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GObject.Object
parent-child markerGObject.InitiallyUnowned
parent-child markerGtk.Widget
parent-child marker Gtk.DrawingArea

Class Gtk.DrawingArea

Import line: Gtk = imports.gi.Gtk;
GIR File: Gtk-3.0.gir
C documentation: GtkDrawingArea
Class : DrawingArea
Implements: Atk.ImplementorIface, Gtk.Buildable
Subclasses: Gkbd.KeyboardDrawing
Extends: Gtk.Widget
The GtkDrawingArea widget is used for creating custom user interface
elements. It's essentially a blank widget; you can draw on it. After
creating a drawing area, the application may want to connect to:



Mouse and button press signals to respond to input from
the user. (Use gtk_widget_add_events() to enable events
you wish to receive.)




The GtkWidget::realize signal to take any necessary actions
when the widget is instantiated on a particular display.
(Create GDK resources in response to this signal.)




The GtkWidget::configure-event signal to take any necessary
actions when the widget changes size.




The GtkWidget::draw signal to handle redrawing the
contents of the widget.



The following code portion demonstrates using a drawing
area to display a circle in the normal widget foreground
color.
Note that GDK automatically clears the exposed area to the
background color before sending the expose event, and that
drawing is implicitly clipped to the exposed area.

Simple GtkDrawingArea usage

gboolean
draw_callback (GtkWidget *widget, cairo_t *cr, gpointer data)
{
guint width, height;
GdkRGBA color;
width = gtk_widget_get_allocated_width (widget);
height = gtk_widget_get_allocated_height (widget);
cairo_arc (cr,
width / 2.0, height / 2.0,
MIN (width, height) / 2.0,
0, 2 * G_PI);
gtk_style_context_get_color (gtk_widget_get_style_context (widget),
0,
&color);
gdk_cairo_set_source_rgba (cr, &color);
cairo_fill (cr);
return FALSE;
}
[...]
GtkWidget *drawing_area = gtk_drawing_area_new ();
gtk_widget_set_size_request (drawing_area, 100, 100);
g_signal_connect (G_OBJECT (drawing_area), "draw",
G_CALLBACK (draw_callback), NULL);


Draw signals are normally delivered when a drawing area first comes
onscreen, or when it's covered by another window and then uncovered.
You can also force an expose event by adding to the "damage region"
of the drawing area's window; gtk_widget_queue_draw_area() and
gdk_window_invalidate_rect() are equally good ways to do this.
You'll then get a draw signal for the invalid region.
The available routines for drawing are documented on the linkend="gdk3-Cairo-Interaction">GDK Drawing Primitives page
and the cairo documentation.
To receive mouse events on a drawing area, you will need to enable
them with gtk_widget_add_events(). To receive keyboard events, you
will need to set the "can-focus" property on the drawing area, and you
should probably draw some user-visible indication that the drawing
area is focused. Use gtk_widget_has_focus() in your expose event
handler to decide whether to draw the focus indicator. See
gtk_render_focus() for one way to draw focus.
Properties
Properties Defined By
Methods / Constructors
Method / Constructor Defined By
Events - usage syntax: this.signals.EVENTNAME.connect( Function )
Event Defined By
Used by These Methods / Signals / Properties- Nowhere other than here
Documentation generated by Introspection Doc Generator Loosely Based on JsDoc Toolkit on Sat Apr 16 2011 17:12:31 GMT+0800 (HKT)