[Webkit-unassigned] [Bug 259634] New: WebKit incorrectly renders upper left quarter of page scaled to the full view size on M1 running Linux

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=259634

            Bug ID: 259634
           Summary: WebKit incorrectly renders upper left quarter of page
                    scaled to the full view size on M1 running Linux
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Mac (Apple Silicon)
                OS: Linux
            Status: NEW
          Severity: Major
          Priority: P2
         Component: WebKitGTK
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: tri.voxel at gmail.com
                CC: bugs-noreply at webkitgtk.org

### Broken:

 * Epiphany version: 45.beta-3-g753bfa489 (nightly and manual build from latest source)
 * WebKitGTK version: WebKitGTK 2.41.6
 * Distributor: Gnome-Nightly Flatpak, source

### Working:

 * Epiphany version: 44.6
 * WebKitGTK version: WebKitGTK 2.40.4
 * Distributor: Flathub

### System specs:

 * OS: Fedora 38 Workstation
 * Desktop: GNOME 44 (on Wayland)
 * Device: Apple MacBook Air M1
 * Kernel: Linux 6.4.4-402.asahi.fc38.aarch64
 * Mesa info:
   ```
   $ glxinfo | grep OpenGL
   OpenGL vendor string: Mesa
   OpenGL renderer string: Apple M1 (G13G B1)
   OpenGL core profile version string: 3.1 Mesa 23.3.0-devel
   OpenGL core profile shading language version string: 1.40
   OpenGL core profile context flags: (none)
   OpenGL core profile extensions:
   OpenGL version string: 3.1 Mesa 23.3.0-devel
   OpenGL shading language version string: 1.40
   OpenGL context flags: (none)
   OpenGL extensions:
   OpenGL ES profile version string: OpenGL ES 3.0 Mesa 23.3.0-devel
   OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.00
   OpenGL ES profile extensions:
   ```

### Description:

On my ARM64 MacBook Air laptop (Apple Silicon M1), the webpage renders ridiculously zoomed in. It's like it's taking the upper left quarter of the rendered page, and zooming it to fill the whole viewport. This only happens at display scaling above 100%, including integer and fractional scaling. At every scaling setting >100, the same behavior can be observed. At 100% scaling, it renders correctly.

### Screenshots:

https://gitlab.gnome.org/GNOME/epiphany/uploads/09837676f6d0e728a310316fd03ea3d3/Screenshot_from_2023-07-30_12-06-05.png
https://gitlab.gnome.org/GNOME/epiphany/uploads/46083cba639d5f89dd1e954a00c87e27/Screenshot_from_2023-07-30_12-05-29.png
https://gitlab.gnome.org/GNOME/epiphany/uploads/60ddf4b8e4012202ff06efd1d0d8a040/Screenshot_from_2023-07-30_12-04-16.png
*Pictured above: Top left quarter of WebKit element filling the whole viewport at fractional scale of 175%*

https://gitlab.gnome.org/GNOME/epiphany/uploads/8b2425b5f6dc94e0b4eb37563d0f611c/Screenshot_from_2023-07-30_12-12-39.png
*Pictured above: Epiphany Devel at 200% display scaling*

https://gitlab.gnome.org/GNOME/epiphany/uploads/906d2e4abfca7ae2d97f1c42946f25f8/Screenshot_from_2023-07-30_12-12-50.png
*Pictured above: Epiphany Devel at 100% display scaling*

https://gitlab.gnome.org/GNOME/epiphany/uploads/e926d154d16003de84f6224def7972e6/Screenshot_from_2023-07-30_12-09-21.png
*Pictured above: Latest stable release not presenting this issue*

### Additional notes:

This may be a GTK4 scaling issue, a problem with the Asahi OpenGL 3.1 GPU drivers, or a WebKit issue. The GNOME/Epiphany issue can be found here: https://gitlab.gnome.org/GNOME/epiphany/-/issues/2141

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