Canvas

Object Hierarchy:

Description:

[ CCode ( type_id = "goo_canvas_get_type ()" ) ]
public class Canvas : Container, Implementor, Buildable, Scrollable

Canvas is the main widget containing a number of canvas items.

Here is a simple example:

<informalexample><programlisting> &num;include <goocanvas.h>

static gboolean on_rect_button_press (GooCanvasItem *view, GooCanvasItem *target, GdkEventButton *event, gpointer data);

int main (int argc, char *argv[]) { GtkWidget *window, *scrolled_win, *canvas; GooCanvasItem *root, *rect_item, *text_item;

/&ast; Initialize GTK+. &ast;/ gtk_init (&argc, &argv);

/&ast; Create the window and widgets. &ast;/ window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_window_set_default_size (GTK_WINDOW ( window), 640, 600); gtk_widget_show (window); g_signal_connect (window, "delete_event", G_CALLBACK (on_delete_event), NULL);

scrolled_win = gtk_scrolled_window_new (NULL, NULL); gtk_scrolled_window_set_shadow_type (GTK_SCROLLED_WINDOW (scrolled_win), GTK_SHADOW_IN); gtk_widget_show (scrolled_win); gtk_container_add (GTK_CONTAINER (window), scrolled_win);

canvas = goo_canvas_new (); gtk_widget_set_size_request (canvas, 600, 450); goo_canvas_set_bounds (GOO_CANVAS (canvas), 0, 0, 1000, 1000); gtk_widget_show (canvas); gtk_container_add (GTK_CONTAINER (scrolled_win), canvas);

root = goo_canvas_get_root_item (GOO_CANVAS (canvas));

/&ast; Add a few simple items. &ast;/ rect_item = goo_canvas_rect_new (root, 100, 100, 400, 400, "line-width", 10.0, "radius-x", 20.0, "radius-y", 10.0, "stroke-color", "yellow", "fill-color", "red", NULL);

text_item = goo_canvas_text_new (root, "Hello World", 300, 300, -1, GOO_CANVAS_ANCHOR_CENTER, "font", "Sans 24", NULL); goo_canvas_item_rotate (text_item, 45, 300, 300);

/&ast; Connect a signal handler for the rectangle item. &ast;/ g_signal_connect (rect_item, "button_press_event", G_CALLBACK ( on_rect_button_press), NULL);

/&ast; Pass control to the GTK+ main event loop. &ast;/ gtk_main ();

return 0; }

/&ast; This handles button presses in item views. We simply output a message to the console. &ast;/ static gboolean on_rect_button_press (GooCanvasItem *item, GooCanvasItem *target, GdkEventButton *event, gpointer data) { g_print ("rect item received button press event\n"); return TRUE; }

</programlisting></informalexample>

A Canvas widget is usually placed inside a ScrolledWindow widget and can be scrolled with the scrollbar or with the scroll wheel on a mouse. To disable mouse wheel scrolling, do this: < informalexample><programlisting> g_signal_connect (canvas, "scroll-event", G_CALLBACK (gtk_true), NULL); </programlisting>< /informalexample>

Namespace: Goo

Package: goocanvas-2.0

Content:

Properties:

public CanvasAnchorType anchor { get; set; }
public bool automatic_bounds { get; set; }
public string background_color { set; }
public RGBA background_color_gdk_rgba { set; }
The color to use for the canvas background, specified as a GdkRGBA.
public uint background_color_rgb { set; }
public bool bounds_from_origin { get; set; }
public double bounds_padding { get; set; }
public bool clear_background { get; set; }
public bool integer_layout { get; set; }
public bool redraw_when_scrolled { get; set; }
public double resolution_x { get; set; }
public double resolution_y { get; set; }
public double scale { get; set; }
public double scale_x { get; set; }
public double scale_y { get; set; }
public Unit units { get; set; }
public double x1 { get; set; }
public double x2 { get; set; }
public double y1 { get; set; }
public double y2 { get; set; }

Static methods:

public static void create_path (Array<CanvasPathCommand?> commands, Context cr)
Creates the path specified by the given CanvasPathCommand array.
public static Array<CanvasPathCommand?> parse_path_data (string path_data)
Parses the given SVG path specification string.

Creation methods:

public Canvas ()
Creates a new Canvas widget.

Methods:

public void convert_bounds_to_item_space (CanvasItem item, ref CanvasBounds bounds)
Converts the given bounds in the canvas coordinate space to a bounding box in item space.
public void convert_from_item_space (CanvasItem item, ref double x, ref double y)
Converts a coordinate from the given item's coordinate space to the canvas coordinate space, applying all transformation matrices including the item's own transformation matrix, if it has one.
public void convert_from_pixels (ref double x, ref double y)
Converts a coordinate from pixels to the canvas coordinate space.
public void convert_to_item_space (CanvasItem item, ref double x, ref double y)
Converts a coordinate from the canvas coordinate space to the given item's coordinate space, applying all transformation matrices including the item's own transformation matrix, if it has one.
public void convert_to_pixels (ref double x, ref double y)
Converts a coordinate from the canvas coordinate space to pixels.
public void convert_units_from_pixels (ref double x, ref double y)
Converts a coordinate from pixels to the canvas's units, ignoring scaling and ignoring the coordinate space specified in the call to set_bounds .
public void convert_units_to_pixels (ref double x, ref double y)
Converts a coordinate from the canvas's units to pixels, ignoring scaling and ignoring the coordinate space specified in the call to set_bounds .
public Context create_cairo_context ()
Creates a cairo context, initialized with the default canvas settings.
public virtual CanvasItem create_item (CanvasItemModel model)
This function is only intended to be used when implementing new canvas items, typically container items such as CanvasGroup.
public void get_bounds (out double left, out double top, out double right, out double bottom)
Gets the bounds of the canvas, in canvas units.
public double get_default_line_width ()
Gets the default line width, which depends on the current units setting.
public unowned CanvasItem get_item (CanvasItemModel model)
Gets the canvas item associated with the given CanvasItemModel.
public unowned CanvasItem get_item_at (double x, double y, bool is_pointer_event)
Gets the item at the given point.
public List<unowned CanvasItem> get_items_at (double x, double y, bool is_pointer_event)
Gets all items at the given point.
public List<unowned CanvasItem> get_items_in_area (CanvasBounds area, bool inside_area, bool allow_overlaps, bool include_containers)
Gets a list of items inside or outside a given area.
public unowned CanvasItem get_root_item ()
Gets the root item of the canvas, usually a CanvasGroup.
public unowned CanvasItemModel get_root_item_model ()
Gets the root item model of the canvas.
public double get_scale ()
Gets the current scale of the canvas.
public unowned CanvasItem get_static_root_item ()
Gets the static root item of the canvas.
public unowned CanvasItemModel get_static_root_item_model ()
Gets the static root item model of the canvas.
public void grab_focus (CanvasItem item)
Grabs the keyboard focus for the given item.
public GrabStatus keyboard_grab (CanvasItem item, bool owner_events, uint32 time)
Attempts to grab the keyboard for the given item.
public void keyboard_ungrab (CanvasItem item, uint32 time)
Ungrabs the keyboard, if the given item has the keyboard grab.
public GrabStatus pointer_grab (CanvasItem item, EventMask event_mask, Cursor? cursor, uint32 time)
Attempts to grab the pointer for the given item.
public void pointer_ungrab (CanvasItem item, uint32 time)
Ungrabs the pointer, if the given item has the pointer grab.
public void register_widget_item (CanvasWidget witem)
This function should only be used by CanvasWidget and subclass implementations.
public void render (Context cr, CanvasBounds? bounds, double scale)
Renders all or part of a canvas to the given cairo context.
public void request_item_redraw (CanvasBounds bounds, bool is_static)
This function is only intended to be used by subclasses of Canvas or CanvasItem implementations.
public void request_redraw (CanvasBounds bounds)
This function is only intended to be used by subclasses of Canvas or CanvasItem implementations.
public void request_update ()
This function is only intended to be used by subclasses of Canvas or CanvasItem implementations.
public void scroll_to (double left, double top)
Scrolls the canvas, placing the given point as close to the top-left of the view as possible.
public void set_bounds (double left, double top, double right, double bottom)
Sets the bounds of the Canvas, in canvas units.
public void set_root_item (CanvasItem item)
Sets the root item of the canvas.
public void set_root_item_model (CanvasItemModel model)
Sets the root item model of the canvas.
public void set_scale (double scale)
Sets the scale of the canvas.
public void set_static_root_item (CanvasItem item)
Sets the static root item.
public void set_static_root_item_model (CanvasItemModel model)
Sets the static root item model.
public void unregister_item (CanvasItemModel model)
This function is only intended to be used when implementing new canvas items.
public void unregister_widget_item (CanvasWidget witem)
This function should only be used by CanvasWidget and subclass implementations.
public void update ()
This function is only intended to be used by subclasses of Canvas or CanvasItem implementations.

Signals:

public virtual signal void item_created (CanvasItem item, CanvasItemModel model)
This is emitted when a new canvas item is created, in model/view mode.

Inherited Members:

All known members inherited from class Gtk.Container

All known members inherited from class Gtk.Widget

All known members inherited from class GLib.Object

All known members inherited from interface Atk.Implementor

ref_accessible

All known members inherited from interface Gtk.Buildable

All known members inherited from interface Gtk.Scrollable