Allow taking screen shot of a non child window which has delegate to paint.

ash/utility/screenshot_controller.cc

+// Copyright 2014 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/utility/screenshot_controller.h"
+
+#include <cmath>
+
+#include "ash/display/mouse_cursor_event_filter.h"
+#include "ash/screenshot_delegate.h"
+#include "ash/shell.h"
+#include "ash/shell_window_ids.h"
+#include "ash/wm/window_util.h"
+#include "base/stl_util.h"
+#include "ui/aura/client/capture_client.h"
+#include "ui/aura/client/screen_position_client.h"
+#include "ui/aura/window_targeter.h"
+#include "ui/compositor/paint_recorder.h"
+#include "ui/events/event.h"
+#include "ui/events/event_handler.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/screen.h"
+#include "ui/views/widget/widget.h"
+#include "ui/wm/core/cursor_manager.h"
+
+namespace ash {
+
+namespace {
+
+// The size to increase the invalidated area in the layer to repaint. The area
+// should be slightly bigger than the actual region because the region indicator
+// rectangles are drawn outside of the selected region.
+const int kInvalidateRegionAdditionalSize = 3;
+
+// This will prevent the user from taking a screenshot across multiple
+// monitors. it will stop the mouse at the any edge of the screen. must
+// swtich back on when the screenshot is complete.
+void EnableMouseWarp(bool enable) {
+  Shell::GetInstance()->mouse_cursor_filter()->set_mouse_warp_enabled(enable);
+}
+
+class ScreenshotWindowTargeter : public aura::WindowTargeter {
+ public:
+  ScreenshotWindowTargeter() = default;
+  ~ScreenshotWindowTargeter() override = default;
+
+  aura::Window* FindWindowForEvent(ui::LocatedEvent* event) {
+    aura::Window* target = static_cast<aura::Window*>(event->target());
+    aura::Window* target_root = target->GetRootWindow();
+
+    aura::client::ScreenPositionClient* position_client =
+        aura::client::GetScreenPositionClient(target_root);
+    gfx::Point location = event->location();
+    position_client->ConvertPointToScreen(target, &location);
+
+    gfx::Display display =
+        gfx::Screen::GetScreen()->GetDisplayNearestPoint(location);
+
+    aura::Window* root_window = Shell::GetInstance()
+                                    ->window_tree_host_manager()
+                                    ->GetRootWindowForDisplayId(display.id());
+
+    position_client->ConvertPointFromScreen(root_window, &location);
+
+    gfx::Point target_location = event->location();
+    event->set_location(location);
+
+    // Ignore capture window when finding the target for located event.
+    aura::client::CaptureClient* original_capture_client =
+        aura::client::GetCaptureClient(root_window);
+    aura::client::SetCaptureClient(root_window, nullptr);
+
+    aura::Window* selected =
+        static_cast<aura::Window*>(FindTargetForEvent(root_window, event));
+
+    // Restore State.
+    aura::client::SetCaptureClient(root_window, original_capture_client);
+    event->set_location(target_location);
+    return selected;
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ScreenshotWindowTargeter);
+};
+
+}  // namespace
+
+class ScreenshotController::ScreenshotLayer : public ui::LayerOwner,
+                                              public ui::LayerDelegate {
+ public:
+  ScreenshotLayer(ui::Layer* parent) {
+    SetLayer(new ui::Layer(ui::LAYER_TEXTURED));
+    layer()->SetFillsBoundsOpaquely(false);
+    layer()->SetBounds(parent->bounds());
+    parent->Add(layer());
+    parent->StackAtTop(layer());
+    layer()->SetVisible(true);
+    layer()->set_delegate(this);
+  }
+  ~ScreenshotLayer() override {}
+
+  const gfx::Rect& region() const { return region_; }
+
+  void SetRegion(const gfx::Rect& region) {
+    // Invalidates the region which covers the current and new region.
+    gfx::Rect union_rect(region_);
+    union_rect.Union(region);
+    union_rect.Inset(-kInvalidateRegionAdditionalSize,
+                     -kInvalidateRegionAdditionalSize);
+    union_rect.Intersects(layer()->bounds());
+    region_ = region;
+    layer()->SchedulePaint(union_rect);
+  }
+
+ private:
+  // ui::LayerDelegate:
+  void OnPaintLayer(const ui::PaintContext& context) override {
+    const SkColor kSelectedAreaOverlayColor = 0x40000000;
+    if (region_.IsEmpty())
+      return;
+    // Screenshot area representation: black rectangle with white
+    // rectangle inside.  To avoid capturing these rectangles when mouse
+    // release, they should be outside of the actual capturing area.
+    gfx::Rect rect(region_);
+    ui::PaintRecorder recorder(context, layer()->size());
+
+    recorder.canvas()->FillRect(region_, kSelectedAreaOverlayColor);
+
+    rect.Inset(-1, -1);
+    recorder.canvas()->DrawRect(rect, SK_ColorWHITE);
+    rect.Inset(-1, -1);
+    recorder.canvas()->DrawRect(rect, SK_ColorBLACK);
+  }
+
+  void OnDelegatedFrameDamage(const gfx::Rect& damage_rect_in_dip) override {}
+
+  void OnDeviceScaleFactorChanged(float device_scale_factor) override {}
+
+  base::Closure PrepareForLayerBoundsChange() override {
+    return base::Closure();
+  }
+
+  gfx::Rect region_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScreenshotLayer);
+};
+
+class ScreenshotController::ScopedCursorSetter {
+ public:
+  ScopedCursorSetter(::wm::CursorManager* cursor_manager,
+                     gfx::NativeCursor cursor)
+      : cursor_manager_(nullptr) {
+    if (cursor_manager->IsCursorLocked())
+      return;
+    gfx::NativeCursor original_cursor = cursor_manager->GetCursor();
+    cursor_manager_ = cursor_manager;
+    cursor_manager_->SetCursor(cursor);
+    if (!cursor_manager_->IsCursorVisible())
+      cursor_manager_->ShowCursor();
+    cursor_manager_->LockCursor();
+    // SetCursor does not make any effects at this point but it sets back to
+    // the original cursor when unlocked.
+    cursor_manager_->SetCursor(original_cursor);
+  }
+
+  ~ScopedCursorSetter() {
+    if (cursor_manager_)
+      cursor_manager_->UnlockCursor();
+  }
+
+ private:
+  ::wm::CursorManager* cursor_manager_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedCursorSetter);
+};
+
+ScreenshotController::ScreenshotController()
+    : mode_(NONE),
+      root_window_(nullptr),
+      selected_(nullptr),
+      screenshot_delegate_(nullptr) {
+  // Keep this here and don't move it to StartPartialScreenshotSession(), as it
+  // needs to be pre-pended by MouseCursorEventFilter in Shell::Init().
+  Shell::GetInstance()->PrependPreTargetHandler(this);
+}
+
+ScreenshotController::~ScreenshotController() {
+  if (screenshot_delegate_)
+    Cancel();
+  Shell::GetInstance()->RemovePreTargetHandler(this);
+}
+
+void ScreenshotController::StartWindowScreenshotSession(
+    ScreenshotDelegate* screenshot_delegate) {
+  if (screenshot_delegate_) {
+    DCHECK_EQ(screenshot_delegate_, screenshot_delegate);
+    return;
+  }
+  screenshot_delegate_ = screenshot_delegate;
+  mode_ = WINDOW;
+
+  gfx::Screen::GetScreen()->AddObserver(this);
+  for (aura::Window* root : Shell::GetAllRootWindows()) {
+    layers_[root] = new ScreenshotLayer(
+        Shell::GetContainer(root, kShellWindowId_OverlayContainer)->layer());
+  }
+  SetSelectedWindow(wm::GetActiveWindow());
+
+  cursor_setter_.reset(new ScopedCursorSetter(
+      Shell::GetInstance()->cursor_manager(), ui::kCursorCross));
+
+  EnableMouseWarp(true);
+}
+
+void ScreenshotController::StartPartialScreenshotSession(
+    ScreenshotDelegate* screenshot_delegate) {
+  // Already in a screenshot session.
+  if (screenshot_delegate_) {
+    DCHECK_EQ(screenshot_delegate_, screenshot_delegate);
+    return;
+  }
+
+  screenshot_delegate_ = screenshot_delegate;
+  mode_ = PARTIAL;
+  gfx::Screen::GetScreen()->AddObserver(this);
+  for (aura::Window* root : Shell::GetAllRootWindows()) {
+    layers_[root] = new ScreenshotLayer(
+        Shell::GetContainer(root, kShellWindowId_OverlayContainer)->layer());
+  }
+
+  cursor_setter_.reset(new ScopedCursorSetter(
+      Shell::GetInstance()->cursor_manager(), ui::kCursorCross));
+
+  EnableMouseWarp(false);
+}
+
+void ScreenshotController::MaybeStart(const ui::LocatedEvent& event) {
+  aura::Window* current_root =
+      static_cast<aura::Window*>(event.target())->GetRootWindow();
+  if (root_window_) {
+    // It's already started. This can happen when the second finger touches
+    // the screen, or combination of the touch and mouse. We should grab the
+    // partial screenshot instead of restarting.
+    if (current_root == root_window_) {
+      Update(event);
+      CompletePartialScreenshot();
+    }
+  } else {
+    root_window_ = current_root;
+    start_position_ = event.root_location();
+  }
+}
+
+void ScreenshotController::CompleteWindowScreenshot() {
+  if (selected_)
+    screenshot_delegate_->HandleTakeWindowScreenshot(selected_);
+  Cancel();
+}
+
+void ScreenshotController::CompletePartialScreenshot() {
+  if (!root_window_) {
+    // If we received a released event before we ever got a pressed event
+    // (resulting in setting |root_window_|), we just return without canceling
+    // to keep the screenshot session active waiting for the next press.
+    //
+    // This is to avoid a crash that used to happen when we start the screenshot
+    // session while the mouse is pressed and then release without moving the
+    // mouse. crbug.com/581432.
+    return;
+  }
+
+  DCHECK(layers_.count(root_window_));
+  const gfx::Rect& region = layers_.at(root_window_)->region();
+  if (!region.IsEmpty()) {
+    screenshot_delegate_->HandleTakePartialScreenshot(
+        root_window_, gfx::IntersectRects(root_window_->bounds(), region));
+  }
+  Cancel();
+}
+
+void ScreenshotController::Cancel() {
+  mode_ = NONE;
+  root_window_ = nullptr;
+  SetSelectedWindow(nullptr);
+  screenshot_delegate_ = nullptr;
+  gfx::Screen::GetScreen()->RemoveObserver(this);
+  STLDeleteValues(&layers_);
+  cursor_setter_.reset();
+  EnableMouseWarp(true);
+}
+
+void ScreenshotController::Update(const ui::LocatedEvent& event) {
+  // Update may happen without MaybeStart() if the partial screenshot session
+  // starts when dragging.
+  if (!root_window_)
+    MaybeStart(event);
+
+  DCHECK(layers_.find(root_window_) != layers_.end());
+  layers_.at(root_window_)
+      ->SetRegion(
+          gfx::Rect(std::min(start_position_.x(), event.root_location().x()),
+                    std::min(start_position_.y(), event.root_location().y()),
+                    ::abs(start_position_.x() - event.root_location().x()),
+                    ::abs(start_position_.y() - event.root_location().y())));
+}
+
+void ScreenshotController::UpdateSelectedWindow(ui::LocatedEvent* event) {
+  aura::Window* selected = ScreenshotWindowTargeter().FindWindowForEvent(event);
+
+  // Find a window that is backed with a widget.
+  while (selected && (selected->type() == ui::wm::WINDOW_TYPE_CONTROL ||
+                      !selected->delegate())) {
+    selected = selected->parent();
+  }
+
+  if (selected->parent()->id() == kShellWindowId_DesktopBackgroundContainer ||
+      selected->parent()->id() == kShellWindowId_LockScreenBackgroundContainer)
+    selected = nullptr;
+
+  SetSelectedWindow(selected);
+}
+
+void ScreenshotController::SetSelectedWindow(aura::Window* selected) {
+  if (selected_ == selected)
+    return;
+
+  if (selected_) {
+    selected_->RemoveObserver(this);
+    layers_.at(selected_->GetRootWindow())->SetRegion(gfx::Rect());
+  }
+
+  selected_ = selected;
+
+  if (selected_) {
+    selected_->AddObserver(this);
+    layers_.at(selected_->GetRootWindow())->SetRegion(selected_->bounds());
+  }
+}
+
+void ScreenshotController::OnKeyEvent(ui::KeyEvent* event) {
+  if (!screenshot_delegate_)
+    return;
+
+  if (event->type() == ui::ET_KEY_RELEASED) {
+    if (event->key_code() == ui::VKEY_ESCAPE) {
+      Cancel();
+    } else if (event->key_code() == ui::VKEY_RETURN && mode_ == WINDOW) {
+      CompleteWindowScreenshot();
+    }
+  }
+
+  // Intercepts all key events.
+  event->StopPropagation();
+}
+
+void ScreenshotController::OnMouseEvent(ui::MouseEvent* event) {
+  if (!screenshot_delegate_)
+    return;
+  switch (mode_) {
+    case NONE:
+      NOTREACHED();
+      break;
+    case WINDOW:
+      switch (event->type()) {
+        case ui::ET_MOUSE_MOVED:
+        case ui::ET_MOUSE_DRAGGED:
+          UpdateSelectedWindow(event);
+          break;
+        case ui::ET_MOUSE_RELEASED:
+          CompleteWindowScreenshot();
+          break;
+        default:
+          // Do nothing.
+          break;
+      }
+      break;
+    case PARTIAL:
+      switch (event->type()) {
+        case ui::ET_MOUSE_PRESSED:
+          MaybeStart(*event);
+          break;
+        case ui::ET_MOUSE_DRAGGED:
+          Update(*event);
+          break;
+        case ui::ET_MOUSE_RELEASED:
+          CompletePartialScreenshot();
+          break;
+        default:
+          // Do nothing.
+          break;
+      }
+      break;
+  }
+  event->StopPropagation();
+}
+
+void ScreenshotController::OnTouchEvent(ui::TouchEvent* event) {
+  if (!screenshot_delegate_)
+    return;
+  switch (mode_) {
+    case NONE:
+      NOTREACHED();
+      break;
+    case WINDOW:
+      switch (event->type()) {
+        case ui::ET_TOUCH_PRESSED:
+        case ui::ET_TOUCH_MOVED:
+          UpdateSelectedWindow(event);
+          break;
+        case ui::ET_TOUCH_RELEASED:
+          CompleteWindowScreenshot();
+          break;
+        default:
+          // Do nothing.
+          break;
+      }
+      break;
+    case PARTIAL:
+      switch (event->type()) {
+        case ui::ET_TOUCH_PRESSED:
+          MaybeStart(*event);
+          break;
+        case ui::ET_TOUCH_MOVED:
+          Update(*event);
+          break;
+        case ui::ET_TOUCH_RELEASED:
+          CompletePartialScreenshot();
+          break;
+        default:
+          // Do nothing.
+          break;
+      }
+      break;
+  }
+  event->StopPropagation();
+}
+
+void ScreenshotController::OnDisplayAdded(const gfx::Display& new_display) {
+  if (!screenshot_delegate_)
+    return;
+  Cancel();
+}
+
+void ScreenshotController::OnDisplayRemoved(const gfx::Display& old_display) {
+  if (!screenshot_delegate_)
+    return;
+  Cancel();
+}
+
+void ScreenshotController::OnDisplayMetricsChanged(const gfx::Display& display,
+                                                   uint32_t changed_metrics) {}
+
+void ScreenshotController::OnWindowDestroying(aura::Window* window) {
+  SetSelectedWindow(nullptr);
+}
+
+}  // namespace ash