athena: Fix switching windows with title-drag in split-view.

When split-view mode, make sure dragging the tiel to switch between
windows works as expected.

BUG=397272
R=mfomitchev@chromium.org, mukai@chromium.org

Review URL: https://codereview.chromium.org/468763002

Cr-Commit-Position: refs/heads/master@{#290008}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290008 0039d316-1c4b-4281-b951-d872f2087c98

athena/wm/split_view_controller.cc

@@ -85,6 +85,28 @@ void SplitViewController::ActivateSplitMode(aura::Window* left,
   UpdateLayout(true);
 }
 
+void SplitViewController::ReplaceWindow(aura::Window* window,
+                                        aura::Window* replace_with) {
+  CHECK(IsSplitViewModeActive());
+  CHECK(replace_with);
+  CHECK(window == left_window_ || window == right_window_);
+  CHECK(replace_with != left_window_ && replace_with != right_window_);
+#if !defined(NDEBUG)
+  aura::Window::Windows windows = window_list_provider_->GetWindowList();
+  DCHECK(std::find(windows.begin(), windows.end(), replace_with) !=
+         windows.end());
+#endif
+
+  replace_with->SetBounds(window->bounds());
+  replace_with->SetTransform(gfx::Transform());
+  if (window == left_window_)
+    left_window_ = replace_with;
+  else
+    right_window_ = replace_with;
+  wm::ActivateWindow(replace_with);
+  window->SetTransform(gfx::Transform());
+}
+
 void SplitViewController::DeactivateSplitMode() {
   CHECK_NE(SCROLLING, state_);
   state_ = INACTIVE;

athena/wm/split_view_controller.h

@@ -39,6 +39,9 @@ class ATHENA_EXPORT SplitViewController
   // making any necessary changes.
   void DeactivateSplitMode();
 
+  void ReplaceWindow(aura::Window* window,
+                     aura::Window* replace_with);
+
   aura::Window* left_window() { return left_window_; }
   aura::Window* right_window() { return right_window_; }
 

athena/wm/split_view_controller_unittest.cc

@@ -6,7 +6,6 @@
 
 #include "athena/common/fill_layout_manager.h"
 #include "athena/test/athena_test_base.h"
-#include "athena/wm/public/window_list_provider.h"
 #include "athena/wm/window_list_provider_impl.h"
 #include "base/memory/scoped_vector.h"
 #include "ui/aura/test/test_window_delegate.h"

athena/wm/title_drag_controller.cc

@@ -60,15 +60,15 @@ void TitleDragController::OnTransitionEnd(aura::Window* window, bool complete) {
   weak_ptr_.InvalidateWeakPtrs();
   if (!tracker_.Contains(window))
     window = NULL;
-  if (complete && window && wm::IsActiveWindow(window))
-    delegate_->OnTitleDragCompleted(window);
-  else
-    delegate_->OnTitleDragCanceled(window);
   shadow_.reset();
   if (window) {
     window->SetTransform(gfx::Transform());
     tracker_.Remove(window);
   }
+  if (complete && window && wm::IsActiveWindow(window))
+    delegate_->OnTitleDragCompleted(window);
+  else
+    delegate_->OnTitleDragCanceled(window);
 }
 
 void TitleDragController::OnGestureEvent(ui::GestureEvent* gesture) {

athena/wm/window_manager_impl.cc

@@ -247,23 +247,58 @@ bool WindowManagerImpl::OnAcceleratorFired(int command_id,
 }
 
 aura::Window* WindowManagerImpl::GetWindowBehind(aura::Window* window) {
-  const aura::Window::Windows& windows = container_->children();
-  aura::Window::Windows::const_iterator iter =
-      std::find(windows.begin(), windows.end(), window);
-  CHECK(iter != windows.end());
-  return (iter == windows.begin()) ? NULL : *(iter - 1);
+  const aura::Window::Windows& windows = window_list_provider_->GetWindowList();
+  aura::Window::Windows::const_reverse_iterator iter =
+      std::find(windows.rbegin(), windows.rend(), window);
+  CHECK(iter != windows.rend());
+  ++iter;
+  aura::Window* behind = NULL;
+  if (iter != windows.rend())
+    behind = *iter++;
+
+  if (split_view_controller_->IsSplitViewModeActive()) {
+    aura::Window* left = split_view_controller_->left_window();
+    aura::Window* right = split_view_controller_->right_window();
+    CHECK(window == left || window == right);
+    if (behind == left || behind == right)
+      behind = (iter == windows.rend()) ? NULL : *iter;
+  }
+
+  return behind;
 }
 
 void WindowManagerImpl::OnTitleDragStarted(aura::Window* window) {
+  aura::Window* next_window = GetWindowBehind(window);
+  if (!next_window)
+    return;
+  // Make sure |window| is active. Also make sure that |next_window| is visible,
+  // and positioned to match the top-left edge of |window|.
+  wm::ActivateWindow(window);
+  next_window->Show();
+  int dx = window->bounds().x() - next_window->bounds().x();
+  if (dx) {
+    gfx::Transform transform;
+    transform.Translate(dx, 0);
+    next_window->SetTransform(transform);
+  }
 }
 
 void WindowManagerImpl::OnTitleDragCompleted(aura::Window* window) {
   aura::Window* next_window = GetWindowBehind(window);
-  if (next_window)
+  if (!next_window)
+    return;
+  if (split_view_controller_->IsSplitViewModeActive())
+    split_view_controller_->ReplaceWindow(window, next_window);
+  else
     OnSelectWindow(next_window);
+  wm::ActivateWindow(next_window);
 }
 
 void WindowManagerImpl::OnTitleDragCanceled(aura::Window* window) {
+  aura::Window* next_window = GetWindowBehind(window);
+  if (!next_window)
+    return;
+  next_window->SetTransform(gfx::Transform());
 }
 
 AthenaContainerLayoutManager::AthenaContainerLayoutManager() {