Add 'shf/' from commit 'b6c5a95b664aeb861d7b33ffc9eefe447ba99dd7'

git-subtree-dir: shf
git-subtree-mainline: 401408448f
git-subtree-split: b6c5a95b66

shf/shell/gl-draw.sml

@@ -0,0 +1,82 @@
+structure GlDraw =
+struct
+  open DrawMsg
+
+  type t =
+    { textVertexBuffer: Word32.word
+    , textProgram: Word32.word
+    , textDrawLength: int
+    }
+
+  fun createShader (shaderType, shaderString) =
+    let
+      val shader = Gles3.createShader shaderType
+      val _ = Gles3.shaderSource (shader, shaderString)
+      val _ = Gles3.compileShader shader
+    in
+      shader
+    end
+
+  fun createProgram (vertexShader, fragmentShader) =
+    let
+      val program = Gles3.createProgram ()
+      val _ = Gles3.attachShader (program, vertexShader)
+      val _ = Gles3.attachShader (program, fragmentShader)
+      val _ = Gles3.linkProgram program
+    in
+      program
+    end
+
+  fun create () =
+    let
+      (* create vertex buffer, program, etc. for text. *)
+      val textVertexBuffer = Gles3.createBuffer ()
+      val xyzRgbVertexShader = createShader
+        (Gles3.VERTEX_SHADER, GlShaders.xyzRgbVertexShaderString)
+
+      val rgbFragmentShader = createShader
+        (Gles3.FRAGMENT_SHADER, GlShaders.rgbFragmentShaderString)
+
+      val textProgram = createProgram (xyzRgbVertexShader, rgbFragmentShader)
+
+      (* clean up shaders which are no longer needed once progran is linked. *)
+      val _ = Gles3.deleteShader xyzRgbVertexShader
+      val _ = Gles3.deleteShader rgbFragmentShader
+
+      (* because we only have a single vertex buffer, 
+       * we only need to bind and set attributes once. *)
+      val _ = Gles3.bindBuffer textVertexBuffer
+
+      (* enable xyz component from uploaded array *)
+      val _ = Gles3.vertexAttribPointer (0, 3, 6, 0)
+      val _ = Gles3.enableVertexAttribArray 0
+      (* enable rgb component from uploaded array *)
+      val _ = Gles3.vertexAttribPointer (1, 3, 6, 12)
+      val _ = Gles3.enableVertexAttribArray 1
+
+      val _ = Gles3.useProgram textProgram
+    in
+      { textVertexBuffer = textVertexBuffer
+      , textProgram = textProgram
+      , textDrawLength = 0
+      }
+    end
+
+  fun uploadText (drawState: t, vec) =
+    let
+      val {textVertexBuffer, textProgram, textDrawLength = _} = drawState
+
+      val _ = Gles3.bufferData (vec, Vector.length vec, Gles3.STATIC_DRAW)
+      val newTextDrawLength = Vector.length vec div 6
+    in
+      { textVertexBuffer = textVertexBuffer
+      , textProgram = textProgram
+      , textDrawLength = newTextDrawLength
+      }
+    end
+
+  fun draw (drawObject: t) =
+    let val {textVertexBuffer, textDrawLength, textProgram} = drawObject
+    in Gles3.drawArrays (Gles3.TRIANGLES, 0, textDrawLength)
+    end
+end