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## com.trolltech.qt.opengl
Class QGLContext

    java.lang.Object
      com.trolltech.qt.QSignalEmitter
          com.trolltech.qt.QtJambiObject
              com.trolltech.qt.opengl.QGLContext

All Implemented Interfaces:
  QtJambiInterface

    public class QGLContext

extends QtJambiObject

The `QGLContext` class encapsulates an OpenGL rendering context.

An OpenGL rendering context is a complete set of OpenGL state variables. The rendering context's format is set in the constructor, but it can also be set later with `setFormat`. The format options that are actually set are returned by `format`; the options you asked for are returned by `requestedFormat`. Note that after a `QGLContext` object has been constructed, the actual OpenGL context must be created by explicitly calling the create() function. The `makeCurrent` function makes this context the current rendering context. You can make no context current using `doneCurrent`. The `reset` function will reset the context and make it invalid.

You can examine properties of the context with, e.g. `isValid`, `isSharing`, `initialized`, `windowCreated` and `overlayTransparentColor`.

If you're using double buffering you can swap the screen contents with the off-screen buffer using `swapBuffers`.

Please note that `QGLContext` is not thread safe.

Nested Class Summary

Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
`QSignalEmitter.AbstractSignal, QSignalEmitter.Signal0, QSignalEmitter.Signal1<A>, QSignalEmitter.Signal2<A,B>, QSignalEmitter.Signal3<A,B,C>, QSignalEmitter.Signal4<A,B,C,D>, QSignalEmitter.Signal5<A,B,C,D,E>, QSignalEmitter.Signal6<A,B,C,D,E,F>, QSignalEmitter.Signal7<A,B,C,D,E,F,G>, QSignalEmitter.Signal8<A,B,C,D,E,F,G,H>, QSignalEmitter.Signal9<A,B,C,D,E,F,G,H,I>`

Constructor Summary
`QGLContext(QGLFormat format)` Constructs an OpenGL context with the given `format` which specifies several display options for the context.
`QGLContext(QGLFormat format, QPaintDeviceInterface device)` This method is obsolete.

Method Summary
`int` | `bindTexture(QImage image)` Equivalent to `bindTexture`(`image`, GL_TEXTURE_2D, GL_RGBA).
`int` | `bindTexture(QImage image, int target)` Equivalent to `bindTexture`(`image`, `target`, GL_RGBA).
`int` | `bindTexture(QImage image, int target, int format)` Generates and binds a 2D GL texture to the current context, based on `image`.
`int` | `bindTexture(QPixmap pixmap)` Equivalent to `bindTexture`(`pixmap`, GL_TEXTURE_2D, GL_RGBA).
`int` | `bindTexture(QPixmap pixmap, int target)` Equivalent to `bindTexture`(`pixmap`, `target`, GL_RGBA).
`int` | `bindTexture(QPixmap pixmap, int target, int format)` Generates and binds a 2D GL texture based on `pixmap`.
`int` | `bindTexture(java.lang.String fileName)` Reads the DirectDrawSurface (DDS) compressed file `fileName` and generates a 2D GL texture from it.
`protected boolean` | `chooseContext()` Equivalent to `chooseContext`(0).
`protected boolean` | `chooseContext(QGLContext shareContext)` This semi-internal function is called by `create`.
`protected int` | `colorIndex(QColor c)`
`boolean` | `create()` Equivalent to create(0).
`boolean` | `create(QGLContext shareContext)` Creates the GL context.
`static QGLContext` | `currentContext()` Returns the current context, i.e. the context to which any OpenGL commands will currently be directed.
`void` | `deleteTexture(int tx_id)` Removes the texture identified by `tx_id` from the texture cache.
`QPaintDeviceInterface` | `device()` Returns the paint device set for this context.
`protected boolean` | `deviceIsPixmap()` Returns true if the paint device of this context is a pixmap; otherwise returns false.
`void` | `doneCurrent()` Makes no GL context the current context.
`QGLFormat` | `format()` Returns the frame buffer format that was obtained (this may be a subset of what was requested).
`static QGLContext` | `fromNativePointer(QNativePointer nativePointer)` This function returns the QGLContext instance pointed to by nativePointer
`protected boolean` | `initialized()` Returns true if this context has been initialized, i.e. if QGLWidget::initializeGL() has been performed on it; otherwise returns false.
`boolean` | `isSharing()` Returns true if this context is sharing its GL context with another `QGLContext`, otherwise false is returned.
`boolean` | `isValid()` Returns true if a GL rendering context has been successfully created; otherwise returns false.
`void` | `makeCurrent()` Makes this context the current OpenGL rendering context.
`QColor` | `overlayTransparentColor()` If this context is a valid context in an overlay plane, returns the plane's transparent color.
`QGLFormat` | `requestedFormat()` Returns the frame buffer format that was originally requested in the constructor or `setFormat`.
`void` | `reset()` Resets the context and makes it invalid.
`void` | `setFormat(QGLFormat format)` Sets a `format` for this context.
`protected void` | `setInitialized(boolean on)` If `on` is true the context has been initialized, i.e. QGLContext::setInitialized() has been called on it.
`static void` | `setTextureCacheLimit(int size)` This function sets the limit for the texture cache to `size`, expressed in kilobytes.
`protected void` | `setValid(boolean valid)`
`protected void` | `setWindowCreated(boolean on)` If `on` is true the context has had a window created for it.
`void` | `swapBuffers()` Swaps the screen contents with an off-screen buffer.
`static int` | `textureCacheLimit()` Returns the current texture cache limit in kilobytes.
`protected boolean` | `windowCreated()` Returns true if a window has been created for this context; otherwise returns false.

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

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

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

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

Constructor Detail

### QGLContext

    public QGLContext(QGLFormat format,
                      QPaintDeviceInterface device)

  This method is obsolete. It is provided to keep old source code working. We strongly advise against using it in new code.

  Constructs an OpenGL context for the given paint `device`, which can be a widget or a pixmap. The `format` specifies several display options for the context.

  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.

  Note that after a `QGLContext` object has been constructed, `create` must be called explicitly to create the actual OpenGL context. The context will be invalid if it was not possible to obtain a GL context at all.

### QGLContext

    public QGLContext(QGLFormat format)

  Constructs an OpenGL context with the given `format` which specifies several display options for the context.

  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.

  Note that after a `QGLContext` object has been constructed, `create` must be called explicitly to create the actual OpenGL context. The context will be invalid if it was not possible to obtain a GL context at all.

  See Also:
    `format`, `isValid`

Method Detail

### bindTexture

    public final int bindTexture(QImage image,
                                 int target)

  Equivalent to `bindTexture`(`image`, `target`, GL_RGBA).

### bindTexture

    public final int bindTexture(QImage image)

  Equivalent to `bindTexture`(`image`, GL_TEXTURE_2D, GL_RGBA).

### bindTexture

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

  Generates and binds a 2D GL texture to the current context, based on `image`. The generated texture id is returned and can be used in later `glBindTexture()` calls.

  The `target` parameter specifies the texture target. The default target is `GL_TEXTURE_2D`.

  The `format` parameter sets the internal format for the texture. The default format is `GL_RGBA8`.

  If the GL implementation supports the `GL_SGIS_generate_mipmap` extension, mipmaps will be automatically generated for the texture. Mipmap generation is only supported for the `GL_TEXTURE_2D` target.

  The texture that is generated is cached, so multiple calls to `bindTexture` with the same `QImage` will return the same texture id.

  See Also:
    `deleteTexture`

### bindTexture

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

  Reads the DirectDrawSurface (DDS) compressed file `fileName` and generates a 2D GL texture from it.

  Only the DXT1, DXT3 and DXT5 DDS formats are supported.

  Note that this will only work if the implementation supports the `GL_ARB_texture_compression` and `GL_EXT_texture_compression_s3tc` extensions.

  See Also:
    `deleteTexture`

### bindTexture

    public final int bindTexture(QPixmap pixmap,
                                 int target)

  Equivalent to `bindTexture`(`pixmap`, `target`, GL_RGBA).

### bindTexture

    public final int bindTexture(QPixmap pixmap)

  Equivalent to `bindTexture`(`pixmap`, GL_TEXTURE_2D, GL_RGBA).

### bindTexture

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

  Generates and binds a 2D GL texture based on `pixmap`.

### colorIndex

    protected final int colorIndex(QColor c)

### deleteTexture

    public final void deleteTexture(int tx_id)

  Removes the texture identified by `tx_id` from the texture cache. If the context is not shared by any other `QGLContext`, glDeleteTextures() will be called to delete the texture from the context.

  See Also:
    `bindTexture`

### device

    public final QPaintDeviceInterface device()

  Returns the paint device set for this context.

  See Also:
    `QGLContext::QGLContext`

### deviceIsPixmap

    protected final boolean deviceIsPixmap()

  Returns true if the paint device of this context is a pixmap; otherwise returns false.

### format

    public final QGLFormat format()

  Returns the frame buffer format that was obtained (this may be a subset of what was requested).

  See Also:
    `setFormat`, `requestedFormat`

### initialized

    protected final boolean initialized()

  Returns true if this context has been initialized, i.e. if QGLWidget::initializeGL() has been performed on it; otherwise returns false.

  See Also:
    `setInitialized`

### isSharing

    public final boolean isSharing()

  Returns true if this context is sharing its GL context with another `QGLContext`, otherwise false is returned. Note that context sharing might not be supported between contexts with different formats.

### isValid

    public final boolean isValid()

  Returns true if a GL rendering context has been successfully created; otherwise returns false.

### overlayTransparentColor

    public final QColor overlayTransparentColor()

  If this context is a valid context in an overlay plane, returns the plane's transparent color. Otherwise returns an invalid color.

  The returned color's pixel value is the index of the transparent color in the colormap of the overlay plane. (Naturally, the color's RGB values are meaningless.)

  The returned `QColor` object will generally work as expected only when passed as the argument to QGLWidget::qglColor() or QGLWidget::qglClearColor(). Under certain circumstances it can also be used to draw transparent graphics with a `QPainter`. See the examples/opengl/overlay_x11 example for details.

### requestedFormat

    public final QGLFormat requestedFormat()

  Returns the frame buffer format that was originally requested in the constructor or `setFormat`.

  See Also:
    `format`

### reset

    public final void reset()

  Resets the context and makes it invalid.

  See Also:
    `create`, `isValid`

### setFormat

    public final void setFormat(QGLFormat format)

  Sets a `format` for this context. The context is reset.

  Call `create` to create a new GL context that tries to match the new format.

          QGLContext *cx;
          //  ...
          QGLFormat f;
          f.setStereo(true);
          cx->setFormat(f);
          if (!cx->create())
              exit(); // no OpenGL support, or cannot render on the specified paintdevice
          if (!cx->format().stereo())
              exit(); // could not create stereo context

  See Also:
    `format`, `reset`, `create`

### setInitialized

    protected final void setInitialized(boolean on)

  If `on` is true the context has been initialized, i.e. QGLContext::setInitialized() has been called on it. If `on` is false the context has not been initialized.

  See Also:
    `initialized`

### setValid

    protected final void setValid(boolean valid)

  See Also:
    `isValid`

### setWindowCreated

    protected final void setWindowCreated(boolean on)

  If `on` is true the context has had a window created for it. If `on` is false no window has been created for the context.

  See Also:
    `windowCreated`

### windowCreated

    protected final boolean windowCreated()

  Returns true if a window has been created for this context; otherwise returns false.

  See Also:
    `setWindowCreated`

### chooseContext

    protected final boolean chooseContext()

  Equivalent to `chooseContext`(0).

### chooseContext

    protected boolean chooseContext(QGLContext shareContext)

  This semi-internal function is called by `create`. It creates a system-dependent OpenGL handle that matches the `format` of `shareContext` as closely as possible, returning true if successful or false if a suitable handle could not be found.

  On Windows, it calls the virtual function choosePixelFormat(), which finds a matching pixel format identifier. On X11, it calls the virtual function chooseVisual() which finds an appropriate X visual. On other platforms it may work differently.

### create

    public final boolean create()

  Equivalent to create(0).

### create

    public boolean create(QGLContext shareContext)

  Creates the GL context. Returns true if it was successful in creating a valid GL rendering context on the paint device specified in the constructor; otherwise returns false (i.e. the context is invalid).

  After successful creation, `format` returns the set of features of the created GL rendering context.

  If `shareContext` points to a valid `QGLContext`, this method will try to establish OpenGL display list and texture object sharing between this context and the `shareContext`. Note that this may fail if the two contexts have different formats. Use `isSharing` to see if sharing is in effect.

  Warning: Implementation note: initialization of C++ class members usually takes place in the class constructor. `QGLContext` is an exception because it must be simple to customize. The virtual functions `chooseContext` (and chooseVisual() for X11) can be reimplemented in a subclass to select a particular context. The problem is that virtual functions are not properly called during construction (even though this is correct C++) because C++ constructs class hierarchies from the bottom up. For this reason we need a `create` function.

  See Also:
    `chooseContext`, `format`, `isValid`

### doneCurrent

    public void doneCurrent()

  Makes no GL context the current context. Normally, you do not need to call this function; `QGLContext` calls it as necessary.

### makeCurrent

    public void makeCurrent()

  Makes this context the current OpenGL rendering context. All GL functions you call operate on this context until another context is made current.

  In some very rare cases the underlying call may fail. If this occurs an error message is output to stderr.

### swapBuffers

    public void swapBuffers()

  Swaps the screen contents with an off-screen buffer. Only works if the context is in double buffer mode.

  See Also:
    `QGLFormat::setDoubleBuffer`

### currentContext

    public static QGLContext currentContext()

  Returns the current context, i.e. the context to which any OpenGL commands will currently be directed. Returns 0 if no context is current.

  See Also:
    `makeCurrent`

### setTextureCacheLimit

    public static void setTextureCacheLimit(int size)

  This function sets the limit for the texture cache to `size`, expressed in kilobytes.

  By default, the cache limit is approximately 64 MB.

  See Also:
    `textureCacheLimit`

### textureCacheLimit

    public static int textureCacheLimit()

  Returns the current texture cache limit in kilobytes.

  See Also:
    `setTextureCacheLimit`

### fromNativePointer

    public static QGLContext fromNativePointer(QNativePointer nativePointer)

  This function returns the QGLContext instance pointed to by nativePointer

  Parameters:
    `nativePointer` - the QNativePointer of which object should be returned.

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