work on moving shader loading/compilation to a separate file

src/shaders.cpp

@@ -0,0 +1,88 @@
+#include <typeinfo>
+#include <stdio.h>
+
+#include "util.hpp"
+#include "shaders.hpp"
+
+#define MAX_ERR_MSG_LEN 256
+
+
+// Visit/Variant overload pattern
+// https://www.modernescpp.com/index.php/visiting-a-std-variant-with-the-overload-pattern/
+template<typename ... Ts>
+struct overload : Ts ... { 
+    using Ts::operator() ...;
+};
+template<class... Ts> overload(Ts...) -> overload<Ts...>;
+
+namespace shader {
+
+bool _compile_shader(uint *out_id, const char* filepath, int shader_type);
+
+bool load(uint* out_id, const char* vertex_filepath, const char* fragment_filepath) {
+    uint vertex_id;
+    if (!_compile_shader(&vertex_id, vertex_filepath, GL_VERTEX_SHADER))
+        return false;
+
+    uint fragment_id;
+    if (!_compile_shader(&fragment_id, fragment_filepath, GL_FRAGMENT_SHADER))
+        return false;
+
+    uint program_id = glCreateProgram();
+    glAttachShader(program_id, vertex_id);
+    glAttachShader(program_id, fragment_id);
+    glLinkProgram(program_id);
+
+    int status;
+    glGetProgramiv(program_id, GL_LINK_STATUS, &status);
+    if (status == GL_FALSE) {
+        char err_msg[MAX_ERR_MSG_LEN];
+        glGetProgramInfoLog(program_id, MAX_ERR_MSG_LEN, NULL, err_msg);
+        printf("Error linking shaders %s and %s\n", vertex_filepath, fragment_filepath);
+        printf("Error msg: %s\n", err_msg);
+        return false;
+    }
+
+    glDeleteShader(vertex_id);
+    glDeleteShader(fragment_id);
+
+    *out_id = program_id;
+    return true;
+}
+
+void use(uint id) { glUseProgram(id); }
+
+void set_uniform(uint id, const char* name, uniform_variant value) {
+    const auto visitor = overload {
+        [id, name](int i) { glUniform1i(glGetUniformLocation(id, name), i); },
+        [id, name](float f) { glUniform1f(glGetUniformLocation(id, name), f); },
+        [id, name](bool b) { glUniform1i(glGetUniformLocation(id, name), b); },
+    };
+    visit(visitor, value);
+}
+
+// Privates
+
+bool _compile_shader(uint *out_id, const char* filepath, int shader_type) {
+    Array<char> source;
+    if (!read_file(&source, filepath))
+        return false;
+
+    uint id = glCreateShader(shader_type);
+    glShaderSource(id, 1, &source._data, (int*)&source.len);
+    glCompileShader(id);
+
+    int status;
+    glGetShaderiv(id, GL_COMPILE_STATUS, &status);
+    if (status == GL_FALSE) {
+        char err_msg[MAX_ERR_MSG_LEN];
+        glGetShaderInfoLog(id, MAX_ERR_MSG_LEN, NULL, err_msg);
+        printf("Error compiling shader %s\n", filepath);
+        printf("%.*s\n", (int)source.len, source._data);
+        printf("Error msg: %s\n", err_msg);
+    }
+    *out_id = id;
+    return status == GL_TRUE;
+}
+
+} // namespace shader