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.
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.
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 @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 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.
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 allowed APIs.
Gets the first ancestor of @widget with type @widget_type.
Retrieves the accessible implementation for the given GtkAccessible.
Returns whether the area is in auto render mode or not.
Returns the baseline that has currently been allocated to @widget.
Gets the ID of the @buildable object.
Determines whether the input focus can enter @widget or any of its children.
Queries whether @widget can be the target of pointer events.
Gets the value set with gtk_widget_set_child_visible().
Gets the clipboard object for @widget.
Retrieves the GdkGLContext used by @area.
Returns the list of style classes applied to @widget.
Returns the CSS name that is used for @self.
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.
Determines whether @widget can own the input focus.
Returns the current focus child of @widget.
Returns whether the widget should grab focus when it is clicked with the mouse.
Gets the font map of @widget.
Obtains the frame clock for a widget.
Returns whether the area has a depth buffer.
Returns whether the area has a stencil buffer.
Returns the current value of the has-tooltip property.
Gets whether the widget would like any available extra horizontal space.
Gets whether gtk_widget_set_hexpand() has been used to explicitly set the expand flag on this widget.
Returns the widget’s last child.
Retrieves the layout manager used by @widget.
Gets the bottom margin of @widget.
Gets the end margin of @widget.
Gets the start margin of @widget.
Gets the top margin of @widget.
Retrieves the next accessible sibling of an accessible object
Returns the widget’s next sibling.
#Fetches the requested opacity for this widget.
Returns the widget’s overflow value.
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.
Determines whether @widget is always treated as the default widget within its toplevel when it has the focus, even if another widget is the default.
Gets whether the widget prefers a height-for-width layout or a width-for-height layout.
Retrieves the internal scale factor that maps from window coordinates to the actual device pixels.
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.
Gets the contents of the tooltip for @widget.
Gets the contents of the tooltip for @widget.
Gets whether the widget would like any available extra vertical space.
Gets whether gtk_widget_set_vexpand() has been used to explicitly set the expand flag on this widget.
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 the allowed APIs to create a context with.
Sets whether the GtkGLArea is in auto render mode.
Specifies whether the input focus can enter the widget or any of its children.
Sets whether @widget can be the target of pointer events.
Sets whether @widget should be mapped along with its parent.
Clear all style classes applied to @widget and replace them with @classes.
Sets a named cursor to be shown when pointer devices point towards @widget.
Sets the reading direction on a particular widget.
Specifies whether @widget can own the input focus.
Set @child as the current focus child of @widget.
Sets whether the widget should grab focus when it is clicked with the mouse.
Sets the font map to use for Pango rendering.
Sets whether the GtkGLArea should use a depth buffer.
Sets whether the GtkGLArea should use a stencil buffer.
Sets the has-tooltip property on @widget to @has_tooltip.
Sets whether the widget would like any available extra horizontal space.
Sets whether the hexpand flag will be used.
Sets the layout manager delegate instance that provides an implementation for measuring and allocating the children of @widget.
Sets the bottom margin of @widget.
Sets the end margin of @widget.
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 start margin of @widget.
Sets the top margin of @widget.
Request the @widget to be rendered partially transparent.
Sets how @widget treats content that is drawn outside the widget's content area.
Specifies whether @widget will be treated as the default widget within its toplevel when it has the focus, even if another widget is the default.
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 @markup as the contents of the tooltip, which is marked up with Pango markup.
Sets @text as the contents of the tooltip.
Sets whether the widget would like any available extra vertical space.
Sets whether the vexpand flag will be used.
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.