webgl: Move framebuffer initialization logic to WebGL thread.

components/script/dom/webglframebuffer.rs

@@ -34,10 +34,17 @@ enum WebGLFramebufferAttachment {
 impl WebGLFramebufferAttachment {
     fn needs_initialization(&self) -> bool {
         match *self {
-            WebGLFramebufferAttachment::Renderbuffer(_) => true,
+            WebGLFramebufferAttachment::Renderbuffer(ref r) => !r.is_initialized(),
             WebGLFramebufferAttachment::Texture { .. } => false,
         }
     }
+
+    fn mark_initialized(&self) {
+        match *self {
+            WebGLFramebufferAttachment::Renderbuffer(ref r) => r.mark_initialized(),
+            WebGLFramebufferAttachment::Texture { .. } => ()
+        }
+    }
 }
 
 #[derive(Clone, JSTraceable, MallocSizeOf)]
@@ -239,15 +246,14 @@ impl WebGLFramebuffer {
             ];
             let mut clear_bits = 0;
             for &(attachment, bits) in &attachments {
-                if attachment.borrow().as_ref().map_or(false, |att| att.needs_initialization()) {
-                    clear_bits |= bits;
+                if let Some(ref att) = *attachment.borrow() {
+                    if att.needs_initialization() {
+                        att.mark_initialized();
+                        clear_bits |= bits;
+                    }
                 }
             }
-            if clear_bits != 0 {
-                self.upcast::<WebGLObject>().context().send_command(
-                    WebGLCommand::Clear(clear_bits)
-                );
-            }
+            self.upcast::<WebGLObject>().context().initialize_framebuffer(clear_bits);
             self.is_initialized.set(true);
         }
 

components/script/dom/webglrenderbuffer.rs

@@ -23,6 +23,7 @@ pub struct WebGLRenderbuffer {
     is_deleted: Cell<bool>,
     size: Cell<Option<(i32, i32)>>,
     internal_format: Cell<Option<u32>>,
+    is_initialized: Cell<bool>,
 }
 
 impl WebGLRenderbuffer {
@@ -34,6 +35,7 @@ impl WebGLRenderbuffer {
             is_deleted: Cell::new(false),
             internal_format: Cell::new(None),
             size: Cell::new(None),
+            is_initialized: Cell::new(false),
         }
     }
 
@@ -66,6 +68,14 @@ impl WebGLRenderbuffer {
         self.internal_format.get().unwrap_or(constants::RGBA4)
     }
 
+    pub fn mark_initialized(&self) {
+        self.is_initialized.set(true);
+    }
+
+    pub fn is_initialized(&self) -> bool {
+        self.is_initialized.get()
+    }
+
     pub fn bind(&self, target: u32) {
         self.ever_bound.set(true);
         self.upcast::<WebGLObject>()

components/script/dom/webglrenderingcontext.rs

@@ -1061,6 +1061,17 @@ impl WebGLRenderingContext {
             _ => Err(InvalidEnum),
         }
     }
+
+    pub fn initialize_framebuffer(&self, clear_bits: u32) {
+        if clear_bits == 0 {
+            return;
+        }
+        self.send_command(WebGLCommand::InitializeFramebuffer {
+            color: clear_bits & constants::COLOR_BUFFER_BIT != 0,
+            depth: clear_bits & constants::DEPTH_BUFFER_BIT != 0,
+            stencil: clear_bits & constants::STENCIL_BUFFER_BIT != 0,
+        });
+    }
 }
 
 impl Drop for WebGLRenderingContext {
@@ -2727,10 +2738,12 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.3
     fn StencilMaskSeparate(&self, face: u32, mask: u32) {
         match face {
-            constants::FRONT | constants::BACK | constants::FRONT_AND_BACK =>
+            constants::FRONT |
+            constants::BACK |
+            constants::FRONT_AND_BACK =>
                 self.send_command(WebGLCommand::StencilMaskSeparate(face, mask)),
             _ => return self.webgl_error(InvalidEnum),
-        }
+        };
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.3