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   int offset_magnitude;
  31   if (scroll_axis_ == SCROLL_AXIS_HORIZONTAL) {
  32     // If the view scrolls horizontally, both horizontal and vertical scroll
  33     // events are valid (since most mouse wheels only have vertical scrolling).
  34     offset_magnitude =
  35         abs(offset.x()) > abs(offset.y()) ? offset.x() : offset.y();
  36   } else {
  37     // If the view scrolls vertically, only vertical scroll events are valid.
  38     offset_magnitude = offset.y();
  39   }
  40
  41   if (abs(offset_magnitude) > kMinScrollToSwitchPage) {
  42     if (!pagination_model_->has_transition()) {
  43       pagination_model_->SelectPageRelative(offset_magnitude > 0 ? -1 : 1,
  44                                             true);
  45     }
  46     return true;
  47   }
  48
  49   return false;
  50 }
  51
  52 bool PaginationController::OnGestureEvent(const ui::GestureEvent& event,
  53                                           const gfx::Rect& bounds) {
  54   const ui::GestureEventDetails& details = event.details();
  55   switch (event.type()) {
  56     case ui::ET_GESTURE_SCROLL_BEGIN:
  57       pagination_model_->StartScroll();
  58       return true;
  59     case ui::ET_GESTURE_SCROLL_UPDATE: {
  60       float scroll = scroll_axis_ == SCROLL_AXIS_HORIZONTAL
  61                          ? details.scroll_x()
  62                          : details.scroll_y();
  63       int width = scroll_axis_ == SCROLL_AXIS_HORIZONTAL ? bounds.width()
  64                                                          : bounds.height();
  65       // scroll > 0 means moving contents right or down. That is, transitioning
  66       // to the previous page.
  67       pagination_model_->UpdateScroll(scroll / width);
  68       return true;
  69     }
  70     case ui::ET_GESTURE_SCROLL_END:
  71       pagination_model_->EndScroll(pagination_model_->transition().progress <
  72                                    kFinishTransitionThreshold);
  73       return true;
  74     case ui::ET_SCROLL_FLING_START: {
  75       float velocity = scroll_axis_ == SCROLL_AXIS_HORIZONTAL
  76                            ? details.velocity_x()
  77                            : details.velocity_y();
  78       pagination_model_->EndScroll(true);
  79       if (fabs(velocity) > kMinHorizVelocityToSwitchPage)
  80         pagination_model_->SelectPageRelative(velocity < 0 ? 1 : -1, true);
  81       return true;
  82     }
  83     default:
  84       return false;
  85   }
  86 }
  87
  88 }  // namespace app_list