Auto merge of #23868 - asajeffrey:webgl-if-used-on-main-thread-use-di…

…rectly-do-not-pass-go, r=jdm

When using the WebGL external image API, use sync calls if we happen to be on the WebGL thread

<!-- Please describe your changes on the following line: -->

When using the external image API, use synchronous method calls if we happen to be on the same thread as WebGL.

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #23832 hopefully
- [x] These changes do not require tests because it's fixing a deadlock

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components/canvas/webgl_mode/inprocess.rs

@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::gl_context::GLContextFactory;
-use crate::webgl_thread::{TexturesMap, WebGLMainThread, WebGLThread, WebGLThreadInit};
+use crate::webgl_thread::{WebGLMainThread, WebGLThread, WebGLThreadInit};
 use canvas_traits::webgl::webgl_channel;
 use canvas_traits::webgl::DOMToTextureCommand;
 use canvas_traits::webgl::{WebGLChan, WebGLContextId, WebGLMsg, WebGLPipeline, WebGLReceiver};
@@ -13,8 +13,6 @@ use euclid::default::Size2D;
 use fnv::FnvHashMap;
 use gleam::gl;
 use servo_config::pref;
-use std::cell::RefCell;
-use std::collections::HashMap;
 use std::default::Default;
 use std::rc::Rc;
 use std::sync::{Arc, Mutex};
@@ -25,20 +23,21 @@ pub struct WebGLThreads(WebGLSender<WebGLMsg>);
 
 pub enum ThreadMode {
     MainThread(Box<dyn EventLoopWaker>),
-    OffThread(Rc<dyn gl::Gl>),
+    OffThread,
 }
 
 impl WebGLThreads {
     /// Creates a new WebGLThreads object
     pub fn new(
         gl_factory: GLContextFactory,
+        webrender_gl: Rc<dyn gl::Gl>,
         webrender_api_sender: webrender_api::RenderApiSender,
         webvr_compositor: Option<Box<dyn WebVRRenderHandler>>,
         external_images: Arc<Mutex<WebrenderExternalImageRegistry>>,
         mode: ThreadMode,
     ) -> (
         WebGLThreads,
-        Option<WebGLMainThread>,
+        Option<Rc<WebGLMainThread>>,
         Box<dyn WebrenderExternalImageApi>,
         Option<Box<dyn webrender::OutputImageHandler>>,
     ) {
@@ -54,33 +53,24 @@ impl WebGLThreads {
         };
 
         let output_handler = if pref!(dom.webgl.dom_to_texture.enabled) {
-            Some(Box::new(match mode {
-                ThreadMode::MainThread(..) => OutputHandler::new_main_thread(),
-                ThreadMode::OffThread(ref webrender_gl) => {
-                    OutputHandler::new_off_thread(webrender_gl.clone(), sender.clone())
-                },
-            }))
+            Some(Box::new(OutputHandler::new(
+                webrender_gl.clone(),
+                sender.clone(),
+            )))
         } else {
             None
         };
 
-        let (external, webgl_thread) = match mode {
+        let external = WebGLExternalImages::new(webrender_gl, sender.clone());
+
+        let webgl_thread = match mode {
             ThreadMode::MainThread(event_loop_waker) => {
-                let textures = Rc::new(RefCell::new(HashMap::new()));
-                let thread_data =
-                    WebGLThread::run_on_current_thread(init, event_loop_waker, textures.clone());
-                (
-                    WebGLExternalImages::new_main_thread(textures),
-                    Some(thread_data),
-                )
+                let thread = WebGLThread::run_on_current_thread(init, event_loop_waker);
+                Some(thread)
             },
-
-            ThreadMode::OffThread(webrender_gl) => {
+            ThreadMode::OffThread => {
                 WebGLThread::run_on_own_thread(init);
-                (
-                    WebGLExternalImages::new_off_thread(webrender_gl, sender.clone()),
-                    None,
-                )
+                None
             },
         };
 
@@ -107,113 +97,90 @@ impl WebGLThreads {
 }
 
 /// Bridge between the webrender::ExternalImage callbacks and the WebGLThreads.
-enum WebGLExternalImages {
-    OffThread {
-        webrender_gl: Rc<dyn gl::Gl>,
-        webgl_channel: WebGLSender<WebGLMsg>,
-        // Used to avoid creating a new channel on each received WebRender request.
-        lock_channel: (
-            WebGLSender<(u32, Size2D<i32>, usize)>,
-            WebGLReceiver<(u32, Size2D<i32>, usize)>,
-        ),
-    },
-    MainThread {
-        textures: TexturesMap,
-    },
+struct WebGLExternalImages {
+    webrender_gl: Rc<dyn gl::Gl>,
+    webgl_channel: WebGLSender<WebGLMsg>,
+    // Used to avoid creating a new channel on each received WebRender request.
+    lock_channel: (
+        WebGLSender<(u32, Size2D<i32>, usize)>,
+        WebGLReceiver<(u32, Size2D<i32>, usize)>,
+    ),
 }
 
 impl WebGLExternalImages {
-    fn new_off_thread(webrender_gl: Rc<dyn gl::Gl>, channel: WebGLSender<WebGLMsg>) -> Self {
-        WebGLExternalImages::OffThread {
+    fn new(webrender_gl: Rc<dyn gl::Gl>, channel: WebGLSender<WebGLMsg>) -> Self {
+        WebGLExternalImages {
             webrender_gl,
             webgl_channel: channel,
             lock_channel: webgl_channel().unwrap(),
         }
     }
-
-    fn new_main_thread(textures: TexturesMap) -> Self {
-        WebGLExternalImages::MainThread { textures }
-    }
 }
 
 impl WebrenderExternalImageApi for WebGLExternalImages {
     fn lock(&mut self, id: u64) -> (u32, Size2D<i32>) {
-        match *self {
-            WebGLExternalImages::OffThread {
-                ref webgl_channel,
-                ref webrender_gl,
-                ref lock_channel,
-            } => {
-                // WebGL Thread has it's own GL command queue that we need to synchronize with the WR GL command queue.
-                // The WebGLMsg::Lock message inserts a fence in the WebGL command queue.
-                webgl_channel
-                    .send(WebGLMsg::Lock(
-                        WebGLContextId(id as usize),
-                        lock_channel.0.clone(),
-                    ))
-                    .unwrap();
-                let (image_id, size, gl_sync) = 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 WebGL texture.
-                // glWaitSync doesn't block WR thread, it affects only internal OpenGL subsystem.
-                webrender_gl.wait_sync(gl_sync as gl::GLsync, 0, gl::TIMEOUT_IGNORED);
-                (image_id, size)
-            },
-
-            WebGLExternalImages::MainThread { ref textures } => {
-                let textures = textures.borrow();
-                let entry = textures
-                    .get(&WebGLContextId(id as usize))
-                    .expect("no texture entry???");
-                (entry.0, entry.1)
-            },
+        if let Some(main_thread) = WebGLMainThread::on_current_thread() {
+            // If we're on the same thread as WebGL, we can get the data directly
+            main_thread
+                .thread_data
+                .borrow_mut()
+                .handle_lock_unsync(WebGLContextId(id as usize))
+        } else {
+            // WebGL Thread has it's own GL command queue that we need to synchronize with the WR GL command queue.
+            // The WebGLMsg::Lock message inserts a fence in the WebGL command queue.
+            self.webgl_channel
+                .send(WebGLMsg::Lock(
+                    WebGLContextId(id as usize),
+                    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 WebGL 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) {
-        match *self {
-            WebGLExternalImages::OffThread {
-                ref webgl_channel, ..
-            } => {
-                webgl_channel
-                    .send(WebGLMsg::Unlock(WebGLContextId(id as usize)))
-                    .unwrap();
-            },
-
-            WebGLExternalImages::MainThread { .. } => {},
+        if let Some(main_thread) = WebGLMainThread::on_current_thread() {
+            // If we're on the same thread as WebGL, we can unlock directly
+            main_thread
+                .thread_data
+                .borrow_mut()
+                .handle_unlock(WebGLContextId(id as usize))
+        } else {
+            self.webgl_channel
+                .send(WebGLMsg::Unlock(WebGLContextId(id as usize)))
+                .unwrap()
         }
     }
 }
 
 /// struct used to implement DOMToTexture feature and webrender::OutputImageHandler trait.
 type OutputHandlerData = Option<(u32, Size2D<i32>)>;
-enum OutputHandler {
-    OffThread {
-        webrender_gl: Rc<dyn gl::Gl>,
-        webgl_channel: WebGLSender<WebGLMsg>,
-        // Used to avoid creating a new channel on each received WebRender request.
-        lock_channel: (
-            WebGLSender<OutputHandlerData>,
-            WebGLReceiver<OutputHandlerData>,
-        ),
-        sync_objects: FnvHashMap<webrender_api::PipelineId, gl::GLsync>,
-    },
-    MainThread,
+struct OutputHandler {
+    webrender_gl: Rc<dyn gl::Gl>,
+    webgl_channel: WebGLSender<WebGLMsg>,
+    // Used to avoid creating a new channel on each received WebRender request.
+    lock_channel: (
+        WebGLSender<OutputHandlerData>,
+        WebGLReceiver<OutputHandlerData>,
+    ),
+    sync_objects: FnvHashMap<webrender_api::PipelineId, gl::GLsync>,
 }
 
 impl OutputHandler {
-    fn new_off_thread(webrender_gl: Rc<dyn gl::Gl>, channel: WebGLSender<WebGLMsg>) -> Self {
-        OutputHandler::OffThread {
+    fn new(webrender_gl: Rc<dyn gl::Gl>, channel: WebGLSender<WebGLMsg>) -> Self {
+        OutputHandler {
             webrender_gl,
             webgl_channel: channel,
             lock_channel: webgl_channel().unwrap(),
             sync_objects: Default::default(),
         }
     }
-
-    fn new_main_thread() -> Self {
-        OutputHandler::MainThread
-    }
 }
 
 /// Bridge between the WR frame outputs and WebGL to implement DOMToTexture synchronization.
@@ -222,49 +189,41 @@ impl webrender::OutputImageHandler for OutputHandler {
         &mut self,
         id: webrender_api::PipelineId,
     ) -> Option<(u32, webrender_api::units::FramebufferIntSize)> {
-        match *self {
-            OutputHandler::OffThread {
-                ref webrender_gl,
-                ref lock_channel,
-                ref webgl_channel,
-                ..
-            } => {
-                // Insert a fence in the WR command queue
-                let gl_sync = webrender_gl.fence_sync(gl::SYNC_GPU_COMMANDS_COMPLETE, 0);
-                // The lock command adds a WaitSync call on the WebGL command flow.
-                let command =
-                    DOMToTextureCommand::Lock(id, gl_sync as usize, lock_channel.0.clone());
-                webgl_channel
-                    .send(WebGLMsg::DOMToTextureCommand(command))
-                    .unwrap();
-                lock_channel.1.recv().unwrap().map(|(tex_id, size)| {
-                    (
-                        tex_id,
-                        webrender_api::units::FramebufferIntSize::new(size.width, size.height),
-                    )
-                })
-            },
+        // Insert a fence in the WR command queue
+        let gl_sync = self
+            .webrender_gl
+            .fence_sync(gl::SYNC_GPU_COMMANDS_COMPLETE, 0);
+        self.sync_objects.insert(id, gl_sync);
+
+        let result = if let Some(main_thread) = WebGLMainThread::on_current_thread() {
+            main_thread
+                .thread_data
+                .borrow_mut()
+                .handle_dom_to_texture_lock(id, gl_sync as usize)
+        } else {
+            // The lock command adds a WaitSync call on the WebGL command flow.
+            let command =
+                DOMToTextureCommand::Lock(id, gl_sync as usize, self.lock_channel.0.clone());
+            self.webgl_channel
+                .send(WebGLMsg::DOMToTextureCommand(command))
+                .unwrap();
+            self.lock_channel.1.recv().unwrap()
+        };
 
-            OutputHandler::MainThread => unimplemented!(),
-        }
+        result.map(|(tex_id, size)| {
+            (
+                tex_id,
+                webrender_api::units::FramebufferIntSize::new(size.width, size.height),
+            )
+        })
     }
 
     fn unlock(&mut self, id: webrender_api::PipelineId) {
-        match *self {
-            OutputHandler::OffThread {
-                ref webrender_gl,
-                ref mut sync_objects,
-                ..
-            } => {
-                if let Some(gl_sync) = sync_objects.remove(&id) {
-                    // Flush the Sync object into the GPU's command queue to guarantee that it it's signaled.
-                    webrender_gl.flush();
-                    // Mark the sync object for deletion.
-                    webrender_gl.delete_sync(gl_sync);
-                }
-            },
-
-            OutputHandler::MainThread => {},
+        if let Some(gl_sync) = self.sync_objects.remove(&id) {
+            // Flush the Sync object into the GPU's command queue to guarantee that it it's signaled.
+            self.webrender_gl.flush();
+            // Mark the sync object for deletion.
+            self.webrender_gl.delete_sync(gl_sync);
         }
     }
 }