[rlgl] rlGetShaderBufferSize seems to always return 0

[kai-kj]

Description

The rlGetShaderBufferSize function seems to always return 0, even after uploading, processing and downloading data with an SSBO (all successfully). Looking at the code, the function is implemented using glGetInteger64v:

// Get SSBO buffer size
unsigned int rlGetShaderBufferSize(unsigned int id) {
    long long size = 0;
    glBindBuffer(GL_SHADER_STORAGE_BUFFER, id);
    glGetInteger64v(GL_SHADER_STORAGE_BUFFER_SIZE, &size);
    return (size > 0)? (unsigned int)size : 0;
}

After looking around a bit, it looks like glGetBufferParameteri64v is probably the correct function to be calling in order to get the size of the SSBO, see below:

// Get SSBO buffer size
unsigned int rlGetShaderBufferSize(unsigned int id) {
    long long size = 0;
    glBindBuffer(GL_SHADER_STORAGE_BUFFER, id);
    glGetBufferParameteri64v(GL_SHADER_STORAGE_BUFFER, GL_BUFFER_SIZE, &size);
    return (size > 0)? (unsigned int)size : 0;
}

With this implementation, the actual size of the buffer is correctly returned. From what I can tell, glGetInteger64v is used to query the maximum value of some property (I'm not exactly sure). Is the current implementation the intended behaviour, or should it actually return the current size of the buffer?

Environment

Windows 11, desktop:

INFO: GL: OpenGL device information:
INFO:     > Vendor:   NVIDIA Corporation
INFO:     > Renderer: NVIDIA GeForce RTX 3060 Laptop GPU/PCIe/SSE2
INFO:     > Version:  4.3.0 NVIDIA 546.30
INFO:     > GLSL:     4.30 NVIDIA via Cg compiler

Code Example

#include <stdio.h>
#include <stdlib.h>

#include "raylib.h"
#include "rlgl.h"

int main(void) {
    InitWindow(800, 600, "pathtracer");

    unsigned int target_size = 100;
    unsigned int buffer = rlLoadShaderBuffer(target_size, NULL, RL_DYNAMIC_COPY);

    unsigned int actual_size = rlGetShaderBufferSize(buffer);
    printf("target size: %u, actual size: %u\n", target_size, actual_size);

    rlUnloadShaderBuffer(buffer);
    CloseWindow();
}

With the glGetInteger64v implementation, the code always outputs target size: 100, actual size: 0, but with the glGetBufferParameteri64v implementation, it outputs target size: 100, actual size: 100.

[raysan5]

@kal39 Good catch! Thanks for the improvement! Actually, it seems previous implementation required glGetInteger64i_v() instead of glGetInteger64v() as per the specs.