Includes better error handling for when page flip failed. If it fails,
we shouldn't set the current buffer as otherwise each new attempt to
present a buffer will fail, too.
* blocks compositor while session is inactive
* prevents page flips while session is inactive
* restores modes when going to inactive
* hides cursor when going to inactive
* blanks screens when going active
* shows cursor again when going active
* triggers a repaint when going active
The DrmOutput corresponds to one output we perform mode setting on.
This implies that page flip is now performed on the DrmOutput. As our
compositor cannot drive multiple outputs yet, we only use the first one
and call into bufferSwapComplete and aboutToBufferSwap when either all
page flips are completed or respectivly the first one is performed.
Setting cursor is also handled on each DrmOutput.
When the DrmOutput is initialized it is blanked with a black buffer which
gets destroyed once the first page flip event has occurred (meanig the
buffer is no longer needed). Before setting the black buffer we store the
current buffer which will be set back on tear down. Because of that
tearing down the DrmBackend needs to wait till all page flips ended.
Creates two buffers with the size queried through the drm capabilities.
The actual cursor image is retrieved using the software cursor
functionality from the AbstractBackend and rendered into the shared
memory buffer. The the buffer is set as the new cursor image and the
rendering buffer for the cursor is swapped.
The position is updated whenever the cursor image changes or the mouse
position changes.
Uses EGL_MESA_platform_gbm to get an EglDisplay from a gbm_device.
The DrmBackend can provide a DrmBuffer for a gbm_surface and present
it.
Unfortunately buffer age seems to be slightly broken and we still have
artefacts.
Introduces a new (optional) dependency: libdrm.
The DrmBackend currently supports finding the first connected output.
It can create shared memory buffers which are used by SceneQPainter to
do double buffered rendering.
There is still lots to do, the following things are not yet working:
* multiple outputs
* page flip
* OpenGL (through gbm)
* restoring mode setting to start value
