[webkit-reviews] review requested: [Bug 81106] [chromium] Infrastructure to allow animating layers to be only partially updated : [Attachment 132465] Patch

[bugzilla-daemon at webkit.org]

vollick at chromium.org has asked	for review:
Bug 81106: [chromium] Infrastructure to allow animating layers to be only
partially updated
https://bugs.webkit.org/show_bug.cgi?id=81106

Attachment 132465: Patch
https://bugs.webkit.org/attachment.cgi?id=132465&action=review

------- Additional Comments from vollick at chromium.org
(In reply to comment #4)
Freshened patch.

> 1.) Not produce frames from the impl thread if we're lacking content due to
an animation because we culled or clipped part of the layer the last time we
were on the main thread.  Instead, stall drawing from the impl thread until we
get a commit that has new data.
> (1) is a purely impl-side patch.

As I understand it, (1) is saying that if we're about to draw invalid textures
during an impl thread animation, we should stop and wait for a valid frame from
the main thread. This assumes that the main thread can and will produce this
frame, but I don't think it can right now. The style system will tell the main
thread what the target value of an animation is, but will not continue to
supply us with intermediate values. In order for the main thread to create this
frame, it will need to know the current animated values. So I think that (1)
involves three patches:

a) (81437) Don't draw invalid textures while animating (this will cause us to
hitch until the end of the animation, currently).
b) (This patch) during a commit, get the current animated values.
c) (no bug yet) Use the animated values to paint, cull, and commit, if
necessary.

I think this also means that this patch is a blocker for 79536.