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

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

            Bug ID: 27513
           Summary: Clarify the behavior of
                    Window.createImageBitmap(HTMLCanvasElement) for WebGL
           Product: HTML WG
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: HTML5 spec
          Assignee: dave.null@w3.org
          Reporter: dongseong.hwang@intel.com
        QA Contact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-admin@w3.org,
                    public-html-wg-issue-tracking@w3.org

http://www.w3.org/html/wg/drafts/html/master/webappapis.html#cropped-to-the-source-rectangle

"Let the ImageBitmap object's bitmap data be a copy of the canvas element's
bitmap data, cropped to the source rectangle.
"

Above description is ambiguous for WebGL. WebGL has two kind of buffers;
drawing buffer (i.e. back buffer) and presented buffer (i.e. front buffer)
The spec should specifies which buffer should be copied to ImageBitmap.

In my opinion, it should be presented buffer, because
1. the spec intends to copy the screenshot of webgl currently displayed.
2. drawing buffer is discarded in the next frame, so it's difficult to use this
API to get RIGHT image.

WDYT?

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Received on Thursday, 4 December 2014 10:44:54 UTC