On Wed, 24 Jun 2020 10:58:41 +0100 Carsten Haitzler (The Rasterman) <ras...@rasterman.com> wrote:
> you keep a sliding window of the last 2 frames with of rect regions you union > (merge with) the current frame's update rects... then render that. you can > play > tricks like copy back some regions from a previous frame instead of > re-rendering them (as it's a read from, not a write to that buffer it's safe.. Yes, copying from a busy buffer is safe. > but beware that readbacks may have issues especially if regions are not mapped > as non-cachable because they are being scanned out/displayed for example. it > depends on hardware entirely so the safe thing is to their shadow them and > make > a copy before you display or just re-render them. it turns out the just > re-render is simpler to do and generally performant). You said you were going to cover only software-rendering, but here you go. ;-) IOW, the caching thing applies to hardware buffers (some of which can be written to by CPU). But a usual desktop application or a toolkit should not use hardware buffers for software rendering. The performance hit you refer to can also happen in the compositor! Thanks, pq
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