CrOS Tablet Window management - Split Screen part I

ash/wm/splitview/split_view_controller.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/wm/splitview/split_view_controller.h"
+
+#include "ash/ash_switches.h"
+#include "ash/public/cpp/shell_window_ids.h"
+#include "ash/screen_util.h"
+#include "ash/shell.h"
+#include "ash/wm/maximize_mode/maximize_mode_controller.h"
+#include "ash/wm/mru_window_tracker.h"
+#include "ash/wm/window_state.h"
+#include "ash/wm/window_util.h"
+#include "ash/wm/wm_event.h"
+#include "base/command_line.h"
+#include "ui/aura/window.h"
+#include "ui/wm/core/coordinate_conversion.h"
+#include "ui/wm/public/activation_client.h"
+
+namespace ash {
+
+namespace {
+
+// Returns true if |window| can be activated and snapped.
+bool CanSnap(aura::Window* window) {
+  if (!wm::CanActivateWindow(window))
+    return false;
+  return wm::GetWindowState(window)->CanSnap();
+}
+
+}  // namespace
+
+SplitViewController::SplitViewController() {
+  Shell::Get()->AddShellObserver(this);
+  Shell::Get()->activation_client()->AddObserver(this);
+}
+
+SplitViewController::~SplitViewController() {
+  Shell::Get()->RemoveShellObserver(this);
+  Shell::Get()->activation_client()->RemoveObserver(this);
+  EndSplitView();
+}
+
+// static
+bool SplitViewController::ShouldAllowSplitView() {
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kAshEnableTabletSplitView)) {
+    return false;
+  }
+  if (!Shell::Get()
+           ->maximize_mode_controller()
+           ->IsMaximizeModeWindowManagerEnabled()) {
+    return false;
+  }
+  return true;
+}
+
+bool SplitViewController::IsSplitViewModeActive() const {
+  return state_ != NOSNAP;
+}
+
+void SplitViewController::SetLeftWindow(aura::Window* left_window) {
+  if (!left_window)
+    return;
+
+  if (state_ == NOSNAP)
+    Shell::Get()->NotifySplitViewModeStarting();
+
+  if (right_window_ == left_window) {
+    StopObservingAndRestore(right_window_);
+    right_window_ = nullptr;
+  }
+  if (left_window_ != left_window) {
+    StopObservingAndRestore(left_window_);
+    left_window_ = nullptr;
+    left_window_ = left_window;
+    left_window_->AddObserver(this);
+    wm::GetWindowState(left_window_)->AddObserver(this);
+  }
+
+  State previous_state = state_;
+  switch (state_) {
+    case NOSNAP:
+      default_snap_position_ = LEFT;
+      state_ = LEFT_SNAPPED;
+      break;
+    case LEFT_SNAPPED:
+      state_ = LEFT_SNAPPED;
+      break;
+    case RIGHT_SNAPPED:
+    case BOTH_SNAPPED:
+      state_ = BOTH_SNAPPED;
+      break;
+  }
+
+  const wm::WMEvent event(wm::WM_EVENT_SNAP_LEFT);
+  wm::GetWindowState(left_window_)->OnWMEvent(&event);
+  wm::ActivateWindow(left_window_);
+
+  NotifySplitViewStateChanged(previous_state, state_);
+}
+
+void SplitViewController::SetRightWindow(aura::Window* right_window) {
+  if (!right_window)
+    return;
+
+  if (state_ == NOSNAP)
+    Shell::Get()->NotifySplitViewModeStarting();
+
+  if (left_window_ == right_window) {
+    StopObservingAndRestore(left_window_);
+    left_window_ = nullptr;
+  }
+  if (right_window_ != right_window) {
+    StopObservingAndRestore(right_window_);
+    right_window_ = nullptr;
+    right_window_ = right_window;
+    right_window_->AddObserver(this);
+    wm::GetWindowState(right_window_)->AddObserver(this);
+  }
+
+  State previous_state = state_;
+  switch (state_) {
+    case NOSNAP:
+      default_snap_position_ = RIGHT;
+      state_ = RIGHT_SNAPPED;
+      break;
+    case RIGHT_SNAPPED:
+      state_ = RIGHT_SNAPPED;
+      break;
+    case LEFT_SNAPPED:
+    case BOTH_SNAPPED:
+      state_ = BOTH_SNAPPED;
+      break;
+  }
+
+  const wm::WMEvent event(wm::WM_EVENT_SNAP_RIGHT);
+  wm::GetWindowState(right_window_)->OnWMEvent(&event);
+  wm::ActivateWindow(right_window_);
+
+  NotifySplitViewStateChanged(previous_state, state_);
+}
+
+aura::Window* SplitViewController::GetDefaultSnappedWindow() {
+  if (default_snap_position_ == LEFT)
+    return left_window_;
+  if (default_snap_position_ == RIGHT)
+    return right_window_;
+  return nullptr;
+}
+
+gfx::Rect SplitViewController::GetLeftWindowBoundsInParent(
+    aura::Window* window) {
+  aura::Window* root_window = window->GetRootWindow();
+  gfx::Rect bounds_in_parent = ScreenUtil::GetDisplayWorkAreaBoundsInParent(
+      root_window->GetChildById(kShellWindowId_DefaultContainer));
+  if (separator_position_ < 0)
+    separator_position_ = bounds_in_parent.width() * 0.5f;
+  gfx::Rect bounds(bounds_in_parent.x(), bounds_in_parent.y(),
+                   separator_position_, bounds_in_parent.height());
+  return bounds;
+}
+
+gfx::Rect SplitViewController::GetRightWindowBoundsInParent(
+    aura::Window* window) {
+  aura::Window* root_window = window->GetRootWindow();
+  gfx::Rect bounds_in_parent = ScreenUtil::GetDisplayWorkAreaBoundsInParent(
+      root_window->GetChildById(kShellWindowId_DefaultContainer));
+  if (separator_position_ < 0)
+    separator_position_ = bounds_in_parent.width() * 0.5f;
+  gfx::Rect bounds(bounds_in_parent.x() + separator_position_,
+                   bounds_in_parent.y(),
+                   bounds_in_parent.width() - separator_position_,
+                   bounds_in_parent.height());
+  return bounds;
+}
+
+gfx::Rect SplitViewController::GetLeftWindowBoundsInScreen(
+    aura::Window* window) {
+  gfx::Rect bounds = GetLeftWindowBoundsInParent(window);
+  ::wm::ConvertRectToScreen(window->GetRootWindow(), &bounds);
+  return bounds;
+}
+
+gfx::Rect SplitViewController::GetRightWindowBoundsInScreen(
+    aura::Window* window) {
+  gfx::Rect bounds = GetRightWindowBoundsInParent(window);
+  ::wm::ConvertRectToScreen(window->GetRootWindow(), &bounds);
+  return bounds;
+}
+
+void SplitViewController::AddObserver(Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void SplitViewController::RemoveObserver(Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void SplitViewController::OnWindowDestroying(aura::Window* window) {
+  // If one of the snapped window gets closed, end the split view mode. The
+  // behavior might change in the future.
+  DCHECK(window == left_window_ || window == right_window_);
+  EndSplitView();

[oshima, 2017/06/14 05:45:47]

you probably should skip restroing the window being destroyed?

[xdai1, 2017/06/15 22:11:42]

Currently StopObservingAndRestore() function only removes SplitViewController as
an observer of Window and WindowState. So if the window is being destroyed, we
still should do these. 

[oshima, 2017/06/16 01:20:57]

Sorry, I misunderstood what Restore means here.

[xdai1, 2017/06/16 18:49:52]

I rename the function to StopObserving() to better describe its function usage. 

+}
+
+void SplitViewController::OnPostWindowStateTypeChange(
+    ash::wm::WindowState* window_state,
+    ash::wm::WindowStateType old_type) {
+  if (window_state->IsFullscreen() || window_state->IsMinimized() ||
+      window_state->IsMaximized()) {
+    // TODO(xdai): Decide what to do if one of the snapped windows gets
+    // minimized /maximized / full-screened. For now we end the split view mode
+    // for simplicity.
+    EndSplitView();
+  }
+}
+
+void SplitViewController::OnWindowActivated(ActivationReason reason,
+                                            aura::Window* gained_active,
+                                            aura::Window* lost_active) {
+  if (!IsSplitViewModeActive())
+    return;
+
+  // Only snap window that can be snapped but hasn't been snapped.
+  if (!gained_active || gained_active == left_window_ ||
+      gained_active == right_window_ || !CanSnap(gained_active)) {
+    return;
+  }
+
+  // Only window in MRU list can be snapped.
+  aura::Window::Windows windows =
+      Shell::Get()->mru_window_tracker()->BuildMruWindowList();
+  if (std::find(windows.begin(), windows.end(), gained_active) == windows.end())
+    return;
+
+  // Snap the window on the non-default side of the screen if split view mode
+  // is active.
+  if (default_snap_position_ == LEFT)
+    SetRightWindow(gained_active);
+  else
+    SetLeftWindow(gained_active);
+}
+
+void SplitViewController::OnOverviewModeStarting() {
+  // If split view mode is active, reset |state_| to make it be able to select
+  // another window from overview window grid.
+  if (IsSplitViewModeActive()) {
+    DCHECK(state_ == BOTH_SNAPPED);
+    if (default_snap_position_ == LEFT) {
+      StopObservingAndRestore(right_window_);
+      state_ = LEFT_SNAPPED;
+    } else {
+      StopObservingAndRestore(left_window_);
+      state_ = RIGHT_SNAPPED;
+    }
+    NotifySplitViewStateChanged(BOTH_SNAPPED, state_);
+  }
+}
+
+void SplitViewController::OnOverviewModeEnded() {
+  // If split view mode is active but only has one snapped window, use the MRU
+  // window list to auto select another window to snap.
+  if (IsSplitViewModeActive() && state_ != BOTH_SNAPPED) {
+    aura::Window::Windows windows =
+        Shell::Get()->mru_window_tracker()->BuildMruWindowList();
+    auto end = std::remove_if(windows.begin(), windows.end(),
+                              std::not1(std::ptr_fun(&CanSnap)));
+    windows.resize(end - windows.begin());
+    for (auto* window : windows) {
+      if (window != GetDefaultSnappedWindow()) {
+        if (default_snap_position_ == LEFT)
+          SetRightWindow(window);
+        else
+          SetLeftWindow(window);
+        break;
+      }
+    }
+  }
+}
+
+void SplitViewController::EndSplitView() {
+  StopObservingAndRestore(left_window_);
+  StopObservingAndRestore(right_window_);
+  left_window_ = nullptr;
+  right_window_ = nullptr;
+  default_snap_position_ = LEFT;
+  separator_position_ = -1;
+
+  State previous_state = state_;
+  state_ = NOSNAP;
+  NotifySplitViewStateChanged(previous_state, state_);
+
+  Shell::Get()->NotifySplitViewModeEnded();
+}
+
+void SplitViewController::StopObservingAndRestore(aura::Window* window) {
+  if (window) {
+    window->RemoveObserver(this);
+    if (wm::GetWindowState(window))
+      wm::GetWindowState(window)->RemoveObserver(this);
+  }
+}
+
+void SplitViewController::NotifySplitViewStateChanged(State previous_state,
+                                                      State state) {
+  for (Observer& observer : observers_)
+    observer.OnSplitViewStateChanged(previous_state, state);
+}
+
+}  // namespace ash