Use the lowest targeter in parent chain.

The targeter can be null and in that case it should use the parents.

Bug: b/157910224
Test: covered by unittest. also tested manually. see bug for repro step.
Change-Id: I13db092a6ee062ef9547aec70b6f7cd077558e2d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2225854
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Jesse Schettler <jschettler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774375}

components/exo/shell_surface_unittest.cc

@@ -973,6 +973,24 @@ TEST_F(ShellSurfaceTest, PopupWithInputRegion) {
     ui::Event::DispatcherApi(&event).set_target(target);
     EXPECT_EQ(popup_surface.get(), GetTargetSurfaceForLocatedEvent(&event));
   }
+  popup_surface.reset();
+  EXPECT_EQ(WMHelper::GetInstance()->GetCaptureClient()->GetCaptureWindow(),
+            nullptr);
+
+  auto window = std::make_unique<aura::Window>(nullptr);
+  window->Init(ui::LAYER_TEXTURED);
+  window->SetBounds(gfx::Rect(0, 0, 256, 256));
+  shell_surface->GetWidget()->GetNativeWindow()->AddChild(window.get());
+  window->Show();
+
+  {
+    // If non surface window covers the window,
+    /// GetTargetSurfaceForLocatedEvent should return nullptr.
+    ui::MouseEvent event(ui::ET_MOUSE_MOVED, gfx::Point(0, 0),
+                         gfx::Point(50, 50), ui::EventTimeForNow(), 0, 0);
+    ui::Event::DispatcherApi(&event).set_target(window.get());
+    EXPECT_EQ(nullptr, GetTargetSurfaceForLocatedEvent(&event));
+  }
 }
 
 TEST_F(ShellSurfaceTest, Caption) {

components/exo/shell_surface_util.cc

@@ -58,6 +58,18 @@ bool ShouldHTComponentBlocked(int component) {
   }
 }
 
+// Find the lowest targeter in the parent chain.
+aura::WindowTargeter* FindTargeter(ui::EventTarget* target) {
+  do {
+    ui::EventTargeter* targeter = target->GetEventTargeter();
+    if (targeter)
+      return static_cast<aura::WindowTargeter*>(targeter);
+    target = target->GetParentTarget();
+  } while (target);
+
+  return nullptr;
+}
+
 }  // namespace
 
 void SetShellApplicationId(aura::Window* window,
@@ -135,9 +147,10 @@ Surface* GetTargetSurfaceForLocatedEvent(
     const ui::LocatedEvent* original_event) {
   aura::Window* window =
       WMHelper::GetInstance()->GetCaptureClient()->GetCaptureWindow();
-  if (!window)
+  if (!window) {
     return Surface::AsSurface(
         static_cast<aura::Window*>(original_event->target()));
+  }
 
   Surface* main_surface = GetShellMainSurface(window);
   // Skip if the event is captured by non exo windows.
@@ -160,8 +173,8 @@ Surface* GetTargetSurfaceForLocatedEvent(
     gfx::PointF location_in_target_f = event->location_f();
     gfx::Point location_in_target = event->location();
     ui::EventTarget* event_target = window;
-    aura::WindowTargeter* targeter =
-        static_cast<aura::WindowTargeter*>(event_target->GetEventTargeter());
+    aura::WindowTargeter* targeter = FindTargeter(event_target);
+    DCHECK(targeter);
 
     aura::Window* focused =
         static_cast<aura::Window*>(targeter->FindTargetForEvent(window, event));