Custom GLSL shaders fail to compile with "#version must appear on the first line" error

[TheSiriuss]

When attempting to use a custom GLSL shader module with Glava, the compilation consistently fails with the error: preprocessor error: #version must appear on the first line. This occurs even when the #version directive is confirmed to be the absolute first line of the shader file, without any preceding characters or whitespace.

This issue does not affect built-in modules (e.g., bars), which compile and run correctly. This suggests the problem lies within Glava's handling of custom shader loading/compilation, rather than the shader file itself or the system's GLSL compiler.

Steps to Reproduce:

1. Ensure Glava is installed and working with default modules (e.g., glava runs bars successfully).
2. Create a new directory for a custom Glava module, e.g., /home/meteor-storm/.config/glava/my_custom_module/.
3. Inside this directory, create a file named 1.frag with the following minimal GLSL content (ensuring #version is the very first character):

1         #version 330 core
2         out vec4 fragColor;
3         void main() {
4             fragColor = vec4(1.0, 0.0, 0.0, 1.0); // Red color
5         }

4. Modify ~/.config/glava/rc.glsl to use this new module: Change #request mod bars to #request mod my_custom_module.
5. Run Glava from the terminal: glava

Expected Behavior: Glava should successfully compile and render the custom shader (e.g., a solid red background).

Actual Behavior: Glava crashes with the following error message:

   1     Shader compilation failed for '/home/meteor-storm/.config/glava/my_custom_module/1.frag':
   2     0:11(1): preprocessor error: #version must appear on the first line
   3     Аварийный останов

Environment: * Operating System: Void Linux * Desktop Environment: XFCE * Glava Version: glava --version output: GLava (glava) unknown (stable, unix/fhs) * GPU/Drivers: Mesa Intel(R) Iris(R) Xe Graphics (ADL GT2), 4.6 (Compatibility Profile) Mesa 25.1.3 535.113.01)

Relevant Logs/Output:

Output of glava --verbose:

1     Using backend: 'glx'
2     Loading module: 'my_custom_module'
3     found GLSL stage: '1.frag'
4     compiling: '1.frag'
5     Shader compilation failed for '/home/meteor-storm/.config/glava/my_custom_module/1.frag':
6     0:11(1): preprocessor error: #version must appear on the first line
7     Аварийный останов

Output of hexdump -C /home/meteor-storm/.config/glava/my_custom_module/1.frag | head -n 2 (confirming #version is on the first line):

1     00000000  23 76 65 72 73 69 6f 6e  20 33 33 30 20 63 6f 72  |#version 330 cor|
2     00000010  65 0a 6f 75 74 20 76 65  63 34 20 66 72 61 67 43  |e.out vec4 fragC|

Analysis/Possible Cause (from external research): Based on similar issues found for glslViewer (which exhibits the same error), it's possible that Glava automatically adds a "prolog" (some text/code) to the beginning of the shader program before compilation. If this prolog is inserted before the #version directive, it would cause the GLSL compiler to throw this error, as #version must be the absolute first line. A potential fix would involve checking if the first line of the user-provided shader is #version, and if so, moving that line to the beginning of Glava's internal prolog before passing the combined source to the GLSL compiler.