RichTextLabel and Label shadow colors multiply the main font color instead of overriding it

[fossegutten]

Godot version:
3.1.1 stable

OS/device including version:
Windows 10

Issue description:
Label and Richtextlabel shadow colors are copied from the font color and then modulated. This affects bitmap fonts, so that only full black shadows can be used. Not sure if other nodes use shadows, in that case they might suffer from the same problem. buttons do not have shadows.

The shadow colors should be a white (255, 255, 255, 255) color instead, so they can be modulated separately from the original font color.

Steps to reproduce:
Add the supplied font to a label

Minimal reproduction project:
fonts.zip
Added a colored font to test with. The 'm' and 'a' characters are colored, use those to test :)

[TheDuriel]

The shadow is managed by the font resource, not the node.

There recently were some changes to how the shadow is generated, this might help track down the relevant code #30168

[KoBeWi]

Can anyone still reproduce this bug in Godot 3.2.3 or any later release?

Some complete reproduction project would be useful. I don't see the result from the screenshot:

(also not sure what exactly the issue is about)

[TheDuriel]

I believe this was fixed ages ago by completely separating the shadow and giving it its own color.

[Calinou]

I can reproduce this on 3.2.3 (Label on top, RichTextLabel at the bottom):

Notice how the green shadow still has a shaded "m" and colored "a".

To fix this, we should override the main font's RGB channels for the shadow texture instead of multiplying them. However, we shouldn't touch the alpha channel as to not break antialiasing.

Minimal reproduction project: bitmap-font-shadows.zip