not working rect

src/main.zig

@@ -9,6 +9,29 @@ const gl = @cImport ({
 });
 
 
+const vertexShaderSource: [*c]const u8 = 
+    \\ #version 460 core
+    \\ layout (location = 0) in vec3 aPos;
+    \\ void main() {
+    \\  gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+    \\ }
+    ;
+
+const fragementShaderSource: [*c]const u8 = 
+    \\ #version 330 core
+    \\ out vec4 FragColor;
+    \\ void main() {
+    \\ FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
+    \\ } 
+    ;
+
+const ShaderInitError = error {
+    VertexCompilation,
+    FragementCompilation,
+    ShaderProgramLinking,
+};
+
+
 pub fn main() void {
 
     // var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
@@ -20,8 +43,6 @@ pub fn main() void {
     if (res != gl.GL_TRUE) {
         std.debug.panic("Could not initialize glfw! Exit code: {d}", .{ res });
     }
-
-
     gl.glfwWindowHint(gl.GLFW_CONTEXT_VERSION_MAJOR, 4);
     gl.glfwWindowHint(gl.GLFW_CONTEXT_VERSION_MINOR, 6);
     gl.glfwWindowHint(gl.GLFW_OPENGL_PROFILE, gl.GLFW_OPENGL_CORE_PROFILE);
@@ -29,7 +50,6 @@ pub fn main() void {
 
     // the two null params are monitor for fullscreen, and share window resources (???)
     const window: ?*gl.GLFWwindow = gl.glfwCreateWindow(800, 600, "LearnOpenGL", null, null);
-
     if (window == null) {
         gl.glfwTerminate();
         std.debug.panic("Could not instantiate window!", .{});
@@ -37,25 +57,81 @@ pub fn main() void {
     }
 
     gl.glfwMakeContextCurrent(window);
-
     const version: c_int = gl.gladLoadGL(gl.glfwGetProcAddress);
-
     if (version == 0) {
         std.debug.panic("Could not initialize GLAD", .{});
         return;
     }
 
     gl.glViewport(0, 0, 800, 600);
-
     // callback function returned?
     _ = gl.glfwSetFramebufferSizeCallback(window, &framebuffer_resize_callback);
 
+    const vertexShader: c_uint = gl.glCreateShader(gl.GL_VERTEX_SHADER);
+    const fragShader: c_uint = gl.glCreateShader(gl.GL_FRAGMENT_SHADER);
+    const shaderProgram: c_uint = gl.glCreateProgram();
+
+    init_shader_program(&vertexShader, &fragShader, &shaderProgram) catch |e| switch (e) {
+            ShaderInitError.VertexCompilation    => std.debug.panic("Could not compile vertex shader!\n", .{}),
+            ShaderInitError.FragementCompilation => std.debug.panic("Could not compile fragment shaders!\n", .{}),
+            ShaderInitError.ShaderProgramLinking => std.debug.panic("Could not link shader program!\n", .{}),
+    };
+
+    var rect_vao: c_uint = undefined;
+    gl.glad_glGenVertexArrays.?(1, @ptrCast(&rect_vao));
+    gl.glad_glBindVertexArray.?(rect_vao);
+    const rect_verts: [4][3]f32 = .{ .{0.2, 0.2, 0.0}, .{0.8, 0.2, 0.0}, .{0.8, 0.4, 0.0}, .{0.2, 0.4, 0.0} };
+    const draw_indices: [2][3]c_uint = .{ .{0, 1, 3}, .{1, 2, 3} };
+
+    var r_vert_buffer: c_uint = undefined;
+    gl.glad_glGenBuffers.?(1, &r_vert_buffer);
+    gl.glad_glBindBuffer.?(gl.GL_ARRAY_BUFFER, r_vert_buffer);
+    gl.glBufferData(gl.GL_ARRAY_BUFFER, 2 * 3 * @sizeOf(f32), @ptrCast(&rect_verts), gl.GL_STATIC_DRAW);
+    // gl.glad_glBindBuffer.?(0);
+
+    var element_buffer: c_uint = undefined;
+    gl.glad_glGenBuffers.?(1, &element_buffer);
+    gl.glad_glBindBuffer.?(gl.GL_ELEMENT_ARRAY_BUFFER, element_buffer);
+    gl.glBufferData(gl.GL_ELEMENT_ARRAY_BUFFER, 2 * 3 * @sizeOf(c_uint), @ptrCast(&draw_indices), gl.GL_STATIC_DRAW);
+    // gl.glad_glBindBuffer.?(0);
+    
+    gl.glEnableVertexAttribArray(0);
+
+
+
+    // ----- Simple Triangle ------
     const verticies: [3][3]f32 = .{ .{-0.5, -0.5, 0.0}, .{0.5, -0.5, 0.0}, .{0.0, 0.5, 0.0} };
-    var vbo: gl.GLuint = undefined;
+    // Vertex array object
+    var vao: c_uint = undefined;
+    gl.glad_glGenVertexArrays.?(1, @ptrCast(&vao));
+    gl.glad_glBindVertexArray.?(vao);
+
+    // vertex buffer object
+    var vbo: c_uint = undefined;
     gl.glad_glGenBuffers.?(1, &vbo);
-    std.debug.print("buffer id: '{d}'\n", .{ vbo });
     gl.glad_glBindBuffer.?(gl.GL_ARRAY_BUFFER, vbo);
+    // type of buffer, size of memory being inserted, the data to be loaded, how the GPU handles the memory
+    // STREAM - write once, used a few times, STATIC - set once, used many times, DYNAMIC - changed a lot
+    // used many times
     gl.glBufferData(gl.GL_ARRAY_BUFFER, 4 * 3 * @sizeOf(f32), @ptrCast(&verticies), gl.GL_STATIC_DRAW);
+    // 0 for location=0 from shader
+    // 3 for number of attributes per stride,
+    // the type of data
+    // if we want it to be normalized
+    // offset of start of data
+    // The target virtual buffer object is defined by the current state from glVertexAttribPointer
+    gl.glVertexAttribPointer(0, 3, gl.GL_FLOAT, gl.GL_FALSE, 3 * @sizeOf(f32), @ptrCast(&0));
+    gl.glEnableVertexAttribArray(0);
+
+    gl.glad_glBindVertexArray.?(0);
+
+    // ------ END Simple Triangle ------
+
+    std.debug.print("Vertex buffer assigned\n", .{});
+
+    var gl_err: gl.GLenum = 0;
+
+    gl.glDisable(gl.GL_CULL_FACE);
 
     while(gl.glfwWindowShouldClose(window) == 0)
     {
@@ -65,10 +141,39 @@ pub fn main() void {
         gl.glClearColor(0.2, 0.3, 0.4, 0.5); // state setting, follo wed by state using
         gl.glClear(gl.GL_COLOR_BUFFER_BIT); // color buffer, depth buffer, and stencil buffer
 
+        gl.glUseProgram(shaderProgram);
+        gl.glad_glBindVertexArray.?(vao);
+        gl.glad_glBindBuffer.?(gl.GL_ARRAY_BUFFER, vbo);
+        // offset into vertexes, and count
+        // gl.glDrawArrays(gl.GL_TRIANGLES, 0, 3);
+        
+        gl_err = gl.glGetError();
+
+        if (gl_err > 0) {
+            std.debug.print("There was an opengl error: {d}", .{gl_err});
+            gl_err = 0;
+        }
+
+        gl.glad_glBindVertexArray.?(rect_vao);
+        gl.glad_glBindBuffer.?(gl.GL_ARRAY_BUFFER, r_vert_buffer);
+        gl.glad_glBindBuffer.?(gl.GL_ELEMENT_ARRAY_BUFFER, element_buffer);
+        gl.glDrawElements(gl.GL_TRIANGLES, 6, gl.GL_UNSIGNED_INT, null);
+        
+        gl_err = gl.glGetError();
+
+        if (gl_err > 0) {
+            std.debug.print("There was an opengl error: {d}", .{gl_err});
+            gl_err = 0;
+        }
+
         // This swaps the "displayed" buffer with the "rendering" buffer
         gl.glfwSwapBuffers(window);
     }
 
+    gl.glDeleteVertexArrays(1, &vao);
+    gl.glDeleteBuffers(1, &vbo);
+    gl.glDeleteProgram(shaderProgram);
+
     gl.glfwTerminate();
 
 }
@@ -82,3 +187,47 @@ fn handle_input(window: *gl.GLFWwindow) void {
         gl.glfwSetWindowShouldClose(window, 1);
     }
 }
+
+fn init_shader_program(vertex_shader: *const c_uint, frag_shader: *const c_uint, program: *const c_uint) ShaderInitError!void {
+    var success: c_int = undefined;
+    var infoLog: [512:0]u8 = undefined;
+
+    gl.glShaderSource(vertex_shader.*, 1, &vertexShaderSource, null);
+    gl.glCompileShader(vertex_shader.*);
+    gl.glGetShaderiv(vertex_shader.*, gl.GL_COMPILE_STATUS, &success);
+    std.debug.print("Vertex Shader compiled\n", .{});
+    if (success == 0) {
+        std.debug.print("Shader compile failed!\n", .{});
+        gl.glGetShaderInfoLog(vertex_shader.*, 512, null, &infoLog);
+        std.debug.print("Error Log: {s}\n", .{infoLog});
+        return ShaderInitError.VertexCompilation;
+    }
+
+    gl.glShaderSource(frag_shader.*, 1, &fragementShaderSource, null);
+    gl.glCompileShader(frag_shader.*);
+    gl.glGetShaderiv(frag_shader.*, gl.GL_COMPILE_STATUS, &success);
+    std.debug.print("Fragment Shader compiled\n", .{});
+    if (success == 0) {
+        std.debug.print("Shader compile failed!\n", .{});
+        gl.glGetShaderInfoLog(frag_shader.*, 512, null, &infoLog);
+        std.debug.print("Error Log: {s}\n", .{infoLog});
+        return ShaderInitError.FragementCompilation;
+    }
+
+    gl.glAttachShader(program.*, vertex_shader.*);
+    gl.glAttachShader(program.*, frag_shader.*);
+    gl.glLinkProgram(program.*);
+    std.debug.print("Shader Linking Complete\n", .{});
+    gl.glGetProgramiv(program.*, gl.GL_LINK_STATUS, &success);
+    if (success == 0) {
+        std.debug.print("Shader linking failed!\n", .{});
+        gl.glGetProgramInfoLog(program.*, 512, null, &infoLog);
+        std.debug.print("Error Log: {s}", .{infoLog});
+        return ShaderInitError.ShaderProgramLinking;
+    }
+
+    gl.glDeleteShader(vertex_shader.*);
+    gl.glDeleteShader(frag_shader.*);
+
+    std.debug.print("Shader program selected, cleaned up compiled shaders\n", .{});
+}