GooCanvasItem: GooCanvas Reference Manual

## GooCanvasItem GooCanvasItem — the interface for canvas items. |

## Functions

void | goo_canvas_item_translate ()
void | goo_canvas_item_scale ()
void | goo_canvas_item_rotate ()
void | goo_canvas_item_skew_x ()
void | goo_canvas_item_skew_y ()
gboolean | goo_canvas_item_get_transform ()
void | goo_canvas_item_set_transform ()
gboolean | goo_canvas_item_get_simple_transform ()
void | goo_canvas_item_set_simple_transform ()
void | goo_canvas_item_get_bounds ()
gboolean | goo_canvas_item_is_visible ()
gboolean | goo_canvas_item_get_is_static ()
void | goo_canvas_item_set_is_static ()
void | goo_canvas_item_animate ()
void | goo_canvas_item_stop_animation ()
void | goo_canvas_item_raise ()
void | goo_canvas_item_lower ()
void | goo_canvas_item_remove ()
GooCanvas * | goo_canvas_item_get_canvas ()
void | goo_canvas_item_set_canvas ()
GooCanvasItem * | goo_canvas_item_get_parent ()
void | goo_canvas_item_set_parent ()
GooCanvasItemModel * | goo_canvas_item_get_model ()
void | goo_canvas_item_set_model ()
gboolean | goo_canvas_item_is_container ()
gint | goo_canvas_item_get_n_children ()
GooCanvasItem * | goo_canvas_item_get_child ()
gint | goo_canvas_item_find_child ()
void | goo_canvas_item_add_child ()
void | goo_canvas_item_move_child ()
void | goo_canvas_item_remove_child ()
gboolean | goo_canvas_item_get_transform_for_child ()
GooCanvasStyle * | goo_canvas_item_get_style ()
void | goo_canvas_item_set_style ()
void | goo_canvas_item_request_update ()
void | goo_canvas_item_ensure_updated ()
void | goo_canvas_item_update ()
gboolean | goo_canvas_item_get_requested_area ()
gboolean | goo_canvas_item_get_requested_area_for_width ()
gdouble | goo_canvas_item_get_requested_height ()
void | goo_canvas_item_allocate_area ()
GList * | goo_canvas_item_get_items_at ()
void | goo_canvas_item_paint ()
void | goo_canvas_item_class_install_child_property ()
GParamSpec ** | goo_canvas_item_class_list_child_properties ()
GParamSpec * | goo_canvas_item_class_find_child_property ()
void | goo_canvas_item_get_child_property ()
void | goo_canvas_item_set_child_property ()
void | goo_canvas_item_get_child_properties ()
void | goo_canvas_item_get_child_properties_valist ()
void | goo_canvas_item_set_child_properties ()
void | goo_canvas_item_set_child_properties_valist ()

## Properties

gboolean | can-focus | Read / Write
char * | description | Read / Write
GooCanvasItem * | parent | Read / Write
GooCanvasPointerEvents | pointer-events | Read / Write
char * | title | Read / Write
char * | tooltip | Read / Write
GooCairoMatrix * | transform | Read / Write
GooCanvasItemVisibility | visibility | Read / Write
double | visibility-threshold | Read / Write

## Signals

void | animation-finished | Run Last
gboolean | button-press-event | Run Last
gboolean | button-release-event | Run Last
void | child-notify | No Hooks
gboolean | enter-notify-event | Run Last
gboolean | focus-in-event | Run Last
gboolean | focus-out-event | Run Last
gboolean | grab-broken-event | Run Last
gboolean | key-press-event | Run Last
gboolean | key-release-event | Run Last
gboolean | leave-notify-event | Run Last
gboolean | motion-notify-event | Run Last
gboolean | query-tooltip | Run Last
gboolean | scroll-event | Run Last

## Types and Values

| GooCanvasItem
struct | GooCanvasItemIface

## Object Hierarchy

        GInterface
        ╰── GooCanvasItem

## Prerequisites

GooCanvasItem requires GObject.

## Known Implementations

GooCanvasItem is implemented by GooCanvasEllipse, GooCanvasGrid, GooCanvasGroup, GooCanvasImage, GooCanvasItemSimple, GooCanvasPath, GooCanvasPolyline, GooCanvasRect, GooCanvasTable, GooCanvasText and GooCanvasWidget.

## Description

GooCanvasItem defines the interface that canvas items must implement, and contains methods for operating on canvas items.

## Functions

### goo_canvas_item_translate ()

    void
    goo_canvas_item_translate (GooCanvasItem *item,
                               gdouble tx,
                               gdouble ty);

Translates the origin of the item's coordinate system by the given amounts.

#### Parameters

item | an item. |
tx | the amount to move the origin in the horizontal direction. |
ty | the amount to move the origin in the vertical direction. |

### goo_canvas_item_scale ()

    void
    goo_canvas_item_scale (GooCanvasItem *item,
                           gdouble sx,
                           gdouble sy);

Scales the item's coordinate system by the given amounts.

#### Parameters

item | an item. |
sx | the amount to scale the horizontal axis. |
sy | the amount to scale the vertical axis. |

### goo_canvas_item_rotate ()

    void
    goo_canvas_item_rotate (GooCanvasItem *item,
                            gdouble degrees,
                            gdouble cx,
                            gdouble cy);

Rotates the item's coordinate system by the given amount, about the given origin.

#### Parameters

item | an item. |
degrees | the clockwise angle of rotation. |
cx | the x coordinate of the origin of the rotation. |
cy | the y coordinate of the origin of the rotation. |

### goo_canvas_item_skew_x ()

    void
    goo_canvas_item_skew_x (GooCanvasItem *item,
                            gdouble degrees,
                            gdouble cx,
                            gdouble cy);

Skews the item's coordinate system along the x axis by the given amount, about the given origin.

#### Parameters

item | an item. |
degrees | the skew angle. |
cx | the x coordinate of the origin of the skew transform. |
cy | the y coordinate of the origin of the skew transform. |

### goo_canvas_item_skew_y ()

    void
    goo_canvas_item_skew_y (GooCanvasItem *item,
                            gdouble degrees,
                            gdouble cx,
                            gdouble cy);

Skews the item's coordinate system along the y axis by the given amount, about the given origin.

#### Parameters

item | an item. |
degrees | the skew angle. |
cx | the x coordinate of the origin of the skew transform. |
cy | the y coordinate of the origin of the skew transform. |

### goo_canvas_item_get_transform ()

    gboolean
    goo_canvas_item_get_transform (GooCanvasItem *item,
                                   cairo_matrix_t *transform);

Gets the transformation matrix of an item.

#### Parameters

item | an item. |
transform | the place to store the transform. | [out]

#### Returns

`TRUE` if a transform is set.

### goo_canvas_item_set_transform ()

    void
    goo_canvas_item_set_transform (GooCanvasItem *item,
                                   const cairo_matrix_t *transform);

Sets the transformation matrix of an item.

#### Parameters

item | an item. |
transform | the new transformation matrix, or `NULL` to reset the transformation to the identity matrix. | [allow-none]

### goo_canvas_item_get_simple_transform ()

    gboolean
    goo_canvas_item_get_simple_transform (GooCanvasItem *item,
                                          gdouble *x,
                                          gdouble *y,
                                          gdouble *scale,
                                          gdouble *rotation);

This function can be used to get the position, scale and rotation of an item, providing that the item has a simple transformation matrix (e.g. set with `goo_canvas_item_set_simple_transform()`, or using a combination of simple translate, scale and rotate operations). If the item has a complex transformation matrix the results will be incorrect.

#### Parameters

item | an item. |
x | returns the x coordinate of the origin of the item's coordinate space. | [out]
y | returns the y coordinate of the origin of the item's coordinate space. | [out]
scale | returns the scale of the item. | [out]
rotation | returns the clockwise rotation of the item, in degrees (0-360). | [out]

#### Returns

`TRUE` if a transform is set.

### goo_canvas_item_set_simple_transform ()

    void
    goo_canvas_item_set_simple_transform (GooCanvasItem *item,
                                          gdouble x,
                                          gdouble y,
                                          gdouble scale,
                                          gdouble rotation);

A convenience function to set the item's transformation matrix.

#### Parameters

item | an item. |
x | the x coordinate of the origin of the item's coordinate space. |
y | the y coordinate of the origin of the item's coordinate space. |
scale | the scale of the item. |
rotation | the clockwise rotation of the item, in degrees. |

### goo_canvas_item_get_bounds ()

    void
    goo_canvas_item_get_bounds (GooCanvasItem *item,
                                GooCanvasBounds *bounds);

Gets the bounds of the item.

Note that the bounds includes the entire fill and stroke extents of the item, whether they are painted or not.

#### Parameters

item | a GooCanvasItem. |
bounds | a GooCanvasBounds to return the bounds in. | [out]

### goo_canvas_item_is_visible ()

    gboolean
    goo_canvas_item_is_visible (GooCanvasItem *item);

Checks if the item is visible.

This entails checking the item's own visibility setting, as well as those of its ancestors.

Note that the item may be scrolled off the screen and so may not be actually visible to the user.

#### Parameters

item | a GooCanvasItem. |

#### Returns

`TRUE` if the item is visible.

### goo_canvas_item_get_is_static ()

    gboolean
    goo_canvas_item_get_is_static (GooCanvasItem *item);

Returns `TRUE` if the item is static. Static items do not move or change size when the canvas is scrolled or the scale changes.

#### Parameters

item | an item. |

#### Returns

`TRUE` if the item is static.

### goo_canvas_item_set_is_static ()

    void
    goo_canvas_item_set_is_static (GooCanvasItem *item,
                                   gboolean is_static);

Notifies the item that it is static. Static items do not move or change size when the canvas is scrolled or the scale changes.

Container items such as GooCanvasGroup should call this function when children are added, to notify children whether they are static or not. Containers should also pass on any changes in their own status to children.

#### Parameters

item | an item. |
is_static | if the item is static. |

### goo_canvas_item_animate ()

    void
    goo_canvas_item_animate (GooCanvasItem *item,
                             gdouble x,
                             gdouble y,
                             gdouble scale,
                             gdouble degrees,
                             gboolean absolute,
                             gint duration,
                             gint step_time,
                             GooCanvasAnimateType type);

Animates an item from its current position to the given offsets, scale and rotation.

#### Parameters

item | an item. |
x | the final x coordinate. |
y | the final y coordinate. |
scale | the final scale. |
degrees | the final rotation. This can be negative to rotate anticlockwise, and can also be greater than 360 to rotate a number of times. |
absolute | if the `x` , `y` , `scale` and `degrees` values are absolute, or relative to the current transform. Note that absolute animations only work if the item currently has a simple transform. If the item has a shear or some other complicated transform it may result in strange animations. |
duration | the duration of the animation, in milliseconds (1/1000ths of a second). |
step_time | the time between each animation step, in milliseconds. |
type | specifies what happens when the animation finishes. |

### goo_canvas_item_stop_animation ()

    void
    goo_canvas_item_stop_animation (GooCanvasItem *item);

Stops any current animation for the given item, leaving it at its current position.

#### Parameters

item | an item. |

### goo_canvas_item_raise ()

    void
    goo_canvas_item_raise (GooCanvasItem *item,
                           GooCanvasItem *above);

Raises an item in the stacking order.

#### Parameters

item | an item. |
above | the item to raise `item` above, or `NULL` to raise `item` to the top of the stack. | [allow-none]

### goo_canvas_item_lower ()

    void
    goo_canvas_item_lower (GooCanvasItem *item,
                           GooCanvasItem *below);

Lowers an item in the stacking order.

#### Parameters

item | an item. |
below | the item to lower `item` below, or `NULL` to lower `item` to the bottom of the stack. | [allow-none]

### goo_canvas_item_remove ()

    void
    goo_canvas_item_remove (GooCanvasItem *item);

Removes an item from its parent. If the item is in a canvas it will be removed.

This would normally also result in the item being freed.

#### Parameters

item | an item. |

### goo_canvas_item_get_canvas ()

    GooCanvas *
    goo_canvas_item_get_canvas (GooCanvasItem *item);

Returns the GooCanvas containing the given GooCanvasItem.

#### Parameters

item | a GooCanvasItem. |

#### Returns

the GooCanvas.

[transfer none]

### goo_canvas_item_set_canvas ()

    void
    goo_canvas_item_set_canvas (GooCanvasItem *item,
                                GooCanvas *canvas);

This function is only intended to be used when implementing new canvas items, specifically container items such as GooCanvasGroup.

It sets the canvas of the item.

#### Parameters

item | a GooCanvasItem. |
canvas | a GooCanvas |

### goo_canvas_item_get_parent ()

    GooCanvasItem *
    goo_canvas_item_get_parent (GooCanvasItem *item);

Gets the parent of the given item.

#### Parameters

item | an item. |

#### Returns

the parent item, or `NULL` if the item has no parent.

[transfer none]

### goo_canvas_item_set_parent ()

    void
    goo_canvas_item_set_parent (GooCanvasItem *item,
                                GooCanvasItem *parent);

This function is only intended to be used when implementing new canvas items (specifically container items such as GooCanvasGroup). It sets the parent of the child item.

This function cannot be used to add an item to a group or to change the parent of an item. To do that use the “parent” property.

#### Parameters

item | an item. |
parent | the new parent item. |

### goo_canvas_item_get_model ()

    GooCanvasItemModel *
    goo_canvas_item_get_model (GooCanvasItem *item);

Gets the model of the given canvas item.

#### Parameters

item | a GooCanvasItem. |

#### Returns

the item's model, or `NULL` if it has no model.

[transfer none]

### goo_canvas_item_set_model ()

    void
    goo_canvas_item_set_model (GooCanvasItem *item,
                               GooCanvasItemModel *model);

Sets the model of the given canvas item.

#### Parameters

item | a GooCanvasItem. |
model | a GooCanvasItemModel. |

### goo_canvas_item_is_container ()

    gboolean
    goo_canvas_item_is_container (GooCanvasItem *item);

Tests to see if the given item is a container.

#### Parameters

item | an item. |

#### Returns

`TRUE` if the item is a container.

### goo_canvas_item_get_n_children ()

    gint
    goo_canvas_item_get_n_children (GooCanvasItem *item);

Gets the number of children of the container.

#### Parameters

item | a container item. |

#### Returns

the number of children.

### goo_canvas_item_get_child ()

    GooCanvasItem *
    goo_canvas_item_get_child (GooCanvasItem *item,
                               gint child_num);

Gets the child item at the given stack position.

#### Parameters

item | a container item. |
child_num | the position of a child in the container's stack. |

#### Returns

the child item at the given stack position, or `NULL` if `child_num` is out of range.

[transfer none]

### goo_canvas_item_find_child ()

    gint
    goo_canvas_item_find_child (GooCanvasItem *item,
                                GooCanvasItem *child);

Attempts to find the given child item with the container's stack.

#### Parameters

item | a container item. |
child | the child item to find. |

#### Returns

the position of the given `child` item, or -1 if it isn't found.

### goo_canvas_item_add_child ()

    void
    goo_canvas_item_add_child (GooCanvasItem *item,
                               GooCanvasItem *child,
                               gint position);

Adds a child item to a container item at the given stack position.

#### Parameters

item | the container to add the item to. |
child | the item to add. |
position | the position of the item, or -1 to place it last (at the top of the stacking order). |

### goo_canvas_item_move_child ()

    void
    goo_canvas_item_move_child (GooCanvasItem *item,
                                gint old_position,
                                gint new_position);

Moves a child item to a new stack position within the container.

#### Parameters

item | a container item. |
old_position | the current position of the child item. |
new_position | the new position of the child item. |

### goo_canvas_item_remove_child ()

    void
    goo_canvas_item_remove_child (GooCanvasItem *item,
                                  gint child_num);

Removes the child item at the given position.

#### Parameters

item | a container item. |
child_num | the position of the child item to remove. |

### goo_canvas_item_get_transform_for_child ()

    gboolean
    goo_canvas_item_get_transform_for_child
                                   (GooCanvasItem *item,
                                    GooCanvasItem *child,
                                    cairo_matrix_t *transform);

Gets the transformation matrix of an item combined with any special transform needed for the given child. These special transforms are used by layout items such as GooCanvasTable.

#### Parameters

item | an item. |
child | a child of `item` . |
transform | the place to store the transform. | [out]

#### Returns

`TRUE` if a transform is set.

### goo_canvas_item_get_style ()

    GooCanvasStyle *
    goo_canvas_item_get_style (GooCanvasItem *item);

Gets the item's style. If the item doesn't have its own style it will return its parent's style.

#### Parameters

item | an item. |

#### Returns

the item's style.

[transfer none]

### goo_canvas_item_set_style ()

    void
    goo_canvas_item_set_style (GooCanvasItem *item,
                               GooCanvasStyle *style);

Sets the item's style, by copying the properties from the given style.

#### Parameters

item | an item. |
style | a style. |

### goo_canvas_item_request_update ()

    void
    goo_canvas_item_request_update (GooCanvasItem *item);

This function is only intended to be used when implementing new canvas items.

It requests that an update of the item is scheduled. It will be performed as soon as the application is idle, and before the canvas is redrawn.

#### Parameters

item | a GooCanvasItem. |

### goo_canvas_item_ensure_updated ()

    void
    goo_canvas_item_ensure_updated (GooCanvasItem *item);

This function is only intended to be used when implementing new canvas items.

It updates the canvas immediately, if an update is scheduled. This ensures that all item bounds are up-to-date.

#### Parameters

item | a GooCanvasItem. |

### goo_canvas_item_update ()

    void
    goo_canvas_item_update (GooCanvasItem *item,
                            gboolean entire_tree,
                            cairo_t *cr,
                            GooCanvasBounds *bounds);

This function is only intended to be used when implementing new canvas items, specifically container items such as GooCanvasGroup.

Updates the item, if needed, and any children.

#### Parameters

item | a GooCanvasItem. |
entire_tree | if the entire subtree should be updated. |
cr | a cairo context. |
bounds | a GooCanvasBounds to return the new bounds in. |

### goo_canvas_item_get_requested_area ()

    gboolean
    goo_canvas_item_get_requested_area (GooCanvasItem *item,
                                        cairo_t *cr,
                                        GooCanvasBounds *requested_area);

This function is only intended to be used when implementing new canvas items, specifically layout items such as GooCanvasTable.

It gets the requested area of a child item.

#### Parameters

item | a GooCanvasItem. |
cr | a cairo context. |
requested_area | a GooCanvasBounds to return the requested area in, in the parent's coordinate space. |

#### Returns

`TRUE` if the item should be allocated space.

### goo_canvas_item_get_requested_area_for_width ()

    gboolean
    goo_canvas_item_get_requested_area_for_width
                                   (GooCanvasItem *item,
                                    cairo_t *cr,
                                    gdouble width,
                                    GooCanvasBounds *requested_area);

This function is only intended to be used when implementing new canvas items, specifically layout items such as GooCanvasTable.

It gets the requested area of a child item, assuming it is allocated the given width. This is useful for text items whose requested height may change depending on the allocated width.

#### Parameters

item | a GooCanvasItem. |
cr | a cairo context. |
width | the allocated width. |
requested_area | a GooCanvasBounds to return the requested area in, in the parent's coordinate space. If `FALSE` is returned, this is undefined. |

#### Returns

`TRUE` if the item's requested area changes due to the new allocated width.

Since: 2.0.1

### goo_canvas_item_get_requested_height ()

    gdouble
    goo_canvas_item_get_requested_height (GooCanvasItem *item,
                                          cairo_t *cr,
                                          gdouble width);

This function is only intended to be used when implementing new canvas items, specifically layout items such as GooCanvasTable.

It gets the requested height of a child item, assuming it is allocated the given width. This is useful for text items whose requested height may change depending on the allocated width.

#### Parameters

item | a GooCanvasItem. |
cr | a cairo context. |
width | the width that the item may be allocated. |

#### Returns

the requested height of the item, given the allocated width, or `-1` if the item doesn't support this method or its height doesn't change when allocated different widths.

### goo_canvas_item_allocate_area ()

    void
    goo_canvas_item_allocate_area (GooCanvasItem *item,
                                   cairo_t *cr,
                                   const GooCanvasBounds *requested_area,
                                   const GooCanvasBounds *allocated_area,
                                   gdouble x_offset,
                                   gdouble y_offset);

This function is only intended to be used when implementing new canvas items, specifically layout items such as GooCanvasTable.

It allocates an area to a child GooCanvasItem.

Note that the parent layout item will use a transform to move each of its children for the layout, so there is no need for the child item to reposition itself. It only needs to recalculate its device bounds.

To help recalculate the item's device bounds, the `x_offset` and `y_offset` of the child item's allocated position from its requested position are provided. Simple items can just add these to their bounds.

#### Parameters

item | a GooCanvasItem. |
cr | a cairo context. |
requested_area | the area that the item originally requested, in the parent's coordinate space. |
allocated_area | the area that the item has been allocated, in the parent's coordinate space. |
x_offset | the x offset of the allocated area from the requested area in the device coordinate space. |
y_offset | the y offset of the allocated area from the requested area in the device coordinate space. |

### goo_canvas_item_get_items_at ()

    GList *
    goo_canvas_item_get_items_at (GooCanvasItem *item,
                                  gdouble x,
                                  gdouble y,
                                  cairo_t *cr,
                                  gboolean is_pointer_event,
                                  gboolean parent_is_visible,
                                  GList *found_items);

This function is only intended to be used when implementing new canvas items, specifically container items such as GooCanvasGroup.

It gets the items at the given point.

#### Parameters

item | a GooCanvasItem. |
x | the x coordinate of the point. |
y | the y coordinate of the point. |
cr | a cairo contect. |
is_pointer_event | `TRUE` if the "pointer-events" properties of items should be used to determine which parts of the item are tested. |
parent_is_visible | `TRUE` if the parent item is visible (which implies that all ancestors are also visible). |
found_items | the list of items found so far. | [element-type GooCanvas.CanvasItem]

#### Returns

the `found_items` list, with any more found items added onto the start of the list, leaving the top item first.

[element-type GooCanvas.CanvasItem][transfer none]

### goo_canvas_item_paint ()

    void
    goo_canvas_item_paint (GooCanvasItem *item,
                           cairo_t *cr,
                           const GooCanvasBounds *bounds,
                           gdouble scale);

This function is only intended to be used when implementing new canvas items, specifically container items such as GooCanvasGroup.

It paints the item and all children if they intersect the given bounds.

Note that the `scale` argument may be different to the current scale in the GooCanvasItem, e.g. when the canvas is being printed.

#### Parameters

item | a GooCanvasItem. |
cr | a cairo context. |
bounds | the bounds that need to be repainted, in device space. |
scale | the scale to use to determine whether an item should be painted. See “visibility-threshold”. |

### goo_canvas_item_class_install_child_property ()

    void
    goo_canvas_item_class_install_child_property
                                   (GObjectClass *iclass,
                                    guint property_id,
                                    GParamSpec *pspec);

This function is only intended to be used when implementing new canvas items, specifically layout container items such as GooCanvasTable.

It installs a child property on a canvas item class.

#### Parameters

iclass | a GObjectClass |
property_id | the id for the property |
pspec | the GParamSpec for the property |

### goo_canvas_item_class_list_child_properties ()

    GParamSpec **
    goo_canvas_item_class_list_child_properties
                                   (GObjectClass *iclass,
                                    guint *n_properties);

This function is only intended to be used when implementing new canvas items, specifically layout container items such as GooCanvasTable.

It returns all child properties of a canvas item class.

#### Parameters

iclass | a GObjectClass |
n_properties | location to return the number of child properties found. | [out]

#### Returns

a newly allocated array of GParamSpec*. The array must be freed with `g_free()`.

[array length=n_properties][transfer container]

### goo_canvas_item_class_find_child_property ()

    GParamSpec *
    goo_canvas_item_class_find_child_property
                                   (GObjectClass *iclass,
                                    const gchar *property_name);

This function is only intended to be used when implementing new canvas items, specifically layout container items such as GooCanvasTable.

It finds a child property of a canvas item class by name.

#### Parameters

iclass | a GObjectClass |
property_name | the name of the child property to find |

#### Returns

the GParamSpec of the child property or `NULL` if `class` has no child property with that name.

[type GObject.ParamSpec][transfer none]

### goo_canvas_item_get_child_property ()

    void
    goo_canvas_item_get_child_property (GooCanvasItem *item,
                                        GooCanvasItem *child,
                                        const gchar *property_name,
                                        GValue *value);

Gets a child property of `child` .

#### Parameters

item | a GooCanvasItem. |
child | a child GooCanvasItem. |
property_name | the name of the child property to get. |
value | a location to return the value. |

### goo_canvas_item_set_child_property ()

    void
    goo_canvas_item_set_child_property (GooCanvasItem *item,
                                        GooCanvasItem *child,
                                        const gchar *property_name,
                                        const GValue *value);

Sets a child property of `child` .

#### Parameters

item | a GooCanvasItem. |
child | a child GooCanvasItem. |
property_name | the name of the child property to set. |
value | the value to set the property to. |

### goo_canvas_item_get_child_properties ()

    void
    goo_canvas_item_get_child_properties (GooCanvasItem *item,
                                          GooCanvasItem *child,
                                          ...);

Gets the values of one or more child properties of `child` .

#### Parameters

item | a GooCanvasItem. |
child | a child GooCanvasItem. |
... | pairs of property names and value pointers, and a terminating `NULL`. |

### goo_canvas_item_get_child_properties_valist ()

    void
    goo_canvas_item_get_child_properties_valist
                                   (GooCanvasItem *item,
                                    GooCanvasItem *child,
                                    va_list var_args);

Gets the values of one or more child properties of `child` .

#### Parameters

item | a GooCanvasItem. |
child | a child GooCanvasItem. |
var_args | pairs of property names and value pointers, and a terminating `NULL`. |

### goo_canvas_item_set_child_properties ()

    void
    goo_canvas_item_set_child_properties (GooCanvasItem *item,
                                          GooCanvasItem *child,
                                          ...);

Sets the values of one or more child properties of `child` .

#### Parameters

item | a GooCanvasItem. |
child | a child GooCanvasItem. |
... | pairs of property names and values, and a terminating `NULL`. |

### goo_canvas_item_set_child_properties_valist ()

    void
    goo_canvas_item_set_child_properties_valist
                                   (GooCanvasItem *item,
                                    GooCanvasItem *child,
                                    va_list var_args);

Sets the values of one or more child properties of `child` .

#### Parameters

item | a GooCanvasItem. |
child | a child GooCanvasItem. |
var_args | pairs of property names and values, and a terminating `NULL`. |

## Types and Values

### GooCanvasItem

    typedef struct _GooCanvasItem GooCanvasItem;

GooCanvasItem is a typedef used for objects that implement the GooCanvasItem interface.

(There is no actual GooCanvasItem struct, since it is only an interface. But using 'GooCanvasItem' is more helpful than using 'GObject'.)

### struct GooCanvasItemIface

    struct GooCanvasItemIface {
      /* Virtual methods that group items must implement. */
      GooCanvas*		(* get_canvas)			(GooCanvasItem		*item);
      void			(* set_canvas)			(GooCanvasItem		*item,
    							 GooCanvas		*canvas);
      gint			(* get_n_children)		(GooCanvasItem		*item);
      GooCanvasItem* (* get_child)			(GooCanvasItem		*item,
    							 gint			 child_num);
      void			(* request_update)		(GooCanvasItem		*item);

      /* Virtual methods that group items may implement. */
      void			(* add_child)			(GooCanvasItem		*item,
    							 GooCanvasItem		*child,
    							 gint			 position);
      void			(* move_child)			(GooCanvasItem		*item,
    							 gint			 old_position,
    							 gint			 new_position);
      void			(* remove_child)		(GooCanvasItem		*item,
    							 gint			 child_num);
      void			(* get_child_property)		(GooCanvasItem		*item,
    							 GooCanvasItem		*child,
    							 guint			 property_id,
    							 GValue			*value,
    							 GParamSpec		*pspec);
      void			(* set_child_property)		(GooCanvasItem		*item,
    							 GooCanvasItem		*child,
    							 guint			 property_id,
    							 const GValue		*value,
    							 GParamSpec		*pspec);
      gboolean		(* get_transform_for_child) (GooCanvasItem		*item,
    							 GooCanvasItem		*child,
    							 cairo_matrix_t		*transform);

      /* Virtual methods that all canvas items must implement. */
      GooCanvasItem* (* get_parent)			(GooCanvasItem		*item);
      void			(* set_parent)			(GooCanvasItem		*item,
    							 GooCanvasItem		*parent);
      void			(* get_bounds)			(GooCanvasItem		*item,
    							 GooCanvasBounds *bounds);
      GList*		(* get_items_at)		(GooCanvasItem		*item,
    							 gdouble		 x,
    							 gdouble		 y,
    							 cairo_t		*cr,
    							 gboolean		 is_pointer_event,
    							 gboolean		 parent_is_visible,
    							 GList                  *found_items);
      void			(* update)			(GooCanvasItem		*item,
    							 gboolean		 entire_tree,
    							 cairo_t		*cr,
    							 GooCanvasBounds *bounds);
      void			(* paint)			(GooCanvasItem		*item,
    							 cairo_t		*cr,
    							 const GooCanvasBounds *bounds,
    							 gdouble		 scale);

      gboolean		(* get_requested_area)		(GooCanvasItem		*item,
    							 cairo_t		*cr,
    							 GooCanvasBounds *requested_area);
      void			(* allocate_area)		(GooCanvasItem		*item,
    							 cairo_t		*cr,
    							 const GooCanvasBounds *requested_area,
    							 const GooCanvasBounds *allocated_area,
    							 gdouble		 x_offset,
    							 gdouble		 y_offset);

      /* Virtual methods that canvas items may implement. */
      gboolean		(* get_transform)		(GooCanvasItem		*item,
    							 cairo_matrix_t		*transform);
      void			(* set_transform)		(GooCanvasItem		*item,
    							 const cairo_matrix_t *transform);
      GooCanvasStyle* (* get_style)			(GooCanvasItem		*item);
      void			(* set_style)			(GooCanvasItem		*item,
    							 GooCanvasStyle		*style);
      gboolean		(* is_visible)			(GooCanvasItem		*item);
      gdouble               (* get_requested_height) (GooCanvasItem		*item,
    							 cairo_t		*cr,
    							 gdouble		 width);

      /* Virtual methods that model/view items must implement. */
      GooCanvasItemModel* (* get_model)			(GooCanvasItem		*item);
      void			(* set_model)			(GooCanvasItem		*item,
    							 GooCanvasItemModel *model);

      /* Signals. */
      gboolean		(* enter_notify_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventCrossing *event);
      gboolean		(* leave_notify_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventCrossing *event);
      gboolean		(* motion_notify_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventMotion		*event);
      gboolean		(* button_press_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventButton		*event);
      gboolean		(* button_release_event) (GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventButton		*event);
      gboolean		(* focus_in_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventFocus		*event);
      gboolean		(* focus_out_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventFocus		*event);
      gboolean		(* key_press_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventKey		*event);
      gboolean		(* key_release_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventKey		*event);
      gboolean		(* grab_broken_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventGrabBroken *event);
      void			(* child_notify)		(GooCanvasItem		*item,
    							 GParamSpec		*pspec);
      gboolean		(* query_tooltip)		(GooCanvasItem		*item,
    							 gdouble		 x,
    							 gdouble		 y,
    							 gboolean		 keyboard_tooltip,
    							 GtkTooltip		*tooltip);

      gboolean		(* get_is_static)		(GooCanvasItem		*item);
      void			(* set_is_static)		(GooCanvasItem		*item,
    							 gboolean		 is_static);

      void			(* animation_finished)		(GooCanvasItem           *item,
    							 gboolean                 stopped);

      gboolean		(* scroll_event)		(GooCanvasItem		*item,
    							 GooCanvasItem		*target,
    							 GdkEventScroll		*event);

      gboolean              (* get_requested_area_for_width)(GooCanvasItem		*item,
    							 cairo_t		*cr,
    							 gdouble		 width,
    							 GooCanvasBounds *requested_area);
    };

GooCanvasItemIFace holds the virtual methods that make up the GooCanvasItem interface.

Simple canvas items only need to implement the `get_parent()`, `set_parent()`, `get_bounds()`, `get_items_at()`, `update()` and `paint()` methods (and also `get_requested_area()` and `allocate_area()` if they are going to be used inside a layout container like GooCanvasTable).

Items that support transforms should also implement `get_transform()` and `set_transform()`. Items that support styles should implement `get_style()` and `set_style()`.

Container items must implement `get_canvas()`, `set_canvas()`, `get_n_children()`, `get_child()` and `request_update()`. Containers that support dynamic changes to their children should implement `add_child()`, `move_child()` and `remove_child()`. Layout containers like GooCanvasTable may implement `get_child_property()`, `set_child_property()` and `get_transform_for_child()`.

#### Members

`get_canvas` () | returns the canvas the item is in. |
`set_canvas` () | sets the canvas the item is in. |
`get_n_children` () | returns the number of children of the item. |
`get_child` () | returns the child at the given index. |
`request_update` () | requests that an update is scheduled. |
`add_child` () | adds a child. |
`move_child` () | moves a child up or down the stacking order. |
`remove_child` () | removes a child. |
`get_child_property` () | gets a child property of a given child item, e.g. the "row" or "column" property of an item in a GooCanvasTable. |
`set_child_property` () | sets a child property for a given child item. |
`get_transform_for_child` () | gets the transform used to lay out a given child. |
`get_parent` () | gets the item's parent. |
`set_parent` () | sets the item's parent. |
`get_bounds` () | gets the bounds of the item. |
`get_items_at` () | gets all the items at the given point. |
`update` () | updates the item, if needed. It recalculates the bounds of the item and requests redraws of parts of the canvas if necessary. |
`paint` () | renders the item to the given cairo context. |
`get_requested_area` () | returns the requested area of the item, in its parent's coordinate space. This is only used for items in layout containers such as GooCanvasTable. |
`allocate_area` () | allocates the item's area, in its parent's coordinate space. The item must recalculate its bounds and request redraws of parts of the canvas if necessary. This is only used for items in layout containers such as GooCanvasTable. |
`get_transform` () | gets the item's transformation matrix. |
`set_transform` () | sets the item's transformation matrix. |
`get_style` () | gets the item's style. |
`set_style` () | sets the item's style. |
`is_visible` () | returns `TRUE` if the item is currently visible. |
`get_requested_height` () | returns the requested height of the item, given a particular allocated width, using the parent's coordinate space. Note that this method should only be used if the position of the item remains unchanged. If the position might change use `get_requested_area_for_width()` instead. |
`get_model` () | gets the model that the canvas item is viewing. |
`set_model` () | sets the model that the canvas item will view. |
`enter_notify_event` () | signal emitted when the mouse enters the item. |
`leave_notify_event` () | signal emitted when the mouse leaves the item. |
`motion_notify_event` () | signal emitted when the mouse moves within the item. |
`button_press_event` () | signal emitted when a mouse button is pressed within the item. |
`button_release_event` () | signal emitted when a mouse button is released. |
`focus_in_event` () | signal emitted when the item receices the keyboard focus. |
`focus_out_event` () | signal emitted when the item loses the keyboard focus. |
`key_press_event` () | signal emitted when a key is pressed. |
`key_release_event` () | signal emitted when a key is released. |
`grab_broken_event` () | signal emitted when a grab that the item has is lost. |
`child_notify` () | signal emitted when a child property is changed. |
`query_tooltip` () | signal emitted to query the tooltip of an item. |
`get_is_static` () | returns `TRUE` if the item is static. |
`set_is_static` () | notifies the item whether it is static or not. |
`animation_finished` () | signal emitted when the item's animation has finished. |
`scroll_event` () | signal emitted when the mouse wheel is activated within the item. |
`get_requested_area_for_width` () | returns the requested bounds of the item, given a particular allocated width, using the parent's coordinate space. |

## Property Details

### The `“can-focus”` property

      “can-focus”                gboolean

If the item can take the keyboard focus.

Owner: GooCanvasItem

Flags: Read / Write

Default value: FALSE

### The `“description”` property

      “description”              char *

A description of the item for use by assistive technologies.

Owner: GooCanvasItem

Flags: Read / Write

Default value: NULL

### The `“parent”` property

      “parent”                   GooCanvasItem *

The parent item.

Owner: GooCanvasItem

Flags: Read / Write

### The `“pointer-events”` property

      “pointer-events”           GooCanvasPointerEvents

Specifies when the item receives pointer events.

Owner: GooCanvasItem

Flags: Read / Write

Default value: GOO_CANVAS_EVENTS_VISIBLE_MASK | GOO_CANVAS_EVENTS_PAINTED_MASK | GOO_CANVAS_EVENTS_FILL_MASK | GOO_CANVAS_EVENTS_STROKE_MASK

### The `“title”` property

      “title”                    char *

A short context-rich description of the item for use by assistive technologies.

Owner: GooCanvasItem

Flags: Read / Write

Default value: NULL

### The `“tooltip”` property

      “tooltip”                  char *

The tooltip to display for the item, or `NULL` to display no tooltip.

Note that this property has no effect unless the “has-tooltip” property is set to `TRUE` on the GooCanvas containing this item.

Owner: GooCanvasItem

Flags: Read / Write

Default value: NULL

### The `“transform”` property

      “transform”                GooCairoMatrix *

The transformation matrix of the item.

Owner: GooCanvasItem

Flags: Read / Write

### The `“visibility”` property

      “visibility”               GooCanvasItemVisibility

When the canvas item is visible.

Owner: GooCanvasItem

Flags: Read / Write

Default value: GOO_CANVAS_ITEM_VISIBLE

### The `“visibility-threshold”` property

      “visibility-threshold”     double

The scale threshold at which the item becomes visible.

Owner: GooCanvasItem

Flags: Read / Write

Allowed values: >= 0

Default value: 0

## Signal Details

### The `“animation-finished”` signal

    void
    user_function (GooCanvasItem *item,
                   gboolean       stopped,
                   gpointer       user_data)

Emitted when the item animation has finished.

#### Parameters

item | the item that received the signal. |
stopped | if the animation was explicitly stopped. |
user_data | user data set when the signal handler was connected. |

Flags: Run Last

### The `“button-press-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when a mouse button is pressed in an item.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. The x & y fields contain the mouse position in the item's coordinate space. The x_root & y_root fields contain the same coordinates converted to the canvas coordinate space. | [type Gdk.EventButton]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“button-release-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when a mouse button is released in an item.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. The x & y fields contain the mouse position in the item's coordinate space. The x_root & y_root fields contain the same coordinates converted to the canvas coordinate space. | [type Gdk.EventButton]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“child-notify”` signal

    void
    user_function (GooCanvasItem *item,
                   GParamSpec    *pspec,
                   gpointer       user_data)

Emitted for each child property that has changed. The signal's detail holds the property name.

#### Parameters

item | the item that received the signal. |
pspec | the GParamSpec of the changed child property. | [type GObject.ParamSpec]
user_data | user data set when the signal handler was connected. |

Flags: No Hooks

### The `“enter-notify-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when the mouse enters an item.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. The x & y fields contain the mouse position in the item's coordinate space. The x_root & y_root fields contain the same coordinates converted to the canvas coordinate space. | [type Gdk.EventCrossing]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“focus-in-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when the item receives the keyboard focus.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. | [type Gdk.EventFocus]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“focus-out-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when the item loses the keyboard focus.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. | [type Gdk.EventFocus]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“grab-broken-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when the item's keyboard or pointer grab was lost unexpectedly.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. | [type Gdk.EventGrabBroken]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“key-press-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when a key is pressed and the item has the keyboard focus.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. | [type Gdk.EventKey]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“key-release-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when a key is released and the item has the keyboard focus.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. | [type Gdk.EventKey]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“leave-notify-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when the mouse leaves an item.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. The x & y fields contain the mouse position in the item's coordinate space. The x_root & y_root fields contain the same coordinates converted to the canvas coordinate space. | [type Gdk.EventCrossing]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“motion-notify-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when the mouse moves within an item.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. The x & y fields contain the mouse position in the item's coordinate space. The x_root & y_root fields contain the same coordinates converted to the canvas coordinate space. | [type Gdk.EventMotion]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last

### The `“query-tooltip”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   double         x,
                   double         y,
                   gboolean       keyboard_mode,
                   GtkTooltip    *tooltip,
                   gpointer       user_data)

Emitted when the mouse has paused over the item for a certain amount of time, or the tooltip was requested via the keyboard.

Note that if `keyboard_mode` is `TRUE`, the values of `x` and `y` are undefined and should not be used.

If the item wants to display a tooltip it should update `tooltip` and return `TRUE`.

#### Parameters

item | the item which received the signal. |
x | the x coordinate of the mouse. |
y | the y coordinate of the mouse. |
keyboard_mode | `TRUE` if the tooltip was triggered using the keyboard. |
tooltip | a GtkTooltip. |
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` if the item has set a tooltip to show.

Flags: Run Last

### The `“scroll-event”` signal

    gboolean
    user_function (GooCanvasItem *item,
                   GooCanvasItem *target_item,
                   GdkEvent      *event,
                   gpointer       user_data)

Emitted when a button in the 4 to 7 range is pressed. Wheel mice are usually configured to generate button press events for buttons 4 and 5 when the wheel is turned in an item.

#### Parameters

item | the item that received the signal. |
target_item | the target of the event. |
event | the event data. The x & y fields contain the mouse position in the item's coordinate space. The x_root & y_root fields contain the same coordinates converted to the canvas coordinate space. | [type Gdk.EventScroll]
user_data | user data set when the signal handler was connected. |

#### Returns

`TRUE` to stop the signal emission, or `FALSE` to let it continue.

Flags: Run Last