Avoid sending a 0 DPR to framework

lib/ui/window/viewport_metrics.cc

@@ -42,22 +42,13 @@ ViewportMetrics::ViewportMetrics(double p_device_pixel_ratio,
       physical_system_gesture_inset_bottom(
           p_physical_system_gesture_inset_bottom),
       physical_system_gesture_inset_left(p_physical_system_gesture_inset_left) {
-  // Ensure we don't have nonsensical dimensions.
-  FML_DCHECK(physical_width >= 0);
-  FML_DCHECK(physical_height >= 0);
-  FML_DCHECK(device_pixel_ratio > 0);
 }
 
 ViewportMetrics::ViewportMetrics(double p_device_pixel_ratio,
                                  double p_physical_width,
                                  double p_physical_height)
     : device_pixel_ratio(p_device_pixel_ratio),
       physical_width(p_physical_width),
-      physical_height(p_physical_height) {
-  // Ensure we don't have nonsensical dimensions.
-  FML_DCHECK(physical_width >= 0);
-  FML_DCHECK(physical_height >= 0);
-  FML_DCHECK(device_pixel_ratio > 0);
-}
+      physical_height(p_physical_height) {}
 
 }  // namespace flutter

shell/common/fixtures/shell_test.dart

@@ -47,6 +47,19 @@ void onPointerDataPacketMain() {
 @pragma('vm:entry-point')
 void emptyMain() {}
 
+@pragma('vm:entry-point')
+void reportMetrics() {
+  window.onMetricsChanged = () {
+    _reportMetrics(
+      window.devicePixelRatio,
+      window.physicalSize.width,
+      window.physicalSize.height,
+    );
+  };
+}
+
+void _reportMetrics(double devicePixelRatio, double width, double height) native 'ReportMetrics';
+
 @pragma('vm:entry-point')
 void dummyReportTimingsMain() {
   window.onReportTimings = (List<FrameTiming> timings) {};

shell/common/shell.cc

@@ -816,6 +816,16 @@ void Shell::OnPlatformViewSetViewportMetrics(const ViewportMetrics& metrics) {
   FML_DCHECK(is_setup_);
   FML_DCHECK(task_runners_.GetPlatformTaskRunner()->RunsTasksOnCurrentThread());
 
+  if (metrics.device_pixel_ratio <= 0 || metrics.physical_width <= 0 ||
+      metrics.physical_height <= 0) {
+    FML_DLOG(ERROR)
+        << "Embedding reported invalid ViewportMetrics, ignoring update."
+        << "\nphysical_width: " << metrics.physical_width
+        << "\nphysical_height: " << metrics.physical_height
+        << "\ndevice_pixel_ratio: " << metrics.device_pixel_ratio;
+    return;
+  }
+
   // This is the formula Android uses.
   // https://android.googlesource.com/platform/frameworks/base/+/master/libs/hwui/renderthread/CacheManager.cpp#41
   size_t max_bytes = metrics.physical_width * metrics.physical_height * 12 * 4;

shell/common/shell_unittests.cc

@@ -2066,5 +2066,74 @@ TEST_F(ShellTest, DiscardLayerTreeOnResize) {
   DestroyShell(std::move(shell));
 }
 
+TEST_F(ShellTest, IgnoresInvalidMetrics) {
+  fml::AutoResetWaitableEvent latch;
+  double last_device_pixel_ratio;
+  double last_width;
+  double last_height;
+  auto native_report_device_pixel_ratio = [&](Dart_NativeArguments args) {
+    auto dpr_handle = Dart_GetNativeArgument(args, 0);
+    ASSERT_TRUE(Dart_IsDouble(dpr_handle));
+    Dart_DoubleValue(dpr_handle, &last_device_pixel_ratio);
+    ASSERT_FALSE(last_device_pixel_ratio == 0.0);
+
+    auto width_handle = Dart_GetNativeArgument(args, 1);
+    ASSERT_TRUE(Dart_IsDouble(width_handle));
+    Dart_DoubleValue(width_handle, &last_width);
+    ASSERT_FALSE(last_width == 0.0);
+
+    auto height_handle = Dart_GetNativeArgument(args, 2);
+    ASSERT_TRUE(Dart_IsDouble(height_handle));
+    Dart_DoubleValue(height_handle, &last_height);
+    ASSERT_FALSE(last_height == 0.0);
+
+    latch.Signal();
+  };
+
+  Settings settings = CreateSettingsForFixture();
+  auto task_runner = CreateNewThread();
+  TaskRunners task_runners("test", task_runner, task_runner, task_runner,
+                           task_runner);
+
+  AddNativeCallback("ReportMetrics",
+                    CREATE_NATIVE_ENTRY(native_report_device_pixel_ratio));
+
+  std::unique_ptr<Shell> shell =
+      CreateShell(std::move(settings), std::move(task_runners));
+
+  auto configuration = RunConfiguration::InferFromSettings(settings);
+  configuration.SetEntrypoint("reportMetrics");
+
+  RunEngine(shell.get(), std::move(configuration));
+
+  task_runner->PostTask([&]() {
+    shell->GetPlatformView()->SetViewportMetrics({0.0, 400, 200});
+    task_runner->PostTask([&]() {
+      shell->GetPlatformView()->SetViewportMetrics({0.8, 0.0, 200});
+      task_runner->PostTask([&]() {
+        shell->GetPlatformView()->SetViewportMetrics({0.8, 400, 0.0});
+        task_runner->PostTask([&]() {
+          shell->GetPlatformView()->SetViewportMetrics({0.8, 400, 200.0});
+        });
+      });
+    });
+  });
+  latch.Wait();
+  ASSERT_EQ(last_device_pixel_ratio, 0.8);
+  ASSERT_EQ(last_width, 400.0);
+  ASSERT_EQ(last_height, 200.0);
+  latch.Reset();
+
+  task_runner->PostTask([&]() {
+    shell->GetPlatformView()->SetViewportMetrics({1.2, 600, 300});
+  });
+  latch.Wait();
+  ASSERT_EQ(last_device_pixel_ratio, 1.2);
+  ASSERT_EQ(last_width, 600.0);
+  ASSERT_EQ(last_height, 300.0);
+
+  DestroyShell(std::move(shell), std::move(task_runners));
+}
+
 }  // namespace testing
 }  // namespace flutter