From 12d80d643f77a0eab18cb1278793aee006bcf289 Mon Sep 17 00:00:00 2001
From: Leo Tenenbaum <pommicket@gmail.com>
Date: Thu, 4 Feb 2021 16:56:28 -0500
Subject: started modern opengl

---
 gl.c | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 gl.c

(limited to 'gl.c')

diff --git a/gl.c b/gl.c
new file mode 100644
index 0000000..6e61742
--- /dev/null
+++ b/gl.c
@@ -0,0 +1,128 @@
+#include "lib/glcorearb.h"
+
+// macro trickery to avoid having to write everything twice
+#define gl_for_each_proc(do)\
+	do(CREATESHADER, CreateShader)\
+	do(DELETESHADER, DeleteShader)\
+	do(CREATEPROGRAM, CreateProgram)\
+	do(SHADERSOURCE, ShaderSource)\
+	do(GETSHADERIV, GetShaderiv)\
+	do(GETSHADERINFOLOG, GetShaderInfoLog)\
+	do(COMPILESHADER, CompileShader)\
+	do(CREATEPROGRAM, CreateProgram)\
+	do(DELETEPROGRAM, DeleteProgram)\
+	do(ATTACHSHADER, AttachShader)\
+	do(LINKPROGRAM, LinkProgram)\
+	do(GETPROGRAMIV, GetProgramiv)\
+	do(GETPROGRAMINFOLOG, GetProgramInfoLog)\
+	do(USEPROGRAM, UseProgram)\
+	do(GETATTRIBLOCATION, GetAttribLocation)\
+	do(GETUNIFORMLOCATION, GetUniformLocation)\
+	do(GENBUFFERS, GenBuffers)\
+	do(DELETEBUFFERS, DeleteBuffers)\
+	do(BINDBUFFER, BindBuffer)\
+	do(BUFFERDATA, BufferData)\
+	do(VERTEXATTRIBPOINTER, VertexAttribPointer)\
+	do(ENABLEVERTEXATTRIBARRAY, EnableVertexAttribArray)\
+	do(DISABLEVERTEXATTRIBARRAY, DisableVertexAttribArray)\
+	do(GENVERTEXARRAYS, GenVertexArrays)\
+	do(BINDVERTEXARRAY, BindVertexArray)\
+	do(UNIFORM1F, Uniform1f)\
+	do(UNIFORM2F, Uniform2f)\
+	do(UNIFORM3F, Uniform3f)\
+	do(UNIFORM4F, Uniform4f)\
+	do(UNIFORM1I, Uniform1i)\
+	do(UNIFORM2I, Uniform2i)\
+	do(UNIFORM3I, Uniform3i)\
+	do(UNIFORM4I, Uniform4i)\
+	do(UNIFORMMATRIX4FV, UniformMatrix4fv)\
+	do(DEBUGMESSAGECALLBACK, DebugMessageCallback)\
+	do(DEBUGMESSAGECONTROL, DebugMessageControl)\
+
+#define gl_declare_proc(upper, lower) static PFNGL##upper##PROC gl##lower;
+gl_for_each_proc(gl_declare_proc)
+#undef gl_declare_proc
+
+// set by main()
+static int gl_version_major;
+static int gl_version_minor;
+
+static void gl_get_procs(void) {
+	#define gl_get_proc(upper, lower) gl##lower = (PFNGL##upper##PROC)SDL_GL_GetProcAddress("gl" #lower);
+	gl_for_each_proc(gl_get_proc)
+	#undef gl_get_proc
+}
+
+// compile a GLSL shader
+static GLuint gl_compile_shader(char const *code, GLenum shader_type) {
+	GLuint shader = glCreateShader(shader_type);
+	glShaderSource(shader, 1, &code, NULL);
+	glCompileShader(shader);
+	GLint status = 0;
+	glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
+	if (status == GL_FALSE) {
+		char log[1024] = {0};
+		glGetShaderInfoLog(shader, sizeof log - 1, NULL, log);
+		debug_println("Error compiling shader: %s", log);
+		return 0;
+	}
+	return shader;
+}
+
+// link together GL shaders
+static GLuint gl_link_program(GLuint *shaders, size_t count) {
+	GLuint program = glCreateProgram();
+	if (program) {
+		for (size_t i = 0; i < count; ++i) {
+			if (!shaders[i]) {
+				glDeleteProgram(program);
+				return 0;
+			}
+			glAttachShader(program, shaders[i]);
+		}
+		glLinkProgram(program);
+		GLint status = 0;
+		glGetProgramiv(program, GL_LINK_STATUS, &status);
+		if (status == GL_FALSE) {
+			char log[1024] = {0};
+			glGetProgramInfoLog(program, sizeof log - 1, NULL, log);
+			debug_println("Error linking shaders: %s", log);
+			glDeleteProgram(program);
+			return 0;
+		}
+	}
+	return program;
+}
+
+static GLuint gl_compile_and_link_shaders(char const *vshader_code, char const *fshader_code) {
+	GLuint shaders[2];
+	shaders[0] = gl_compile_shader(vshader_code, GL_VERTEX_SHADER);
+	shaders[1] = gl_compile_shader(fshader_code, GL_FRAGMENT_SHADER);
+	GLuint program = gl_link_program(shaders, 2);
+	if (shaders[0]) glDeleteShader(shaders[0]);
+	if (shaders[1]) glDeleteShader(shaders[1]);
+	if (program) {
+		debug_print("Successfully linked program %u.\n", program);
+	}
+	return program;
+}
+
+static GLuint gl_attrib_loc(GLuint program, char const *attrib) {
+	GLint loc = glGetAttribLocation(program, attrib);
+	if (loc == -1) {
+		debug_print("Couldn't find vertex attribute %s.\n", attrib);
+		return 0;
+	}
+	return (GLuint)loc;
+}
+
+static GLint gl_uniform_loc(GLuint program, char const *uniform) {
+	GLint loc = glGetUniformLocation(program, uniform);
+	if (loc == -1) {
+		debug_print("Couldn't find uniform: %s.\n", uniform);
+		return -1;
+	}
+	return loc;
+}
+
+
-- 
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