GtkDrawingArea
a widget for custom user interface elements.
The #GtkDrawingArea widget is used for creating custom
user interface elements. After creating a drawing
area, the application may want to connect to:
Mouse and button press signals to respond to input from
the user.
The "realize" signal to take any necessary actions
when the widget
The "size_allocate" signal to take any necessary actions
when the widget changes size.
The "expose_event" signal to handle redrawing the
contents of the widget.
As a convenience, the #GtkDrawingArea widget synthesizes
a "configure_event" when the widget is realized
and any time the size of a widget changes when it
is realized. It often suffices to connect to this
signal instead of "realize" and "size_allocate".
The following code portion demonstrates using a drawing
area to implement a widget that draws a circle.
As this example demonstrates, an expose handler should
draw only the pixels within the requested area and
should draw or clear all these pixels.
Simple <structname>GtkDrawingArea</structname> usage.
gboolean
expose_event (GdkWidget *widget, GdkEventExpose *event, gpointer data)
{
gdk_window_clear_area (widget->window,
event->area.x, event->area.y,
event->area.width, event->area.height);
gdk_gc_set_clip_rectangle (widget->style->fg_gc[widget->state],
&event->area);
gdk_draw_arc (widget->window,
widget->style->fg_gc[widget->state],
TRUE,
0, 0, widget->allocation.width, widget->allocation.height,
0, 64 * 360);
gdk_gc_set_clip_rectangle (widget->style->fg_gc[widget->state],
NULL);
return TRUE;
}
[...]
GtkWidget *drawing_area = gtk_drawing_area_new ();
gtk_drawing_area_size (GTK_DRAWING_AREA (drawing_area),
100, 100);
gtk_signal_connect (GTK_OBJECT (drawing_area),
The #GtkDrawingArea struct contains private data only, and
should be accessed using the functions below.
Creates a new drawing area.
@Returns: a new #GtkDrawingArea
Sets the size that the drawing area will request
in response to a "size_request" signal. The
drawing area may actually be allocated a size
larger than this depending on how it is packed
within the enclosing containers.
@darea: a #GtkDrawingArea.
@width: the width to request.
@height: the height to request.