Gamescope display blank when compositing

[njdom24]

Easily reproducible with gamescope --force-composition -- vkgears. Doesn't happen on Sway or KWin.
This also prevents the Gamescope flag --hdr-itm-enable from working, and appears when opening the Steam overlay in Big Picture mode with upscaling, making the overlay unusable in games running below native res (gamescope -e -F fsr -- steam -tenfoot).

I tried adding a check for textureless surfaces in

Hyprland/src/render/Renderer.cpp

Line 614 in e584a8b

[this, &renderdata, &pWindow](SP<CWLSurfaceResource> s, const Vector2D& offset, void* data) {

to no avail.

So I figured I'd post here in case anyone more knowledgeable might now how to handle these

[njdom24]

Update: Posting our findings from Discord so they don't get lost.

This bit in Gamescope is supposed to return a buffer from Gamescope's own swapchain during its composition path. But for some reason, Hyprland is causing it to drop that buffer too early, so it returns nothing.

This seems to present as white on AMD and black on NVidia(?)