Windows: Prevent platform thread from deadlocking during window resize

Author: Aleksey Bekker

shell/platform/windows/flutter_windows_view.cc

@@ -13,23 +13,29 @@
 
 namespace flutter {
 
+namespace {
+// The maximum duration to block the platform thread for while waiting
+// for a window resize operation to complete.
+constexpr std::chrono::milliseconds kWindowResizeTimeout{100};
+
 /// Returns true if the surface will be updated as part of the resize process.
 ///
 /// This is called on window resize to determine if the platform thread needs
 /// to be blocked until the frame with the right size has been rendered. It
 /// should be kept in-sync with how the engine deals with a new surface request
 /// as seen in `CreateOrUpdateSurface` in `GPUSurfaceGL`.
-static bool SurfaceWillUpdate(size_t cur_width,
-                              size_t cur_height,
-                              size_t target_width,
-                              size_t target_height) {
+bool SurfaceWillUpdate(size_t cur_width,
+                       size_t cur_height,
+                       size_t target_width,
+                       size_t target_height) {
   // TODO (https://github.com/flutter/flutter/issues/65061) : Avoid special
   // handling for zero dimensions.
   bool non_zero_target_dims = target_height > 0 && target_width > 0;
   bool not_same_size =
       (cur_height != target_height) || (cur_width != target_width);
   return non_zero_target_dims && not_same_size;
 }
+}  // namespace
 
 FlutterWindowsView::FlutterWindowsView(
     std::unique_ptr<WindowBindingHandler> window_binding) {
@@ -150,9 +156,10 @@ void FlutterWindowsView::OnWindowSizeChanged(size_t width, size_t height) {
     // Block the platform thread until:
     //   1. GetFrameBufferId is called with the right frame size.
     //   2. Any pending SwapBuffers calls have been invoked.
-    resize_cv_.wait(lock, [&resize_status = resize_status_] {
-      return resize_status == ResizeState::kDone;
-    });
+    resize_cv_.wait_for(lock, kWindowResizeTimeout,
+                        [&resize_status = resize_status_] {
+                          return resize_status == ResizeState::kDone;
+                        });
   }
 }
 

shell/platform/windows/flutter_windows_view_unittests.cc

@@ -8,6 +8,7 @@
 #include <comutil.h>
 #include <oleacc.h>
 
+#include <future>
 #include <iostream>
 #include <vector>
 
@@ -546,5 +547,35 @@ TEST(FlutterWindowsViewTest, AccessibilityHitTesting) {
   EXPECT_EQ(varchild.pdispVal, node3_delegate->GetNativeViewAccessible());
 }
 
+TEST(FlutterWindowsViewTest, WindowResizeTests) {
+  std::unique_ptr<FlutterWindowsEngine> engine = GetTestEngine();
+  EngineModifier modifier(engine.get());
+
+  auto window_binding_handler =
+      std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
+
+  FlutterWindowsView view(std::move(window_binding_handler));
+  view.SetEngine(std::move(engine));
+
+  bool send_window_metrics_event_called = false;
+  modifier.embedder_api().SendWindowMetricsEvent = MOCK_ENGINE_PROC(
+      SendWindowMetricsEvent,
+      ([&send_window_metrics_event_called](
+           auto engine, const FlutterWindowMetricsEvent* even) {
+        send_window_metrics_event_called = true;
+        return kSuccess;
+      }));
+
+  std::promise<bool> resize_completed;
+  std::thread([&resize_completed, &view]() {
+    view.OnWindowSizeChanged(500, 500);
+    resize_completed.set_value(true);
+  }).detach();
+
+  auto result = resize_completed.get_future().wait_for(std::chrono::seconds(1));
+  EXPECT_EQ(std::future_status::ready, result);
+  EXPECT_TRUE(send_window_metrics_event_called);
+}
+
 }  // namespace testing
 }  // namespace flutter