Add the partial screen magnifier to Chrome OS.

ash/magnifier/partial_magnification_controller.cc

+// Copyright (c) 2012 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/magnifier/partial_magnification_controller.h"
+
+#include "ash/shell.h"
+#include "ash/shell_window_ids.h"
+#include "ui/aura/event_filter.h"
+#include "ui/aura/root_window.h"
+#include "ui/aura/shared/compound_event_filter.h"
+#include "ui/aura/window.h"
+#include "ui/aura/window_observer.h"
+#include "ui/aura/window_property.h"
+#include "ui/gfx/point3.h"
+#include "ui/gfx/screen.h"
+#include "ui/compositor/layer.h"
+#include "ui/views/widget/widget.h"
+#include "ui/views/widget/widget_delegate.h"
+
+namespace {
+
+const float kMinPartialMagnifiedScaleThreshold = 1.1f;
+
+// Number of pixels to make the border of the magnified area.
+const int kZoomInset = 16;
+
+// Width of the magnified area.
+const int kMagnifierWidth = 200;
+
+// Height of the magnified area.
+const int kMagnifierHeight = 200;
+
+}  // namespace
+
+namespace ash {
+namespace internal {
+
+class ZoomDelegateView : public views::WidgetDelegateView {
+ public:
+  ZoomDelegateView();
+  virtual ~ZoomDelegateView();
+
+  // views::View overrides
+  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual void Layout() OVERRIDE;
+
+  // views::WidgetZoomDelegateView overrides:
+  virtual bool CanActivate() const OVERRIDE {
+    return false;
+  }
+
+ private:
+

[sky, 2012/10/11 17:00:49]

remove newline

[Zachary Kuznia, 2012/10/12 08:41:35]

Done.

+  DISALLOW_COPY_AND_ASSIGN(ZoomDelegateView);
+};
+
+ZoomDelegateView::ZoomDelegateView() {
+}
+
+ZoomDelegateView::~ZoomDelegateView() {
+}
+
+gfx::Size ZoomDelegateView::GetPreferredSize() {
+  return child_count() > 0 ? child_at(0)->GetPreferredSize() : gfx::Size();

[sky, 2012/10/11 17:00:49]

Set the layout manager to FillLayout and you can remove this and Layout.

[Zachary Kuznia, 2012/10/12 08:41:35]

Done.

+}
+
+void ZoomDelegateView::Layout() {
+  if (child_count())
+    child_at(0)->SetBounds(0, 0, width(), height());
+}
+
+
+////////////////////////////////////////////////////////////////////////////////
+// PartialMagnificationControllerImpl:
+
+class PartialMagnificationControllerImpl
+  : public PartialMagnificationController,
+    public aura::EventFilter,
+    public aura::WindowObserver {
+ public:
+  PartialMagnificationControllerImpl();
+  virtual ~PartialMagnificationControllerImpl();
+
+  // PartialMagnificationController overrides:
+  virtual void SetEnabled(bool enabled) OVERRIDE;
+  virtual bool IsEnabled() const OVERRIDE;
+  virtual void SetScale(float scale) OVERRIDE;
+  virtual float GetScale() const OVERRIDE { return scale_; }
+
+ private:
+  void OnMouseMove(const gfx::Point& location_in_root);
+
+  // Switch PartialMagnified RootWindow to |new_root_window|. This does
+  // following:
+  //  - Remove the magnifier from the current root window.
+  //  - Create a magnifier in the new root_window |new_root_window|.
+  //  - Switch the target window from current window to |new_root_window|.
+  void SwitchTargetRootWindow(aura::RootWindow* new_root_window);
+
+  // Returns the root window that contains the mouse cursor.
+  aura::RootWindow* GetCurrentRootWindow();
+
+  // Return true if the magnification scale > kMinPartialMagnifiedScaleThreshold
+  bool IsPartialMagnified() const;
+
+  // Cleans up the window if needed.
+  void CloseMagnifierWindow();
+
+  // aura::EventFilter overrides:
+  virtual bool PreHandleKeyEvent(aura::Window* target,
+                                 ui::KeyEvent* event) OVERRIDE;
+  virtual bool PreHandleMouseEvent(aura::Window* target,
+                                   ui::MouseEvent* event) OVERRIDE;
+  virtual ui::TouchStatus PreHandleTouchEvent(
+      aura::Window* target,
+      ui::TouchEvent* event) OVERRIDE;
+  virtual ui::EventResult PreHandleGestureEvent(
+      aura::Window* target,
+      ui::GestureEvent* event) OVERRIDE;
+
+  // Overridden from WindowObserver:
+  virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
+
+  // True if the magnified window is in motion of zooming or un-zooming effect.
+  // Otherwise, false.
+  bool is_on_zooming_;
+
+  bool is_enabled_;
+
+  // Current scale, origin (left-top) position of the magnification window.
+  float scale_;
+  gfx::Point origin_;
+
+  aura::Window* zoom_window_;

[sky, 2012/10/11 17:00:49]

scoped_ptr

[sky, 2012/10/11 17:00:49]

Why do you need zoom_window_? AFAICT you create it only to parent zoom_widget_
to it. Why can't you create zoom_widget_ parented to the root?

[Zachary Kuznia, 2012/10/12 08:41:35]

Done.

+  views::Widget* zoom_widget_;
+
+  DISALLOW_COPY_AND_ASSIGN(PartialMagnificationControllerImpl);
+};
+
+////////////////////////////////////////////////////////////////////////////////
+// PartialMagnificationControllerImpl:
+
+PartialMagnificationControllerImpl::PartialMagnificationControllerImpl()
+  : is_on_zooming_(false),
+    is_enabled_(false),
+    scale_(kNonPartialMagnifiedScale),
+    zoom_window_(NULL),
+    zoom_widget_(NULL) {
+  Shell::GetInstance()->AddEnvEventFilter(this);
+}
+
+PartialMagnificationControllerImpl::~PartialMagnificationControllerImpl() {
+  CloseMagnifierWindow();
+
+  Shell::GetInstance()->RemoveEnvEventFilter(this);
+}
+
+void PartialMagnificationControllerImpl::OnMouseMove(

[sky, 2012/10/11 17:00:49]

What if someone is using touch input?

[Zachary Kuznia, 2012/10/12 08:41:35]

Support for touch input will come in a future patch.  We haven't decided the
proper gestures yet.

+    const gfx::Point& location_in_root) {
+  gfx::Point origin(location_in_root);
+
+  origin.Offset(-kMagnifierWidth / 2, -kMagnifierHeight / 2);
+
+  if (zoom_window_) {
+    zoom_widget_->SetBounds(gfx::Rect(origin.x(), origin.y(),
+                                      kMagnifierWidth, kMagnifierHeight));
+  }
+}
+
+bool PartialMagnificationControllerImpl::IsPartialMagnified() const {
+  return scale_ >= kMinPartialMagnifiedScaleThreshold;
+}
+
+void PartialMagnificationControllerImpl::CloseMagnifierWindow() {
+  if (zoom_window_) {
+    zoom_window_->RemoveObserver(this);
+    aura::RootWindow* root_window = zoom_window_->GetRootWindow();
+    if (root_window)
+      root_window->RemoveObserver(this);
+
+    zoom_widget_->Close();
+    delete zoom_window_;
+    zoom_window_ = NULL;
+    zoom_widget_ = NULL;
+  }
+}
+
+void PartialMagnificationControllerImpl::SwitchTargetRootWindow(
+    aura::RootWindow* new_root_window) {
+  if (zoom_window_ && new_root_window == zoom_window_->GetRootWindow())
+    return;
+
+  float scale = GetScale();
+
+  CloseMagnifierWindow();
+  SetScale(scale);
+}
+
+aura::RootWindow* PartialMagnificationControllerImpl::GetCurrentRootWindow() {
+  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+  for (Shell::RootWindowList::const_iterator iter = root_windows.begin();
+       iter != root_windows.end(); ++iter) {
+    aura::RootWindow* root_window = *iter;
+    if (root_window->ContainsPointInRoot(
+            root_window->GetLastMouseLocationInRoot()))
+      return root_window;
+  }
+  return NULL;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// PartialMagnificationControllerImpl:
+// PartialMagnificationController implementation
+
+void PartialMagnificationControllerImpl::SetScale(float scale) {
+  if (!is_enabled_)
+    return;
+
+  scale_ = scale;
+
+  if (IsPartialMagnified()) {
+    if (!zoom_window_) {
+      aura::RootWindow* root_window = GetCurrentRootWindow();

[sky, 2012/10/11 17:00:49]

Move all this into a function, maybe CreateZoomWindow or something.

[Zachary Kuznia, 2012/10/12 08:41:35]

Done.

+      if (!root_window)
+        return;
+
+      root_window->AddObserver(this);
+
+      gfx::Point mouse(root_window->GetLastMouseLocationInRoot());
+
+      zoom_window_ = new aura::Window(NULL);
+      zoom_window_->Init(ui::LAYER_NOT_DRAWN);
+      root_window->AddChild(zoom_window_);
+
+      zoom_widget_ = new views::Widget;
+      views::Widget::InitParams params(
+          views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
+      params.transparent = true;
+      params.parent = zoom_window_;

[sky, 2012/10/11 17:00:49]

Do you want to set can_activate and accept_events to false?

[Zachary Kuznia, 2012/10/12 08:41:35]

Done.

+      ZoomDelegateView* delegate_view = new ZoomDelegateView;
+      params.delegate = delegate_view;
+      zoom_widget_->Init(params);
+      zoom_widget_->SetBounds(gfx::Rect(mouse.x() - kMagnifierWidth / 2,
+                                        mouse.y() - kMagnifierHeight / 2,
+                                        kMagnifierWidth, kMagnifierHeight));
+      zoom_widget_->set_focus_on_creation(false);
+      zoom_widget_->SetContentsView(delegate_view);

[sky, 2012/10/11 17:00:49]

You should override GetContentsView() on ZoomDelegateView to return 'this'
instead of explicitly setting the contents view. Doing so avoid unnecessary
creation.

[Zachary Kuznia, 2012/10/12 08:41:35]

Doing this causes it to crash in FillLayout().  Does it require a matching
change to the layout code?

[sky, 2012/10/12 17:09:19]

what is the crash. Maybe FillLayoutGetPreferredSize needs to do notify if
!has_children like Layout?

[Zachary Kuznia, 2012/10/15 08:28:40]

Actually, it turns out that since I removed zoom_window_, I don't need the
delegate anymore, so I removed it.

+      zoom_widget_->Show();
+      zoom_window_->layer()->SetBounds(gfx::Rect(0, 0,
+                                                 kMagnifierWidth,
+                                                 kMagnifierHeight));
+      zoom_window_->Show();
+
+      zoom_widget_->GetNativeView()->layer()->SetBackgroundZoom(
+          (kMagnifierWidth - (kMagnifierWidth / scale_)) / 2,
+          (kMagnifierHeight - (kMagnifierHeight / scale_)) / 2,
+          scale_,
+          kZoomInset);
+
+      zoom_window_->AddObserver(this);
+    }
+  } else {
+    CloseMagnifierWindow();
+  }
+}
+
+void PartialMagnificationControllerImpl::SetEnabled(bool enabled) {
+  if (enabled) {

[sky, 2012/10/11 17:00:49]

Do you need both is_enabled_ and the scale? If you have a non-zero scale doesn't
that mean its enabled?

[Zachary Kuznia, 2012/10/12 08:41:35]

They are different.  When it's enabled, you can toggle the scale between
kDefaultPartialMagnifiedScale and kNonPartialMagnifiedScale via a hotkey.

+    is_enabled_ = enabled;
+    SetScale(kDefaultPartialMagnifiedScale);
+  } else {
+    SetScale(kNonPartialMagnifiedScale);
+    is_enabled_ = enabled;
+  }
+}
+
+bool PartialMagnificationControllerImpl::IsEnabled() const {
+  return is_enabled_;
+}
+
+
+////////////////////////////////////////////////////////////////////////////////
+// PartialMagnificationControllerImpl: aura::EventFilter implementation
+
+bool PartialMagnificationControllerImpl::PreHandleKeyEvent(
+    aura::Window* target,
+    ui::KeyEvent* event) {
+  return false;
+}
+
+bool PartialMagnificationControllerImpl::PreHandleMouseEvent(
+    aura::Window* target,
+    ui::MouseEvent* event) {
+  if (IsPartialMagnified() && event->type() == ui::ET_MOUSE_MOVED) {
+    aura::RootWindow* current_root = target->GetRootWindow();
+    gfx::Rect root_bounds = current_root->bounds();
+
+    if (root_bounds.Contains(event->root_location())) {
+      SwitchTargetRootWindow(current_root);
+
+      OnMouseMove(event->root_location());
+    }
+  }
+
+  return false;
+}
+
+ui::TouchStatus PartialMagnificationControllerImpl::PreHandleTouchEvent(
+    aura::Window* target,
+    ui::TouchEvent* event) {
+  return ui::TOUCH_STATUS_UNKNOWN;
+}
+
+ui::EventResult PartialMagnificationControllerImpl::PreHandleGestureEvent(
+    aura::Window* target,
+    ui::GestureEvent* event) {
+  return ui::ER_UNHANDLED;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// PartialMagnificationControllerImpl: aura::WindowObserver implementation
+
+void PartialMagnificationControllerImpl::OnWindowDestroying(
+    aura::Window* window) {
+  if (window == zoom_window_) {
+    aura::RootWindow* root_window = zoom_window_->GetRootWindow();
+    if (root_window)
+      root_window->RemoveObserver(this);
+    zoom_window_ = NULL;
+    zoom_widget_ = NULL;
+  } else {
+    CloseMagnifierWindow();
+
+    aura::RootWindow* new_root_window = GetCurrentRootWindow();
+    if (new_root_window != window)
+      SwitchTargetRootWindow(new_root_window);
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// PartialMagnificationController:
+
+// static
+PartialMagnificationController*
+PartialMagnificationController::CreateInstance() {
+  return new PartialMagnificationControllerImpl();
+}
+
+}  // namespace internal
+}  // namespace ash