2d hdr + font msdf causes broken text rendering

[scgm0]

Godot version

4.2.dev3

System information

Godot v4.2.dev3 - Arch Linux #0~20230811.g489fabdc SMP PREEMPT_DYNAMIC Sat Aug 12 02:04:20 UT - X11 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1650 (nvidia; 535.98) - Intel(R) Core(TM) i5-9300H CPU @ 2.40GHz (8 Threads)

Issue description

After turning on 2d hdr and font msdf at the same time, there is a problem with ui text rendering.

2d hdr off:

2d hdr on:

Steps to reproduce

1. Open msdf for default font or custom font.
2. Turn on 2d hdr.
3. Add a Label node and enter text, the text rendering is destroyed.

Minimal reproduction project

N/A

[akien-mga]

Did you restart the editor as the message asks you to?

[scgm0]

Did you restart the editor as the message asks you to?

This is also the case after restarting. There is no restart in the screenshot, but I am lazy(

[akien-mga]

CC @clayjohn @bruvzg

[clayjohn]

I can reproduce this issue. For me the text totally disappears unless the camera is zoomed out quite far.

My best guess is that there is a space-encoding issue going on here. Likely the MSDF channels are encoded in an unexpected color space. When HDR is disabled, in 2D the engine ignores color space and just reads the texture as written. With HDR enabled, the engine ensures that you are reading the texture in linear space. If you have non-color data encoded in sRGB-space, then the engine will erroneously do a sRGB->linear conversion and break the data.

[clayjohn]

PR incoming