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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "ui/views/controls/slide_out_view.h"
      6 
      7 #include "ui/compositor/layer.h"
      8 #include "ui/compositor/scoped_layer_animation_settings.h"
      9 #include "ui/gfx/transform.h"
     10 
     11 namespace views {
     12 
     13 SlideOutView::SlideOutView()
     14     : gesture_scroll_amount_(0.f) {
     15   // If accelerated compositing is not available, this widget tracks the
     16   // OnSlideOut event but does not render any visible changes.
     17   SetPaintToLayer(true);
     18   SetFillsBoundsOpaquely(false);
     19 }
     20 
     21 SlideOutView::~SlideOutView() {
     22 }
     23 
     24 void SlideOutView::OnGestureEvent(ui::GestureEvent* event) {
     25   if (event->type() == ui::ET_SCROLL_FLING_START) {
     26     // The threshold for the fling velocity is computed empirically.
     27     // The unit is in pixels/second.
     28     const float kFlingThresholdForClose = 800.f;
     29     if (fabsf(event->details().velocity_x()) > kFlingThresholdForClose) {
     30       SlideOutAndClose(event->details().velocity_x() < 0 ? SLIDE_LEFT :
     31                        SLIDE_RIGHT);
     32       event->StopPropagation();
     33       return;
     34     }
     35     RestoreVisualState();
     36     return;
     37   }
     38 
     39   if (!event->IsScrollGestureEvent())
     40     return;
     41 
     42   if (event->type() == ui::ET_GESTURE_SCROLL_BEGIN) {
     43     gesture_scroll_amount_ = 0.f;
     44   } else if (event->type() == ui::ET_GESTURE_SCROLL_UPDATE) {
     45     // The scroll-update events include the incremental scroll amount.
     46     gesture_scroll_amount_ += event->details().scroll_x();
     47 
     48     gfx::Transform transform;
     49     transform.Translate(gesture_scroll_amount_, 0.0);
     50     layer()->SetTransform(transform);
     51     layer()->SetOpacity(
     52         1.f - std::min(fabsf(gesture_scroll_amount_) / width(), 1.f));
     53 
     54   } else if (event->type() == ui::ET_GESTURE_SCROLL_END) {
     55     const float kScrollRatioForClosingNotification = 0.5f;
     56     float scrolled_ratio = fabsf(gesture_scroll_amount_) / width();
     57     if (scrolled_ratio >= kScrollRatioForClosingNotification) {
     58       SlideOutAndClose(gesture_scroll_amount_ < 0 ? SLIDE_LEFT : SLIDE_RIGHT);
     59       event->StopPropagation();
     60       return;
     61     }
     62     RestoreVisualState();
     63   }
     64 
     65   event->SetHandled();
     66 }
     67 
     68 void SlideOutView::RestoreVisualState() {
     69   // Restore the layer state.
     70   const int kSwipeRestoreDurationMS = 150;
     71   ui::ScopedLayerAnimationSettings settings(layer()->GetAnimator());
     72   settings.SetTransitionDuration(
     73       base::TimeDelta::FromMilliseconds(kSwipeRestoreDurationMS));
     74   layer()->SetTransform(gfx::Transform());
     75   layer()->SetOpacity(1.f);
     76 }
     77 
     78 void SlideOutView::SlideOutAndClose(SlideDirection direction) {
     79   const int kSwipeOutTotalDurationMS = 150;
     80   int swipe_out_duration = kSwipeOutTotalDurationMS * layer()->opacity();
     81   ui::ScopedLayerAnimationSettings settings(layer()->GetAnimator());
     82   settings.SetTransitionDuration(
     83       base::TimeDelta::FromMilliseconds(swipe_out_duration));
     84   settings.AddObserver(this);
     85 
     86   gfx::Transform transform;
     87   transform.Translate(direction == SLIDE_LEFT ? -width() : width(), 0.0);
     88   layer()->SetTransform(transform);
     89   layer()->SetOpacity(0.f);
     90 }
     91 
     92 void SlideOutView::OnImplicitAnimationsCompleted() {
     93   OnSlideOut();
     94 }
     95 
     96 }  // namespace views
     97