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#include "utils.h"
// Mostly inspired by CC0 https://gist.github.com/koute/7391344
void gl_mat4x4_ortho(t_mat4x4 out, float left, float right, float bottom, float top, float znear, float zfar)
{
#define T(a, b) (a * 4 + b)
out[T(0,0)] = 2.0f / (right - left);
out[T(0,1)] = 0.0f;
out[T(0,2)] = 0.0f;
out[T(0,3)] = 0.0f;
out[T(1,1)] = 2.0f / (top - bottom);
out[T(1,0)] = 0.0f;
out[T(1,2)] = 0.0f;
out[T(1,3)] = 0.0f;
out[T(2,2)] = -2.0f / (zfar - znear);
out[T(2,0)] = 0.0f;
out[T(2,1)] = 0.0f;
out[T(2,3)] = 0.0f;
out[T(3,0)] = -(right + left) / (right - left);
out[T(3,1)] = -(top + bottom) / (top - bottom);
out[T(3,2)] = -(zfar + znear) / (zfar - znear);
out[T(3,3)] = 1.0f;
#undef T
}
// Mostly inspired from https://en.wikibooks.org/wiki/OpenGL_Programming/Modern_OpenGL_Tutorial_02
// Store all the file's contents in memory, useful to pass shaders source code to OpenGL.
const GLchar* gl_shaderfile_read(const char* path, Sint64 *out_fsize) {
GLchar *buf, *cursor;
SDL_RWops *rw;
Sint64 fsize;
size_t read;
rw = SDL_RWFromFile(path, "rb"); if (rw == NULL) return NULL;
fsize = SDL_RWsize(rw); if (fsize == -1) return NULL;
buf = malloc(fsize+1); if (buf == NULL) return NULL;
cursor = buf;
read = 0;
do {
cursor += read;
// Read at most to the end of buf
read = SDL_RWread(rw, cursor, 1, (fsize - (cursor-buf)));
} while ( read > 0 );
*cursor = '\0'; // Where the +1 is used from malloc() call
SDL_RWclose(rw);
// Check if we have read the whole thing
if ( (cursor-buf) != fsize) {
free(buf);
return NULL;
}
if (out_fsize != NULL) *out_fsize = fsize;
return buf;
}
/**
* Display compilation errors from the OpenGL shader compiler
*/
void gl_trace_shader_or_program_log(GLuint object) {
GLint log_length = 0;
char *log;
if (glIsShader(object)) {
glGetShaderiv(object, GL_INFO_LOG_LENGTH, &log_length);
} else if (glIsProgram(object)) {
glGetProgramiv(object, GL_INFO_LOG_LENGTH, &log_length);
} else {
TRACE("not a shader or a program");
return;
}
log = (char*)malloc(log_length);
if ( log == NULL ) {
TRACE("malloc failed");
return;
}
if (glIsShader(object))
glGetShaderInfoLog(object, log_length, NULL, log);
else if (glIsProgram(object))
glGetProgramInfoLog(object, log_length, NULL, log);
TRACE(log);
free(log);
}
GLint gl_compile_shader_from_file(GLuint shader, const char* path) {
Sint64 fsize;
GLint gl_fsize, status;
const GLchar *source = gl_shaderfile_read(path, &fsize);
if (source == NULL) return 1;
gl_fsize = (GLint) fsize;
glShaderSource(shader, 1, &source, &gl_fsize);
glCompileShader(shader);
glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
if(status == GL_FALSE) {
gl_trace_shader_or_program_log(shader);
return 2;
}
return 0;
}
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