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## com.trolltech.qt.opengl
Class QGLWidget

    java.lang.Object
      com.trolltech.qt.internal.QSignalEmitterInternal
          com.trolltech.qt.QSignalEmitter
              com.trolltech.qt.QtJambiObject
                  com.trolltech.qt.core.QObject
                      com.trolltech.qt.gui.QWidget
                          com.trolltech.qt.opengl.QGLWidget

All Implemented Interfaces:
  QPaintDeviceInterface, QtJambiInterface

    public class QGLWidget

extends QWidget

The `QGLWidget` class is a widget for rendering OpenGL graphics. `QGLWidget` provides functionality for displaying OpenGL graphics integrated into a Qt application. It is very simple to use. You inherit from it and use the subclass like any other `QWidget`, except that you have the choice between using `QPainter` and standard OpenGL rendering commands.

`QGLWidget` provides three convenient virtual functions that you can reimplement in your subclass to perform the typical OpenGL tasks:

- `paintGL()` - Renders the OpenGL scene. Gets called whenever the widget needs to be updated.
- `resizeGL()` - Sets up the OpenGL viewport, projection, etc. Gets called whenever the the widget has been resized (and also when it is shown for the first time because all newly created widgets get a resize event automatically).
- `initializeGL()` - Sets up the OpenGL rendering context, defines display lists, etc. Gets called once before the first time `resizeGL()` or `paintGL()` is called.

Here is a rough outline of how a `QGLWidget` subclass might look:

        class MyGLDrawer extends QGLWidget
        {
            GL func = null;
            GLContext ctx = null;

            public MyGLDrawer(QWidget parent)
            {
            super(parent);
            }

            protected void initializeGL()
            {
            GLDrawableFactory factory = GLDrawableFactory.getFactory();
            ctx = factory.createExternalGLContext();
            func = ctx.getGL();

            // Set up the rendering context, define display lists etc.:
            // ...
            func.glClearColor(0, 0, 0, 0);
            func.glEnable(GL.GL_DEPTH_TEST);
            // ...
            }

            protected void resizeGL(int w, int h)
            {
            // setup viewport, projection etc.:
            func.glViewport(0, 0, w, h);
            // ...
            func.glFrustum(0.0, 1.0, 0.0, 1.0, 1.0, 2.0);
            // ...
            }

            protected void paintGL()
            {
            // draw the scene:
            // ...
            func.glRotatef(10, 0, 1, 0);
            func.glMaterialf(GL.GL_FRONT, GL.GL_SHININESS, 1);
            func.glBegin(GL.GL_QUADS);
            func.glVertex3f(1, 1, 1);
            func.glVertex3f(1, 2, 1);
            // ...
            func.glEnd();
            // ...
            }

        }

If you need to trigger a repaint from places other than `paintGL()` (a typical example is when using `timers` to animate scenes), you should call the widget's `updateGL()` function.

Your widget's OpenGL rendering context is made current when `paintGL()`, `resizeGL()`, or `initializeGL()` is called. If you need to call the standard OpenGL API functions from other places (e.g. in your widget's constructor or in your own paint functions), you must call `makeCurrent()` first.

`QGLWidget` provides functions for requesting a new display `format` and you can also create widgets with customized rendering `contexts`.

You can also share OpenGL display lists between QGLWidgets (see the documentation of the `QGLWidget` constructors for details).

Note that under Windows, the `QGLContext` belonging to a `QGLWidget` has to be recreated when the `QGLWidget` is reparented. This is necessary due to limitations on the Windows platform. This will most likely cause problems for users that have subclassed and installed their own `QGLContext` on a `QGLWidget`. It is possible to work around this issue by putting the `QGLWidget` inside a dummy widget and then reparenting the dummy widget, instead of the `QGLWidget`. This will side-step the issue altogether, and is what we recommend for users that need this kind of functionality.

## Overlays

The `QGLWidget` creates a GL overlay context in addition to the normal context if overlays are supported by the underlying system.

If you want to use overlays, you specify it in the `format`. (Note: Overlay must be requested in the format passed to the `QGLWidget` constructor.) Your GL widget should also implement some or all of these virtual methods:

- `paintOverlayGL()`
- `resizeOverlayGL()`
- `initializeOverlayGL()`

These methods work in the same way as the normal `paintGL()` etc. functions, except that they will be called when the overlay context is made current. You can explicitly make the overlay context current by using `makeOverlayCurrent()`, and you can access the overlay context directly (e.g. to ask for its transparent color) by calling `overlayContext()`.

On X servers in which the default visual is in an overlay plane, non-GL Qt windows can also be used for overlays.

## Painting Techniques

As described above, subclass `QGLWidget` to render pure 3D content in the following way:

- Reimplement the `QGLWidget::initializeGL()` and `QGLWidget::resizeGL()` to set up the OpenGL state and provide a perspective transformation.
- Reimplement `QGLWidget::paintGL()` to paint the 3D scene, calling only OpenGL functions to draw on the widget.

It is also possible to draw 2D graphics onto a `QGLWidget` subclass, it is necessary to reimplement `QGLWidget::paintEvent()` and do the following:

- Construct a `QPainter` object.
- Initialize it for use on the widget with the `QPainter::begin()` function.
- Draw primitives using `QPainter`'s member functions.
- Call `QPainter::end()` to finish painting.

Overpainting 2D content on top of 3D content takes a little more effort. One approach to doing this is shown in the Overpainting example.

OpenGL is a trademark of Silicon Graphics, Inc. in the United States and other countries.

See also:
  `QGLPixelBuffer`, Hello GL Example, 2D Painting Example, Overpainting Example, and Grabber Example.

Nested Class Summary

Nested classes/interfaces inherited from class com.trolltech.qt.gui.QWidget
`QWidget.RenderFlag, QWidget.RenderFlags`

Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
`QSignalEmitter.AbstractSignal, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9`

Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
`com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal`

Field Summary

Fields inherited from class com.trolltech.qt.gui.QWidget
`customContextMenuRequested`

Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
`currentSender`

Constructor Summary
`QGLWidget()` Constructs an OpenGL widget with a `parent` widget.
`QGLWidget(QGLContext context)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLContext context, QWidget parent)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLContext context, QWidget parent, QGLWidget shareWidget)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLContext context, QWidget parent, QGLWidget shareWidget, Qt.WindowFlags f)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLContext context, QWidget parent, QGLWidget shareWidget, Qt.WindowType[] f)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLFormat format)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLFormat format, QWidget parent)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLFormat format, QWidget parent, QGLWidget shareWidget)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLFormat format, QWidget parent, QGLWidget shareWidget, Qt.WindowFlags f)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QGLFormat format, QWidget parent, QGLWidget shareWidget, Qt.WindowType[] f)` Constructs an OpenGL widget with parent `parent`.
`QGLWidget(QWidget parent)` Constructs an OpenGL widget with a `parent` widget.
`QGLWidget(QWidget parent, QGLWidget shareWidget)` Constructs an OpenGL widget with a `parent` widget.
`QGLWidget(QWidget parent, QGLWidget shareWidget, Qt.WindowFlags f)` Constructs an OpenGL widget with a `parent` widget.
`QGLWidget(QWidget parent, QGLWidget shareWidget, Qt.WindowType[] f)` Constructs an OpenGL widget with a `parent` widget.

Method Summary
`protected boolean` | `autoBufferSwap()` Returns true if the widget is doing automatic GL buffer swapping; otherwise returns false.
`int` | `bindTexture(QImage image)` Calls QGLContext.::bindTexture(`image`, `target`, `format`) on the currently set context.
`int` | `bindTexture(QImage image, int target)` Calls QGLContext.::bindTexture(`image`, `target`, `format`) on the currently set context.
`int` | `bindTexture(QImage image, int target, int format)` Calls QGLContext.::bindTexture(`image`, `target`, `format`) on the currently set context.
`int` | `bindTexture(QPixmap pixmap)` Calls QGLContext.::bindTexture(`pixmap`, `target`, `format`) on the currently set context.
`int` | `bindTexture(QPixmap pixmap, int target)` Calls QGLContext.::bindTexture(`pixmap`, `target`, `format`) on the currently set context.
`int` | `bindTexture(QPixmap pixmap, int target, int format)` Calls QGLContext.::bindTexture(`pixmap`, `target`, `format`) on the currently set context.
`int` | `bindTexture(java.lang.String fileName)` Calls QGLContext.:bindTexture(`fileName`) on the currently set context.
`QGLColormap` | `colormap()` Returns the colormap for this widget.
`QGLContext` | `context()` Returns the context of this widget.
`static QImage` | `convertToGLFormat(QImage img)` Converts the image `img` into the unnamed format expected by OpenGL functions such as glTexImage2D().
`void` | `deleteTexture(int tx_id)` Calls QGLContext.:deleteTexture(`id`) on the currently set context.
`void` | `doneCurrent()` Makes no GL context the current context.
`boolean` | `doubleBuffer()` Returns true if the contained GL rendering context has double buffering; otherwise returns false.
`void` | `drawTexture(QPointF point, int textureId)` Draws the given texture, `textureId`, at the given `point` in OpenGL model space.
`void` | `drawTexture(QPointF point, int textureId, int textureTarget)` Draws the given texture, `textureId`, at the given `point` in OpenGL model space.
`void` | `drawTexture(QRectF target, int textureId)` Draws the given texture, `textureId` to the given target rectangle, `target`, in OpenGL model space.
`void` | `drawTexture(QRectF target, int textureId, int textureTarget)` Draws the given texture, `textureId` to the given target rectangle, `target`, in OpenGL model space.
`QGLFormat` | `format()` Returns the format of the contained GL rendering context.
`protected void` | `glDraw()` Executes the virtual function `paintGL()`.
`protected void` | `glInit()` Initializes OpenGL for this widget's context.
`QImage` | `grabFrameBuffer()` Returns an image of the frame buffer.
`QImage` | `grabFrameBuffer(boolean withAlpha)` Returns an image of the frame buffer.
`protected void` | `initializeGL()` This virtual function is called once before the first call to `paintGL()` or `resizeGL()`, and then once whenever the widget has been assigned a new `QGLContext`.
`protected void` | `initializeOverlayGL()` This virtual function is used in the same manner as `initializeGL()` except that it operates on the widget's overlay context instead of the widget's main context.
`boolean` | `isSharing()` Returns true if this widget's GL context is shared with another GL context, otherwise false is returned.
`boolean` | `isValid()` Returns true if the widget has a valid GL rendering context; otherwise returns false.
`void` | `makeCurrent()` Makes this widget the current widget for OpenGL operations, i.e.
`void` | `makeOverlayCurrent()` Makes the overlay context of this widget current.
`QGLContext` | `overlayContext()` Returns the overlay context of this widget, or 0 if this widget has no overlay.
`protected void` | `paintGL()` This virtual function is called whenever the widget needs to be painted.
`protected void` | `paintOverlayGL()` This virtual function is used in the same manner as `paintGL()` except that it operates on the widget's overlay context instead of the widget's main context.
`void` | `qglClearColor(QColor c)` Convenience function for specifying the clearing color to OpenGL.
`void` | `qglColor(QColor c)` Convenience function for specifying a drawing color to OpenGL.
`QPixmap` | `renderPixmap()` Renders the current scene on a pixmap and returns the pixmap.
`QPixmap` | `renderPixmap(int w)` Renders the current scene on a pixmap and returns the pixmap.
`QPixmap` | `renderPixmap(int w, int h)` Renders the current scene on a pixmap and returns the pixmap.
`QPixmap` | `renderPixmap(int w, int h, boolean useContext)` Renders the current scene on a pixmap and returns the pixmap.
`void` | `renderText(double x, double y, double z, java.lang.String str)` `x`, `y` and `z` are specified in scene or object coordinates relative to the currently set projection and model matrices.
`void` | `renderText(double x, double y, double z, java.lang.String str, QFont fnt)` `x`, `y` and `z` are specified in scene or object coordinates relative to the currently set projection and model matrices.
`void` | `renderText(double x, double y, double z, java.lang.String str, QFont fnt, int listBase)` `x`, `y` and `z` are specified in scene or object coordinates relative to the currently set projection and model matrices.
`void` | `renderText(int x, int y, java.lang.String str)` Renders the string `str` into the GL context of this widget.
`void` | `renderText(int x, int y, java.lang.String str, QFont fnt)` Renders the string `str` into the GL context of this widget.
`void` | `renderText(int x, int y, java.lang.String str, QFont fnt, int listBase)` Renders the string `str` into the GL context of this widget.
`protected void` | `resizeGL(int w, int h)` This virtual function is called whenever the widget has been resized.
`protected void` | `resizeOverlayGL(int w, int h)` This virtual function is used in the same manner as `paintGL()` except that it operates on the widget's overlay context instead of the widget's main context.
`protected void` | `setAutoBufferSwap(boolean on)` If `on` is true automatic GL buffer swapping is switched on; otherwise it is switched off.
`void` | `setColormap(QGLColormap map)` Set the colormap for this widget to `cmap`.
`void` | `swapBuffers()` Swaps the screen contents with an off-screen buffer.
`void` | `updateGL()` Updates the widget by calling `glDraw()`.
`void` | `updateOverlayGL()` Updates the widget's overlay (if any).

Methods inherited from class com.trolltech.qt.gui.QWidget
`acceptDrops, accessibleDescription, accessibleName, actionEvent, actions, activateWindow, addAction, addActions, adjustSize, autoFillBackground, backgroundRole, baseSize, changeEvent, childAt, childAt, childrenRect, childrenRegion, clearFocus, clearMask, close, closeEvent, contentsRect, contextMenuEvent, contextMenuPolicy, cursor, depth, destroy, destroy, destroy, dragEnterEvent, dragLeaveEvent, dragMoveEvent, dropEvent, effectiveWinId, ensurePolished, enterEvent, focusInEvent, focusNextChild, focusNextPrevChild, focusOutEvent, focusPolicy, focusPreviousChild, focusProxy, focusWidget, font, fontInfo, fontMetrics, foregroundRole, frameGeometry, frameSize, geometry, getContentsMargins, grabKeyboard, grabMouse, grabMouse, grabShortcut, grabShortcut, hasFocus, hasMouseTracking, height, heightForWidth, heightMM, hide, hideEvent, inputContext, inputMethodEvent, inputMethodQuery, insertAction, insertActions, isActiveWindow, isAncestorOf, isEnabled, isEnabledTo, isFullScreen, isHidden, isMaximized, isMinimized, isModal, isVisible, isVisibleTo, isWindow, isWindowModified, keyboardGrabber, keyPressEvent, keyReleaseEvent, languageChange, layout, layoutDirection, leaveEvent, locale, logicalDpiX, logicalDpiY, lower, mapFrom, mapFromGlobal, mapFromParent, mapTo, mapToGlobal, mapToParent, mask, maximumHeight, maximumSize, maximumWidth, metric, minimumHeight, minimumSize, minimumSizeHint, minimumWidth, mouseDoubleClickEvent, mouseGrabber, mouseMoveEvent, mousePressEvent, mouseReleaseEvent, move, move, moveEvent, nativeParentWidget, nextInFocusChain, normalGeometry, numColors, overrideWindowFlags, overrideWindowFlags, paintEngine, paintEvent, paintingActive, palette, parentWidget, physicalDpiX, physicalDpiY, pos, raise, rect, releaseKeyboard, releaseMouse, releaseShortcut, removeAction, render, render, render, render, render, render, render, render, render, repaint, repaint, repaint, repaint, resetInputContext, resize, resize, resizeEvent, restoreGeometry, saveGeometry, scroll, scroll, setAcceptDrops, setAccessibleDescription, setAccessibleName, setAttribute, setAttribute, setAutoFillBackground, setBackgroundRole, setBaseSize, setBaseSize, setContentsMargins, setContentsMargins, setContextMenuPolicy, setCursor, setDisabled, setEnabled, setFixedHeight, setFixedSize, setFixedSize, setFixedWidth, setFocus, setFocus, setFocusPolicy, setFocusProxy, setFont, setForegroundRole, setGeometry, setGeometry, setHidden, setInputContext, setLayout, setLayoutDirection, setLocale, setMask, setMask, setMaximumHeight, setMaximumSize, setMaximumSize, setMaximumWidth, setMinimumHeight, setMinimumSize, setMinimumSize, setMinimumWidth, setMouseTracking, setPalette, setParent, setParent, setParent, setShortcutAutoRepeat, setShortcutAutoRepeat, setShortcutEnabled, setShortcutEnabled, setSizeIncrement, setSizeIncrement, setSizePolicy, setSizePolicy, setStatusTip, setStyle, setStyleSheet, setTabOrder, setToolTip, setUpdatesEnabled, setVisible, setWhatsThis, setWindowFilePath, setWindowFlags, setWindowFlags, setWindowIcon, setWindowIconText, setWindowModality, setWindowModified, setWindowOpacity, setWindowRole, setWindowState, setWindowState, setWindowTitle, show, showEvent, showFullScreen, showMaximized, showMinimized, showNormal, size, sizeHint, sizeIncrement, sizePolicy, stackUnder, statusTip, style, styleSheet, tabletEvent, testAttribute, toolTip, underMouse, unsetCursor, unsetLayoutDirection, unsetLocale, update, update, update, update, updateGeometry, updateMicroFocus, updatesEnabled, visibleRegion, whatsThis, wheelEvent, width, widthMM, window, windowFilePath, windowFlags, windowIcon, windowIconText, windowModality, windowOpacity, windowRole, windowState, windowTitle, windowType, winId, x, y`

Methods inherited from class com.trolltech.qt.core.QObject
`childEvent, children, connectSlotsByName, customEvent, disposeLater, dumpObjectInfo, dumpObjectTree, dynamicPropertyNames, event, eventFilter, findChild, findChild, findChild, findChildren, findChildren, findChildren, findChildren, indexOfProperty, installEventFilter, isWidgetType, killTimer, moveToThread, objectName, parent, properties, property, removeEventFilter, setObjectName, setParent, setProperty, startTimer, timerEvent, toString, userProperty`

Methods inherited from class com.trolltech.qt.QtJambiObject
`dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr`

Methods inherited from class com.trolltech.qt.QSignalEmitter
`blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread`

Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
`__qt_signalInitialization`

Methods inherited from class java.lang.Object
`clone, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Methods inherited from interface com.trolltech.qt.QtJambiInterface
`disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership`

Constructor Detail

### QGLWidget

    public QGLWidget(QGLContext context,
                     QWidget parent,
                     QGLWidget shareWidget,
                     Qt.WindowType[] f)

  Constructs an OpenGL widget with parent `parent`.

  The `context` argument is a pointer to the `QGLContext` that you wish to be bound to this widget. This allows you to pass in your own `QGLContext` sub-classes.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QGLContext context,
                     QWidget parent,
                     QGLWidget shareWidget)

  Constructs an OpenGL widget with parent `parent`.

  The `context` argument is a pointer to the `QGLContext` that you wish to be bound to this widget. This allows you to pass in your own `QGLContext` sub-classes.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QGLContext context,
                     QWidget parent)

  Constructs an OpenGL widget with parent `parent`.

  The `context` argument is a pointer to the `QGLContext` that you wish to be bound to this widget. This allows you to pass in your own `QGLContext` sub-classes.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QGLContext context)

  Constructs an OpenGL widget with parent `parent`.

  The `context` argument is a pointer to the `QGLContext` that you wish to be bound to this widget. This allows you to pass in your own `QGLContext` sub-classes.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QGLContext context,
                     QWidget parent,
                     QGLWidget shareWidget,
                     Qt.WindowFlags f)

  Constructs an OpenGL widget with parent `parent`.

  The `context` argument is a pointer to the `QGLContext` that you wish to be bound to this widget. This allows you to pass in your own `QGLContext` sub-classes.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QWidget parent,
                     QGLWidget shareWidget,
                     Qt.WindowType[] f)

  Constructs an OpenGL widget with a `parent` widget.

  The `default format` is used. The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and Textures Example.

### QGLWidget

    public QGLWidget(QWidget parent,
                     QGLWidget shareWidget)

  Constructs an OpenGL widget with a `parent` widget.

  The `default format` is used. The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and Textures Example.

### QGLWidget

    public QGLWidget(QWidget parent)

  Constructs an OpenGL widget with a `parent` widget.

  The `default format` is used. The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and Textures Example.

### QGLWidget

    public QGLWidget()

  Constructs an OpenGL widget with a `parent` widget.

  The `default format` is used. The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and Textures Example.

### QGLWidget

    public QGLWidget(QWidget parent,
                     QGLWidget shareWidget,
                     Qt.WindowFlags f)

  Constructs an OpenGL widget with a `parent` widget.

  The `default format` is used. The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and Textures Example.

### QGLWidget

    public QGLWidget(QGLFormat format,
                     QWidget parent,
                     QGLWidget shareWidget,
                     Qt.WindowType[] f)

  Constructs an OpenGL widget with parent `parent`.

  The `format` argument specifies the desired `rendering options`. If the underlying OpenGL/Window system cannot satisfy all the features requested in `format`, the nearest subset of features will be used. After creation, the `format()` method will return the actual format obtained.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QGLFormat format,
                     QWidget parent,
                     QGLWidget shareWidget)

  Constructs an OpenGL widget with parent `parent`.

  The `format` argument specifies the desired `rendering options`. If the underlying OpenGL/Window system cannot satisfy all the features requested in `format`, the nearest subset of features will be used. After creation, the `format()` method will return the actual format obtained.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QGLFormat format,
                     QWidget parent)

  Constructs an OpenGL widget with parent `parent`.

  The `format` argument specifies the desired `rendering options`. If the underlying OpenGL/Window system cannot satisfy all the features requested in `format`, the nearest subset of features will be used. After creation, the `format()` method will return the actual format obtained.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QGLFormat format)

  Constructs an OpenGL widget with parent `parent`.

  The `format` argument specifies the desired `rendering options`. If the underlying OpenGL/Window system cannot satisfy all the features requested in `format`, the nearest subset of features will be used. After creation, the `format()` method will return the actual format obtained.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

### QGLWidget

    public QGLWidget(QGLFormat format,
                     QWidget parent,
                     QGLWidget shareWidget,
                     Qt.WindowFlags f)

  Constructs an OpenGL widget with parent `parent`.

  The `format` argument specifies the desired `rendering options`. If the underlying OpenGL/Window system cannot satisfy all the features requested in `format`, the nearest subset of features will be used. After creation, the `format()` method will return the actual format obtained.

  The widget will be `invalid` if the system has no `OpenGL support`.

  The `parent` and widget flag, `f`, arguments are passed to the `QWidget` constructor.

  If `shareWidget` is a valid `QGLWidget`, this widget will share OpenGL display lists and texture objects with `shareWidget`. But if `shareWidget` and this widget have different `formats`, sharing might not be possible. You can check whether sharing is in effect by calling `isSharing()`.

  The initialization of OpenGL rendering state, etc. should be done by overriding the `initializeGL()` function, rather than in the constructor of your `QGLWidget` subclass.

See also:
  `QGLFormat::defaultFormat()`, and `isValid()`.

Method Detail

### autoBufferSwap

    protected final boolean autoBufferSwap()

  Returns true if the widget is doing automatic GL buffer swapping; otherwise returns false.

See also:
  `setAutoBufferSwap()`.

### bindTexture

    public final int bindTexture(QImage image,
                                 int target)

  Calls QGLContext.::bindTexture(`image`, `target`, `format`) on the currently set context.

See also:
  `deleteTexture()`.

### bindTexture

    public final int bindTexture(QImage image)

  Calls QGLContext.::bindTexture(`image`, `target`, `format`) on the currently set context.

See also:
  `deleteTexture()`.

### bindTexture

    public final int bindTexture(QImage image,
                                 int target,
                                 int format)

  Calls QGLContext.::bindTexture(`image`, `target`, `format`) on the currently set context.

See also:
  `deleteTexture()`.

### bindTexture

    public final int bindTexture(QPixmap pixmap,
                                 int target)

  Calls QGLContext.::bindTexture(`pixmap`, `target`, `format`) on the currently set context.

See also:
  `deleteTexture()`.

### bindTexture

    public final int bindTexture(QPixmap pixmap)

  Calls QGLContext.::bindTexture(`pixmap`, `target`, `format`) on the currently set context.

See also:
  `deleteTexture()`.

### bindTexture

    public final int bindTexture(QPixmap pixmap,
                                 int target,
                                 int format)

  Calls QGLContext.::bindTexture(`pixmap`, `target`, `format`) on the currently set context.

See also:
  `deleteTexture()`.

### bindTexture

    public final int bindTexture(java.lang.String fileName)

  Calls QGLContext.:bindTexture(`fileName`) on the currently set context.

See also:
  `deleteTexture()`.

### colormap

    public final QGLColormap colormap()

  Returns the colormap for this widget.

  Usually it is only top-level widgets that can have different colormaps installed. Asking for the colormap of a child widget will return the colormap for the child's top-level widget.

  If no colormap has been set for this widget, the `QColormap` returned will be empty.

See also:
  `setColormap()`.

### context

    public final QGLContext context()

  Returns the context of this widget.

  It is possible that the context is not valid (see `isValid()`), for example, if the underlying hardware does not support the format attributes that were requested.

### deleteTexture

    public final void deleteTexture(int tx_id)

  Calls QGLContext.:deleteTexture(`id`) on the currently set context.

See also:
  `bindTexture()`.

### doneCurrent

    public final void doneCurrent()

  Makes no GL context the current context. Normally, you do not need to call this function; `QGLContext` calls it as necessary. However, it may be useful in multithreaded environments.

### doubleBuffer

    public final boolean doubleBuffer()

  Returns true if the contained GL rendering context has double buffering; otherwise returns false.

See also:
  `QGLFormat::doubleBuffer()`.

### drawTexture

    public final void drawTexture(QPointF point,
                                  int textureId)

  Draws the given texture, `textureId`, at the given `point` in OpenGL model space. The `textureTarget` should be a 2D texture target.

  Equivalent to the corresponding `QGLContext::drawTexture()`.

### drawTexture

    public final void drawTexture(QPointF point,
                                  int textureId,
                                  int textureTarget)

  Draws the given texture, `textureId`, at the given `point` in OpenGL model space. The `textureTarget` should be a 2D texture target.

  Equivalent to the corresponding `QGLContext::drawTexture()`.

### drawTexture

    public final void drawTexture(QRectF target,
                                  int textureId)

  Draws the given texture, `textureId` to the given target rectangle, `target`, in OpenGL model space. The `textureTarget` should be a 2D texture target.

  Equivalent to the corresponding `QGLContext::drawTexture()`.

### drawTexture

    public final void drawTexture(QRectF target,
                                  int textureId,
                                  int textureTarget)

  Draws the given texture, `textureId` to the given target rectangle, `target`, in OpenGL model space. The `textureTarget` should be a 2D texture target.

  Equivalent to the corresponding `QGLContext::drawTexture()`.

### format

    public final QGLFormat format()

  Returns the format of the contained GL rendering context.

See also:
  setFormat().

### grabFrameBuffer

    public final QImage grabFrameBuffer()

  Returns an image of the frame buffer. If `withAlpha` is true the alpha channel is included.

  Depending on your hardware, you can explicitly select which color buffer to grab with a glReadBuffer() call before calling this function.

### grabFrameBuffer

    public final QImage grabFrameBuffer(boolean withAlpha)

  Returns an image of the frame buffer. If `withAlpha` is true the alpha channel is included.

  Depending on your hardware, you can explicitly select which color buffer to grab with a glReadBuffer() call before calling this function.

### isSharing

    public final boolean isSharing()

  Returns true if this widget's GL context is shared with another GL context, otherwise false is returned. Context sharing might not be possible if the QGLWidgets use different formats.

See also:
  `format()`.

### isValid

    public final boolean isValid()

  Returns true if the widget has a valid GL rendering context; otherwise returns false. A widget will be invalid if the system has no `OpenGL support`.

### makeCurrent

    public final void makeCurrent()

  Makes this widget the current widget for OpenGL operations, i.e. makes the widget's rendering context the current OpenGL rendering context.

### makeOverlayCurrent

    public final void makeOverlayCurrent()

  Makes the overlay context of this widget current. Use this if you need to issue OpenGL commands to the overlay context outside of `initializeOverlayGL()`, `resizeOverlayGL()`, and `paintOverlayGL()`.

  Does nothing if this widget has no overlay.

See also:
  `makeCurrent()`.

### overlayContext

    public final QGLContext overlayContext()

  Returns the overlay context of this widget, or 0 if this widget has no overlay.

See also:
  `context()`.

### qglClearColor

    public final void qglClearColor(QColor c)

  Convenience function for specifying the clearing color to OpenGL. Calls glClearColor (in RGBA mode) or glClearIndex (in color-index mode) with the color `c`. Applies to this widgets GL context.

See also:
  `qglColor()`, `QGLContext::currentContext()`, and `QColor`.

### qglColor

    public final void qglColor(QColor c)

  Convenience function for specifying a drawing color to OpenGL. Calls glColor4 (in RGBA mode) or glIndex (in color-index mode) with the color `c`. Applies to this widgets GL context.

See also:
  `qglClearColor()`, `QGLContext::currentContext()`, and `QColor`.

### renderPixmap

    public final QPixmap renderPixmap(int w,
                                      int h)

  Renders the current scene on a pixmap and returns the pixmap.

  You can use this method on both visible and invisible QGLWidgets.

  This method will create a pixmap and a temporary `QGLContext` to render on the pixmap. It will then call `initializeGL()`, `resizeGL()`, and `paintGL()` on this context. Finally, the widget's original GL context is restored.

  The size of the pixmap will be `w` pixels wide and `h` pixels high unless one of these parameters is 0 (the default), in which case the pixmap will have the same size as the widget.

  If `useContext` is true, this method will try to be more efficient by using the existing GL context to render the pixmap. The default is false. Only use true if you understand the risks. Note that under Windows a temporary context has to be created and usage of the useContext parameter is not supported.

  Overlays are not rendered onto the pixmap.

  If the GL rendering context and the desktop have different bit depths, the result will most likely look surprising.

  Note that the creation of display lists, modifications of the view frustum etc. should be done from within `initializeGL()`. If this is not done, the temporary `QGLContext` will not be initialized properly, and the rendered pixmap may be incomplete/corrupted.

### renderPixmap

    public final QPixmap renderPixmap(int w)

  Renders the current scene on a pixmap and returns the pixmap.

  You can use this method on both visible and invisible QGLWidgets.

  This method will create a pixmap and a temporary `QGLContext` to render on the pixmap. It will then call `initializeGL()`, `resizeGL()`, and `paintGL()` on this context. Finally, the widget's original GL context is restored.

  The size of the pixmap will be `w` pixels wide and `h` pixels high unless one of these parameters is 0 (the default), in which case the pixmap will have the same size as the widget.

  If `useContext` is true, this method will try to be more efficient by using the existing GL context to render the pixmap. The default is false. Only use true if you understand the risks. Note that under Windows a temporary context has to be created and usage of the useContext parameter is not supported.

  Overlays are not rendered onto the pixmap.

  If the GL rendering context and the desktop have different bit depths, the result will most likely look surprising.

  Note that the creation of display lists, modifications of the view frustum etc. should be done from within `initializeGL()`. If this is not done, the temporary `QGLContext` will not be initialized properly, and the rendered pixmap may be incomplete/corrupted.

### renderPixmap

    public final QPixmap renderPixmap()

  Renders the current scene on a pixmap and returns the pixmap.

  You can use this method on both visible and invisible QGLWidgets.

  This method will create a pixmap and a temporary `QGLContext` to render on the pixmap. It will then call `initializeGL()`, `resizeGL()`, and `paintGL()` on this context. Finally, the widget's original GL context is restored.

  The size of the pixmap will be `w` pixels wide and `h` pixels high unless one of these parameters is 0 (the default), in which case the pixmap will have the same size as the widget.

  If `useContext` is true, this method will try to be more efficient by using the existing GL context to render the pixmap. The default is false. Only use true if you understand the risks. Note that under Windows a temporary context has to be created and usage of the useContext parameter is not supported.

  Overlays are not rendered onto the pixmap.

  If the GL rendering context and the desktop have different bit depths, the result will most likely look surprising.

  Note that the creation of display lists, modifications of the view frustum etc. should be done from within `initializeGL()`. If this is not done, the temporary `QGLContext` will not be initialized properly, and the rendered pixmap may be incomplete/corrupted.

### renderPixmap

    public final QPixmap renderPixmap(int w,
                                      int h,
                                      boolean useContext)

  Renders the current scene on a pixmap and returns the pixmap.

  You can use this method on both visible and invisible QGLWidgets.

  This method will create a pixmap and a temporary `QGLContext` to render on the pixmap. It will then call `initializeGL()`, `resizeGL()`, and `paintGL()` on this context. Finally, the widget's original GL context is restored.

  The size of the pixmap will be `w` pixels wide and `h` pixels high unless one of these parameters is 0 (the default), in which case the pixmap will have the same size as the widget.

  If `useContext` is true, this method will try to be more efficient by using the existing GL context to render the pixmap. The default is false. Only use true if you understand the risks. Note that under Windows a temporary context has to be created and usage of the useContext parameter is not supported.

  Overlays are not rendered onto the pixmap.

  If the GL rendering context and the desktop have different bit depths, the result will most likely look surprising.

  Note that the creation of display lists, modifications of the view frustum etc. should be done from within `initializeGL()`. If this is not done, the temporary `QGLContext` will not be initialized properly, and the rendered pixmap may be incomplete/corrupted.

### renderText

    public final void renderText(double x,
                                 double y,
                                 double z,
                                 java.lang.String str,
                                 QFont fnt)

  `x`, `y` and `z` are specified in scene or object coordinates relative to the currently set projection and model matrices. This can be useful if you want to annotate models with text labels and have the labels move with the model as it is rotated etc.

### renderText

    public final void renderText(double x,
                                 double y,
                                 double z,
                                 java.lang.String str)

  `x`, `y` and `z` are specified in scene or object coordinates relative to the currently set projection and model matrices. This can be useful if you want to annotate models with text labels and have the labels move with the model as it is rotated etc.

### renderText

    public final void renderText(double x,
                                 double y,
                                 double z,
                                 java.lang.String str,
                                 QFont fnt,
                                 int listBase)

  `x`, `y` and `z` are specified in scene or object coordinates relative to the currently set projection and model matrices. This can be useful if you want to annotate models with text labels and have the labels move with the model as it is rotated etc.

### renderText

    public final void renderText(int x,
                                 int y,
                                 java.lang.String str,
                                 QFont fnt)

  Renders the string `str` into the GL context of this widget.

  `x` and `y` are specified in window coordinates, with the origin in the upper left-hand corner of the window. If `font` is not specified, the currently set application font will be used to render the string. To change the color of the rendered text you can use the glColor() call (or the `qglColor()` convenience function), just before the `renderText()` call.

  The `listBase` parameter is obsolete and will be removed in a future version of Qt.

  Note: This function clears the stencil buffer.

### renderText

    public final void renderText(int x,
                                 int y,
                                 java.lang.String str)

  Renders the string `str` into the GL context of this widget.

  `x` and `y` are specified in window coordinates, with the origin in the upper left-hand corner of the window. If `font` is not specified, the currently set application font will be used to render the string. To change the color of the rendered text you can use the glColor() call (or the `qglColor()` convenience function), just before the `renderText()` call.

  The `listBase` parameter is obsolete and will be removed in a future version of Qt.

  Note: This function clears the stencil buffer.

### renderText

    public final void renderText(int x,
                                 int y,
                                 java.lang.String str,
                                 QFont fnt,
                                 int listBase)

  Renders the string `str` into the GL context of this widget.

  `x` and `y` are specified in window coordinates, with the origin in the upper left-hand corner of the window. If `font` is not specified, the currently set application font will be used to render the string. To change the color of the rendered text you can use the glColor() call (or the `qglColor()` convenience function), just before the `renderText()` call.

  The `listBase` parameter is obsolete and will be removed in a future version of Qt.

  Note: This function clears the stencil buffer.

### setAutoBufferSwap

    protected final void setAutoBufferSwap(boolean on)

  If `on` is true automatic GL buffer swapping is switched on; otherwise it is switched off.

  If `on` is true and the widget is using a double-buffered format, the background and foreground GL buffers will automatically be swapped after each `paintGL()` call.

  The buffer auto-swapping is on by default.

See also:
  `autoBufferSwap()`, `doubleBuffer()`, and `swapBuffers()`.

### setColormap

    public final void setColormap(QGLColormap map)

  Set the colormap for this widget to `cmap`. Usually it is only top-level widgets that can have colormaps installed.

See also:
  `colormap()`.

### swapBuffers

    public final void swapBuffers()

  Swaps the screen contents with an off-screen buffer. This only works if the widget's format specifies double buffer mode.

  Normally, there is no need to explicitly call this function because it is done automatically after each widget repaint, i.e. each time after `paintGL()` has been executed.

See also:
  `doubleBuffer()`, `setAutoBufferSwap()`, and `QGLFormat::setDoubleBuffer()`.

### glDraw

    protected void glDraw()

  Executes the virtual function `paintGL()`.

  The widget's rendering context will become the current context and `initializeGL()` will be called if it hasn't already been called.

### glInit

    protected void glInit()

  Initializes OpenGL for this widget's context. Calls the virtual function `initializeGL()`.

### initializeGL

    protected void initializeGL()

  This virtual function is called once before the first call to `paintGL()` or `resizeGL()`, and then once whenever the widget has been assigned a new `QGLContext`. Reimplement it in a subclass.

  This function should set up any required OpenGL context rendering flags, defining display lists, etc.

  There is no need to call `makeCurrent()` because this has already been done when this function is called.

### initializeOverlayGL

    protected void initializeOverlayGL()

  This virtual function is used in the same manner as `initializeGL()` except that it operates on the widget's overlay context instead of the widget's main context. This means that `initializeOverlayGL()` is called once before the first call to `paintOverlayGL()` or `resizeOverlayGL()`. Reimplement it in a subclass.

  This function should set up any required OpenGL context rendering flags, defining display lists, etc. for the overlay context.

  There is no need to call `makeOverlayCurrent()` because this has already been done when this function is called.

### paintGL

    protected void paintGL()

  This virtual function is called whenever the widget needs to be painted. Reimplement it in a subclass.

  There is no need to call `makeCurrent()` because this has already been done when this function is called.

### paintOverlayGL

    protected void paintOverlayGL()

  This virtual function is used in the same manner as `paintGL()` except that it operates on the widget's overlay context instead of the widget's main context. This means that `paintOverlayGL()` is called whenever the widget's overlay needs to be painted. Reimplement it in a subclass.

  There is no need to call `makeOverlayCurrent()` because this has already been done when this function is called.

### resizeGL

    protected void resizeGL(int w,
                            int h)

  This virtual function is called whenever the widget has been resized. The new size is passed in `width` and `height`. Reimplement it in a subclass.

  There is no need to call `makeCurrent()` because this has already been done when this function is called.

### resizeOverlayGL

    protected void resizeOverlayGL(int w,
                                   int h)

  This virtual function is used in the same manner as `paintGL()` except that it operates on the widget's overlay context instead of the widget's main context. This means that `resizeOverlayGL()` is called whenever the widget has been resized. The new size is passed in `width` and `height`. Reimplement it in a subclass.

  There is no need to call `makeOverlayCurrent()` because this has already been done when this function is called.

### updateGL

    public void updateGL()

  Updates the widget by calling `glDraw()`.

### updateOverlayGL

    public void updateOverlayGL()

  Updates the widget's overlay (if any). Will cause the virtual function `paintOverlayGL()` to be executed.

  The widget's rendering context will become the current context and `initializeGL()` will be called if it hasn't already been called.

### convertToGLFormat

    public static QImage convertToGLFormat(QImage img)

  Converts the image `img` into the unnamed format expected by OpenGL functions such as glTexImage2D(). The returned image is not usable as a `QImage`, but `QImage::width()`, `QImage::height()` and `QImage::bits()` may be used with OpenGL. The GL format used is `GL_RGBA`.

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