;;;; bitmap.lisp

(in-package #:wheelwork)

(defvar *bitmap-shader-program* nil
  "Cached for later cleanup.")
(defvar *bitmap-vao* nil)

(defvar *bitmap-count* 0
  "Used by finalizers to determin if the shader should be destroyed.")

(defun bitmap-finalizer ()
  "executed after a bitmap has been reclaimed by gc. decrements bitmap
count and destroys shader-program if necessary."
  (decf *bitmap-count*)
  (when (zerop *bitmap-count*)
    (when *bitmap-vao*
      (gl:delete-vertex-arrays (list *bitmap-vao*))
      (setf *bitmap-vao* nil))
    (when *bitmap-shader-program*
      (gl:delete-program *bitmap-shader-program*)
      (setf *bitmap-shader-program* nil))))

(defclass/std bitmap (affine interactive)
  ((texture :ri :std (error "A bitmap requires a texture."))))

(defmethod initialize-instance :after ((bitmap bitmap) &key)
  (incf *bitmap-count*)
  (trivial-garbage:finalize bitmap #'bitmap-finalizer)
  (with-slots (base-width base-height texture) bitmap
    (setf base-height (texture-height texture)
          base-width (texture-width texture))
    (unless *bitmap-shader-program*
      (setf *bitmap-shader-program*
            (create-shader
             '(:vertex
               ((vert :vec2))
               ((transform :mat4))
               ((values
                 (* transform (vari:vec4 vert 0.0 1.0))
                 vert))) ;color
             '(:fragment
               ((tc :vec2))
               ((tex :sampler-2d))
               ((let ((frag  (vari:texture tex tc)))
                  (if (< (aref frag 3) 0.01)
                      (vari:discard)
                      frag))))))
      (gl:program-uniformi
       *bitmap-shader-program*
       (gl:get-uniform-location *bitmap-shader-program* "TEX")
       0))
    (unless *bitmap-vao*
      (setf *bitmap-vao* (gl:gen-vertex-array))
      (gl:bind-vertex-array *bitmap-vao*)
      (let ((vbo (gl:gen-buffer)))
        (with-gl-array (verts :float
                              0.0 1.0 
                              1.0 0.0 
                              0.0 0.0 
                              
                              0.0 1.0 
                              1.0 1.0 
                              1.0 0.0 )
          (gl:bind-buffer :array-buffer vbo)
          (gl:buffer-data :array-buffer :static-draw verts)))
      (gl:enable-vertex-attrib-array 0)
      (gl:vertex-attrib-pointer 0 2 :float 0 (* +float-size+ 2) 0)
      (gl:bind-buffer :array-buffer 0)
      (gl:bind-vertex-array 0))))

(defmethod cleanup ((bitmap bitmap))
  (bitmap-finalizer))

(defmethod render ((bitmap bitmap))
  (with-slots (texture) bitmap
    (gl:active-texture 0)
    (gl:bind-texture :texture-2d (texture-id texture))
    (gl:use-program *bitmap-shader-program*)
    (gl:program-uniform-matrix-4fv
     *bitmap-shader-program*
     (gl:get-uniform-location *bitmap-shader-program* "TRANSFORM")
     (projected-matrix bitmap))
    (gl:bind-vertex-array *bitmap-vao*)    
    (gl:draw-arrays :triangles 0 6)
    (gl:bind-vertex-array 0)))