1480616 - [blob-img] Avoid redrawing entire source for filter inputs for each tile.

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, enhancement, P3)

Description

[Jeff Muizelaar [:jrmuizel]]

Currently we redraw the entire source for filter inputs for each tile.

We can avoid this with the following scheme:
- Add BeginShared(), EndSharedSource(SourceSurface *) functions to DrawTarget
- In DrawTargetRecording each BeginShared stores an incrementing id to the command stream
- When we encounter a BeginShared during replay we take a lock on a shared array. If the shared surface is stored in the slot for that id than we take it out, otherwise we replay the commands between BeginShared and EndSharedSource(). We store the resulting SourceSurface in the slot and release the lock.

Comment 1

[Ashley Hale [:ahale]]

With gfx.webrender.svg-filter-effects enabled, the source picture rendering is aggressively clipped according to the visible rect (which is itself limited by tile bounds), so this shouldn't be very costly in most cases; we're not re-rendering the entire thing, just the portion relevant to this tile.