ui/app_list/pagination_controller.cc

   1 // Copyright 2014 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/app_list/pagination_controller.h"
   6
   7 #include "ui/app_list/pagination_model.h"
   8 #include "ui/events/event.h"
   9 #include "ui/gfx/geometry/rect.h"
  10 #include "ui/gfx/geometry/vector2d.h"
  11
  12 namespace app_list {
  13
  14 namespace {
  15
  16 // Constants for dealing with scroll events.
  17 const int kMinScrollToSwitchPage = 20;
  18 const int kMinHorizVelocityToSwitchPage = 800;
  19
  20 const double kFinishTransitionThreshold = 0.33;
  21
  22 }  // namespace
  23
  24 PaginationController::PaginationController(PaginationModel* model,
  25                                            ScrollAxis scroll_axis)
  26     : pagination_model_(model), scroll_axis_(scroll_axis) {
  27 }
  28
  29 bool PaginationController::OnScroll(const gfx::Vector2d& offset,
  30                                     ScrollEventType type) {
  31   int offset_magnitude;
  32   if (scroll_axis_ == SCROLL_AXIS_HORIZONTAL) {
  33     // If the view scrolls horizontally, both horizontal and vertical scroll
  34     // events are valid (since most mouse wheels only have vertical scrolling).
  35     offset_magnitude =
  36         abs(offset.x()) > abs(offset.y()) ? offset.x() : offset.y();
  37   } else {
  38     // If the view scrolls vertically, only vertical scroll events are valid.
  39     offset_magnitude = offset.y();
  40   }
  41
  42   // Do not scroll on very small touchpad events. Mouse wheel events should
  43   // scroll, no matter how small the value change.
  44   if (type == SCROLL_MOUSE_WHEEL ||
  45       abs(offset_magnitude) > kMinScrollToSwitchPage) {
  46     if (!pagination_model_->has_transition()) {
  47       pagination_model_->SelectPageRelative(offset_magnitude > 0 ? -1 : 1,
  48                                             true);
  49     }
  50     return true;
  51   }
  52
  53   return false;
  54 }
  55
  56 bool PaginationController::OnGestureEvent(const ui::GestureEvent& event,
  57                                           const gfx::Rect& bounds) {
  58   const ui::GestureEventDetails& details = event.details();
  59   switch (event.type()) {
  60     case ui::ET_GESTURE_SCROLL_BEGIN:
  61       pagination_model_->StartScroll();
  62       return true;
  63     case ui::ET_GESTURE_SCROLL_UPDATE: {
  64       float scroll = scroll_axis_ == SCROLL_AXIS_HORIZONTAL
  65                          ? details.scroll_x()
  66                          : details.scroll_y();
  67       int width = scroll_axis_ == SCROLL_AXIS_HORIZONTAL ? bounds.width()
  68                                                          : bounds.height();
  69       // scroll > 0 means moving contents right or down. That is, transitioning
  70       // to the previous page.
  71       pagination_model_->UpdateScroll(scroll / width);
  72       return true;
  73     }
  74     case ui::ET_GESTURE_SCROLL_END:
  75       pagination_model_->EndScroll(pagination_model_->transition().progress <
  76                                    kFinishTransitionThreshold);
  77       return true;
  78     case ui::ET_SCROLL_FLING_START: {
  79       float velocity = scroll_axis_ == SCROLL_AXIS_HORIZONTAL
  80                            ? details.velocity_x()
  81                            : details.velocity_y();
  82       pagination_model_->EndScroll(true);
  83       if (fabs(velocity) > kMinHorizVelocityToSwitchPage)
  84         pagination_model_->SelectPageRelative(velocity < 0 ? 1 : -1, true);
  85       return true;
  86     }
  87     default:
  88       return false;
  89   }
  90 }
  91
  92 }  // namespace app_list