Windows 10 - Qt 5.15.2
Ubuntu 21.04 / X11 - Qt 5.15.2
Arch Linux / X11 - Qt 5.15.2
When using a layer with a ShaderEffect on an item that contains text, the text renders incorrectly when the layer is enabled. Seems like a premultiplication issue but I'm not sure.
I noticed the issue with a custom made shader but it can be replicated with a "native" ShaderEffect.
Define a MyItem.qml file:
And use it (in the screenshots it is used in an orange window)
This shader is supposed to have no effect since it just passes the premultiplied source to the output that expects a premultiplied color. I should get the same result whether I enable or not the layer. But I get the results seen in the screenshots attached.
Note that the same issue can be replicated by replacing my custom made shader by a ColorOverlay with "transparent" as color which preserves the input.
Expected behavior: I should have not visual difference between enabled/disabled shader effects when the shader does not alter the source.
|Shader Effect Disabled
|Shader Effect Enabled