Subviewport content cannot be rendered correctly on MacOS Chrome after exporting to html5

[tiomke]

Tested versions

• Reproducible in Godot 4.2.stable，4.3.stable

System information

MacOS 14.1(M3 Pro) - Godot v4.3.stable - Chrome 128.0.6613.114 (arm 64)

Issue description

When I use Subviewport to draw content, whether it is through SubviewportContainer or ViewportTexture, after exporting to HTML5, it cannot be rendered normally on Chrome.

some additional information:

• When using Godot4.2.stable to export HTML5, it cannot be rendered normally on Safari 17.1 too.
• It seems that the two settings of Render Target (Clear Mode, Update Mode) on the Subviewport Inspect panel do not take effect.
• If MRP is uploaded to itchio, it will be rendered correctly on Chrome.
• It seems OK when html5 running on Chrome in Windows.

Scene Node Tree:

Inspect pannel:

Expect View:

View in Chrome:

Steps to reproduce

Just add Subviewport to Scene and use Remote Debug - Run in Browser

Minimal reproduction project (MRP)

MRP.zip

[passivestar]

Noticed this too while looking through gmtk submissions, for example this game can't render the shadow on the wall that's most likely a subviewport in Brave. But it works fine in Firefox

macOS 14.5