First crack at implementing the touch explaration mode.

ash/touch/touch_exploration_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/touch/touch_exploration_controller.h"
+
+#include "ash/root_window_settings.h"
+#include "ash/shell.h"
+#include "ash/wm/coordinate_conversion.h"
+#include "base/logging.h"
+#include "ui/aura/window_tree_host.h"
+#include "ui/events/event.h"
+#include "ui/events/event_processor.h"
+#include "ui/gfx/point.h"
+
+namespace ash {
+namespace internal {
+
+TouchExplorationController::TouchExplorationController(
+    aura::Window* root_window) :
+        display_id_(GetRootWindowSettings(root_window)->display_id),
+        root_window_(root_window) {
+  Shell::GetInstance()->display_controller()->AddObserver(this);
+  root_window_->AddPreTargetHandler(this);
+}
+
+TouchExplorationController::~TouchExplorationController() {
+  Shell::GetInstance()->display_controller()->RemoveObserver(this);
+  if (root_window_)
+    root_window_->RemovePreTargetHandler(this);
+}
+
+void TouchExplorationController::OnTouchEvent(ui::TouchEvent* event) {
+  ui::EventType type = event->type();
+  if (type == ui::ET_TOUCH_PRESSED) {
+    LOG(ERROR) << "ET_TOUCH_PRESSED";
+    // If this is the first and only finger touching - we are entering the
+    // mouse move mode.
+    if (touch_ids_.size() == 0) {
+      // TODO: Here and in other cases we take the flags from the touch event

[mfomitchev, 2014/04/11 21:00:58]

Question here

[sadrul, 2014/04/14 20:22:11]

Yes. The EventRewriter implementation should do the same. It may be a good idea
to set the IS_SYNTHETIZED and/or FROM_TOUCH flags on the mouse-event created.

+      // and send them along with the synthesized mouse event - is that correct?
+      GenerateMouseEvent(
+          ui::ET_MOUSE_ENTERED, event->location(), event->flags());
+      event->SetHandled();
+      event->StopPropagation();

[mfomitchev, 2014/04/11 21:00:58]

If I don't call StopPropagation() (here and in other places), gestures don't
seem to work.

[sadrul, 2014/04/14 20:22:11]

Yeah. We need to stop propagating the touch-event to make sure it doesn't
contribute to any gestures.

+    }
+    // If this is the second finger - we should exit the mouse move mode (which
+    // we should have entered when the first finger touch started), and we
+    // should let this touch go through as is.
+    if (touch_ids_.size() == 1) {
+      // Generate ET_MOUSE_EXITED in the location of the _first_ touch.
+      int first_touch_id = touch_ids_.at(0);
+      gfx::Point first_touch_location = touch_locations_[first_touch_id];
+      GenerateMouseEvent(

[sadrul, 2014/04/14 20:22:11]

WindowEventDispatcher takes care of dispatching mouse-enter/exit events from
mouse-move events. If that is working correctly, you shouldn't need to generate
the ENTER/EXIT events from here.

+          ui::ET_MOUSE_EXITED, first_touch_location, event->flags());
+    }
+    touch_ids_.push_back(event->touch_id());
+    touch_locations_.insert(
+        std::pair<int, gfx::Point>(event->touch_id(), event->location()));
+  // Ignore the synthesized release events - we are synthesizing them below.
+  } else if ((type == ui::ET_TOUCH_RELEASED || type == ui::ET_TOUCH_CANCELLED)
+      && !(event->flags() & ui::EF_IS_SYNTHESIZED)) {
+    LOG(ERROR) << (type == ui::ET_TOUCH_RELEASED ?
+        "ET_TOUCH_RELEASED" : "ET_TOUCH_CANCELLED");
+    int touch_id = event->touch_id();
+    std::vector<int>::iterator it =
+        std::find(touch_ids_.begin(), touch_ids_.end(), touch_id);
+    if (it != touch_ids_.end()) {
+      // If it was the first finger that was lifted, we need to do a few
+      // things depending on how many fingers were on the screen:
+      // 1. If only one finger was on the screen, this is simply equivalent to
+      //    the end of the mouse move.
+      // 2. If there were multiple fingers on the screen, this is equivalent
+      //    to lifting the _second_ finger. Also, if there were exactly two
+      //    fingers touching, we are only left with one, so we are entering the
+      //    mouse move mode, and so we should also generate ET_MOUSE_ENTERED.
+      if (it == touch_ids_.begin()) {
+        if (touch_ids_.size() == 1) {
+          GenerateMouseEvent(
+              ui::ET_MOUSE_EXITED, event->location(), event->flags());
+        } else {
+          LOG(ERROR) << "Generating touch release event";
+          // Generate a touch release event for the second finger.
+          int second_touch_id = touch_ids_.at(1);
+          gfx::Point second_touch_location = touch_locations_[second_touch_id];
+          aura::Window* root = wm::GetRootWindowAt(second_touch_location);
+          DCHECK(root)
+              << "Root window not found while generating touch release event.";
+          aura::WindowTreeHost* host = root->GetHost();
+          // TODO: Should I use another constructor to pass in the flags?

[mfomitchev, 2014/04/11 21:00:58]

Question here

+          ui::TouchEvent touch_event(ui::ET_TOUCH_RELEASED,
+                                     second_touch_location,
+                                     second_touch_id,
+                                     event->time_stamp());
+          host->event_processor()->OnEventFromSource(&touch_event);
+          // If there were exactly two fingers touching - generate
+          // ET_MOUSE_ENTERED.
+          if (touch_ids_.size() == 2) {
+            GenerateMouseEvent(
+                ui::ET_MOUSE_ENTERED, second_touch_location, event->flags());
+          }
+        }
+        event->SetHandled();
+        event->StopPropagation();
+      }
+      touch_ids_.erase(it);
+      touch_locations_.erase(touch_id);
+    } else {
+      NOTREACHED();
+    }
+  } else if (type == ui::ET_TOUCH_MOVED) {
+    LOG(ERROR) << "ET_TOUCH_MOVED";
+    // Consume if it is the first finger.
+    // If it is the only finger - generate a mouse move event.
+    std::vector<int>::iterator it =
+        std::find(touch_ids_.begin(), touch_ids_.end(), event->touch_id());
+    if (it != touch_ids_.end()) {
+      if (it == touch_ids_.begin()) {
+          if (touch_ids_.size() == 1) {
+            GenerateMouseEvent(
+                ui::ET_MOUSE_MOVED, event->location(), event->flags());
+          }
+          event->SetHandled();
+          event->StopPropagation();
+      }
+      touch_locations_[*it] = event->location();
+    } else {
+      NOTREACHED();
+    }
+  }
+}
+
+void TouchExplorationController::OnDisplaysInitialized() {
+  OnDisplayConfigurationChanged();
+}
+
+void TouchExplorationController::OnDisplayConfigurationChanging() {
+  if (!root_window_)
+    return;
+
+  root_window_->RemovePreTargetHandler(this);
+  root_window_ = NULL;
+}
+
+void TouchExplorationController::OnDisplayConfigurationChanged() {
+  if (root_window_)
+    return;
+
+  root_window_ = Shell::GetInstance()->display_controller()->
+      GetRootWindowForDisplayId(display_id_);
+  root_window_->AddPreTargetHandler(this);
+}
+
+void TouchExplorationController::GenerateMouseEvent(ui::EventType event_type,
+                                                    gfx::Point location,
+                                                    int flags) {
+  aura::Window* root_window = wm::GetRootWindowAt(location);
+  DCHECK(root_window)
+      << "Root window not found while converting touch to mouse event.";
+  aura::WindowTreeHost* host = root_window->GetHost();
+
+  LOG(ERROR) << "Generating mouse event: type=" << event_type;
+  ui::MouseEvent mouse_event(event_type,
+                             location,
+                             location,
+                             ui::EF_IS_SYNTHESIZED | flags,
+                             0);
+
+  // TODO: Should I use  WindowEventDispatcher instead?

[mfomitchev, 2014/04/11 21:00:58]

Question here

[sadrul, 2014/04/14 20:22:11]

This is fine.

+  host->event_processor()->OnEventFromSource(&mouse_event);
+}
+
+}  // namespace internal
+}  // namespace ash