Incorrect GLSL shader output with GLCore (GLES) video driver

[cmitu]

Is there an existing issue for this?

• [x] This is a bug in RetroArch frontend
• [x] I have searched the existing issues

Description

When using a GLSL Shader preset with the GLCore video driver, the video output is incorect, the output image dimensions seem to be incorrectly calculated.

This is related to https://github.com/libretro/RetroArch/pull/18455 - which fixes the RetroArch crashing when loading a GLSL shader, but hasn't fixed the video output in my case (probably related to the GLES 3.1 supported GL version).

A verbose log file from reproducing the erro - https://gist.github.com/cmitu/26adf4e5bb65c7c260ecce4cf9bd3744. Note the repeated GL error messages in the log file.

[ERROR] [GL debug (High, API, Error)] GL_INVALID_OPERATION in glUniform2(uniform "MVPMatrix"@0 is matrix)

Expected behavior

Expecting the shader output to be correct. If I load the same GLSL shader using the gl core, then the output is correct.

Steps to reproduce the bug

1. Start RetroArch using the glcore video driver and load a game.
2. Open a GLSL shader preset (for instance crt-blurPi.glslp).
3. Note the incorrecy video output.

Version/Commit

1.22.2, git: 1e74653899

Bisect Results

No response

Present in the nightly version

Yes, this is reproduced in the nightly build

Platform & operating system

Linux aarch64, RaspiOS 'Trixie', Mesa 25.0.7

Affected Cores

No response

Environment information

• Raspberry Pi4
• KMSDRM display driver
• up-to-date RaspiOS Trixie, 64 bit arch & kernel.

Relevant log output

See https://gist.github.com/cmitu/26adf4e5bb65c7c260ecce4cf9bd3744