javax.media.opengl
Class GLContext

java.lang.Object
  javax.media.opengl.GLContext

public abstract class GLContext

extends Object

Abstraction for an OpenGL rendering context. In order to perform OpenGL rendering, a context must be "made current" on the current thread. OpenGL rendering semantics specify that only one context may be current on the current thread at any given time, and also that a given context may be current on only one thread at any given time. Because components can be added to and removed from the component hierarchy at any time, it is possible that the underlying OpenGL context may need to be destroyed and recreated multiple times over the lifetime of a given component. This process is handled by the implementation, and the GLContext abstraction provides a stable object which clients can use to refer to a given context.

Field Summary

static int	CONTEXT_CURRENT Indicates that the context was made current during the last call to makeCurrent.
static int	CONTEXT_CURRENT_NEW Indicates that a newly-created context was made current during the last call to makeCurrent.
static int	CONTEXT_NOT_CURRENT Indicates that the context was not made current during the last call to makeCurrent.

Constructor Summary

GLContext()

Method Summary

abstract void	copy(GLContext source, int mask) Copies selected groups of OpenGL state variables from the supplied source context into this one.
abstract void	destroy() Destroys this OpenGL context and frees its associated resources.
static GLContext	getCurrent() Returns the context which is current on the current thread.
abstract GL	getGL() Returns the GL pipeline object for this GLContext.
abstract GLDrawable	getGLDrawable() Returns the GLDrawable to which this context may be used to draw.
abstract boolean	isSynchronized() Returns true if 'makeCurrent' will exhibit synchronized behavior.
abstract int	makeCurrent() Makes this GLContext current on the calling thread.
abstract void	release() Releases control of this GLContext from the current thread.
protected static void	setCurrent(GLContext cur) Sets the thread-local variable returned by getCurrent() and has no other side-effects.
abstract void	setGL(GL gl) Sets the GL pipeline object for this GLContext.
abstract void	setSynchronized(boolean isSynchronized) Determines whether 'makeCurrent' will exhibit synchronized behavior.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CONTEXT_NOT_CURRENT

public static final int CONTEXT_NOT_CURRENT

Indicates that the context was not made current during the last call to makeCurrent.

See Also:

Constant Field Values

CONTEXT_CURRENT

public static final int CONTEXT_CURRENT

Indicates that the context was made current during the last call to makeCurrent.

See Also:

Constant Field Values

CONTEXT_CURRENT_NEW

public static final int CONTEXT_CURRENT_NEW

Indicates that a newly-created context was made current during the last call to makeCurrent.

See Also:

Constant Field Values

Constructor Detail

GLContext

public GLContext()

Method Detail

getGLDrawable

public abstract GLDrawable getGLDrawable()

Returns the GLDrawable to which this context may be used to draw.

makeCurrent

public abstract int makeCurrent()
                         throws GLException

Makes this GLContext current on the calling thread. There are two return values that indicate success and one that indicates failure. A return value of CONTEXT_CURRENT_NEW indicates that that context has been made current, and that this is the first time this context has been made current, or that the state of the underlying context or drawable may have changed since the last time this context was made current. In this case, the application may wish to initialize the state. A return value of CONTEXT_CURRENT indicates that the context has been made currrent, with its previous state restored. If the context could not be made current (for example, because the underlying drawable has not ben realized on the display) , a value of CONTEXT_NOT_CURRENT is returned. If the context is in use by another thread at the time of the call, then if isSynchronized() is true the call will block. If isSynchronized() is false, an exception will be thrown and the context will remain current on the other thread.

Returns:

CONTEXT_CURRENT if the context was successfully made current

Throws:

GLException - if synchronization is disabled and the context is current on another thread, or because the context could not be created or made current due to non-recoverable, window system-specific errors.

release

public abstract void release()
                      throws GLException

Releases control of this GLContext from the current thread.

Throws:

GLException - if the context had not previously been made current on the current thread

copy

public abstract void copy(GLContext source,
                          int mask)
                   throws GLException

Copies selected groups of OpenGL state variables from the supplied source context into this one. The mask parameter indicates which groups of state variables are to be copied. mask contains the bitwise OR of the same symbolic names that are passed to the GL command glPushAttrib. The single symbolic constant GL_ALL_ATTRIB_BITS can be used to copy the maximum possible portion of rendering state.

Not all values for GL state can be copied. For example, pixel pack and unpack state, render mode state, and select and feedback state are not copied. The state that can be copied is exactly the state that is manipulated by the GL command glPushAttrib.

On most platforms, this context may not be current to any thread, including the calling thread, when this method is called. Some platforms have additional requirements such as whether this context or the source context must occasionally be made current in order for the results of the copy to be seen; these requirements are beyond the scope of this specification.

Parameters:

source - the source OpenGL context from which to copy state

mask - a mask of symbolic names indicating which groups of state to copy

Throws:

GLException - if an OpenGL-related error occurred

getCurrent

public static GLContext getCurrent()

Returns the context which is current on the current thread. If no context is current, returns null.

Returns:

the context current on this thread, or null if no context is current.

setCurrent

protected static void setCurrent(GLContext cur)

Sets the thread-local variable returned by getCurrent() and has no other side-effects. For use by third parties adding new GLContext implementations; not for use by end users.

destroy

public abstract void destroy()

Destroys this OpenGL context and frees its associated resources. The context should have been released before this method is called.

isSynchronized

public abstract boolean isSynchronized()

Returns true if 'makeCurrent' will exhibit synchronized behavior.

setSynchronized

public abstract void setSynchronized(boolean isSynchronized)

Determines whether 'makeCurrent' will exhibit synchronized behavior.

getGL

public abstract GL getGL()

Returns the GL pipeline object for this GLContext.

setGL

public abstract void setGL(GL gl)

Sets the GL pipeline object for this GLContext.