cc/layers/scrollbar_layer_impl_base.cc

   1 // Copyright 2013 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 "cc/layers/scrollbar_layer_impl_base.h"
   6
   7 #include <algorithm>
   8 #include "cc/trees/layer_tree_impl.h"
   9 #include "ui/gfx/geometry/rect_conversions.h"
  10
  11 namespace cc {
  12
  13 ScrollbarLayerImplBase::ScrollbarLayerImplBase(
  14     LayerTreeImpl* tree_impl,
  15     int id,
  16     ScrollbarOrientation orientation,
  17     bool is_left_side_vertical_scrollbar,
  18     bool is_overlay)
  19     : LayerImpl(tree_impl, id),
  20       scroll_layer_(nullptr),
  21       clip_layer_(nullptr),
  22       is_overlay_scrollbar_(is_overlay),
  23       thumb_thickness_scale_factor_(1.f),
  24       current_pos_(0.f),
  25       maximum_(0),
  26       orientation_(orientation),
  27       is_left_side_vertical_scrollbar_(is_left_side_vertical_scrollbar),
  28       vertical_adjust_(0.f),
  29       visible_to_total_length_ratio_(1.f) {
  30 }
  31
  32 ScrollbarLayerImplBase::~ScrollbarLayerImplBase() {}
  33
  34 void ScrollbarLayerImplBase::PushPropertiesTo(LayerImpl* layer) {
  35   float active_opacity = layer->opacity();
  36   bool active_hidden = layer->hide_layer_and_subtree();
  37   LayerImpl::PushPropertiesTo(layer);
  38   layer->SetOpacity(active_opacity);
  39   layer->SetHideLayerAndSubtree(active_hidden);
  40   DCHECK(layer->ToScrollbarLayer());
  41   layer->ToScrollbarLayer()->set_is_overlay_scrollbar(is_overlay_scrollbar_);
  42   PushScrollClipPropertiesTo(layer);
  43 }
  44
  45 void ScrollbarLayerImplBase::PushScrollClipPropertiesTo(LayerImpl* layer) {
  46   DCHECK(layer->ToScrollbarLayer());
  47   layer->ToScrollbarLayer()->SetScrollLayerAndClipLayerByIds(ScrollLayerId(),
  48                                                              ClipLayerId());
  49 }
  50
  51 ScrollbarLayerImplBase* ScrollbarLayerImplBase::ToScrollbarLayer() {
  52   return this;
  53 }
  54
  55 namespace {
  56
  57 typedef void (LayerImpl::*ScrollbarRegistrationOperation)(
  58     ScrollbarLayerImplBase*);
  59
  60 void RegisterScrollbarWithLayers(ScrollbarLayerImplBase* scrollbar,
  61                                  LayerImpl* container_layer,
  62                                  LayerImpl* scroll_layer,
  63                                  ScrollbarRegistrationOperation operation) {
  64   if (!container_layer || !scroll_layer)
  65     return;
  66
  67   DCHECK(scrollbar);
  68
  69   // Scrollbars must be notifed of changes to their scroll and container layers
  70   // and all scrollable layers in between.
  71   for (LayerImpl* current_layer = scroll_layer;
  72        current_layer && current_layer != container_layer->parent();
  73        current_layer = current_layer->parent()) {
  74     (current_layer->*operation)(scrollbar);
  75   }
  76 }
  77 }  // namespace
  78
  79 void ScrollbarLayerImplBase::SetScrollLayerAndClipLayerByIds(
  80     int scroll_layer_id,
  81     int clip_layer_id) {
  82   LayerImpl* scroll_layer = layer_tree_impl()->LayerById(scroll_layer_id);
  83   LayerImpl* clip_layer = layer_tree_impl()->LayerById(clip_layer_id);
  84   if (scroll_layer_ == scroll_layer && clip_layer_ == clip_layer)
  85     return;
  86
  87   RegisterScrollbarWithLayers(
  88       this, clip_layer_, scroll_layer_, &LayerImpl::RemoveScrollbar);
  89   scroll_layer_ = scroll_layer;
  90   clip_layer_ = clip_layer;
  91   RegisterScrollbarWithLayers(
  92       this, clip_layer_, scroll_layer_, &LayerImpl::AddScrollbar);
  93
  94   ScrollbarParametersDidChange(false);
  95 }
  96
  97 bool ScrollbarLayerImplBase::SetCurrentPos(float current_pos) {
  98   if (current_pos_ == current_pos)
  99     return false;
 100   current_pos_ = current_pos;
 101   NoteLayerPropertyChanged();
 102   return true;
 103 }
 104
 105 bool ScrollbarLayerImplBase::SetMaximum(int maximum) {
 106   if (maximum_ == maximum)
 107     return false;
 108   maximum_ = maximum;
 109   NoteLayerPropertyChanged();
 110   return true;
 111 }
 112
 113 bool ScrollbarLayerImplBase::CanScrollOrientation() const {
 114   if (!scroll_layer_)
 115     return false;
 116   return scroll_layer_->user_scrollable(orientation()) && (0 < maximum());
 117 }
 118
 119 bool ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
 120   if (vertical_adjust_ == vertical_adjust)
 121     return false;
 122   vertical_adjust_ = vertical_adjust;
 123   NoteLayerPropertyChanged();
 124   return true;
 125 }
 126
 127 bool ScrollbarLayerImplBase::SetVisibleToTotalLengthRatio(float ratio) {
 128   if (!IsThumbResizable())
 129     return false;
 130
 131   if (visible_to_total_length_ratio_ == ratio)
 132     return false;
 133   visible_to_total_length_ratio_ = ratio;
 134   NoteLayerPropertyChanged();
 135   return true;
 136 }
 137
 138 bool ScrollbarLayerImplBase::SetThumbThicknessScaleFactor(float factor) {
 139   if (thumb_thickness_scale_factor_ == factor)
 140     return false;
 141   thumb_thickness_scale_factor_ = factor;
 142   NoteLayerPropertyChanged();
 143   return true;
 144 }
 145
 146 gfx::Rect ScrollbarLayerImplBase::ComputeThumbQuadRect() const {
 147   // Thumb extent is the length of the thumb in the scrolling direction, thumb
 148   // thickness is in the perpendicular direction. Here's an example of a
 149   // horizontal scrollbar - inputs are above the scrollbar, computed values
 150   // below:
 151   //
 152   //    |<------------------- track_length_ ------------------->|
 153   //
 154   // |--| <-- start_offset
 155   //
 156   // +--+----------------------------+------------------+-------+--+
 157   // |<||                            |##################|       ||>|
 158   // +--+----------------------------+------------------+-------+--+
 159   //
 160   //                                 |<- thumb_length ->|
 161   //
 162   // |<------- thumb_offset -------->|
 163   //
 164   // For painted, scrollbars, the length is fixed. For solid color scrollbars we
 165   // have to compute it. The ratio of the thumb's length to the track's length
 166   // is the same as that of the visible viewport to the total viewport, unless
 167   // that would make the thumb's length less than its thickness.
 168   //
 169   // vertical_adjust_ is used when the layer geometry from the main thread is
 170   // not in sync with what the user sees. For instance on Android scrolling the
 171   // top bar controls out of view reveals more of the page content. We want the
 172   // root layer scrollbars to reflect what the user sees even if we haven't
 173   // received new layer geometry from the main thread.  If the user has scrolled
 174   // down by 50px and the initial viewport size was 950px the geometry would
 175   // look something like this:
 176   //
 177   // vertical_adjust_ = 50, scroll position 0, visible ratios 99%
 178   // Layer geometry:             Desired thumb positions:
 179   // +--------------------+-+   +----------------------+   <-- 0px
 180   // |                    |v|   |                     #|
 181   // |                    |e|   |                     #|
 182   // |                    |r|   |                     #|
 183   // |                    |t|   |                     #|
 184   // |                    |i|   |                     #|
 185   // |                    |c|   |                     #|
 186   // |                    |a|   |                     #|
 187   // |                    |l|   |                     #|
 188   // |                    | |   |                     #|
 189   // |                    |l|   |                     #|
 190   // |                    |a|   |                     #|
 191   // |                    |y|   |                     #|
 192   // |                    |e|   |                     #|
 193   // |                    |r|   |                     #|
 194   // +--------------------+-+   |                     #|
 195   // | horizontal  layer  | |   |                     #|
 196   // +--------------------+-+   |                     #|  <-- 950px
 197   // |                      |   |                     #|
 198   // |                      |   |##################### |
 199   // +----------------------+   +----------------------+  <-- 1000px
 200   //
 201   // The layer geometry is set up for a 950px tall viewport, but the user can
 202   // actually see down to 1000px. Thus we have to move the quad for the
 203   // horizontal scrollbar down by the vertical_adjust_ factor and lay the
 204   // vertical thumb out on a track lengthed by the vertical_adjust_ factor. This
 205   // means the quads may extend outside the layer's bounds.
 206
 207   // With the length known, we can compute the thumb's position.
 208   float track_length = TrackLength();
 209   int thumb_length = ThumbLength();
 210   int thumb_thickness = ThumbThickness();
 211
 212   // With the length known, we can compute the thumb's position.
 213   float clamped_current_pos =
 214       std::min(std::max(current_pos_, 0.f), static_cast<float>(maximum_));
 215
 216   int thumb_offset = TrackStart();
 217   if (maximum_ > 0) {
 218     float ratio = clamped_current_pos / maximum_;
 219     float max_offset = track_length - thumb_length;
 220     thumb_offset += static_cast<int>(ratio * max_offset);
 221   }
 222
 223   float thumb_thickness_adjustment =
 224       thumb_thickness * (1.f - thumb_thickness_scale_factor_);
 225
 226   gfx::RectF thumb_rect;
 227   if (orientation_ == HORIZONTAL) {
 228     thumb_rect = gfx::RectF(thumb_offset,
 229                             vertical_adjust_ + thumb_thickness_adjustment,
 230                             thumb_length,
 231                             thumb_thickness - thumb_thickness_adjustment);
 232   } else {
 233     thumb_rect = gfx::RectF(
 234         is_left_side_vertical_scrollbar_
 235             ? bounds().width() - thumb_thickness
 236             : thumb_thickness_adjustment,
 237         thumb_offset,
 238         thumb_thickness - thumb_thickness_adjustment,
 239         thumb_length);
 240   }
 241
 242   return gfx::ToEnclosingRect(thumb_rect);
 243 }
 244
 245 void ScrollbarLayerImplBase::ScrollbarParametersDidChange(bool on_resize) {
 246   if (!clip_layer_ || !scroll_layer_)
 247     return;
 248
 249   scroll_layer_->SetScrollbarPosition(this, clip_layer_, on_resize);
 250 }
 251
 252 }  // namespace cc