Hi,
we have a very slow arm v5 device without hardware acceleration. When using QT5
and directfb we see a huge performance difference compared to qt4. After
looking deeper into the code to find the reason for this, I saw that the
QDirectFbWindow::createDirectFbWindow method always sets the capability
doublebuffered and alpha channel. As a result whenever something is painted on
the window the content of update rect is blit using alpha blending:
description.options = DFBWindowOptions(DWOP_ALPHACHANNEL);
description.caps =
DFBWindowCapabilities(DWCAPS_DOUBLEBUFFER|DWCAPS_ALPHACHANNEL);
Since the window is opaque I don't expect any transparency to be kept and a
simple memcpy which Is fast enough on the device would be okay. I already
tested this by modifying the code, but I am not sure what's the best way to fix
this.
Is there another way to disable the use of alpha blending for the back buffer
using a DEFINE or setting attribute somewhere?
Best Regards
Heiko
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