Struct gtk4::DrawingArea[][src]

pub struct DrawingArea(_);
Expand description

DrawingArea is a widget that allows drawing with cairo.

An example GtkDrawingArea

It’s essentially a blank widget; you can draw on it. After creating a drawing area, the application may want to connect to:

  • The signal::Widget::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 signal::DrawingArea::resize signal to take any necessary actions when the widget changes size.

  • Call DrawingAreaExt::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

⚠️ The following code is in 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 WidgetExt::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][gdk4-Cairo-Interaction] 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.

Implements

DrawingAreaExt, WidgetExt, glib::ObjectExt, AccessibleExt, BuildableExt, ConstraintTargetExt, DrawingAreaExtManual, WidgetExtManual, AccessibleExtManual

Implementations

Creates a new drawing area.

Returns

a new DrawingArea

Creates a new builder-pattern struct instance to construct DrawingArea objects.

This method returns an instance of DrawingAreaBuilder which can be used to create DrawingArea objects.

Trait Implementations

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Override the virtual methods of this class for the given subclass and do other class initialization. Read more

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This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Returns the type identifier of Self.

Auto Trait Implementations

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Same as connect but takes a SignalId instead of a signal name.

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The resulting type after obtaining ownership.

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