline:
            return

        self._xml_start_tag("c:trendline")

        # Write the c:name element.
        self._write_name(trendline.get("name"))

        # Write the c:spPr element.
        self._write_sp_pr(trendline)

        # Write the c:trendlineType element.
        self._write_trendline_type(trendline["type"])

        # Write the c:order element for polynomial trendlines.
        if trendline["type"] == "poly":
            self._write_trendline_order(trendline.get("order"))

        # Write the c:period element for moving average trendlines.
        if trendline["type"] == "movingAvg":
            self._write_period(trendline.get("period"))

        # Write the c:forward element.
        self._write_forward(trendline.get("forward"))

        # Write the c:backward element.
        self._write_backward(trendline.get("backward"))

        if "intercept" in trendline:
            # Write the c:intercept element.
            self._write_c_intercept(trendline["intercept"])

        if trendline.get("display_r_squared"):
            # Write the c:dispRSqr element.
            self._write_c_disp_rsqr()

        if trendline.get("display_equation"):
            # Write the c:dispEq element.
            self._write_c_disp_eq()

            # Write the c:trendlineLbl element.
            self._write_c_trendline_lbl(trendline)

        self._xml_end_tag("c:trendline")

    def _write_trendline_type(self, val):
        # Write the <c:trendlineType> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:trendlineType", attributes)

    def _write_name(self, data):
        # Write the <c:name> element.

        if data is None:
            return

        self._xml_data_element("c:name", data)

    def _write_trendline_order(self, val):
        # Write the <c:order> element.
        val = max(val, 2)

        attributes = [("val", val)]

        self._xml_empty_tag("c:order", attributes)

    def _write_period(self, val):
        # Write the <c:period> element.
        val = max(val, 2)

        attributes = [("val", val)]

        self._xml_empty_tag("c:period", attributes)

    def _write_forward(self, val):
        # Write the <c:forward> element.

        if not val:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:forward", attributes)

    def _write_backward(self, val):
        # Write the <c:backward> element.

        if not val:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:backward", attributes)

    def _write_c_intercept(self, val):
        # Write the <c:intercept> element.
        attributes = [("val", val)]

        self._xml_empty_tag("c:intercept", attributes)

    def _write_c_disp_eq(self):
        # Write the <c:dispEq> element.
        attributes = [("val", 1)]

        self._xml_empty_tag("c:dispEq", attributes)

    def _write_c_disp_rsqr(self):
        # Write the <c:dispRSqr> element.
        attributes = [("val", 1)]

        self._xml_empty_tag("c:dispRSqr", attributes)

    def _write_c_trendline_lbl(self, trendline):
        # Write the <c:trendlineLbl> element.
        self._xml_start_tag("c:trendlineLbl")

        # Write the c:layout element.
        self._write_layout(None, None)

        # Write the c:numFmt element.
        self._write_trendline_num_fmt()

        # Write the c:spPr element.
        self._write_sp_pr(trendline["label"])

        # Write the data label font elements.
        if trendline["label"]:
            font = trendline["label"].get("font")
            if font:
                self._write_axis_font(font)

        self._xml_end_tag("c:trendlineLbl")

    def _write_trendline_num_fmt(self):
        # Write the <c:numFmt> element.
        attributes = [
            ("formatCode", "General"),
            ("sourceLinked", 0),
        ]

        self._xml_empty_tag("c:numFmt", attributes)

    def _write_hi_low_lines(self):
        # Write the <c:hiLowLines> element.
        hi_low_lines = self.hi_low_lines

        if hi_low_lines is None:
            return

        if "line" in hi_low_lines and hi_low_lines["line"]["defined"]:
            self._xml_start_tag("c:hiLowLines")

            # Write the c:spPr element.
            self._write_sp_pr(hi_low_lines)

            self._xml_end_tag("c:hiLowLines")
        else:
            self._xml_empty_tag("c:hiLowLines")

    def _write_drop_lines(self):
        # Write the <c:dropLines> element.
        drop_lines = self.drop_lines

        if drop_lines is None:
            return

        if drop_lines["line"]["defined"]:
            self._xml_start_tag("c:dropLines")

            # Write the c:spPr element.
            self._write_sp_pr(drop_lines)

            self._xml_end_tag("c:dropLines")
        else:
            self._xml_empty_tag("c:dropLines")

    def _write_overlap(self, val):
        # Write the <c:overlap> element.

        if val is None:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:overlap", attributes)

    def _write_num_cache(self, data):
        # Write the <c:numCache> element.
        if data:
            count = len(data)
        else:
            count = 0

        self._xml_start_tag("c:numCache")

        # Write the c:formatCode element.
        self._write_format_code("General")

        # Write the c:ptCount element.
        self._write_pt_count(count)

        for i in range(count):
            token = data[i]

            if token is None:
                continue

            try:
                float(token)
            except ValueError:
                # Write non-numeric data as 0.
                token = 0

            # Write the c:pt element.
            self._write_pt(i, token)

        self._xml_end_tag("c:numCache")

    def _write_str_cache(self, data):
        # Write the <c:strCache> element.
        count = len(data)

        self._xml_start_tag("c:strCache")

        # Write the c:ptCount element.
        self._write_pt_count(count)

        for i in range(count):
            # Write the c:pt element.
            self._write_pt(i, data[i])

        self._xml_end_tag("c:strCache")

    def _write_format_code(self, data):
        # Write the <c:formatCode> element.

        self._xml_data_element("c:formatCode", data)

    def _write_pt_count(self, val):
        # Write the <c:ptCount> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:ptCount", attributes)

    def _write_pt(self, idx, value):
        # Write the <c:pt> element.

        if value is None:
            return

        attributes = [("idx", idx)]

        self._xml_start_tag("c:pt", attributes)

        # Write the c:v element.
        self._write_v(value)

        self._xml_end_tag("c:pt")

    def _write_v(self, data):
        # Write the <c:v> element.

        self._xml_data_element("c:v", data)

    def _write_protection(self):
        # Write the <c:protection> element.
        if not self.protection:
            return

        self._xml_empty_tag("c:protection")

    def _write_d_pt(self, points):
        # Write the <c:dPt> elements.
        index = -1

        if not points:
            return

        for point in points:
            index += 1
            if not point:
                continue

            self._write_d_pt_point(index, point)

    def _write_d_pt_point(self, index, point):
        # Write an individual <c:dPt> element.

        self._xml_start_tag("c:dPt")

        # Write the c:idx element.
        self._write_idx(index)

        # Write the c:spPr element.
        self._write_sp_pr(point)

        self._xml_end_tag("c:dPt")

    def _write_d_lbls(self, labels):
        # Write the <c:dLbls> element.

        if not labels:
            return

        self._xml_start_tag("c:dLbls")

        # Write the custom c:dLbl elements.
        if labels.get("custom"):
            self._write_custom_labels(labels, labels["custom"])

        # Write the c:numFmt element.
        if labels.get("num_format"):
            self._write_data_label_number_format(labels["num_format"])

        # Write the c:spPr element for the plotarea formatting.
        self._write_sp_pr(labels)

        # Write the data label font elements.
        if labels.get("font"):
            self._write_axis_font(labels["font"])

        # Write the c:dLblPos element.
        if labels.get("position"):
            self._write_d_lbl_pos(labels["position"])

        # Write the c:showLegendKey element.
        if labels.get("legend_key"):
            self._write_show_legend_key()

        # Write the c:showVal element.
        if labels.get("value"):
            self._write_show_val()

        # Write the c:showCatName element.
        if labels.get("category"):
            self._write_show_cat_name()

        # Write the c:showSerName element.
        if labels.get("series_name"):
            self._write_show_ser_name()

        # Write the c:showPercent element.
        if labels.get("percentage"):
            self._write_show_percent()

        # Write the c:separator element.
        if labels.get("separator"):
            self._write_separator(labels["separator"])

        # Write the c:showLeaderLines element.
        if labels.get("leader_lines"):
            self._write_show_leader_lines()

        self._xml_end_tag("c:dLbls")

    def _write_custom_labels(self, parent, labels):
        # Write the <c:showLegendKey> element.
        index = 0

        for label in labels:
            index += 1

            if label is None:
                continue

            self._xml_start_tag("c:dLbl")

            # Write the c:idx element.
            self._write_idx(index - 1)

            delete_label = label.get("delete")

            if delete_label:
                self._write_delete(1)

            elif label.get("formula"):
                self._write_custom_label_formula(label)

                if parent.get("position"):
                    self._write_d_lbl_pos(parent["position"])

                if parent.get("value"):
                    self._write_show_val()
                if parent.get("category"):
                    self._write_show_cat_name()
                if parent.get("series_name"):
                    self._write_show_ser_name()

            elif label.get("value"):
                self._write_custom_label_str(label)

                if parent.get("position"):
                    self._write_d_lbl_pos(parent["position"])

                if parent.get("value"):
                    self._write_show_val()
                if parent.get("category"):
                    self._write_show_cat_name()
                if parent.get("series_name"):
                    self._write_show_ser_name()
            else:
                self._write_custom_label_format_only(label)

            self._xml_end_tag("c:dLbl")

    def _write_custom_label_str(self, label):
        # Write parts of the <c:dLbl> element for strings.
        title = label.get("value")
        font = label.get("font")
        has_formatting = self._has_fill_formatting(label)

        # Write the c:layout element.
        self._write_layout(None, None)

        self._xml_start_tag("c:tx")

        # Write the c:rich element.
        self._write_rich(title, font, False, not has_formatting)

        self._xml_end_tag("c:tx")

        # Write the c:spPr element.
        self._write_sp_pr(label)

    def _write_custom_label_formula(self, label):
        # Write parts of the <c:dLbl> element for formulas.
        formula = label.get("formula")
        data_id = label.get("data_id")
        data = None

        if data_id is not None:
            data = self.formula_data[data_id]

        # Write the c:layout element.
        self._write_layout(None, None)

        self._xml_start_tag("c:tx")

        # Write the c:strRef element.
        self._write_str_ref(formula, data, "str")

        self._xml_end_tag("c:tx")

        # Write the data label formatting, if any.
        self._write_custom_label_format_only(label)

    def _write_custom_label_format_only(self, label):
        # Write parts of the <c:dLbl> labels with changed formatting.
        font = label.get("font")
        has_formatting = self._has_fill_formatting(label)

        if has_formatting:
            self._write_sp_pr(label)
            self._write_tx_pr(font)
        elif font:
            self._xml_empty_tag("c:spPr")
            self._write_tx_pr(font)

    def _write_show_legend_key(self):
        # Write the <c:showLegendKey> element.
        val = "1"

        attributes = [("val", val)]

        self._xml_empty_tag("c:showLegendKey", attributes)

    def _write_show_val(self):
        # Write the <c:showVal> element.
        val = 1

        attributes = [("val", val)]

        self._xml_empty_tag("c:showVal", attributes)

    def _write_show_cat_name(self):
        # Write the <c:showCatName> element.
        val = 1

        attributes = [("val", val)]

        self._xml_empty_tag("c:showCatName", attributes)

    def _write_show_ser_name(self):
        # Write the <c:showSerName> element.
        val = 1

        attributes = [("val", val)]

        self._xml_empty_tag("c:showSerName", attributes)

    def _write_show_percent(self):
        # Write the <c:showPercent> element.
        val = 1

        attributes = [("val", val)]

        self._xml_empty_tag("c:showPercent", attributes)

    def _write_separator(self, data):
        # Write the <c:separator> element.
        self._xml_data_element("c:separator", data)

    def _write_show_leader_lines(self):
        # Write the <c:showLeaderLines> element.
        #
        # This is different for Pie/Doughnut charts. Other chart types only
        # supported leader lines after Excel 2015 via an extension element.
        #
        uri = "{CE6537A1-D6FC-4f65-9D91-7224C49458BB}"
        xmlns_c_15 = "http://schemas.microsoft.com/office/drawing/2012/chart"

        attributes = [
            ("uri", uri),
            ("xmlns:c15", xmlns_c_15),
        ]

        self._xml_start_tag("c:extLst")
        self._xml_start_tag("c:ext", attributes)
        self._xml_empty_tag("c15:showLeaderLines", [("val", 1)])
        self._xml_end_tag("c:ext")
        self._xml_end_tag("c:extLst")

    def _write_d_lbl_pos(self, val):
        # Write the <c:dLblPos> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:dLblPos", attributes)

    def _write_delete(self, val):
        # Write the <c:delete> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:delete", attributes)

    def _write_c_invert_if_negative(self, invert):
        # Write the <c:invertIfNegative> element.
        val = 1

        if not invert:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:invertIfNegative", attributes)

    def _write_axis_font(self, font):
        # Write the axis font elements.

        if not font:
            return

        self._xml_start_tag("c:txPr")
        self._write_a_body_pr(font.get("rotation"), None)
        self._write_a_lst_style()
        self._xml_start_tag("a:p")

        self._write_a_p_pr_rich(font)

        self._write_a_end_para_rpr()
        self._xml_end_tag("a:p")
        self._xml_end_tag("c:txPr")

    def _write_a_latin(self, attributes):
        # Write the <a:latin> element.
        self._xml_empty_tag("a:latin", attributes)

    def _write_d_table(self):
        # Write the <c:dTable> element.
        table = self.table

        if not table:
            return

        self._xml_start_tag("c:dTable")

        if table["horizontal"]:
            # Write the c:showHorzBorder element.
            self._write_show_horz_border()

        if table["vertical"]:
            # Write the c:showVertBorder element.
            self._write_show_vert_border()

        if table["outline"]:
            # Write the c:showOutline element.
            self._write_show_outline()

        if table["show_keys"]:
            # Write the c:showKeys element.
            self._write_show_keys()

        if table["font"]:
            # Write the table font.
            self._write_tx_pr(table["font"])

        self._xml_end_tag("c:dTable")

    def _write_show_horz_border(self):
        # Write the <c:showHorzBorder> element.
        attributes = [("val", 1)]

        self._xml_empty_tag("c:showHorzBorder", attributes)

    def _write_show_vert_border(self):
        # Write the <c:showVertBorder> element.
        attributes = [("val", 1)]

        self._xml_empty_tag("c:showVertBorder", attributes)

    def _write_show_outline(self):
        # Write the <c:showOutline> element.
        attributes = [("val", 1)]

        self._xml_empty_tag("c:showOutline", attributes)

    def _write_show_keys(self):
        # Write the <c:showKeys> element.
        attributes = [("val", 1)]

        self._xml_empty_tag("c:showKeys", attributes)

    def _write_error_bars(self, error_bars):
        # Write the X and Y error bars.

        if not error_bars:
            return

        if error_bars["x_error_bars"]:
            self._write_err_bars("x", error_bars["x_error_bars"])

        if error_bars["y_error_bars"]:
            self._write_err_bars("y", error_bars["y_error_bars"])

    def _write_err_bars(self, direction, error_bars):
        # Write the <c:errBars> element.

        if not error_bars:
            return

        self._xml_start_tag("c:errBars")

        # Write the c:errDir element.
        self._write_err_dir(direction)

        # Write the c:errBarType element.
        self._write_err_bar_type(error_bars["direction"])

        # Write the c:errValType element.
        self._write_err_val_type(error_bars["type"])

        if not error_bars["endcap"]:
            # Write the c:noEndCap element.
            self._write_no_end_cap()

        if error_bars["type"] == "stdErr":
            # Don't need to write a c:errValType tag.
            pass
        elif error_bars["type"] == "cust":
            # Write the custom error tags.
            self._write_custom_error(error_bars)
        else:
            # Write the c:val element.
            self._write_error_val(error_bars["value"])

        # Write the c:spPr element.
        self._write_sp_pr(error_bars)

        self._xml_end_tag("c:errBars")

    def _write_err_dir(self, val):
        # Write the <c:errDir> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:errDir", attributes)

    def _write_err_bar_type(self, val):
        # Write the <c:errBarType> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:errBarType", attributes)

    def _write_err_val_type(self, val):
        # Write the <c:errValType> element.

        attributes = [("val", val)]

        self._xml_empty_tag("c:errValType", attributes)

    def _write_no_end_cap(self):
        # Write the <c:noEndCap> element.
        attributes = [("val", 1)]

        self._xml_empty_tag("c:noEndCap", attributes)

    def _write_error_val(self, val):
        # Write the <c:val> element for error bars.

        attributes = [("val", val)]

        self._xml_empty_tag("c:val", attributes)

    def _write_custom_error(self, error_bars):
        # Write the custom error bars tags.

        if error_bars["plus_values"]:
            # Write the c:plus element.
            self._xml_start_tag("c:plus")

            if isinstance(error_bars["plus_values"], list):
                self._write_num_lit(error_bars["plus_values"])
            else:
                self._write_num_ref(
                    error_bars["plus_values"], error_bars["plus_data"], "num"
                )
            self._xml_end_tag("c:plus")

        if error_bars["minus_values"]:
            # Write the c:minus element.
            self._xml_start_tag("c:minus")

            if isinstance(error_bars["minus_values"], list):
                self._write_num_lit(error_bars["minus_values"])
            else:
                self._write_num_ref(
                    error_bars["minus_values"], error_bars["minus_data"], "num"
                )
            self._xml_end_tag("c:minus")

    def _write_num_lit(self, data):
        # Write the <c:numLit> element for literal number list elements.
        count = len(data)

        # Write the c:numLit element.
        self._xml_start_tag("c:numLit")

        # Write the c:formatCode element.
        self._write_format_code("General")

        # Write the c:ptCount element.
        self._write_pt_count(count)

        for i in range(count):
            token = data[i]

            if token is None:
                continue

            try:
                float(token)
            except ValueError:
                # Write non-numeric data as 0.
                token = 0

            # Write the c:pt element.
            self._write_pt(i, token)

        self._xml_end_tag("c:numLit")

    def _write_up_down_bars(self):
        # Write the <c:upDownBars> element.
        up_down_bars = self.up_down_bars

        if up_down_bars is None:
            return

        self._xml_start_tag("c:upDownBars")

        # Write the c:gapWidth element.
        self._write_gap_width(150)

        # Write the c:upBars element.
        self._write_up_bars(up_down_bars.get("up"))

        # Write the c:downBars element.
        self._write_down_bars(up_down_bars.get("down"))

        self._xml_end_tag("c:upDownBars")

    def _write_gap_width(self, val):
        # Write the <c:gapWidth> element.

        if val is None:
            return

        attributes = [("val", val)]

        self._xml_empty_tag("c:gapWidth", attributes)

    def _write_up_bars(self, bar_format):
        # Write the <c:upBars> element.

        if bar_format["line"] and bar_format["line"]["defined"]:
            self._xml_start_tag("c:upBars")

            # Write the c:spPr element.
            self._write_sp_pr(bar_format)

            self._xml_end_tag("c:upBars")
        else:
            self._xml_empty_tag("c:upBars")

    def _write_down_bars(self, bar_format):
        # Write the <c:downBars> element.

        if bar_format["line"] and bar_format["line"]["defined"]:
            self._xml_start_tag("c:downBars")

            # Write the c:spPr element.
            self._write_sp_pr(bar_format)

            self._xml_end_tag("c:downBars")
        else:
            self._xml_empty_tag("c:downBars")

    def _write_disp_units(self, units, display):
        # Write the <c:dispUnits> element.

        if not units:
            return

        attributes = [("val", units)]

        self._xml_start_tag("c:dispUnits")
        self._xml_empty_tag("c:builtInUnit", attributes)

        if display:
            self._xml_start_tag("c:dispUnitsLbl")
            self._xml_empty_tag("c:layout")
            self._xml_end_tag("c:dispUnitsLbl")

        self._xml_end_tag("c:dispUnits")

    def _write_a_grad_fill(self, gradient):
        # Write the <a:gradFill> element.

        attributes = [("flip", "none"), ("rotWithShape", "1")]

        if gradient["type"] == "linear":
            attributes = []

        self._xml_start_tag("a:gradFill", attributes)

        # Write the a:gsLst element.
        self._write_a_gs_lst(gradient)

        if gradient["type"] == "linear":
            # Write the a:lin element.
            self._write_a_lin(gradient["angle"])
        else:
            # Write the a:path element.
            self._write_a_path(gradient["type"])

            # Write the a:tileRect element.
            self._write_a_tile_rect(gradient["type"])

        self._xml_end_tag("a:gradFill")

    def _write_a_gs_lst(self, gradient):
        # Write the <a:gsLst> element.
        positions = gradient["positions"]
        colors = gradient["colors"]

        self._xml_start_tag("a:gsLst")

        for i, color in enumerate(colors):
            pos = int(positions[i] * 1000)
            attributes = [("pos", pos)]
            self._xml_start_tag("a:gs", attributes)

            # Write the a:srgbClr element.
            color = _get_rgb_color(color)
            self._write_a_srgb_clr(color)

            self._xml_end_tag("a:gs")

        self._xml_end_tag("a:gsLst")

    def _write_a_lin(self, angle):
        # Write the <a:lin> element.

        angle = int(60000 * angle)

        attributes = [
            ("ang", angle),
            ("scaled", "0"),
        ]

        self._xml_empty_tag("a:lin", attributes)

    def _write_a_path(self, gradient_type):
        # Write the <a:path> element.

        attributes = [("path", gradient_type)]

        self._xml_start_tag("a:path", attributes)

        # Write the a:fillToRect element.
        self._write_a_fill_to_rect(gradient_type)

        self._xml_end_tag("a:path")

    def _write_a_fill_to_rect(self, gradient_type):
        # Write the <a:fillToRect> element.

        if gradient_type == "shape":
            attributes = [
                ("l", "50000"),
                ("t", "50000"),
                ("r", "50000"),
                ("b", "50000"),
            ]
        else:
            attributes = [
                ("l", "100000"),
                ("t", "100000"),
            ]

        self._xml_empty_tag("a:fillToRect", attributes)

    def _write_a_tile_rect(self, gradient_type):
        # Write the <a:tileRect> element.

        if gradient_type == "shape":
            attributes = []
        else:
            attributes = [
                ("r", "-100000"),
                ("b", "-100000"),
            ]

        self._xml_empty_tag("a:tileRect", attributes)

    def _write_a_patt_fill(self, pattern):
        # Write the <a:pattFill> element.

        attributes = [("prst", pattern["pattern"])]

        self._xml_start_tag("a:pattFill", attributes)

        # Write the a:fgClr element.
        self._write_a_fg_clr(pattern["fg_color"])

        # Write the a:bgClr element.
        self._write_a_bg_clr(pattern["bg_color"])

        self._xml_end_tag("a:pattFill")

    def _write_a_fg_clr(self, color):
        # Write the <a:fgClr> element.

        color = _get_rgb_color(color)

        self._xml_start_tag("a:fgClr")

        # Write the a:srgbClr element.
        self._write_a_srgb_clr(color)

        self._xml_end_tag("a:fgClr")

    def _write_a_bg_clr(self, color):
        # Write the <a:bgClr> element.

        color = _get_rgb_color(color)

        self._xml_start_tag("a:bgClr")

        # Write the a:srgbClr element.
        self._write_a_srgb_clr(color)

        self._xml_end_tag("a:bgClr")
