Got first triangle drawing

src/OpenGL.cake

@@ -7,6 +7,28 @@
           ;; Use galogen-generated header. See (generate-gl-header)
           "gl46.h") ;; "GL/gl.h"
 
+(def-type-alias-global gl-id (unsigned int))
+
+(defun opengl-shader-was-compiled-sucessfully (shader gl-id &return bool)
+  (var success int)
+  (var output-buffer ([] 512 char))
+  (glGetShaderiv shader GL_COMPILE_STATUS (addr success))
+  (unless success
+    (glGetShaderInfoLog shader (sizeof output-buffer) null output-buffer)
+    (fprintf stderr "error: Shader compilation failed:\n%s\n" output-buffer)
+    (return false))
+  (return true))
+
+(defun opengl-program-was-linked-sucessfully (program gl-id &return bool)
+  (var success int)
+  (var output-buffer ([] 512 char))
+  (glGetProgramiv program GL_LINK_STATUS (addr success))
+  (unless success
+    (glGetProgramInfoLog program (sizeof output-buffer) null output-buffer)
+    (fprintf stderr "error: Program link failed:\n%s\n" output-buffer)
+    (return false))
+  (return true))
+
 (comptime-cond
  ('auto-test
   (defun test--opengl (&return int)
@@ -17,17 +39,80 @@
     ;; TODO: Support resizing with window resize callback
     (glViewport 0 0 640 480)
 
-    (scope ;; Make our triangle vertex array object
-     (var vertex-buffer-id (unsigned int))
+    (var shader-program gl-id (glCreateProgram))
+    (scope ;; Prepare program
+     (var vertex-shader gl-id (glCreateShader GL_VERTEX_SHADER))
+     (scope ;; Vertex shader
+      ;; TODO: Generate this via a new Cakelisp language/dialect feature?
+      (var vertex-shader-code (* (const char))
+        "#version 460 core\n
+layout (location = 0) in vec3 position;\n
+void main()\n
+{\n
+    gl_Position = vec4(position.x, position.y, position.z, 1.0);\n
+}")
+      (glShaderSource vertex-shader 1 (addr vertex-shader-code) null)
+      (glCompileShader vertex-shader)
+      (unless (opengl-shader-was-compiled-sucessfully vertex-shader)
+        (sdl-shutdown window)
+        (return 1)))
+
+     (var fragment-shader gl-id (glCreateShader GL_FRAGMENT_SHADER))
+     (scope ;; Fragment shader
+      ;; TODO: Generate this via a new Cakelisp language/dialect feature?
+      (var fragment-shader-code (* (const char))
+        "#version 460 core\n
+out vec4 FragmentColor;\n
+void main()\n
+{\n
+    FragmentColor = vec4(1.f, 0.5f, 0.2f, 1.0f);\n
+}")
+      (glShaderSource fragment-shader 1 (addr fragment-shader-code) null)
+      (glCompileShader fragment-shader)
+      (unless (opengl-shader-was-compiled-sucessfully fragment-shader)
+        (sdl-shutdown window)
+        (return 1)))
+
+     (scope ;; Link vertex and fragment shader
+      (glAttachShader shader-program vertex-shader)
+      (glAttachShader shader-program fragment-shader)
+      (glLinkProgram shader-program)
+      (unless (opengl-program-was-linked-sucessfully shader-program)
+        (sdl-shutdown window)
+        (return 1)))
+
+     (scope ;; Clean up shaders
+      (glDeleteShader vertex-shader)
+      (glDeleteShader fragment-shader)))
+
+    (var triangle-array-object gl-id)
+    (glGenVertexArrays 1 (addr triangle-array-object))
+    (var start-triangles int 0)
+    (var num-triangles int 3)
+    (scope
+     ;; From this point on, configuration will be saved in the vertex array object
+     (glBindVertexArray triangle-array-object)
+
+     ;; Make our triangle vertex array
+     (var vertex-buffer-id gl-id)
      (glGenBuffers 1 (addr vertex-buffer-id))
      (glBindBuffer GL_ARRAY_BUFFER vertex-buffer-id)
 
-     (var vertices ([] float)
+     (var-static vertices ([] float)
        (array
         0.25f 0.25f 0.25f
-        0.5f 0.5f 0.5f
-        0.75f 0.75f 0.75f))
-     (glBufferData GL_ARRAY_BUFFER (sizeof vertices) vertices GL_STATIC_DRAW))
+        0.5f 0.25f 0.25f
+        0.5f 0.75f 0.25f))
+     (glBufferData GL_ARRAY_BUFFER (sizeof vertices) vertices GL_STATIC_DRAW)
+
+     (var layout-location int 0) ;; Should match vertex shader layout
+     (glVertexAttribPointer layout-location 3 GL_FLOAT
+                            GL_FALSE ;; Normalize?
+                            ;; Stride
+                            (* 3 (sizeof float))
+                            ;; Buffer start offset
+                            (type-cast 0 (* void)))
+     (glEnableVertexAttribArray layout-location))
 
     (var exit-reason (* (const char)) null)
     (while (not exit-reason)
@@ -39,9 +124,13 @@
       (when (at SDL_SCANCODE_ESCAPE currentKeyStates)
         (set exit-reason "Escape pressed"))
 
-      (glClearColor 0.2f 0.3f 0.3f 1.f)
+      (glClearColor 0.2f 0.2f 0.2f 1.f)
       (glClear GL_COLOR_BUFFER_BIT)
 
+      (glUseProgram shader-program)
+      (glBindVertexArray triangle-array-object)
+      (glDrawArrays GL_TRIANGLES start-triangles num-triangles)
+
       (SDL_GL_SwapWindow window))
 
     (when exit-reason