`GtkDrawingArea` is a widget that allows drawing with cairo.
It’s essentially a blank widget; you can draw on it. After creating a drawing area, the application may want to connect to:
- The [[email protected]:
GtkDrawingArea: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 [[email protected]:
GtkDrawingArea:resize] signal to take any necessary actions when the widget changes size.
- Call [[email protected]_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
```c 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 [
[email protected]_draw]. This will cause the drawing area to call the draw function again.
The available routines for drawing are documented in the Cairo
documentation; GDK offers additional API to integrate with Cairo, like [[email protected]_set_source_rgba] or [
[email protected]_set_source_pixbuf].
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 `GtkWidget` subclass.