UI: don't multiply color channels by alpha

[mockersf]

Objective

• since Add border radius to UI nodes (adopted) #12500, text is a little bit more gray in UI

Solution

• don't multiply color by alpha. I think this was done in the original PR (UI Node Border Radius and Shadows #8973) for shadows which were not added in Add border radius to UI nodes (adopted) #12500

[JMS55]

This might've been related to the aliasing we saw in the original PR on rounded corners? I'm not sure, could be shadows like you said. Probably needs testing. If it turns out we need to keep this, we can do it in the shader only for non-text or something.

[mockersf]

I'm not seeing aliasing issues, at least it looks the same to me from main

this PR:

main:

[rparrett]

I believe this comment: #12500 (comment) is what lead to the alpha multiplication, but I don't fully understand it and can't find the discussion or review it is referencing.

But it seems like we should probably test with either border or background colors, or parent UI nodes with partial transparency?

edit: Maybe the referenced "halo" is visible in this comment: #8973 (comment). But as far as I can tell, ickshonpe seemed to think the issue was fixed by the time the PR was adopted.

[mockersf]

with a background color at rgba(0.0, 0.0, 1.0, 0.5):

this PR:

main:

Looking through changes from #12500, this PR also fix the change on the ui example where one of the square wasn't the same color

[rparrett]

edit: more comprehensive tests below

[rparrett]

Did some experiments with the same transparent border/bg color over the default clear color.

This PR restores behavior to pre-round-corners state. I think at the very least, it's pretty clear that this alpha multiplication shouldn't happen for text. (see the transparency_ui example before/after this PR).

The chrome comparison is quite interesting, but maybe not relevant.

[viridia]

Yeah, I thought that earlier code looked suspicious, but I wasn't sure.