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EGL NullWS QScreen Driver
=========================
If your application draws everything within a single full-screen QGLWidget then
you may wish to use this QScreen plugin driver. This driver simply returns 0
(as a EGLNativeWindowType value) when asked by the QtOpenGl module to create a
native window. Some OpenGL ES implementations (including PowerVR) interpret this
to mean that a full-screen OpenGL context is desired without any windowing
support (NullWS).
To tell a Qt/Embedded application to use this driver use the -display command
line option or the QWS_DISPLAY environment variable. The following driver
options are supported:
size=WIDTHxHEIGHT Screen size reported by the driver
format=FORMAT Screen format
Run with '-display eglnullws:help' to get a full list of options (including a
list of supported format strings).
If you choose a screen format that is not supported by the hardware then the
QtOpenGl module will write out a list of supported EGL configurations. Use
one of the supported screen formats from this list.
Using this driver with PowerVR hardware
---------------------------------------
Using this plugin with PowerVR hardware should give a significant speedup
compared to running with the Qt powervr driver (with a full-screen QGLWidget).
This is because sacrificing the window system allows less work to be done in
order to get graphics on the screen. Using this driver also avoids the memory
fragmentation issues present in the powervr driver and avoids any direct
dependencies on the deprecated PVR2D API from Imagination Technologies.
To use this driver ensure you have /etc/powervr.ini with contents similar to
this:
[default]
WindowSystem=libpvrPVR2D_FLIPWSEGL.so
This driver will also function with libpvrPVR2D_FRONTWSEGL.so, but that draws
straight into the framebuffer and will therefore cause flickering (it can be
useful for performance testing though). The flip plugin uses triple buffering,
so you will need to set the virtual vertical resolution of your framebuffer to
be three times the physical vertical resolution of your screen. This can be
done with 'fbset -vyres'. Failure to do this can cause system crashes. You
should also ensure that the plugin you choose in powervr.ini is in your library
path (it may just silently default to the flip plugin if not).
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