[Chromecast] Fix window ordering

The curent implementation tries to order one window in a list of
potentially unordered windows. The window list is not always ordered
since we never order hidden windows.

Use stable_sort to order all windows by ID. Between windows with the
same ID, promote the window currently becoming visible.

BUG=NONE
TEST=Verified on device and wrote unittests to cover window ordering.

Change-Id: I52a760a6fbb84752a523c89ba39963f443ab4712
Reviewed-on: https://chromium-review.googlesource.com/1103296Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567989}

chromecast/graphics/cast_window_manager_aura.cc

@@ -177,27 +177,21 @@ void CastLayoutManager::OnChildWindowVisibilityChanged(aura::Window* child,
 
   // Determine z-order relative to existing windows.
   aura::Window::Windows windows = parent->children();
-  aura::Window* above = nullptr;
-  aura::Window* below = nullptr;
-  for (auto* other : windows) {
-    if (other == child) {
-      continue;
-    }
-    if ((other->id() < child->id()) && (!below || other->id() > below->id())) {
-      below = other;
-    } else if ((other->id() > child->id()) &&
-               (!above || other->id() < above->id())) {
-      above = other;
-    }
-  }
-
-  // Adjust the z-order of the new child window.
-  if (above) {
-    parent->StackChildBelow(child, above);
-  } else if (below) {
-    parent->StackChildAbove(child, below);
-  } else {
-    parent->StackChildAtBottom(child);
+  std::stable_sort(windows.begin(), windows.end(),
+                   [child](aura::Window* lhs, aura::Window* rhs) {
+                     // Promote |child| to the top of the stack of windows with
+                     // the same ID.
+                     if (lhs->id() == rhs->id() && rhs == child)
+                       return true;
+
+                     return lhs->id() < rhs->id();
+                   });
+
+  for (size_t i = 0; i < windows.size(); ++i) {
+    if (i == 0)
+      parent->StackChildAtBottom(windows[i]);
+    else
+      parent->StackChildAbove(windows[i], windows[i - 1]);
   }
 }
 

chromecast/graphics/cast_window_manager_aura_test.cc

@@ -35,6 +35,23 @@ class CastTestWindowDelegate : public aura::test::TestWindowDelegate {
   DISALLOW_COPY_AND_ASSIGN(CastTestWindowDelegate);
 };
 
+class TestWindow {
+ public:
+  TestWindow(int id) : window_(&delegate_) {
+    window_.Init(ui::LAYER_NOT_DRAWN);
+    window_.set_id(id);
+    window_.SetBounds(gfx::Rect(0, 0, 1280, 720));
+  }
+
+  aura::Window* window() { return &window_; }
+
+ private:
+  CastTestWindowDelegate delegate_;
+  aura::Window window_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestWindow);
+};
+
 TEST_F(CastWindowManagerAuraTest, InitialWindowId) {
   CastTestWindowDelegate window_delegate;
   aura::Window window(&window_delegate);
@@ -102,5 +119,59 @@ TEST_F(CastWindowManagerAuraTest, WindowInputDisabled) {
   EXPECT_EQ(ui::VKEY_UNKNOWN, window_delegate.key_code());
 }
 
+void VerifyWindowOrder(aura::Window* root_window) {
+  for (size_t i = 0; i < root_window->children().size() - 1; ++i)
+    EXPECT_LE(root_window->children()[i]->id(),
+              root_window->children()[i + 1]->id());
+}
+
+TEST_F(CastWindowManagerAuraTest, CheckProperWindowOrdering) {
+  std::unique_ptr<CastWindowManagerAura> window_manager =
+      std::make_unique<CastWindowManagerAura>(false /* enable input */);
+
+  TestWindow window1(1);
+  TestWindow window3(3);
+  window_manager->AddWindow(window1.window());
+  window_manager->AddWindow(window3.window());
+  window1.window()->Show();
+  window3.window()->Show();
+  // Verify update for top window.
+  VerifyWindowOrder(window_manager->GetRootWindow());
+
+  TestWindow window0(0);
+  window_manager->AddWindow(window0.window());
+  window0.window()->Show();
+  // Verify update for bottom window.
+  VerifyWindowOrder(window_manager->GetRootWindow());
+
+  TestWindow window2(2);
+  window_manager->AddWindow(window2.window());
+  window2.window()->Show();
+  // Verify update for middle window.
+  VerifyWindowOrder(window_manager->GetRootWindow());
+
+  TestWindow window4(4);
+  TestWindow window5(5);
+  TestWindow window6(6);
+  window_manager->AddWindow(window6.window());
+  window_manager->AddWindow(window4.window());
+  window_manager->AddWindow(window5.window());
+  window5.window()->Show();
+  // Verify update with hidden windows.
+  VerifyWindowOrder(window_manager->GetRootWindow());
+
+  TestWindow window7(2);
+  window_manager->AddWindow(window7.window());
+  window7.window()->Show();
+  // Verify update with same window ID.
+  VerifyWindowOrder(window_manager->GetRootWindow());
+  EXPECT_EQ(window7.window(), window_manager->GetRootWindow()->children()[3]);
+
+  window2.window()->Hide();
+  window2.window()->Show();
+  // Verify update ordering with same window ID.
+  EXPECT_EQ(window2.window(), window_manager->GetRootWindow()->children()[3]);
+}
+
 }  // namespace test
 }  // namespace chromecast