chromeos: Clean up ExtendedDesktopTest.PassiveGrab

The assertions were unclear because the test window was being created
partially outside the display work area, resulting in it being moved
from its initial coordinates.

Make the simulated display bigger so the window isn't moved.
Clarify and document the expectations.

Bug: 890633
Test: ash_unittests
Change-Id: Ie0ba065bc4d8f46a2cfd6ad24250d808845e8cd5
Reviewed-on: https://chromium-review.googlesource.com/1252384
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595456}

ash/extended_desktop_unittest.cc

@@ -84,13 +84,18 @@ class MoveWindowByClickEventHandler : public ui::EventHandler {
 // An event handler which records the event's locations.
 class EventLocationRecordingEventHandler : public ui::EventHandler {
  public:
-  explicit EventLocationRecordingEventHandler() { reset(); }
+  EventLocationRecordingEventHandler() { Reset(); }
   ~EventLocationRecordingEventHandler() override = default;
 
-  std::string GetLocationsAndReset() {
-    std::string result = location_.ToString() + " " + root_location_.ToString();
-    reset();
-    return result;
+  // |location_| is relative to the target window.
+  std::string GetLocation() const { return location_.ToString(); }
+
+  // |root_location_| is relative to the display where the event started.
+  std::string GetRootLocation() const { return root_location_.ToString(); }
+
+  void Reset() {
+    location_.SetPoint(-999, -999);
+    root_location_.SetPoint(-999, -999);
   }
 
  private:
@@ -103,11 +108,6 @@ class EventLocationRecordingEventHandler : public ui::EventHandler {
     }
   }
 
-  void reset() {
-    location_.SetPoint(-999, -999);
-    root_location_.SetPoint(-999, -999);
-  }
-
   gfx::Point root_location_;
   gfx::Point location_;
 
@@ -866,35 +866,63 @@ TEST_F(ExtendedDesktopTest, KeyEventsOnLockScreen) {
   EXPECT_EQ("abcde", base::UTF16ToASCII(textfield->text()));
 }
 
+// Verifies that clicking in the primary display and dragging to the secondary
+// display correctly sets the event location (window local) and root_location
+// (in screen coordinates) for the mouse event. https://crrev.com/11691010
 TEST_F(ExtendedDesktopTest, PassiveGrab) {
   // This test deals with input events but not visuals so don't throttle input
   // on visuals.
   Shell::Get()->aura_env()->set_throttle_input_on_resize_for_testing(false);
   EventLocationRecordingEventHandler event_handler;
-  ash::Shell::Get()->AddPreTargetHandler(&event_handler);
+  Shell::Get()->AddPreTargetHandler(&event_handler);
 
-  UpdateDisplay("300x300,200x200");
+  // Create large displays so the widget won't be moved after creation.
+  // https://crbug.com/890633
+  UpdateDisplay("1000x1000,1000x1000");
 
   views::Widget* widget = CreateTestWidget(gfx::Rect(50, 50, 200, 200));
   widget->Show();
-  ASSERT_EQ("50,44 200x200", widget->GetWindowBoundsInScreen().ToString());
+  ASSERT_EQ("50,50 200x200", widget->GetWindowBoundsInScreen().ToString());
 
+  // Move the mouse to the center of the window.
   ui::test::EventGenerator* generator = GetEventGenerator();
   generator->MoveMouseTo(150, 150);
-  EXPECT_EQ("100,106 150,150", event_handler.GetLocationsAndReset());
 
+  // Location is relative to the window.
+  EXPECT_EQ("100,100", event_handler.GetLocation());
+
+  // Root location is relative to the display.
+  EXPECT_EQ("150,150", event_handler.GetRootLocation());
+  event_handler.Reset();
+
+  // Drag the mouse to the secondary display. Does not drag the window.
   generator->PressLeftButton();
-  generator->MoveMouseTo(400, 150);
+  generator->MoveMouseBy(1000, 0);
 
-  EXPECT_EQ("350,106 400,150", event_handler.GetLocationsAndReset());
+  // Location is relative to the original window.
+  EXPECT_EQ("1100,100", event_handler.GetLocation());
 
+  // Root location is relative to the original display.
+  EXPECT_EQ("1150,150", event_handler.GetRootLocation());
+  event_handler.Reset();
+
+  // End the drag.
   generator->ReleaseLeftButton();
-  EXPECT_EQ("-999,-999 -999,-999", event_handler.GetLocationsAndReset());
+  EXPECT_EQ("-999,-999", event_handler.GetRootLocation());
+  EXPECT_EQ("-999,-999", event_handler.GetLocation());
+  event_handler.Reset();
+
+  // Move the mouse to the top-left of the secondary display.
+  generator->MoveMouseTo(1001, 1);
+
+  // Location is relative to the new display.
+  EXPECT_EQ("1,1", event_handler.GetLocation());
 
-  generator->MoveMouseTo(400, 150);
-  EXPECT_EQ("100,6 100,150", event_handler.GetLocationsAndReset());
+  // Root location is relative to the new display.
+  EXPECT_EQ("1,1", event_handler.GetRootLocation());
+  event_handler.Reset();
 
-  ash::Shell::Get()->RemovePreTargetHandler(&event_handler);
+  Shell::Get()->RemovePreTargetHandler(&event_handler);
 }
 
 }  // namespace ash