Reduce the fullscreen window height by 1px on activation loss.

ui/views/widget/widget_unittest.cc

Index: ui/views/widget/widget_unittest.cc
diff --git a/ui/views/widget/widget_unittest.cc b/ui/views/widget/widget_unittest.cc
index 1ca9e88b8737a441cb7da5cd4fa9e88e7bfcad7c..a677ee7184ff9a024d3aea8f00b93c22a30d424c 100644
--- a/ui/views/widget/widget_unittest.cc
+++ b/ui/views/widget/widget_unittest.cc
@@ -3391,6 +3391,56 @@ TEST_F(WidgetTest, DestroyInSysCommandNCLButtonDownOnCaption) {
   widget.CloseNow();
 }
 
+// On Windows if we create a fullscreen window on a thread, then it affects the
+// way other windows on the thread interact with the taskbar. To workaround
+// this we reduce the bounds of a fullscreen window by 1px when it loses
+// activation. This test verifies the same.
+TEST_F(WidgetTest, FullscreenBoundsReducedOnActivationLoss) {
+  Widget widget1;
+  Widget::InitParams params =
+      CreateParams(Widget::InitParams::TYPE_WINDOW);
+  params.native_widget = new PlatformDesktopNativeWidget(&widget1);
+  params.ownership = Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
+  widget1.Init(params);
+  widget1.SetBounds(gfx::Rect(0, 0, 200, 200));
+  widget1.Show();
+
+  Widget widget2;
+  params.native_widget = new PlatformDesktopNativeWidget(&widget2);
+  params.ownership = Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
+  widget2.Init(params);
+  widget2.SetBounds(gfx::Rect(0, 0, 200, 200));
+  widget2.Show();
+
+  widget1.SetFullscreen(true);
+  EXPECT_TRUE(widget1.IsFullscreen());
+  // Ensure that the StopIgnoringPosChanges task in HWNDMessageHandler runs.
+  // This task is queued when a widget becomes fullscreen.
+  RunPendingMessages();
+
+  gfx::Rect fullscreen_bounds = widget1.GetWindowBoundsInScreen();
+
+  widget2.Activate();
+
+  gfx::Rect fullscreen_bounds_after_activation_loss =
+      widget1.GetWindowBoundsInScreen();
+
+  // After deactivation loss the bounds of the fullscreen widget should be
+  // reduced by 1px.
+  EXPECT_EQ(fullscreen_bounds.height() -
+            fullscreen_bounds_after_activation_loss.height(), 1);
+
+  widget1.Activate();
+
+  gfx::Rect fullscreen_bounds_after_activate =
+      widget1.GetWindowBoundsInScreen();
+
+  // After activation the bounds of the fullscreen widget should be restored.
+  EXPECT_EQ(fullscreen_bounds, fullscreen_bounds_after_activate);
+
+  widget1.CloseNow();
+  widget2.CloseNow();
+}
 #endif
 
 // Test that SetAlwaysOnTop and IsAlwaysOnTop are consistent.