WebGL readPixels shouldn't call EnsureBackbufferClearedAsNeeded

RESOLVED FIXED in mozilla16

Status

()

Core
Canvas: WebGL
RESOLVED FIXED
5 years ago
5 years ago

People

(Reporter: bjacob, Assigned: bjacob)

Tracking

unspecified
mozilla16
x86_64
Linux
Points:
---

Firefox Tracking Flags

(Not tracked)

Details

(Whiteboard: webgl-conformance)

Attachments

(1 attachment)

Created attachment 631660 [details] [diff] [review]
readPixels should not clear the backbuffer

See this discussion:

  https://www.khronos.org/webgl/public-mailing-list/archives/1206/msg00006.html

Section 2.2 in the spec has been updated to clarify that with preserveDrawingBuffer=false, the clearing only occurs if the canvas has been invalidated by a draw operation. In this respect, readPixels is not a draw operation hence it shouldn't request a clear.

Gregg's testcase,

  http://jsfiddle.net/greggman/hDcxp/1/

clears the canvas in green and does a readPixels in a setTimeout callback. It should not result in a clearing of the buffer. Currently in Firefox it does, because our readPixels implementation calls EnsureBackbufferClearedAsNeeded. This seems unneeded, and removing it fixes it. Notice that there is no security issue here because this only applies to the default framebuffer (non-default FBOs are still initialized if they had uninitialized renderbuffers) and on context creation the default framebuffer does get cleared already.
Attachment #631660 - Flags: review?(jgilbert)
Attachment #631660 - Flags: review?(jgilbert) → review+
(Assignee)

Comment 1

5 years ago
https://tbpl.mozilla.org/?tree=Try&rev=8cd80ba5c8f3
(Assignee)

Comment 2

5 years ago
http://hg.mozilla.org/integration/mozilla-inbound/rev/d4820f5ac825
Assignee: nobody → bjacob
Target Milestone: --- → mozilla16

Comment 3

5 years ago
https://hg.mozilla.org/mozilla-central/rev/d4820f5ac825
Status: NEW → RESOLVED
Last Resolved: 5 years ago
Resolution: --- → FIXED
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