Add eglnullws QScreen driver

This QScreen driver can be used for embedded Qt applications that draw
everything within a single full-screen QGLWidget. It uses underlying
support for a null window system (NullWS) such as is present in PowerVR
systems. It offers performance and stability improvements over the powervr
QScreen driver for applications that do not need full QWS windowing
support.

Reviewed-by: Jørgen Lind <jorgen.lind@nokia.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/src/plugins/gfxdrivers/eglnullws/README b/src/plugins/gfxdrivers/eglnullws/README
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index 0000000..80b88c7
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+++ b/src/plugins/gfxdrivers/eglnullws/README
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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).