UI Compositing Alpha Overflow

[CrazyCritic89]

Your system information

• Steam client version: 1699498641
• SteamOS version: 20231011.100
• Opted into Steam client beta?: Yes
• Opted into SteamOS beta?: Yes
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

Ever since some time in February, the Steam Main Menu, or in-game Steam menu (whatever you call it), has had its transparency broken for a while. This is caused by the fact when the "MainMenu" web element and "Steam Big Picture Mode" elements get composited together, the alpha (transparency) overflows past 1 causing it to darken. The worst part is this bug was made to be a "feature", and instead of hard coding opaque values, it just uses this overflow to have it black. :P

With the recent UI changes as well, I think fixing this would fit perfectly in with the new all glossy look they seem to be going for.

Here's how it looked like before (this is sadly the only raw pic I have of it)

Here's how it looked when it was first broken (why are these all in Chrome)

And here's how it's broken now (screenshots are broken in 3.5 and don't include the UI)

[CrazyCritic89]

Oh, and to add onto this. When "fixed", the blur doesn't apply over games in the latest preview: It wasn't like this in stable.