Touch gestures for System Tray/ IME/ Stylus/ Notifications

ash/system/tray_drag_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/system/tray_drag_controller.h"
+
+#include "ash/shell.h"
+#include "ash/system/tray/tray_background_view.h"
+#include "ash/wm/maximize_mode/maximize_mode_controller.h"
+
+namespace ash {
+
+TrayDragController::TrayDragController(Shelf* shelf) : shelf_(shelf) {}
+
+bool TrayDragController::ProcessGestureEvent(ui::GestureEvent* event,
+                                             TrayBackgroundView* tray_view) {
+  if (!Shell::Get()
+           ->maximize_mode_controller()
+           ->IsMaximizeModeWindowManagerEnabled() ||
+      !shelf_->IsHorizontalAlignment()) {
+    return false;
+  }
+
+  tray_view_ = tray_view;
+  is_on_bubble_ = event->target() != tray_view;
+  if (event->type() == ui::ET_GESTURE_SCROLL_BEGIN) {
+    bool should_start_dragging = StartGestureDrag(*event);

[tdanderson, 2017/07/17 22:44:37]

nit: const

[minch1, 2017/07/18 03:58:59]

Done.

+    if (should_start_dragging)
+      event->SetHandled();
+    return should_start_dragging;
+  }
+
+  if (!tray_view_->GetBubbleView() || !is_in_drag_)
+    return false;
+
+  if (event->type() == ui::ET_GESTURE_SCROLL_UPDATE) {
+    UpdateGestureDrag(*event);
+    event->SetHandled();
+    return true;
+  }
+
+  if (event->type() == ui::ET_GESTURE_SCROLL_END ||
+      event->type() == ui::ET_SCROLL_FLING_START) {
+    CompleteGestureDrag(*event);
+    event->SetHandled();
+    return true;
+  }
+
+  // Unexpected event. Reset the drag state and close the bubble.
+  is_in_drag_ = false;
+  tray_view_->CloseBubble();
+  return false;
+}
+
+bool TrayDragController::StartGestureDrag(const ui::GestureEvent& gesture) {
+  if (!is_on_bubble_) {
+    // Dragging happens on the tray view. Close the bubble if there is already
+    // one opened. And return false to let shelf handle the event.
+    if (tray_view_->GetBubbleView()) {
+      tray_view_->CloseBubble();
+      return false;
+    }
+
+    // If the scroll sequence begins to scroll downward, return false so that
+    // the event will instead by handled by the shelf.
+    if (gesture.details().scroll_y_hint() > 0)
+      return false;
+
+    tray_view_->ShowBubble();
+  }
+
+  if (!tray_view_->GetBubbleView())
+    return false;
+
+  is_in_drag_ = true;
+  gesture_drag_amount_ = 0.f;
+  tray_bubble_bounds_ =
+      tray_view_->GetBubbleView()->GetWidget()->GetWindowBoundsInScreen();
+  UpdateBubbleBounds();
+  return true;
+}
+
+void TrayDragController::UpdateGestureDrag(const ui::GestureEvent& gesture) {
+  gesture_drag_amount_ += gesture.details().scroll_y();
+  UpdateBubbleBounds();
+}
+
+void TrayDragController::CompleteGestureDrag(const ui::GestureEvent& gesture) {
+  const bool hide_bubble = !ShouldShowBubbleAfterScrollSequence(gesture);
+  gfx::Rect target_bounds = tray_bubble_bounds_;
+
+  if (hide_bubble)
+    target_bounds.set_y(shelf_->GetIdealBounds().y());
+
+  tray_view_->AnimateToTargetBounds(target_bounds, hide_bubble);
+  is_in_drag_ = false;
+}
+
+void TrayDragController::UpdateBubbleBounds() {
+  DCHECK(tray_view_->GetBubbleView());
+
+  gfx::Rect current_tray_bubble_bounds = tray_bubble_bounds_;
+  int bounds_y =

[tdanderson, 2017/07/17 22:44:37]

nit: const

[minch1, 2017/07/18 03:58:59]

Done.

+      (is_on_bubble_ ? tray_bubble_bounds_.y() : shelf_->GetIdealBounds().y()) +
+      gesture_drag_amount_;
+  current_tray_bubble_bounds.set_y(std::max(bounds_y, tray_bubble_bounds_.y()));
+  tray_view_->GetBubbleView()->GetWidget()->SetBounds(
+      current_tray_bubble_bounds);
+}
+
+bool TrayDragController::ShouldShowBubbleAfterScrollSequence(
+    const ui::GestureEvent& sequence_end) {
+  // If the scroll sequence terminates with a fling, show the bubble if the
+  // fling was fast enough and in the correct direction.

[tdanderson, 2017/07/17 22:44:37]

If |is_on_bubble_| is true and I'm flinging downward with sufficient velocity,
shouldn't that close the bubble?

[minch1, 2017/07/18 03:58:59]

Yes, that should close the bubble. And the logic here will achieve that. I am
sorry, I don't quite get the concern here. Should I update the comment or logic
here?

[tdanderson, 2017/07/18 16:38:05]

My mistake, sorry, thank you for clarifying. I had mis-read some of the code.
This looks good. 

+  if (sequence_end.type() == ui::ET_SCROLL_FLING_START &&
+      fabs(sequence_end.details().velocity_y()) > kFlingVelocity) {
+    return sequence_end.details().velocity_y() < 0;
+  }
+
+  DCHECK(sequence_end.type() == ui::ET_GESTURE_SCROLL_END ||
+         sequence_end.type() == ui::ET_SCROLL_FLING_START);
+
+  // Keep the bubble's original state if the |gesture_drag_amount_| doesn't
+  // exceed one-third of the bubble's height.
+  if (is_on_bubble_)
+    return gesture_drag_amount_ < tray_bubble_bounds_.height() / 3.0;
+  return -gesture_drag_amount_ >= tray_bubble_bounds_.height() / 3.0;
+}
+
+}  // namespace ash