GlArea
GtkGLArea is a widget that allows drawing with OpenGL.
GtkGLArea sets up its own class@Gdk.GLContext, 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 signal@Gtk.GLArea::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 signal@Gtk.GLArea::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 signal@Gtk.Widget::realize signal; you can use the signal@Gtk.Widget::unrealize signal to clean up. Since the GdkGLContext creation and initialization may fail, you will need to check for errors, using method@Gtk.GLArea.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 signal@Gtk.GLArea::create-context signal.
Skipped during bindings generation
parameter
major: major: Out parameter is not supportedsignal
render: Signal render is ignored
Constructors
Properties
The accessible role of the given GtkAccessible implementation.
The allowed APIs.
If set to true the ::render signal will be emitted every time the widget draws.
A list of css classes applied to this widget.
Whether the widget should grab focus when it is clicked with the mouse.
If set to true the widget will allocate and enable a depth buffer for the target framebuffer.
If set to true the widget will allocate and enable a stencil buffer for the target framebuffer.
Enables or disables the emission of the ::query-tooltip signal on @widget.
Whether to use the hexpand property.
The GtkLayoutManager instance to use to compute the preferred size of the widget, and allocate its children.
Margin on bottom side of widget.
Margin on start of widget, horizontally.
Whether the widget will receive the default action when it is focused.
The scale factor of the widget.
Sets the text of tooltip to be the given string, which is marked up with Pango markup.
Sets the text of tooltip to be the given string.
Whether to use the vexpand property.
Functions
Enable or disable an action installed with gtk_widget_class_install_action().
Looks up the action in the action groups associated with
Activates the default.activate action from @widget.
For widgets that can be “activated” (buttons, menu items, etc.), this function activates them.
Adds @controller to @widget so that it will receive events.
Adds a style class to @widget.
Adds a widget to the list of mnemonic labels for this widget.
Queues an animation frame update and adds a callback to be called before each frame.
This function is only used by GtkWidget subclasses, to assign a size, position and (optionally) baseline to their child widgets.
Requests the user's screen reader to announce the given message.
Binds buffers to the framebuffer.
Called by widgets as the user moves around the window using keyboard shortcuts.
Computes the bounds for @widget in the coordinate space of @target.
Computes whether a container should give this widget extra space when possible.
Translates the given @point in @widget's coordinates to coordinates relative to @target’s coordinate system.
Computes a matrix suitable to describe a transformation from
Emitted when the widget is being realized.
Signals that all holders of a reference to the widget should release the reference that they hold.
Emitted when the text direction of a widget changes.
Emitted when @widget is hidden.
Emitted if keyboard navigation fails.
Emitted when @widget is going to be mapped.
Emitted when a widget is activated via a mnemonic.
Emitted when the focus is moved.
Emitted when the widget’s tooltip is about to be shown.
Emitted when @widget is associated with a GdkSurface.
Emitted once when the widget is realized, and then each time the widget is changed while realized.
Emitted when @widget is shown.
Emitted when the widget state changes.
Emitted when @widget is going to be unmapped.
Emitted when the GdkSurface associated with @widget is destroyed.
Creates a new PangoContext with the appropriate font map, font options, font description, and base direction for drawing text for this widget.
Creates a new PangoLayout with the appropriate font map, font description, and base direction for drawing text for this widget.
Clears the template children for the given widget.
Checks to see if a drag movement has passed the GTK drag threshold.
Retrieves the accessible parent for an accessible object.
Retrieves the accessible role of an accessible object.
Returns the baseline that has currently been allocated to @widget.
Returns the height that has currently been allocated to @widget.
Returns the width that has currently been allocated to @widget.
Gets the first ancestor of @widget with type @widget_type.
Retrieves the accessible implementation for the given GtkAccessible.
Returns the baseline that has currently been allocated to @widget.
Gets the ID of the @buildable object.
Gets the value set with gtk_widget_set_child_visible().
Gets the clipboard object for @widget.
Gets the reading direction for a particular widget.
Get the GdkDisplay for the toplevel window associated with this widget.
Retrieves the first accessible child of an accessible object.
Returns the widget’s first child.
Returns the current focus child of @widget.
Gets the font map of @widget.
Obtains the frame clock for a widget.
Returns the widget’s last child.
Retrieves the next accessible sibling of an accessible object
Returns the widget’s next sibling.
Gets a PangoContext with the appropriate font map, font description, and base direction for this widget.
Query a platform state, such as focus.
Retrieves the minimum and natural size of a widget, taking into account the widget’s preference for height-for-width management.
Returns the widget’s previous sibling.
Gets the primary clipboard of @widget.
Determines whether @widget is realized.
Gets whether the widget prefers a height-for-width layout or a width-for-height layout.
Returns the widget’s sensitivity.
Gets the settings object holding the settings used for this widget.
Returns the content width or height of the widget.
Returns the widget state as a flag set.
Returns the style context associated to @widget.
Fetch an object build from the template XML for @widget_type in this @widget instance.
Determines whether the widget is visible.
Returns whether @css_class is currently applied to @widget.
Determines whether @widget is the current default widget within its toplevel.
Determines if the widget should show a visible indication that it has the global input focus.
Returns whether the widget is currently being destroyed.
Creates and initializes child widgets defined in templates.
Inserts @group into @widget.
Inserts @widget into the child widget list of @parent.
Inserts @widget into the child widget list of @parent.
Determines whether @widget is somewhere inside @ancestor, possibly with intermediate containers.
Determines whether @widget can be drawn to.
Returns the widget’s effective sensitivity.
Emits the ::keynav-failed signal on the widget.
Returns the widgets for which this widget is the target of a mnemonic.
Ensures that the GdkGLContext used by @area is associated with the GtkGLArea.
Emits the ::mnemonic-activate signal.
Returns a GListModel to track the children of @widget.
Returns a GListModel to track the class@Gtk.EventControllers of @widget.
Flags the widget for a rerun of the vfunc@Gtk.Widget.size_allocate function.
Marks the currently rendered data (if any) as invalid, and queues a redraw of the widget.
Flags a widget to have its size renegotiated.
Removes @controller from @widget, so that it doesn't process events anymore.
Removes a style from @widget.
Removes a widget from the list of mnemonic labels for this widget.
Removes a tick callback previously registered with gtk_widget_add_tick_callback().
Resets the accessible @property to its default value.
Resets the accessible @relation to its default value.
Resets the accessible @state to its default value.
Sets the parent and sibling of an accessible object.
Sets whether @widget should be mapped along with its parent.
Sets a named cursor to be shown when pointer devices point towards @widget.
Sets the reading direction on a particular widget.
Set @child as the current focus child of @widget.
Sets the font map to use for Pango rendering.
Set all margins to the same value.
Set start and end margin to horizontal and top and bottom margin to vertical
Set margins.
Sets the required version of OpenGL to be used when creating the context for the widget.
Sets the sensitivity of a widget.
Sets the minimum size of a widget.
Turns on flag values in the current widget state.
Sets the visibility state of @widget.
Returns whether @widget should contribute to the measuring and allocation of its parent.
Triggers a tooltip query on the display where the toplevel of @widget is located.
Turns off flag values for the current widget state.
Updates the next accessible sibling of @self.