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) {
+  return wm::CanActivateWindow(window) ? wm::GetWindowState(window)->CanSnap()
+                                       : false;
+}
+
+}  // 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_ != NO_SNAP;
+}
+
+void SplitViewController::SnapWindow(aura::Window* window,
+                                     SnapPosition snap_position) {
+  DCHECK(window && CanSnap(window));
+
+  if (state_ == NO_SNAP)
+    Shell::Get()->NotifySplitViewModeStarting();
+
+  State previous_state = state_;
+  if (snap_position == LEFT) {
+    if (left_window_ != window) {
+      StopObserving(left_window_);
+      left_window_ = window;
+    }
+    right_window_ = (window == right_window_) ? nullptr : right_window_;
+
+    switch (state_) {
+      case NO_SNAP:
+        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;
+    }
+  } else if (snap_position == RIGHT) {
+    if (right_window_ != window) {
+      StopObserving(right_window_);
+      right_window_ = window;
+    }
+    left_window_ = (window == left_window_) ? nullptr : left_window_;
+
+    switch (state_) {
+      case NO_SNAP:
+        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;
+    }
+  }
+
+  StartObserving(window);
+  const wm::WMEvent event((snap_position == LEFT) ? wm::WM_EVENT_SNAP_LEFT
+                                                  : wm::WM_EVENT_SNAP_RIGHT);
+  wm::GetWindowState(window)->OnWMEvent(&event);
+  wm::ActivateWindow(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::GetSnappedWindowBoundsInParent(
+    aura::Window* window,
+    State snap_state) {
+  if (snap_state == LEFT_SNAPPED)
+    return GetLeftWindowBoundsInParent(window);
+  else if (snap_state == RIGHT_SNAPPED)
+    return GetRightWindowBoundsInParent(window);
+
+  NOTREACHED();
+  return gfx::Rect();
+}
+
+gfx::Rect SplitViewController::GetSnappedWindowBoundsInScreen(
+    aura::Window* window,
+    State snap_state) {
+  if (snap_state == LEFT_SNAPPED)
+    return GetLeftWindowBoundsInScreen(window);
+  else if (snap_state == RIGHT_SNAPPED)
+    return GetRightWindowBoundsInScreen(window);
+
+  NOTREACHED();
+  return gfx::Rect();
+}
+
+gfx::Rect SplitViewController::GetDisplayWorkAreaBoundsInParent(
+    aura::Window* window) {
+  aura::Window* root_window = window->GetRootWindow();
+  return ScreenUtil::GetDisplayWorkAreaBoundsInParent(
+      root_window->GetChildById(kShellWindowId_DefaultContainer));
+}
+
+gfx::Rect SplitViewController::GetDisplayWorkAreaBoundsInScreen(
+    aura::Window* window) {
+  gfx::Rect bounds = GetDisplayWorkAreaBoundsInParent(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();
+}
+
+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;
+
+  // If |gained_active| was activated as a side effect of a window disposition
+  // change, do nothing. For example, when a snapped window is closed, another
+  // window will be activated before OnWindowDestroying() is called. We should
+  // not try to snap another window in this case.
+  if (reason == ActivationReason::WINDOW_DISPOSITION_CHANGED)
+    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)
+    SnapWindow(gained_active, SplitViewController::RIGHT);
+  else
+    SnapWindow(gained_active, SplitViewController::LEFT);
+}
+
+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()) {
+    State previous_state = state_;
+    if (default_snap_position_ == LEFT) {
+      StopObserving(right_window_);
+      state_ = LEFT_SNAPPED;
+    } else {
+      StopObserving(left_window_);
+      state_ = RIGHT_SNAPPED;
+    }
+    NotifySplitViewStateChanged(previous_state, 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();
+    for (auto* window : windows) {
+      if (CanSnap(window) && window != GetDefaultSnappedWindow()) {
+        if (default_snap_position_ == LEFT)
+          SnapWindow(window, SplitViewController::RIGHT);
+        else
+          SnapWindow(window, SplitViewController::LEFT);
+        break;
+      }
+    }
+  }
+}
+
+void SplitViewController::EndSplitView() {
+  StopObserving(left_window_);
+  StopObserving(right_window_);
+  left_window_ = nullptr;
+  right_window_ = nullptr;
+  default_snap_position_ = LEFT;
+  divider_position_ = -1;
+
+  State previous_state = state_;
+  state_ = NO_SNAP;
+  NotifySplitViewStateChanged(previous_state, state_);
+
+  Shell::Get()->NotifySplitViewModeEnded();
+}
+
+void SplitViewController::StartObserving(aura::Window* window) {
+  if (window && !window->HasObserver(this)) {
+    window->AddObserver(this);
+    wm::GetWindowState(window)->AddObserver(this);
+  }
+}
+
+void SplitViewController::StopObserving(aura::Window* window) {
+  if (window && window->HasObserver(this)) {
+    window->RemoveObserver(this);
+    wm::GetWindowState(window)->RemoveObserver(this);
+  }
+}
+
+void SplitViewController::NotifySplitViewStateChanged(State previous_state,
+                                                      State state) {
+  if (previous_state == state)
+    return;
+  for (Observer& observer : observers_)
+    observer.OnSplitViewStateChanged(previous_state, state);
+}
+
+gfx::Rect SplitViewController::GetLeftWindowBoundsInParent(
+    aura::Window* window) {
+  gfx::Rect bounds = GetLeftWindowBoundsInScreen(window);
+  ::wm::ConvertRectFromScreen(window->GetRootWindow(), &bounds);
+  return bounds;
+}
+
+gfx::Rect SplitViewController::GetRightWindowBoundsInParent(
+    aura::Window* window) {
+  gfx::Rect bounds = GetRightWindowBoundsInScreen(window);
+  ::wm::ConvertRectFromScreen(window->GetRootWindow(), &bounds);
+  return bounds;
+}
+
+gfx::Rect SplitViewController::GetLeftWindowBoundsInScreen(
+    aura::Window* window) {
+  const gfx::Rect display_bounds_in_screen =
+      GetDisplayWorkAreaBoundsInScreen(window);
+  if (divider_position_ < 0) {
+    divider_position_ =
+        display_bounds_in_screen.x() + display_bounds_in_screen.width() * 0.5f;
+  }
+  return gfx::Rect(display_bounds_in_screen.x(), display_bounds_in_screen.y(),
+                   divider_position_ - display_bounds_in_screen.x(),
+                   display_bounds_in_screen.height());
+}
+
+gfx::Rect SplitViewController::GetRightWindowBoundsInScreen(
+    aura::Window* window) {
+  const gfx::Rect display_bounds_in_screen =
+      GetDisplayWorkAreaBoundsInScreen(window);
+  if (divider_position_ < 0) {
+    divider_position_ =
+        display_bounds_in_screen.x() + display_bounds_in_screen.width() * 0.5f;
+  }
+  return gfx::Rect(divider_position_, display_bounds_in_screen.y(),
+                   display_bounds_in_screen.x() +
+                       display_bounds_in_screen.width() - divider_position_,
+                   display_bounds_in_screen.height());
+}
+
+}  // namespace ash