#[repr(transparent)]
pub struct GLArea { /* private fields */ }
Expand description

GLArea is a widget that allows drawing with OpenGL.

GLArea sets up its own gdk::GLContext for the window it creates, 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.

In order to draw, you have to connect to the signal::GLArea::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 signal::GLArea::render signal:

⚠️ The following code is in C ⚠️

  // 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);

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

⚠️ 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;
  }

If you need to initialize OpenGL state, e.g. buffer objects or shaders, you should use the signal::Widget::realize signal; you can use the signal::Widget::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 signal::GLArea::create-context signal.

Implements

GLAreaExt, WidgetExt, glib::ObjectExt, BuildableExt, WidgetExtManual, BuildableExtManual

Implementations

Creates a new GLArea widget.

Returns

a new GLArea

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

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Returns the “default value” for a type. Read more
Formats the value using the given formatter. Read more
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Restrict a value to a certain interval. Read more
This method tests for self and other values to be equal, and is used by ==. Read more
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
This method returns an ordering between self and other values if one exists. Read more
This method tests less than (for self and other) and is used by the < operator. Read more
This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
This method tests greater than (for self and other) and is used by the > operator. Read more
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

Blanket Implementations

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
Upcasts an object to a superclass or interface T. Read more
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Tries to cast to reference to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more
Casts to T unconditionally. Read more
Casts to &T unconditionally. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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Sets the property property_name of the object to value value. Read more
Sets the property property_name of the object to value value. Read more
Sets multiple properties of the object at once. Read more
Sets multiple properties of the object at once. Read more
Gets the property property_name of the object and cast it to the type V. Read more
Gets the property property_name of the object. Read more
Check if the object has a property property_name of the given type_. Read more
Get the type of the property property_name of this object. Read more
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Return all ParamSpec of the properties of this object.
Freeze all property notifications until the return guard object is dropped. Read more
Set arbitrary data on this object with the given key. Read more
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Set arbitrary data on this object with the given key. Read more
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Block a given signal handler. Read more
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Stop emission of the currently emitted signal.
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Connect to the signal signal_name on this object. Read more
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Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect to the signal signal_name on this object. Read more
Connect to the signal signal_id on this object. Read more
Connect a closure to the signal signal_name on this object. Read more
Connect a closure to the signal signal_id on this object. Read more
Limits the lifetime of closure to the lifetime of the object. When the object’s reference count drops to zero, the closure will be invalidated. An invalidated closure will ignore any calls to invoke_with_values, or invoke when using Rust closures. Read more
Emit signal by signal id. Read more
Same as Self::emit but takes Value for the arguments.
Emit signal by its name. Read more
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Emit signal by its name with details. Read more
Emit signal by its name with details. Read more
Emit signal by signal id with details. Read more
Emit signal by signal id with details. Read more
Disconnect a previously connected signal handler.
Connect to the notify signal of the object. Read more
Connect to the notify signal of the object. Read more
Connect to the notify signal of the object. Read more
Notify that the given property has changed its value. Read more
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Downgrade this object to a weak reference.
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