Bug 230618 – WebGL first clear is lost when scissor is used for preserveDrawingBuffer:true in some conditions

• Component: WebGL
• Status: RESOLVED FIXED

[Kimmo Kinnunen]

WebGL first clear is lost when scissor is used for preserveDrawingBuffer:true in some conditions

Possibly
        c.enable(c.SCISSOR_TEST);
       
        c.clearColor(0., 1., 0., 0.5);
        c.scissor(0, 0, 300, 50);
        c.clear(c.COLOR_BUFFER_BIT);
        
        c.scissor(125, 50, 50, 50);
        c.clearColor(0., 1., 0., 1.);
        c.clear(c.COLOR_BUFFER_BIT);
        c.scissor(0, 0, 300, 50);
        c.clear(c.COLOR_BUFFER_BIT);

[Kenneth Russell]

Great find - let's try to write a conformance test for this once it's understood.

[Radar WebKit Bug Importer]

<rdar://problem/83668270>

[Kimmo Kinnunen]

Created attachment 439850 [details]
Patch

[Kimmo Kinnunen]

Created attachment 439852 [details]
Patch

[Dean Jackson]

Comment on attachment 439852 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=439852&action=review

> LayoutTests/ChangeLog:9
> +        done-scissor

?

[Kimmo Kinnunen]

Created attachment 439969 [details]
Patch for landing

[Kenneth Russell]

I defer to Dean's review, but have filed:

Add test for scissor affecting compositing
https://github.com/KhronosGroup/WebGL/issues/3337

to make sure this doesn't get lost, and is handled properly in other browsers.

[EWS]

Committed r283979 (242825@main): <https://commits.webkit.org/242825@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 439969 [details].