Class

GtkGLArea

Description [src]

class Gtk.GLArea : Gtk.Widget
  implements Gtk.Accessible, Gtk.Buildable, Gtk.ConstraintTarget {
  /* No available fields */
}

GtkGLArea is a widget that allows drawing with OpenGL.

An example GtkGLArea

GtkGLArea sets up its own GdkGLContext, and creates a custom GL framebuffer that the widget will do GL rendering onto. It also ensures that this framebuffer is the default GL rendering target when rendering. The completed rendering is integrated into the larger GTK scene graph as a texture.

In order to draw, you have to connect to the GtkGLArea::render signal, or subclass GtkGLArea and override the GtkGLAreaClass.render virtual function.

The GtkGLArea widget ensures that the GdkGLContext is associated with the widget’s drawing area, and it is kept updated when the size and position of the drawing area changes.

Drawing with GtkGLArea

The simplest way to draw using OpenGL commands in a GtkGLArea is to create a widget instance and connect to the GtkGLArea::render signal:

The render() function will be called when the GtkGLArea is ready for you to draw its content:

The initial contents of the framebuffer are transparent.

static gboolean
render (GtkGLArea *area, GdkGLContext *context)
{
  // inside this function it's safe to use GL; the given
  // GdkGLContext has been made current to the drawable
  // surface used by the `GtkGLArea` and the viewport has
  // already been set to be the size of the allocation

  // we can start by clearing the buffer
  glClearColor (0, 0, 0, 0);
  glClear (GL_COLOR_BUFFER_BIT);

  // draw your object
  // draw_an_object ();

  // we completed our drawing; the draw commands will be
  // flushed at the end of the signal emission chain, and
  // the buffers will be drawn on the window
  return TRUE;
}

void setup_glarea (void)
{
  // create a GtkGLArea instance
  GtkWidget *gl_area = gtk_gl_area_new ();

  // connect to the "render" signal
  g_signal_connect (gl_area, "render", G_CALLBACK (render), NULL);
}

If you need to initialize OpenGL state, e.g. buffer objects or shaders, you should use the GtkWidget::realize signal; you can use the GtkWidget::unrealize signal to clean up. Since the GdkGLContext creation and initialization may fail, you will need to check for errors, using gtk_gl_area_get_error().

An example of how to safely initialize the GL state is:

static void
on_realize (GtkGLarea *area)
{
  // We need to make the context current if we want to
  // call GL API
  gtk_gl_area_make_current (area);

  // If there were errors during the initialization or
  // when trying to make the context current, this
  // function will return a GError for you to catch
  if (gtk_gl_area_get_error (area) != NULL)
    return;

  // You can also use gtk_gl_area_set_error() in order
  // to show eventual initialization errors on the
  // GtkGLArea widget itself
  GError *internal_error = NULL;
  init_buffer_objects (&error);
  if (error != NULL)
    {
      gtk_gl_area_set_error (area, error);
      g_error_free (error);
      return;
    }

  init_shaders (&error);
  if (error != NULL)
    {
      gtk_gl_area_set_error (area, error);
      g_error_free (error);
      return;
    }
}

If you need to change the options for creating the GdkGLContext you should use the GtkGLArea::create-context signal.

Hierarchy

Ancestors

Implements

Constructors

gtk_gl_area_new

Creates a new GtkGLArea widget.

Instance methods

gtk_gl_area_attach_buffers

Binds buffers to the framebuffer.

gtk_gl_area_get_allowed_apis

Gets the allowed APIs.

since: 4.12

gtk_gl_area_get_api

Gets the API that is currently in use.

since: 4.12

gtk_gl_area_get_auto_render

Returns whether the area is in auto render mode or not.

gtk_gl_area_get_context

Retrieves the GdkGLContext used by area.

gtk_gl_area_get_error

Gets the current error set on the area.

gtk_gl_area_get_has_depth_buffer

Returns whether the area has a depth buffer.

gtk_gl_area_get_has_stencil_buffer

Returns whether the area has a stencil buffer.

gtk_gl_area_get_required_version

Retrieves the required version of OpenGL.

gtk_gl_area_get_use_es

Returns whether the GtkGLArea should use OpenGL ES.

deprecated: 4.12

gtk_gl_area_make_current

Ensures that the GdkGLContext used by area is associated with the GtkGLArea.

gtk_gl_area_queue_render

Marks the currently rendered data (if any) as invalid, and queues a redraw of the widget.

gtk_gl_area_set_allowed_apis

Sets the allowed APIs to create a context with.

since: 4.12

gtk_gl_area_set_auto_render

Sets whether the GtkGLArea is in auto render mode.

gtk_gl_area_set_error

Sets an error on the area which will be shown instead of the GL rendering.

gtk_gl_area_set_has_depth_buffer

Sets whether the GtkGLArea should use a depth buffer.

gtk_gl_area_set_has_stencil_buffer

Sets whether the GtkGLArea should use a stencil buffer.

gtk_gl_area_set_required_version

Sets the required version of OpenGL to be used when creating the context for the widget.

gtk_gl_area_set_use_es

Sets whether the area should create an OpenGL or an OpenGL ES context.

deprecated: 4.12

Methods inherited from GtkWidget (162)

Please see GtkWidget for a full list of methods.

Methods inherited from GObject (43)

Please see GObject for a full list of methods.

Methods inherited from GtkAccessible (19)

gtk_accessible_announce

Requests the user’s screen reader to announce the given message.

since: 4.14

gtk_accessible_get_accessible_parent

Retrieves the accessible parent for an accessible object.

since: 4.10

gtk_accessible_get_accessible_role

Retrieves the accessible role of an accessible object.

gtk_accessible_get_at_context

Retrieves the implementation for the given accessible object.

since: 4.10

gtk_accessible_get_bounds

Queries the coordinates and dimensions of this accessible.

since: 4.10

gtk_accessible_get_first_accessible_child

Retrieves the first accessible child of an accessible object.

since: 4.10

gtk_accessible_get_next_accessible_sibling

Retrieves the next accessible sibling of an accessible object.

since: 4.10

gtk_accessible_get_platform_state

Queries a platform state, such as focus.

since: 4.10

gtk_accessible_reset_property

Resets the accessible property to its default value.

gtk_accessible_reset_relation

Resets the accessible relation to its default value.

gtk_accessible_reset_state

Resets the accessible state to its default value.

gtk_accessible_set_accessible_parent

Sets the parent and sibling of an accessible object.

since: 4.10

gtk_accessible_update_next_accessible_sibling

Updates the next accessible sibling.

since: 4.10

gtk_accessible_update_property

Updates a list of accessible properties.

gtk_accessible_update_property_value

Updates an array of accessible properties.

gtk_accessible_update_relation

Updates a list of accessible relations.

gtk_accessible_update_relation_value

Updates an array of accessible relations.

gtk_accessible_update_state

Updates a list of accessible states.

gtk_accessible_update_state_value

Updates an array of accessible states.

Methods inherited from GtkBuildable (1)

gtk_buildable_get_buildable_id

Gets the ID of the buildable object.

Properties

Gtk.GLArea:allowed-apis

The allowed APIs.

since: 4.12

Gtk.GLArea:api

The API currently in use.

since: 4.12

Gtk.GLArea:auto-render

If set to TRUE the ::render signal will be emitted every time the widget draws.

Gtk.GLArea:context

The GdkGLContext used by the GtkGLArea widget.

Gtk.GLArea:has-depth-buffer

If set to TRUE the widget will allocate and enable a depth buffer for the target framebuffer.

Gtk.GLArea:has-stencil-buffer

If set to TRUE the widget will allocate and enable a stencil buffer for the target framebuffer.

Gtk.GLArea:use-es

If set to TRUE the widget will try to create a GdkGLContext using OpenGL ES instead of OpenGL.

deprecated: 4.12

Properties inherited from GtkAccessible (1)

GtkAccessible:accessible-role

The accessible role of the given GtkAccessible implementation.

Signals inherited from GObject (1)

GObject::notify

The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.

Class structure

struct GtkGLAreaClass {
  gboolean (* render) (
    GtkGLArea* area,
    GdkGLContext* context
  );
  void (* resize) (
    GtkGLArea* area,
    int width,
    int height
  );
  GdkGLContext* (* create_context) (
    GtkGLArea* area
  );
  
}

The GtkGLAreaClass structure contains only private data.

Class members

render: gboolean (* render) ( GtkGLArea* area, GdkGLContext* context ): Class closure for the GtkGLArea::render signal.
resize: void (* resize) ( GtkGLArea* area, int width, int height ): Class closeure for the GtkGLArea::resize signal.
create_context: GdkGLContext* (* create_context) ( GtkGLArea* area ): Class closure for the GtkGLArea::create-context signal.

Description [src]

Drawing with GtkGLArea

Hierarchy

Ancestors

Implements

Constructors

Instance methods

Methods inherited from GtkWidget (162)

Methods inherited from GObject (43)

Methods inherited from GtkAccessible (19)

Methods inherited from GtkBuildable (1)

Properties

Properties inherited from GtkWidget (34)

Properties inherited from GtkAccessible (1)

Signals

Signals inherited from GtkWidget (13)

Signals inherited from GObject (1)

Class structure

Class members

Virtual methods