Text elements do not render correct background colors

[revery-ui]

Text elements do not render correct background colors

[bryphe]

Nice catch @Akin909. Definitely a bug with how we render text.

The shader where we color / render the text is here:
https://github.com/bryphe/revery/blob/c20634b72ab39dea1372aaef7d0b519452773df2/src/UI/FontShader.re#L31

The 'texture' we use to read the font has only a single channel (t.a is a float value from 0.0 -> 1.0). In theory - this code should work OK to make the text transparent (since it's setting the alpha value to 0), but we don't set the appropriate blend modes (which tell the GPU how to combine pixels that are already drawn with pixels that you are sending).

Some useful references I found for WebGL / Shaders:

• LearnOpenGL - there's a specific section on text rendering too: https://learnopengl.com/In-Practice/Text-Rendering
• MDN WebGL Tutorial

[bryphe]

@Akin909 - hope you don't mind - I took a go at this w/ #60.

[bryphe]

This should be fixed now, @Akin909 ! Let me know if it's not for you 👍