[Webkit-unassigned] [Bug 178223] New: WebGL clamps to 4096 pixels on a 5120 monitor

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Oct 12 12:09:53 PDT 2017


https://bugs.webkit.org/show_bug.cgi?id=178223

            Bug ID: 178223
           Summary: WebGL clamps to 4096 pixels on a 5120 monitor
           Product: WebKit
           Version: Safari 11
          Hardware: Macintosh
                OS: macOS 10.12
            Status: NEW
          Severity: Major
          Priority: P2
         Component: WebGL
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: alecazam123 at gmail.com
                CC: dino at apple.com

Created attachment 323543

  --> https://bugs.webkit.org/attachment.cgi?id=323543&action=review

Example showing clamping of WebGL renderBuffer

Safari currently clamps the WebGL context to 4096 pixels horizontally and vertically.  This is what Chrome/Firefox used to do, but they made the clamp on total pixels (4k x 4k) instead of per side.  It looks like the WebKit implementation is using the old behavior.  This is problematic on both 5K displays including the 5K iMac.

Enclosed is a simple WebGL sample.  Expand the window on a 5K display, and at a canvas size of 4097 pixels, you'll see a jump in the color and then aliasing bands.  The drawingBufferWidth is clamped to 4096 pixels, and the checkerboard pattern is non-uniformly scaled up to 5120 pixels if you expand the browser fully or go fullscreen.

This is problematic for design tools like ours, where we rely on pixel precision.  Now the experience on a 5K display will be letterboxed bars around the interactive canvas when the UI is hidden.  You can see this in figma.com rendering on 5K monitor with "Show UI" disabled.  

We would prefer to not have to wait for a long update cycle (another OSX release) on WebKit to see this corrected.

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