Distorted Android

I am pretty sure this time the flashing issues on Mali T880 r12 driver are finally fixed.

The fix: a queue of FBOs render to, just like before, but this time in DistortedScreen we blit not the current FBO, but the one computed several frames ago.

This of course introduces a delay and uses more memory, but it appears to work and does not seem to have any effects on speed.

Revert last changes to the postprocessing FBO.

This reverts commit 2dbed690bdbee80d9bfb22c800073855eb5d0946.

I spoke too soon, the ARM Mali flashing is of course not fixed yet. The previous commit fixed Triblur, but the bug is still reproducible elsewhere (only in the 'postprocessed' apps though).

This commit introduces a circular queue in case of the postprocessing FBOs - with little success though.

Finally properly fix the flashing on ARM Mali T880 GPU.

The flashing is caused by a 'full pipeline flush' (see DarkPhoton, https://www.opengl.org/discussion_boards/showthread.php/200754-Flashes-on-ARM-Mali?p=1291679&viewfull=1#post1291679 ). In order to combat it, first introduce the possibility that a single DistortedOutputSurface is backed up by more than one FBO. Then make DistortedScreen be derived from DistortedFramebuffer (which itself is derived from DistortedOutputSurface) and make it contain 3 FBOs, render to them in a circular queue fashion, and blit from a given FBO to the system FBO. The 'more than 1 intermediate FBO' queue prevents the pipeline flush....

Minor.

Port all the 'non-controversial' changes from order-independent-transparency branch.

Try and avoid re-sorting the children by buckets (if we can!). This makes change in rendering order in the 'Transparency' app actually work.

In an attempt to contain the flashes on Mali GPU, re-structure the post-processing FBOs from 1 FBO with 2 color attachments + combined depth-stencil to 2 separate FBOs sharing a depth-stencil texture.

Result: this appears to make the flashes slightly worse.

Minor

OIT: fixes for Mali: fix a broken loop in the oitRender fragment shader that resulted in flashing.

Adjustments for the 'Flag' app.

OIT: fix for 'out of memory' crash on Mali GPUs.

~The thing still does not fully work there - there are still strange flashes in apps that innvolve OIT, for example in 'Triblur'.

OIT: more fixes

OIT: fixes. Everything looks correct now except for the curious return of the 'dancing lower-left corner' small glitch in the 'Transparency' app.

OIT: correction for blending in Pass4

OIT: move towards 4 passes ( clear - build - collapse - render )

correct oitRender again: we need to disable stencil reading and writing and restore after

correct oitRenddr again; correct coming to paused state (we could crash)

Make sure we don't create a feedback loop in oitRender

Make sure we don't create a feedback loop in oitRender

Make us read only the DEPTH part of a DEPTH24_STENCIL8 attachment.

Reengineer DistortedScreen

OIT: correct depth

Postprocessing: dont crash when we fail to compile postprocessing programs

OIT: some progress