// This is free and unencumbered software released into the public domain.
// 
// Anyone is free to copy, modify, publish, use, compile, sell, or distribute
// this software, either in source code form or as a compiled binary, for any
// purpose, commercial or non-commercial, and by any means.
// 
// In jurisdictions that recognize copyright laws, the author or authors of this
// software dedicate any and all copyright interest in the software to the
// public domain. We make this dedication for the benefit of the public at large
// and to the detriment of our heirs and successors. We intend this dedication
// to be an overt act of relinquishment in perpetuity of all present and future
// rights to this software under copyright law.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
// AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
// 
// For more information, please refer to <http://unlicense.org/>

// REQUIREMENTS: OpenGL version with the KHR_debug extension available.

// Callback function for printing debug statements
void APIENTRY GLDebugMessageCallback(GLenum source, GLenum type, GLuint id,
                            GLenum severity, GLsizei length,
                            const GLchar *msg, const void *data)
{
    char* _source;
    char* _type;
    char* _severity;

    switch (source) {
        case GL_DEBUG_SOURCE_API:
        _source = "API";
        break;

        case GL_DEBUG_SOURCE_WINDOW_SYSTEM:
        _source = "WINDOW SYSTEM";
        break;

        case GL_DEBUG_SOURCE_SHADER_COMPILER:
        _source = "SHADER COMPILER";
        break;

        case GL_DEBUG_SOURCE_THIRD_PARTY:
        _source = "THIRD PARTY";
        break;

        case GL_DEBUG_SOURCE_APPLICATION:
        _source = "APPLICATION";
        break;

        case GL_DEBUG_SOURCE_OTHER:
        _source = "UNKNOWN";
        break;

        default:
        _source = "UNKNOWN";
        break;
    }

    switch (type) {
        case GL_DEBUG_TYPE_ERROR:
        _type = "ERROR";
        break;

        case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR:
        _type = "DEPRECATED BEHAVIOR";
        break;

        case GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR:
        _type = "UDEFINED BEHAVIOR";
        break;

        case GL_DEBUG_TYPE_PORTABILITY:
        _type = "PORTABILITY";
        break;

        case GL_DEBUG_TYPE_PERFORMANCE:
        _type = "PERFORMANCE";
        break;

        case GL_DEBUG_TYPE_OTHER:
        _type = "OTHER";
        break;

        case GL_DEBUG_TYPE_MARKER:
        _type = "MARKER";
        break;

        default:
        _type = "UNKNOWN";
        break;
    }

    switch (severity) {
        case GL_DEBUG_SEVERITY_HIGH:
        _severity = "HIGH";
        break;

        case GL_DEBUG_SEVERITY_MEDIUM:
        _severity = "MEDIUM";
        break;

        case GL_DEBUG_SEVERITY_LOW:
        _severity = "LOW";
        break;

        case GL_DEBUG_SEVERITY_NOTIFICATION:
        _severity = "NOTIFICATION";
        break;

        default:
        _severity = "UNKNOWN";
        break;
    }

    printf("%d: %s of %s severity, raised from %s: %s\n",
            id, _type, _severity, _source, msg);
}

// =============== INIT DEBUG OUTPUT ================
// The following function calls should be made directly after OpenGL
// initialization.

// Enable the debugging layer of OpenGL
//
// GL_DEBUG_OUTPUT - Faster version but not useful for breakpoints
// GL_DEBUG_OUTPUT_SYNCHRONUS - Callback is in sync with errors, so a breakpoint
// can be placed on the callback in order to get a stacktrace for the GL error.

glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS);

// Set the function that will be triggered by the callback, the second parameter
// is the data parameter of the callback, it can be useful for different
// contexts but isn't necessary for our simple use case.
glDebugMessageCallback(GLDebugMessageCallback, NULL);