Regression: Element material mask not applied on Firefox for Android (worked in previous engine version)

https://forum.playcanvas.com/t/element-component-mask-not-working-on-firefox-mobile/42525/13

Description

Element component masks using a material as the mask source do not render correctly on Firefox for Android. The mask has no visual effect — elements render as plain rectangles. Element masks using an image work correctly.

This is a regression: the same material-based mask worked on Firefox for Android with the previous engine version.

Reproduction

Project: https://playcanvas.com/editor/project/1584168

Steps:

1. Open the reproduction project on Firefox for Android
2. Observe the hotspot elements — they should appear as circular masked images (material mask)
3. They instead appear as unmasked squares

Expected behaviour

Circular masked element, as visible on desktop, Chrome for Android, and Firefox for Android on the previous engine version.

Actual behaviour

Material-based mask has no effect. Element renders as a plain rectangle.

Platform

Platform | Result -- | -- Desktop browsers | ✅ Working Chrome for Android | ✅ Working Firefox for Android — image mask | ✅ Working Firefox for Android — material mask | ❌ Broken Firefox for Android — previous engine (material mask) | ✅ Working

Start with the linked reproduction project on Firefox for Android and compare material masks with image masks and the previous engine version. Trace the Element component mask rendering path and verify the fix against the listed desktop, Chrome Android, and Firefox Android cases. Done means material-based masks render circularly instead of as plain rectangles without regressing image masks.