com.trolltech.qt.opengl
Class QGLContext

java.lang.Object
  extended by com.trolltech.qt.internal.QSignalEmitterInternal
      extended by com.trolltech.qt.QSignalEmitter
          extended by com.trolltech.qt.QtJambiObject
              extended by 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.PrivateSignal0, QSignalEmitter.PrivateSignal1, QSignalEmitter.PrivateSignal2, QSignalEmitter.PrivateSignal3, QSignalEmitter.PrivateSignal4, QSignalEmitter.PrivateSignal5, QSignalEmitter.PrivateSignal6, QSignalEmitter.PrivateSignal7, QSignalEmitter.PrivateSignal8, QSignalEmitter.PrivateSignal9, 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.internal.QSignalEmitterInternal
currentSender
 
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)
          Constructs an OpenGL context for the given paint device, which can be a widget or a pixmap.
 
Method Summary
 int bindTexture(QImage image)
          Generates and binds a 2D GL texture to the current context, based on image.
 int bindTexture(QImage image, int target)
          Generates and binds a 2D GL texture to the current context, based on image.
 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)
          This is an overloaded member function, provided for convenience.
 int bindTexture(QPixmap pixmap, int target)
          This is an overloaded member function, provided for convenience.
 int bindTexture(QPixmap pixmap, int target, int format)
          This is an overloaded member function, provided for convenience.
 int bindTexture(java.lang.String fileName)
          This is an overloaded member function, provided for convenience.
protected  boolean chooseContext()
          This semi-internal function is called by create().
protected  boolean chooseContext(QGLContext shareContext)
          This semi-internal function is called by create().
 boolean create()
          Creates the GL context.
 boolean create(QGLContext shareContext)
          Creates the GL context.
static QGLContext currentContext()
          Returns the current context, i.
 void deleteTexture(int tx_id)
          Removes the texture identified by id from the texture cache, and calls glDeleteTextures() to delete the texture from the context.
 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.
 void drawTexture(QPointF point, int textureId)
          Draws the given texture at the given point in OpenGL model space.
 void drawTexture(QPointF point, int textureId, int textureTarget)
          Draws the given texture 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 frame buffer format that was obtained (this may be a subset of what was requested).
protected  boolean initialized()
          Returns true if this context has been initialized, i.
 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.
static void setTextureCacheLimit(int size)
          This function sets the limit for the texture cache to size, expressed in kilobytes.
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, 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, toString, wait, wait, wait
 
Methods inherited from interface com.trolltech.qt.QtJambiInterface
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership
 

Constructor Detail

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(), and isValid().


QGLContext

public QGLContext(QGLFormat format,
                  QPaintDeviceInterface device)
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.

Method Detail

bindTexture

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

Note that we assume default values for the glPixelStore() and glPixelTransfer() parameters.

See also:
deleteTexture().


bindTexture

public final int bindTexture(QImage image)
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.

Note that we assume default values for the glPixelStore() and glPixelTransfer() parameters.

See also:
deleteTexture().


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.

Note that we assume default values for the glPixelStore() and glPixelTransfer() parameters.

See also:
deleteTexture().


bindTexture

public final int bindTexture(QPixmap pixmap,
                             int target)
This is an overloaded member function, provided for convenience.

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


bindTexture

public final int bindTexture(QPixmap pixmap)
This is an overloaded member function, provided for convenience.

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


bindTexture

public final int bindTexture(QPixmap pixmap,
                             int target,
                             int format)
This is an overloaded member function, provided for convenience.

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


bindTexture

public final int bindTexture(java.lang.String fileName)
This is an overloaded member function, provided for convenience.

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().


deleteTexture

public final void deleteTexture(int tx_id)
Removes the texture identified by id from the texture cache, and calls glDeleteTextures() 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.


drawTexture

public final void drawTexture(QPointF point,
                              int textureId)
Draws the given texture 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 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 frame buffer format that was obtained (this may be a subset of what was requested).

See also:
setFormat(), and requestedFormat().


initialized

protected final boolean initialized()
Returns true if this context has been initialized, i. . 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(), and 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.

    //  ...
    QGLFormat f = new QGLFormat();
    f.setStereo(true);
    QGLContext cx = new QGLContext(f);
    if (!cx.create())
        throw new RuntimeException("No OpenGL support, or cannot render on the specified paintdevice.");
    if (!cx.format().stereo())
        throw new RuntimeException("Could not create stereo context.");

See also:
format(), reset(), and create().


setInitialized

protected final void setInitialized(boolean on)
If on is true the context has been initialized, i. . QGLContext::setInitialized() has been called on it. If on is false the context has not been initialized.

See also:
initialized().


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()
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.


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()
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(), and isValid().


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(), and 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. . 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().