Struct GLArea

pub struct GLArea { /* private fields */ }

GLArea is a widget that allows drawing with OpenGL.

GLArea sets up its own 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 render signal, or subclass GLArea and override the GtkGLAreaClass.render virtual function.

The GLArea widget ensures that the gdk::GLContext 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 GLArea is to create a widget instance and connect to the render signal:

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

The initial contents of the framebuffer are transparent.

⚠️ The following code is in c ⚠️

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 realize signal; you can use the unrealize signal to clean up. Since the gdk::GLContext creation and initialization may fail, you will need to check for errors, using GLAreaExt::error().

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

⚠️ The following code is in c ⚠️

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 gdk::GLContext you should use the create-context signal.

Properties

allowed-apis

The allowed APIs.

Readable | Writeable

api

The API currently in use.

Readable

auto-render

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

This is the default and is useful if drawing the widget is faster.

If set to false the data from previous rendering is kept around and will be used for drawing the widget the next time, unless the window is resized. In order to force a rendering GLAreaExt::queue_render() must be called. This mode is useful when the scene changes seldom, but takes a long time to redraw.

Readable | Writeable

context

The gdk::GLContext used by the GLArea widget.

The GLArea widget is responsible for creating the gdk::GLContext instance. If you need to render with other kinds of buffers (stencil, depth, etc), use render buffers.

Readable

has-depth-buffer

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

Setting this property will enable GL’s depth testing as a side effect. If you don’t need depth testing, you should call glDisable(GL_DEPTH_TEST) in your GtkGLArea::render handler.

Readable | Writeable

has-stencil-buffer

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

Readable | Writeable

use-es

If set to true the widget will try to create a gdk::GLContext using OpenGL ES instead of OpenGL.

Readable | Writeable

Widget

can-focus

Whether the widget or any of its descendents can accept the input focus.

This property is meant to be set by widget implementations, typically in their instance init function.

Readable | Writeable

can-target

Whether the widget can receive pointer events.

Readable | Writeable

css-classes

A list of css classes applied to this widget.

Readable | Writeable

css-name

The name of this widget in the CSS tree.

This property is meant to be set by widget implementations, typically in their instance init function.

Readable | Writeable | Construct Only

cursor

The cursor used by @widget.

Readable | Writeable

focus-on-click

Whether the widget should grab focus when it is clicked with the mouse.

This property is only relevant for widgets that can take focus.

Readable | Writeable

focusable

Whether this widget itself will accept the input focus.

Readable | Writeable

halign

How to distribute horizontal space if widget gets extra space.

Readable | Writeable

has-default

Whether the widget is the default widget.

Readable

has-focus

Whether the widget has the input focus.

Readable

has-tooltip

Enables or disables the emission of the query-tooltip signal on @widget.

A true value indicates that @widget can have a tooltip, in this case the widget will be queried using query-tooltip to determine whether it will provide a tooltip or not.

Readable | Writeable

height-request

Overrides for height request of the widget.

If this is -1, the natural request will be used.

Readable | Writeable

hexpand

Whether to expand horizontally.

Readable | Writeable

hexpand-set

Whether to use the hexpand property.

Readable | Writeable

layout-manager

The LayoutManager instance to use to compute the preferred size of the widget, and allocate its children.

This property is meant to be set by widget implementations, typically in their instance init function.

Readable | Writeable

margin-bottom

Margin on bottom side of widget.

This property adds margin outside of the widget’s normal size request, the margin will be added in addition to the size from WidgetExt::set_size_request() for example.

Readable | Writeable

margin-end

Margin on end of widget, horizontally.

This property supports left-to-right and right-to-left text directions.

This property adds margin outside of the widget’s normal size request, the margin will be added in addition to the size from WidgetExt::set_size_request() for example.

Readable | Writeable

margin-start

Margin on start of widget, horizontally.

This property supports left-to-right and right-to-left text directions.

This property adds margin outside of the widget’s normal size request, the margin will be added in addition to the size from WidgetExt::set_size_request() for example.

Readable | Writeable

margin-top

Margin on top side of widget.

This property adds margin outside of the widget’s normal size request, the margin will be added in addition to the size from WidgetExt::set_size_request() for example.

Readable | Writeable

name

The name of the widget.

Readable | Writeable

opacity

The requested opacity of the widget.

Readable | Writeable

overflow

How content outside the widget’s content area is treated.

This property is meant to be set by widget implementations, typically in their instance init function.

Readable | Writeable

parent

The parent widget of this widget.

Readable

receives-default

Whether the widget will receive the default action when it is focused.

Readable | Writeable

root

The Root widget of the widget tree containing this widget.

This will be NULL if the widget is not contained in a root widget.

Readable

scale-factor

The scale factor of the widget.

Readable

sensitive

Whether the widget responds to input.

Readable | Writeable

tooltip-markup

Sets the text of tooltip to be the given string, which is marked up with Pango markup.

Also see Tooltip::set_markup().

This is a convenience property which will take care of getting the tooltip shown if the given string is not NULL: has-tooltip will automatically be set to true and there will be taken care of query-tooltip in the default signal handler.

Note that if both tooltip-text and tooltip-markup are set, the last one wins.

Readable | Writeable

tooltip-text

Sets the text of tooltip to be the given string.

Also see Tooltip::set_text().

This is a convenience property which will take care of getting the tooltip shown if the given string is not NULL: has-tooltip will automatically be set to true and there will be taken care of query-tooltip in the default signal handler.

Note that if both tooltip-text and tooltip-markup are set, the last one wins.

Readable | Writeable

valign

How to distribute vertical space if widget gets extra space.

Readable | Writeable

vexpand

Whether to expand vertically.

Readable | Writeable

vexpand-set

Whether to use the vexpand property.

Readable | Writeable

visible

Whether the widget is visible.

Readable | Writeable

width-request

Overrides for width request of the widget.

If this is -1, the natural request will be used.

Readable | Writeable

Accessible

accessible-role

The accessible role of the given Accessible implementation.

The accessible role cannot be changed once set.

Readable | Writeable

Signals

create-context

Emitted when the widget is being realized.

This allows you to override how the GL context is created. This is useful when you want to reuse an existing GL context, or if you want to try creating different kinds of GL options.

If context creation fails then the signal handler can use GLAreaExt::set_error() to register a more detailed error of how the construction failed.

render

Emitted every time the contents of the GLArea should be redrawn.

The @context is bound to the @area prior to emitting this function, and the buffers are painted to the window once the emission terminates.

resize

Emitted once when the widget is realized, and then each time the widget is changed while realized.

This is useful in order to keep GL state up to date with the widget size, like for instance camera properties which may depend on the width/height ratio.

The GL context for the area is guaranteed to be current when this signal is emitted.

The default handler sets up the GL viewport.

Widget

destroy

Signals that all holders of a reference to the widget should release the reference that they hold.

May result in finalization of the widget if all references are released.

This signal is not suitable for saving widget state.

direction-changed

Emitted when the text direction of a widget changes.

hide

Emitted when @widget is hidden.

keynav-failed

Emitted if keyboard navigation fails.

See WidgetExt::keynav_failed() for details.

map

Emitted when @widget is going to be mapped.

A widget is mapped when the widget is visible (which is controlled with visible) and all its parents up to the toplevel widget are also visible.

The ::map signal can be used to determine whether a widget will be drawn, for instance it can resume an animation that was stopped during the emission of unmap.

mnemonic-activate

Emitted when a widget is activated via a mnemonic.

The default handler for this signal activates @widget if @group_cycling is false, or just makes @widget grab focus if @group_cycling is true.

move-focus

Emitted when the focus is moved.

The ::move-focus signal is a keybinding signal.

The default bindings for this signal are Tab to move forward, and Shift+Tab to move backward.

Action

query-tooltip

Emitted when the widget’s tooltip is about to be shown.

This happens when the has-tooltip property is true and the hover timeout has expired with the cursor hovering above @widget; or emitted when @widget got focus in keyboard mode.

Using the given coordinates, the signal handler should determine whether a tooltip should be shown for @widget. If this is the case true should be returned, false otherwise. Note that if @keyboard_mode is true, the values of @x and @y are undefined and should not be used.

The signal handler is free to manipulate @tooltip with the therefore destined function calls.

realize

Emitted when @widget is associated with a gdk::Surface.

This means that WidgetExt::realize() has been called or the widget has been mapped (that is, it is going to be drawn).

show

Emitted when @widget is shown.

state-flags-changed

Emitted when the widget state changes.

See WidgetExt::state_flags().

unmap

Emitted when @widget is going to be unmapped.

A widget is unmapped when either it or any of its parents up to the toplevel widget have been set as hidden.

As ::unmap indicates that a widget will not be shown any longer, it can be used to, for example, stop an animation on the widget.

unrealize

Emitted when the gdk::Surface associated with @widget is destroyed.

This means that WidgetExt::unrealize() has been called or the widget has been unmapped (that is, it is going to be hidden).

Implements

GLAreaExt, WidgetExt, [trait@glib::ObjectExt], AccessibleExt, BuildableExt, ConstraintTargetExt, WidgetExtManual, AccessibleExtManual

GLib type: GObject with reference counted clone semantics.

Implementations

impl GLArea

pub const NONE: Option<&'static GLArea> = None

pub fn new() -> GLArea

Creates a new GLArea widget.

Returns

a new GLArea

pub fn builder() -> GLAreaBuilder

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

This method returns an instance of GLAreaBuilder which can be used to create GLArea objects.

Trait Implementations

impl Clone for GLArea

fn clone(&self) -> Self

Makes a clone of this shared reference.

This increments the strong reference count of the object. Dropping the object will decrement it again.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for GLArea

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for GLArea

fn default() -> Self

Returns the “default value” for a type.

impl HasParamSpec for GLArea

type ParamSpec = ParamSpecObject

type SetValue = GLArea

Preferred value to be used as setter for the associated ParamSpec.

type BuilderFn = fn(_: &str) -> ParamSpecObjectBuilder<'_, GLArea>

fn param_spec_builder() -> Self::BuilderFn

impl Hash for GLArea

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Hashes the memory address of this object.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T: GLAreaImpl> IsSubclassable<T> for GLArea

fn class_init(class: &mut Class<Self>)

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

fn instance_init(instance: &mut InitializingObject<T>)

Instance specific initialization.

impl Ord for GLArea

fn cmp(&self, other: &Self) -> Ordering

Comparison for two GObjects.

Compares the memory addresses of the provided objects.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl ParentClassIs for GLArea

type Parent = Widget

impl<OT: ObjectType> PartialEq<OT> for GLArea

fn eq(&self, other: &OT) -> bool

Equality for two GObjects.

Two GObjects are equal if their memory addresses are equal.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<OT: ObjectType> PartialOrd<OT> for GLArea

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

Partial comparison for two GObjects.

Compares the memory addresses of the provided objects.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for GLArea

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for GLArea

impl IsA<Accessible> for GLArea

impl IsA<Buildable> for GLArea

impl IsA<ConstraintTarget> for GLArea

impl IsA<Widget> for GLArea