HP Visualize J5000 HP Workstations - Graphics Administration Guide For Red Hat - Page 19

Miscellaneous topics, Double buffer extension (DBE), Performing buffer swaps on vertical blank

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Double buffer extension (DBE) DBE is an extension to the X server that provides a doublebuffering Application Programming Interface (API). For more information about DBE and the API, consult the DBE man pages: DBE XdbeQueryExtension XdbeGetVisualInfo XdbeFreeVisualInfo XdbeAllocateBackBufferName XdbeDeallocateBackBufferName XdbeSwapBuffers XdbeBeginIdiom XdbeEndIdiom XdbeGetBackBufferAttributes Performing buffer swaps on vertical blank For performance reasons, the default DBE behavior is to not synchronize buffer swaps with the monitor's vertical retrace period. In some instances, therefore, image tearing (seeing part of the old image and part of the new image on the display at the same time) could be visible while swapping large DBE windows. For those instances where tearing would occur and is undesirable, an optional X server mode is available to allow for synchronization of buffer swaps with vertical retrace. To activate this optional X server mode, set the following screen option in the X*screens File before the X server is started: SwapBuffersOnVBlank For example: Screen /dev/mem [DefaultVisual] ScreenOptions Linux_BusID 1:1:0 MonitorRefreshRate 1280,1024,135000 SwapBuffersOnVBlank OverlayTransparentIndex0 Determining swap performance The DBE API does not allow users to determine if doublebuffering in a visual is through software or hardware. However, the API does provide a way to determine Graphics Administration Guide For Red Hat Linux 6.2

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Double buffer extension (DBE)
DBE is an extension to the X server that provides a doublebuffering Application
Programming Interface (API). For more information about DBE and the API,
consult the DBE man pages:
DBE
XdbeQueryExtension
XdbeGetVisualInfo
XdbeFreeVisualInfo
XdbeAllocateBackBufferName
XdbeDeallocateBackBufferName
XdbeSwapBuffers
XdbeBeginIdiom
XdbeEndIdiom
XdbeGetBackBufferAttributes
Performing buffer swaps on vertical blank
For performance reasons, the default DBE behavior is to
not
synchronize buffer
swaps with the monitor's vertical retrace period. In some instances, therefore,
image tearing (seeing part of the old image and part of the new image on the
display at the same time) could be visible while swapping large DBE windows.
For those instances where tearing would occur and is undesirable, an optional X
server mode is available to allow for synchronization of buffer swaps with vertical
retrace. To activate this optional X server mode, set the following screen option in
the
X*screens
File before the X server is started:
SwapBuffersOnVBlank
For example:
Screen /dev/mem
[
DefaultVisual
]
ScreenOptions
Linux_BusID 1:1:0
MonitorRefreshRate 1280,1024,135000
SwapBuffersOnVBlank
OverlayTransparentIndex0
Determining swap performance
The DBE API does not allow users to determine if doublebuffering in a visual is
through software or hardware. However, the API does provide a way to determine
Graphics Administration Guide For Red Hat Linux 6.2