DrawingArea


Object Hierarchy:

Object hierarchy for DrawingArea

Description:

[ CCode ( type_id = "gtk_drawing_area_get_type ()" ) ]
public class DrawingArea : Widget, Accessible, Buildable, ConstraintTarget

The DrawingArea 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:

  • The 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 resize signal to take any necessary actions when the widget changes size.
  • Call set_draw_func 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.

Simple GtkDrawingArea usage

static void
draw_function (GtkDrawingArea *area,
cairo_t *cr,
int width,
int height,
gpointer data)
{
GdkRGBA color;
GtkStyleContext *context;

context = gtk_widget_get_style_context (GTK_WIDGET (area));

cairo_arc (cr,
width / 2.0, height / 2.0,
MIN (width, height) / 2.0,
0, 2 * G_PI);

gtk_style_context_get_color (context,
&color);
gdk_cairo_set_source_rgba (cr, &color);

cairo_fill (cr);
}

int
main (int argc, char **argv)
{
gtk_init ();

GtkWidget *area = gtk_drawing_area_new ();
gtk_drawing_area_set_content_width (GTK_DRAWING_AREA (area), 100);
gtk_drawing_area_set_content_height (GTK_DRAWING_AREA (area), 100);
gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (area),
draw_function,
NULL, NULL);
return 0;
}

The draw function is normally called when a drawing area first comes onscreen, or when it’s covered by another window and then uncovered. You can also force a redraw by adding to the “damage region” of the drawing area’s window using queue_draw. This will cause the drawing area to call the draw function again.

The available routines for drawing are documented on the GDK Drawing Primitives page and the cairo documentation.

To receive mouse events on a drawing area, you will need to use event controllers. 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.

If you need more complex control over your widget, you should consider creating your own Widget subclass.


Namespace: Gtk
Package: gtk4

Content:

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Inherited Members:

All known members inherited from class Gtk.Widget