#glxswapbuffer

[davincescode]

Gang swap....'Gang' swap

Gang swap (multipipe synchronized buffer swaps) is not supported on RealityEngine, RealityEngine2, and VTX systems. This will be fixed in a future release. 

- extracted from here

[davincescode]

Double Buffering

For drawables that are double buffered, the contents of the back buffer can be made potentially visible (i.e., become the contents of the front buffer) by calling

void glXSwapBuffers(Display *dpy, GLXDrawable draw);

The contents of the back buffer then become undefined. This operation is a no-op if draw was created with a non-double-buffered GLXFBConfig, or if draw is a GLXPixmap.

All GLX rendering contexts share the same notion of which are front buffers and which are back buffers for a given drawable. This notion is also shared with the X double buffer extension (DBE).

When multiple threads are rendering to the same drawable, only one of them need call glXSwapBuffers and all of them will see the effect of the swap. The client must synchronize the threads that perform the swap and the rendering, using some means outside the scope of GLX, to insure that each new frame is completely rendered before it is made visible.

If dpy and draw are the display and drawable for the calling thread’s current context, glXSwapBuffers performs an implicit glFlush. Subsequent OpenGL commands can be issued immediately, but will not be executed until the buffer swapping has completed, typically during vertical retrace of the display monitor.

If draw is not a valid GLX drawable, glXSwapBuffers generates a GLXBadDrawable error. If dpy and draw are the display and drawable associated with the calling thread’s current context, and if draw is a window that is no longer valid, a GLXBadCurrentDrawable error is generated. If the X Window underlying draw is no longer valid, a GLXBadWindow error is generated.

Concerning Drawables

 In X, a rendering surface is called a Drawable. X provides two types of Drawables: Windows which are located onscreen and Pixmaps which are maintained offscreen. The GLX equivalent to a Window is a GLXWindow and the GLX equivalent to a Pixmap is a GLXPixmap. GLX introduces a third type of drawable, called a GLXPbuffer, for which there is no X equivalent. GLXPbuffers are used for offscreen rendering but they have different semantics than GLXPixmaps that make it easier to allocate them in non-visible frame buffer memory.

GLXWindows, GLXPixmaps and GLXPbuffers are created with respect to a GLXFBConfig; the GLXFBConfig describes the depth of the color buffer components and the types, quantities and sizes of the ancillary buffers (i.e., the depth, accumulation, auxiliary, multisample, and stencil buffers). Double buffering and stereo capability is also fixed by the GLXFBConfig.

Ancillary buffers are associated with a GLXDrawable, not with a rendering context. If several rendering contexts are all writing to the same window, they will share those buffers. Rendering operations to one window never affect the unobscured pixels of another window, or the corresponding pixels of ancillary buffers of that window.

If an Expose event is received by the client, the values in the ancillary buffers and in the back buffers for regions corresponding to the exposed region become undefined.