GlyphView (Java Platform SE 8 )
Keywords: javax.swing.text.GlyphView class
Date: 2016-12-09

javax.swing.text

## Class GlyphView

- java.lang.Object
- - javax.swing.text.View
  - - javax.swing.text.GlyphView

- All Implemented Interfaces:
    Cloneable, SwingConstants, TabableView
  Direct Known Subclasses:
    LabelView

      public class GlyphView
      extends View
      implements TabableView, Cloneable

  A GlyphView is a styled chunk of text that represents a view mapped over an element in the text model. This view is generally responsible for displaying text glyphs using character level attributes in some way. An implementation of the GlyphPainter class is used to do the actual rendering and model/view translations. This separates rendering from layout and management of the association with the model.

  The view supports breaking for the purpose of formatting. The fragments produced by breaking share the view that has primary responsibility for the element (i.e. they are nested classes and carry only a small amount of state of their own) so they can share its resources.

  Since this view represents text that may have tabs embedded in it, it implements the `TabableView` interface. Tabs will only be expanded if this view is embedded in a container that does tab expansion. ParagraphView is an example of a container that does tab expansion.

  Since:
    1.3

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `GlyphView.GlyphPainter` A class to perform rendering of the glyphs.

  - ### Field Summary

    - ### Fields inherited from class javax.swing.text.View

      `BadBreakWeight, ExcellentBreakWeight, ForcedBreakWeight, GoodBreakWeight, X_AXIS, Y_AXIS`

    - ### Fields inherited from interface javax.swing.SwingConstants

      `BOTTOM, CENTER, EAST, HORIZONTAL, LEADING, LEFT, NEXT, NORTH, NORTH_EAST, NORTH_WEST, PREVIOUS, RIGHT, SOUTH, SOUTH_EAST, SOUTH_WEST, TOP, TRAILING, VERTICAL, WEST`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `GlyphView(Element elem)` Constructs a new view wrapped on an element.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `View` | `breakView(int axis, int p0, float pos, float len)` Breaks this view on the given axis at the given length.
    `void` | `changedUpdate(DocumentEvent e, Shape a, ViewFactory f)` Gives notification from the document that attributes were changed in a location that this view is responsible for.
    `protected void` | `checkPainter()` Check to see that a glyph painter exists.
    `protected Object` | `clone()` Creates a shallow copy.
    `View` | `createFragment(int p0, int p1)` Creates a view that represents a portion of the element.
    `float` | `getAlignment(int axis)` Determines the desired alignment for this view along an axis.
    `Color` | `getBackground()` Fetch the background color to use to render the glyphs.
    `int` | `getBreakWeight(int axis, float pos, float len)` Determines how attractive a break opportunity in this view is.
    `int` | `getEndOffset()` Fetches the portion of the model that this view is responsible for.
    `Font` | `getFont()` Fetch the font that the glyphs should be based upon.
    `Color` | `getForeground()` Fetch the foreground color to use to render the glyphs.
    `GlyphView.GlyphPainter` | `getGlyphPainter()` Fetch the currently installed glyph painter.
    `float` | `getMinimumSpan(int axis)` Determines the minimum span for this view along an axis.
    `int` | `getNextVisualPositionFrom(int pos, Position.Bias b, Shape a, int direction, Position.Bias[] biasRet)` Provides a way to determine the next visually represented model location that one might place a caret.
    `float` | `getPartialSpan(int p0, int p1)` Determines the span along the same axis as tab expansion for a portion of the view.
    `float` | `getPreferredSpan(int axis)` Determines the preferred span for this view along an axis.
    `int` | `getStartOffset()` Fetches the portion of the model that this view is responsible for.
    `float` | `getTabbedSpan(float x, TabExpander e)` Determines the desired span when using the given tab expansion implementation.
    `TabExpander` | `getTabExpander()` Fetch the TabExpander to use if tabs are present in this view.
    `Segment` | `getText(int p0, int p1)` Fetch a reference to the text that occupies the given range.
    `void` | `insertUpdate(DocumentEvent e, Shape a, ViewFactory f)` Gives notification that something was inserted into the document in a location that this view is responsible for.
    `boolean` | `isStrikeThrough()` Determine if the glyphs should have a strikethrough line.
    `boolean` | `isSubscript()` Determine if the glyphs should be rendered as superscript.
    `boolean` | `isSuperscript()` Determine if the glyphs should be rendered as subscript.
    `boolean` | `isUnderline()` Determine if the glyphs should be underlined.
    `Shape` | `modelToView(int pos, Shape a, Position.Bias b)` Provides a mapping from the document model coordinate space to the coordinate space of the view mapped to it.
    `void` | `paint(Graphics g, Shape a)` Renders a portion of a text style run.
    `void` | `removeUpdate(DocumentEvent e, Shape a, ViewFactory f)` Gives notification that something was removed from the document in a location that this view is responsible for.
    `void` | `setGlyphPainter(GlyphView.GlyphPainter p)` Sets the painter to use for rendering glyphs.
    `int` | `viewToModel(float x, float y, Shape a, Position.Bias[] biasReturn)` Provides a mapping from the view coordinate space to the logical coordinate space of the model.

    - ### Methods inherited from class javax.swing.text.View

      `append, forwardUpdate, forwardUpdateToView, getAttributes, getChildAllocation, getContainer, getDocument, getElement, getGraphics, getMaximumSpan, getParent, getResizeWeight, getToolTipText, getView, getViewCount, getViewFactory, getViewIndex, getViewIndex, insert, isVisible, modelToView, modelToView, preferenceChanged, remove, removeAll, replace, setParent, setSize, updateChildren, updateLayout, viewToModel`

    - ### Methods inherited from class java.lang.Object

      `equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### GlyphView

          public GlyphView(Element elem)

      Constructs a new view wrapped on an element.
      Parameters:
        `elem` - the element

  - ### Method Detail

    - #### clone

          protected final Object clone()

      Creates a shallow copy. This is used by the createFragment and breakView methods.
      Overrides:
        `clone` in class `Object`
      Returns:
        the copy
      See Also:
        `Cloneable`

    - #### getGlyphPainter

          public GlyphView.GlyphPainter getGlyphPainter()

      Fetch the currently installed glyph painter. If a painter has not yet been installed, and a default was not yet needed, null is returned.

    - #### setGlyphPainter

          public void setGlyphPainter(GlyphView.GlyphPainter p)

      Sets the painter to use for rendering glyphs.

    - #### getText

          public Segment getText(int p0,
                                 int p1)

      Fetch a reference to the text that occupies the given range. This is normally used by the GlyphPainter to determine what characters it should render glyphs for.
      Parameters:
        `p0` - the starting document offset >= 0
        `p1` - the ending document offset >= p0
      Returns:
        the `Segment` containing the text

    - #### getBackground

          public Color getBackground()

      Fetch the background color to use to render the glyphs. If there is no background color, null should be returned. This is implemented to call `StyledDocument.getBackground` if the associated document is a styled document, otherwise it returns null.

    - #### getForeground

          public Color getForeground()

      Fetch the foreground color to use to render the glyphs. If there is no foreground color, null should be returned. This is implemented to call `StyledDocument.getBackground` if the associated document is a StyledDocument. If the associated document is not a StyledDocument, the associated components foreground color is used. If there is no associated component, null is returned.

    - #### getFont

          public Font getFont()

      Fetch the font that the glyphs should be based upon. This is implemented to call `StyledDocument.getFont` if the associated document is a StyledDocument. If the associated document is not a StyledDocument, the associated components font is used. If there is no associated component, null is returned.

    - #### isUnderline

          public boolean isUnderline()

      Determine if the glyphs should be underlined. If true, an underline should be drawn through the baseline.

    - #### isStrikeThrough

          public boolean isStrikeThrough()

      Determine if the glyphs should have a strikethrough line. If true, a line should be drawn through the center of the glyphs.

    - #### isSubscript

          public boolean isSubscript()

      Determine if the glyphs should be rendered as superscript.

    - #### isSuperscript

          public boolean isSuperscript()

      Determine if the glyphs should be rendered as subscript.

    - #### getTabExpander

          public TabExpander getTabExpander()

      Fetch the TabExpander to use if tabs are present in this view.

    - #### checkPainter

          protected void checkPainter()

      Check to see that a glyph painter exists. If a painter doesn't exist, a default glyph painter will be installed.

    - #### getTabbedSpan

          public float getTabbedSpan(float x,
                                     TabExpander e)

      Determines the desired span when using the given tab expansion implementation.
      Specified by:
        `getTabbedSpan` in interface `TabableView`
      Parameters:
        `x` - the position the view would be located at for the purpose of tab expansion >= 0.
        `e` - how to expand the tabs when encountered.
      Returns:
        the desired span >= 0
      See Also:
        `TabableView.getTabbedSpan(float, javax.swing.text.TabExpander)`

    - #### getPartialSpan

          public float getPartialSpan(int p0,
                                      int p1)

      Determines the span along the same axis as tab expansion for a portion of the view. This is intended for use by the TabExpander for cases where the tab expansion involves aligning the portion of text that doesn't have whitespace relative to the tab stop. There is therefore an assumption that the range given does not contain tabs.

      This method can be called while servicing the getTabbedSpan or getPreferredSize. It has to arrange for its own text buffer to make the measurements.

      Specified by:
        `getPartialSpan` in interface `TabableView`
      Parameters:
        `p0` - the starting document offset >= 0
        `p1` - the ending document offset >= p0
      Returns:
        the span >= 0

    - #### getStartOffset

          public int getStartOffset()

      Fetches the portion of the model that this view is responsible for.
      Overrides:
        `getStartOffset` in class `View`
      Returns:
        the starting offset into the model
      See Also:
        `View.getStartOffset()`

    - #### getEndOffset

          public int getEndOffset()

      Fetches the portion of the model that this view is responsible for.
      Overrides:
        `getEndOffset` in class `View`
      Returns:
        the ending offset into the model
      See Also:
        `View.getEndOffset()`

    - #### paint

          public void paint(Graphics g,
                            Shape a)

      Renders a portion of a text style run.
      Specified by:
        `paint` in class `View`
      Parameters:
        `g` - the rendering surface to use
        `a` - the allocated region to render into

    - #### getMinimumSpan

          public float getMinimumSpan(int axis)

      Determines the minimum span for this view along an axis.

      This implementation returns the longest non-breakable area within the view as a minimum span for `View.X_AXIS`.

      Overrides:
        `getMinimumSpan` in class `View`
      Parameters:
        `axis` - may be either `View.X_AXIS` or `View.Y_AXIS`
      Returns:
        the minimum span the view can be rendered into
      Throws:
        `IllegalArgumentException` - if the `axis` parameter is invalid
      See Also:
        `View.getMinimumSpan(int)`

    - #### getPreferredSpan

          public float getPreferredSpan(int axis)

      Determines the preferred span for this view along an axis.
      Specified by:
        `getPreferredSpan` in class `View`
      Parameters:
        `axis` - may be either View.X_AXIS or View.Y_AXIS
      Returns:
        the span the view would like to be rendered into >= 0. Typically the view is told to render into the span that is returned, although there is no guarantee. The parent may choose to resize or break the view.
      See Also:
        `View.getPreferredSpan(int)`

    - #### getAlignment

          public float getAlignment(int axis)

      Determines the desired alignment for this view along an axis. For the label, the alignment is along the font baseline for the y axis, and the superclasses alignment along the x axis.
      Overrides:
        `getAlignment` in class `View`
      Parameters:
        `axis` - may be either View.X_AXIS or View.Y_AXIS
      Returns:
        the desired alignment. This should be a value between 0.0 and 1.0 inclusive, where 0 indicates alignment at the origin and 1.0 indicates alignment to the full span away from the origin. An alignment of 0.5 would be the center of the view.

    - #### modelToView

          public Shape modelToView(int pos,
                                   Shape a,
                                   Position.Bias b)
                            throws BadLocationException

      Provides a mapping from the document model coordinate space to the coordinate space of the view mapped to it.
      Specified by:
        `modelToView` in class `View`
      Parameters:
        `pos` - the position to convert >= 0
        `a` - the allocated region to render into
        `b` - either `Position.Bias.Forward` or `Position.Bias.Backward`
      Returns:
        the bounding box of the given position
      Throws:
        `BadLocationException` - if the given position does not represent a valid location in the associated document
      See Also:
        `View.modelToView(int, java.awt.Shape, javax.swing.text.Position.Bias)`

    - #### viewToModel

          public int viewToModel(float x,
                                 float y,
                                 Shape a,
                                 Position.Bias[] biasReturn)

      Provides a mapping from the view coordinate space to the logical coordinate space of the model.
      Specified by:
        `viewToModel` in class `View`
      Parameters:
        `x` - the X coordinate >= 0
        `y` - the Y coordinate >= 0
        `a` - the allocated region to render into
        `biasReturn` - either `Position.Bias.Forward` or `Position.Bias.Backward` is returned as the zero-th element of this array
      Returns:
        the location within the model that best represents the given point of view >= 0
      See Also:
        `View.viewToModel(float, float, java.awt.Shape, javax.swing.text.Position.Bias[])`

    - #### getBreakWeight

          public int getBreakWeight(int axis,
                                    float pos,
                                    float len)

      Determines how attractive a break opportunity in this view is. This can be used for determining which view is the most attractive to call `breakView` on in the process of formatting. The higher the weight, the more attractive the break. A value equal to or lower than `View.BadBreakWeight` should not be considered for a break. A value greater than or equal to `View.ForcedBreakWeight` should be broken.

      This is implemented to forward to the superclass for the Y_AXIS. Along the X_AXIS the following values may be returned.

      View.ExcellentBreakWeight
        if there is whitespace proceeding the desired break location.
      View.BadBreakWeight
        if the desired break location results in a break location of the starting offset.
      View.GoodBreakWeight
        if the other conditions don't occur.
      This will normally result in the behavior of breaking on a whitespace location if one can be found, otherwise breaking between characters.
      Overrides:
        `getBreakWeight` in class `View`
      Parameters:
        `axis` - may be either View.X_AXIS or View.Y_AXIS
        `pos` - the potential location of the start of the broken view >= 0. This may be useful for calculating tab positions.
        `len` - specifies the relative length from pos where a potential break is desired >= 0.
      Returns:
        the weight, which should be a value between View.ForcedBreakWeight and View.BadBreakWeight.
      See Also:
        `LabelView`, `ParagraphView`, `View.BadBreakWeight`, `View.GoodBreakWeight`, `View.ExcellentBreakWeight`, `View.ForcedBreakWeight`

    - #### breakView

          public View breakView(int axis,
                                int p0,
                                float pos,
                                float len)

      Breaks this view on the given axis at the given length. This is implemented to attempt to break on a whitespace location, and returns a fragment with the whitespace at the end. If a whitespace location can't be found, the nearest character is used.
      Overrides:
        `breakView` in class `View`
      Parameters:
        `axis` - may be either View.X_AXIS or View.Y_AXIS
        `p0` - the location in the model where the fragment should start it's representation >= 0.
        `pos` - the position along the axis that the broken view would occupy >= 0. This may be useful for things like tab calculations.
        `len` - specifies the distance along the axis where a potential break is desired >= 0.
      Returns:
        the fragment of the view that represents the given span, if the view can be broken. If the view doesn't support breaking behavior, the view itself is returned.
      See Also:
        `View.breakView(int, int, float, float)`

    - #### createFragment

          public View createFragment(int p0,
                                     int p1)

      Creates a view that represents a portion of the element. This is potentially useful during formatting operations for taking measurements of fragments of the view. If the view doesn't support fragmenting (the default), it should return itself.

      This view does support fragmenting. It is implemented to return a nested class that shares state in this view representing only a portion of the view.

      Overrides:
        `createFragment` in class `View`
      Parameters:
        `p0` - the starting offset >= 0. This should be a value greater or equal to the element starting offset and less than the element ending offset.
        `p1` - the ending offset > p0. This should be a value less than or equal to the elements end offset and greater than the elements starting offset.
      Returns:
        the view fragment, or itself if the view doesn't support breaking into fragments
      See Also:
        `LabelView`

    - #### getNextVisualPositionFrom

          public int getNextVisualPositionFrom(int pos,
                                               Position.Bias b,
                                               Shape a,
                                               int direction,
                                               Position.Bias[] biasRet)
                                        throws BadLocationException

      Provides a way to determine the next visually represented model location that one might place a caret. Some views may not be visible, they might not be in the same order found in the model, or they just might not allow access to some of the locations in the model. This method enables specifying a position to convert within the range of >=0. If the value is -1, a position will be calculated automatically. If the value < -1, the `BadLocationException` will be thrown.
      Overrides:
        `getNextVisualPositionFrom` in class `View`
      Parameters:
        `pos` - the position to convert
        `a` - the allocated region to render into
        `direction` - the direction from the current position that can be thought of as the arrow keys typically found on a keyboard. This may be SwingConstants.WEST, SwingConstants.EAST, SwingConstants.NORTH, or SwingConstants.SOUTH.
      Returns:
        the location within the model that best represents the next location visual position.
      Throws:
        `BadLocationException` - the given position is not a valid position within the document
        `IllegalArgumentException` - for an invalid direction

    - #### insertUpdate

          public void insertUpdate(DocumentEvent e,
                                   Shape a,
                                   ViewFactory f)

      Gives notification that something was inserted into the document in a location that this view is responsible for. This is implemented to call preferenceChanged along the axis the glyphs are rendered.
      Overrides:
        `insertUpdate` in class `View`
      Parameters:
        `e` - the change information from the associated document
        `a` - the current allocation of the view
        `f` - the factory to use to rebuild if the view has children
      See Also:
        `View.insertUpdate(javax.swing.event.DocumentEvent, java.awt.Shape, javax.swing.text.ViewFactory)`

    - #### removeUpdate

          public void removeUpdate(DocumentEvent e,
                                   Shape a,
                                   ViewFactory f)

      Gives notification that something was removed from the document in a location that this view is responsible for. This is implemented to call preferenceChanged along the axis the glyphs are rendered.
      Overrides:
        `removeUpdate` in class `View`
      Parameters:
        `e` - the change information from the associated document
        `a` - the current allocation of the view
        `f` - the factory to use to rebuild if the view has children
      See Also:
        `View.removeUpdate(javax.swing.event.DocumentEvent, java.awt.Shape, javax.swing.text.ViewFactory)`

    - #### changedUpdate

          public void changedUpdate(DocumentEvent e,
                                    Shape a,
                                    ViewFactory f)

      Gives notification from the document that attributes were changed in a location that this view is responsible for. This is implemented to call preferenceChanged along both the horizontal and vertical axis.
      Overrides:
        `changedUpdate` in class `View`
      Parameters:
        `e` - the change information from the associated document
        `a` - the current allocation of the view
        `f` - the factory to use to rebuild if the view has children
      See Also:
        `View.changedUpdate(javax.swing.event.DocumentEvent, java.awt.Shape, javax.swing.text.ViewFactory)`

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