Implement webrender::ExternalImageHandler for player

Added trait GLPlayerExternalImageApi and its implementation
Implemented webrender::ExternalImageHandler using
GLPlayerExternalImageApi

components/canvas/media_mode/inprocess.rs

@@ -2,8 +2,12 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use crate::media_thread::GLPlayerThread;
-use canvas_traits::media::{GLPlayerChan, GLPlayerMsg, GLPlayerPipeline, GLPlayerSender};
+use crate::media_thread::{GLPlayerExternalImageApi, GLPlayerExternalImageHandler, GLPlayerThread};
+use canvas_traits::media::glplayer_channel;
+use canvas_traits::media::{
+    GLPlayerChan, GLPlayerMsg, GLPlayerPipeline, GLPlayerReceiver, GLPlayerSender,
+};
+use euclid::Size2D;
 
 /// GLPlayer Threading API entry point that lives in the constellation.
 pub struct GLPlayerThreads(GLPlayerSender<GLPlayerMsg>);
@@ -28,3 +32,50 @@ impl GLPlayerThreads {
             .map_err(|_| "Failed to send Exit message")
     }
 }
+
+/// Bridge between the webrender::ExternalImage callbacks and the
+/// GLPlayerThreads.
+struct GLPlayerExternalImages {
+    // @FIXME(victor): this should be added when GstGLSyncMeta is
+    // added
+    //webrender_gl: Rc<dyn gl::Gl>,
+    glplayer_channel: GLPlayerSender<GLPlayerMsg>,
+    // Used to avoid creating a new channel on each received WebRender
+    // request.
+    lock_channel: (
+        GLPlayerSender<(u32, Size2D<i32>, usize)>,
+        GLPlayerReceiver<(u32, Size2D<i32>, usize)>,
+    ),
+}
+
+impl GLPlayerExternalImages {
+    fn new(channel: GLPlayerSender<GLPlayerMsg>) -> Self {
+        Self {
+            glplayer_channel: channel,
+            lock_channel: glplayer_channel().unwrap(),
+        }
+    }
+}
+
+impl GLPlayerExternalImageApi for GLPlayerExternalImages {
+    fn lock(&mut self, id: u64) -> (u32, Size2D<i32>) {
+        // The GLPlayerMsgForward::Lock message inserts a fence in the
+        // GLPlayer command queue.
+        self.glplayer_channel
+            .send(GLPlayerMsg::Lock(id, self.lock_channel.0.clone()))
+            .unwrap();
+        let (image_id, size, _gl_sync) = self.lock_channel.1.recv().unwrap();
+        // The next glWaitSync call is run on the WR thread and it's
+        // used to synchronize the two flows of OpenGL commands in
+        // order to avoid WR using a semi-ready GLPlayer texture.
+        // glWaitSync doesn't block WR thread, it affects only
+        // internal OpenGL subsystem.
+        //self.webrender_gl
+        //    .wait_sync(gl_sync as gl::GLsync, 0, gl::TIMEOUT_IGNORED);
+        (image_id, size)
+    }
+
+    fn unlock(&mut self, id: u64) {
+        self.glplayer_channel.send(GLPlayerMsg::Unlock(id)).unwrap();
+    }
+}

components/canvas/media_thread.rs

@@ -3,6 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use canvas_traits::media::*;
+use euclid::Size2D;
 use fnv::FnvHashMap;
 use std::thread;
 
@@ -80,3 +81,60 @@ impl GLPlayerThread {
         false
     }
 }
+
+/// This trait is used as a bridge between the `GLPlayerThreads`
+/// implementation and the WR ExternalImageHandler API implemented in
+/// the `GLPlayerExternalImageHandler` struct.
+//
+/// `GLPlayerExternalImageHandler<T>` takes care of type conversions
+/// between WR and GLPlayer info (e.g keys, uvs).
+//
+/// It uses this trait to notify lock/unlock messages and get the
+/// required info that WR needs.
+//
+/// `GLPlayerThreads` receives lock/unlock message notifications and
+/// takes care of sending the unlock/lock messages to the appropiate
+/// `GLPlayerThread`.
+pub trait GLPlayerExternalImageApi {
+    fn lock(&mut self, id: u64) -> (u32, Size2D<i32>);
+    fn unlock(&mut self, id: u64);
+}
+
+/// WebRender External Image Handler implementation
+pub struct GLPlayerExternalImageHandler<T: GLPlayerExternalImageApi> {
+    handler: T,
+}
+
+impl<T: GLPlayerExternalImageApi> GLPlayerExternalImageHandler<T> {
+    pub fn new(handler: T) -> Self {
+        Self { handler: handler }
+    }
+}
+
+impl<T: GLPlayerExternalImageApi> webrender::ExternalImageHandler
+    for GLPlayerExternalImageHandler<T>
+{
+    /// Lock the external image. Then, WR could start to read the
+    /// image content.
+    /// The WR client should not change the image content until the
+    /// unlock() call.
+    fn lock(
+        &mut self,
+        key: webrender_api::ExternalImageId,
+        _channel_index: u8,
+        _rendering: webrender_api::ImageRendering,
+    ) -> webrender::ExternalImage {
+        let (texture_id, size) = self.handler.lock(key.0);
+
+        webrender::ExternalImage {
+            uv: webrender_api::TexelRect::new(0.0, 0.0, size.width as f32, size.height as f32),
+            source: webrender::ExternalImageSource::NativeTexture(texture_id),
+        }
+    }
+
+    /// Unlock the external image. The WR should not read the image
+    /// content after this call.
+    fn unlock(&mut self, key: webrender_api::ExternalImageId, _channel_index: u8) {
+        self.handler.unlock(key.0);
+    }
+}