[Bug 27513] Clarify the behavior of Window.createImageBitmap(HTMLCanvasElement) for WebGL

https://www.w3.org/Bugs/Public/show_bug.cgi?id=27513

--- Comment #1 from Kenneth Russell <kbr@google.com> ---
Thanks for pointing this out. I think this behavior probably needs to be
defined in the WebGL spec, because otherwise the canvas spec will have to be
modified to incorporate WebGL-specific concepts.

I think the behavior should be:

 - If any rendering commands have been issued to the WebGL context since the
last time its results were presented to the page compositor, the ImageBitmap
should read the context's current contents (the "back buffer").

 - Otherwise, the ImageBitmap should read the canvas's current contents (the
"front buffer").

This will have less surprising behavior to developers that do the following:

 1. Draw some WebGL to a canvas
 2. Turn that canvas into an ImageBitmap
 3. When the ImageBitmap is resolved, draw it to a different canvas's 2D
context

The intent here would be to have the ImageBitmap contain the rendering results
from (1), but if the ImageBitmap always reads the canvas's "front buffer" then
it'll contain whatever the canvas was displaying before step (1).

-- 
You are receiving this mail because:
You are the QA Contact for the bug.

Received on Friday, 5 December 2014 03:00:53 UTC