void RenderViewMLGPU::PrepareClears() {
// We don't do any clearing if we're copying from a source backdrop.
if (mContainer && mContainer->NeedsSurfaceCopy()) {
return;
}
// Get the list of rects to clear. If using the depth buffer, we don't
// care if it's accurate since the GPU will do occlusion testing for us.
// If not using the depth buffer, we subtract out the occluded region.
LayerIntRegion region = LayerIntRect::FromUnknownRect(mInvalidBounds);
if (!mUseDepthBuffer) {
// Don't let the clear region become too complicated.
region.SubOut(mOccludedRegion);
region.SimplifyOutward(kMaxClearViewRects);
}
Maybe<int32_t> sortIndex;
if (mUseDepthBuffer) {
// Note that we use the lowest available sorting index, to ensure that when
// using the z-buffer, we don't draw over already-drawn content.
sortIndex = Some(mNextSortIndex++);
}
nsTArray<IntRect> rects = ToRectArray(region);
mDevice->PrepareClearRegion(&mPreClear, std::move(rects), sortIndex);
if (!mPostClearRegion.IsEmpty()) {
// Prepare the final clear as well. Note that we always do this clear at the
// very end, even when the depth buffer is enabled, so we don't bother
// setting a useful sorting index. If and when we try to ship the depth
// buffer, we would execute this clear earlier in the pipeline and give it
// the closest possible z-ordering to the screen.
nsTArray<IntRect> rects = ToRectArray(mPostClearRegion);
mDevice->PrepareClearRegion(&mPostClear, std::move(rects), Nothing());
}
}
