There are multiple SurfacePools: Main thread painting and the non-WebRender compositors create a new pool per window, and WebRender creates one shared pool across all windows. The non-WebRender users set the pool size limit to zero, i.e. no recycling across paints. This preserves the pre-existing behavior.
WebRender's pool size is configurable with the gfx.webrender.compositor.surface-pool-size pref.
Every window holds on to a SurfacePoolHandle. A SurfacePoolHandle has an owning reference to the pool, via a surface pool wrapper. Once all handles are gone, the surface pool goes away, too.
The SurfacePool holds on to IOSurfaces and MozFramebuffers. Both are created on demand, independently, but are associated with each other.
A given NativeLayer uses only one surface pool handle during its lifetime. The native layer no longer influences which GLContext its framebuffers are created for; the GL context is now managed by the surface pool handle.
As a result, a NativeLayer can no longer change which GLContext its framebuffers are created by.
So in the future, if we ever need to migrate a window frome one GLContext to another, we will need to recreate the NativeLayers inside it. I think that's ok.
Differential Revision: https://phabricator.services.mozilla.com/D54859
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extra : moz-landing-system : lando
Markus Stange