1 files changed, 114 insertions, 0 deletions
diff --git a/src/utils.c b/src/utils.c
new file mode 100644
index 0000000..a3c878e
--- /dev/null
+++ b/src/utils.c
@@ -0,0 +1,114 @@
+#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;
+}
+