webgl: Refactor implementation to move logic inside the DOM interfaces

This improves the encapsulation and consistency in our WebGL
implementation.

Also allows to implement new methods such as `getShaderSource()`.

It will also allow us to use `delete()` in the destructors of them (note
that we will want to keep track of them from the context).

components/script/dom/webglprogram.rs

@@ -13,27 +13,114 @@ use dom::webglobject::WebGLObject;
 pub struct WebGLProgram {
     webgl_object: WebGLObject,
     id: u32,
+    is_deleted: Cell<bool>,
+    fragment_shader: MutNullableHeap<JS<WebGLShader>>,
+    vertex_shader: MutNullableHeap<JS<WebGLShader>>,
+    renderer: Sender<CanvasMsg>,
 }
 
 impl WebGLProgram {
-    fn new_inherited(id: u32) -> WebGLProgram {
+    fn new_inherited(renderer: Sender<CanvasMsg>, id: u32) -> WebGLProgram {
         WebGLProgram {
             webgl_object: WebGLObject::new_inherited(),
             id: id,
+            is_deleted: Cell::new(false),
+            fragment_shader: Default::default(),
+            vertex_shader: Default::default(),
+            renderer: renderer,
         }
     }
 
-    pub fn new(global: GlobalRef, id: u32) -> Root<WebGLProgram> {
-        reflect_dom_object(box WebGLProgram::new_inherited(id), global, WebGLProgramBinding::Wrap)
+    pub fn maybe_new(global: GlobalRef, renderer: Sender<CanvasMsg>) -> Option<Root<WebGLProgram>> {
+        let (sender, receiver) = channel();
+        renderer.send(CanvasMsg::WebGL(CanvasWebGLMsg::CreateProgram(sender))).unwrap();
+        receiver.recv().unwrap()
+            .map(|program_id| WebGLProgram::new(global, renderer, *program_id))
+    }
+
+    pub fn new(global: GlobalRef, renderer: Sender<CanvasMsg>, id: u32) -> Root<WebGLProgram> {
+        reflect_dom_object(box WebGLProgram::new_inherited(renderer, id), global, WebGLProgramBinding::Wrap)
     }
 }
 
 pub trait WebGLProgramHelpers {
-    fn get_id(self) -> u32;
+    fn delete(self);
+    fn link(self);
+    fn use_program(self);
+    fn attach_shader(self, shader: JSRef<WebGLShader>) -> WebGLResult<()>;
+    fn get_attrib_location(self, name: String) -> WebGLResult<Option<i32>>;
+    fn get_uniform_location(self, name: String) -> WebGLResult<Option<i32>>;
 }
 
 impl<'a> WebGLProgramHelpers for &'a WebGLProgram {
-    fn get_id(self) -> u32 {
-        self.id
+    /// glDeleteProgram
+    fn delete(self) {
+        if !self.is_deleted.get() {
+            self.is_deleted.set(true);
+            self.renderer.send(CanvasMsg::WebGL(CanvasWebGLMsg::DeleteProgram(self.id))).unwrap();
+        }
+    }
+
+    /// glLinkProgram
+    fn link(self) {
+        self.renderer.send(CanvasMsg::WebGL(CanvasWebGLMsg::LinkProgram(self.id))).unwrap();
+    }
+
+    /// glUseProgram
+    fn use_program(self) {
+        self.renderer.send(CanvasMsg::WebGL(CanvasWebGLMsg::UseProgram(self.id))).unwrap();
+    }
+
+    /// glAttachShader
+    fn attach_shader(self, shader: &'a WebGLShader) -> WebGLResult<()> {
+        let shader_slot = match shader.gl_type() {
+            constants::FRAGMENT_SHADER => &self.fragment_shader,
+            constants::VERTEX_SHADER => &self.vertex_shader,
+            _ => return Err(WebGLError::InvalidOperation),
+        };
+
+        // TODO(ecoal95): Differenciate between same shader already assigned and other previous
+        // shader.
+        if shader_slot.get().is_some() {
+            return Err(WebGLError::InvalidOperation);
+        }
+
+        shader_slot.set(Some(JS::from_rooted(shader)));
+
+        self.renderer.send(CanvasMsg::WebGL(CanvasWebGLMsg::AttachShader(self.id, shader.id()))).unwrap();
+
+        Ok(())
+    }
+
+    /// glGetAttribLocation
+    fn get_attrib_location(self, name: String) -> WebGLResult<Option<i32>> {
+        if name.len() > MAX_UNIFORM_AND_ATTRIBUTE_LEN {
+            return Err(WebGLError::InvalidValue);
+        }
+
+        // Check if the name is reserved
+        if name.starts_with("webgl") || name.starts_with("_webgl_") {
+            return Ok(None);
+        }
+
+        let (sender, receiver) = channel();
+        self.renderer.send(CanvasMsg::WebGL(CanvasWebGLMsg::GetAttribLocation(self.id, name, sender))).unwrap();
+        Ok(receiver.recv().unwrap())
+    }
+
+    /// glGetUniformLocation
+    fn get_uniform_location(self, name: String) -> WebGLResult<Option<i32>> {
+        if name.len() > MAX_UNIFORM_AND_ATTRIBUTE_LEN {
+            return Err(WebGLError::InvalidValue);
+        }
+
+        // Check if the name is reserved
+        if name.starts_with("webgl") || name.starts_with("_webgl_") {
+            return Ok(None);
+        }
+
+        let (sender, receiver) = channel();
+        self.renderer.send(CanvasMsg::WebGL(CanvasWebGLMsg::GetUniformLocation(self.id, name, sender))).unwrap();
+        Ok(receiver.recv().unwrap())
     }
 }