Bug 229989

Summary: WebGL scissor drawing results have changed in iOS 15 beta
Product: WebKit Reporter: Takuya Yamazaki <zproject.develop>
Component: WebGLAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Normal CC: dino, gman, kbr, kkinnunen, kpiddington, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: Safari Technology Preview   
Hardware: iPhone / iPad   
OS: Other   
See Also: https://bugs.webkit.org/show_bug.cgi?id=230618
Attachments:
Description Flags
test case to observe gl.scissor(0,0,0,0); appers to work none

Description Takuya Yamazaki 2021-09-07 02:53:27 PDT 
In WebGLRenderingContext.scissor(), the drawing result when width or height are set to 0 has changed from iOS15.

Until iOS14: Nothing is drawn
From iOS15: All drawn
Comment 1 Kenneth Russell 2021-09-07 16:24:08 PDT 
Sounds like a potential regression in
Comment 2 Kenneth Russell 2021-09-07 16:24:42 PDT 
(oops, didn't mean to press "enter")

Sounds like a potential regression in ANGLE's Metal backend. Is this tested in the conformance suite?
Comment 3 Kimmo Kinnunen 2021-09-09 06:37:17 PDT 
Created attachment 437740 [details]
test case to observe     gl.scissor(0,0,0,0); appers to work
Comment 4 Kimmo Kinnunen 2021-09-09 06:38:10 PDT 
Cannot reproduce the problem with brief tests.
Takuya Yamazaki, would you be able to upload a reproduction test case for the problem?
Comment 5 Radar WebKit Bug Importer 2021-09-14 02:54:23 PDT 
<rdar://problem/83095006>
Comment 6 Kimmo Kinnunen 2021-10-01 06:50:33 PDT 
To the original reporter:
If you are using preserveDrawingBuffer: true, then you might try if setting that to false affects the result. If so, then this would be related to bug 230618
Comment 7 Takuya Yamazaki 2022-04-14 02:03:09 PDT 
Sorry for the delay in confirming this.
This issue was fixed in at least iOS 15.4.
It was not fixed in iOS 15.2.
We are not aware of iOS 15.3.