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/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_(NULL),
  21       clip_layer_(NULL),
  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 ScrollbarLayerImplBase::~ScrollbarLayerImplBase() {}
  32
  33 void ScrollbarLayerImplBase::PushPropertiesTo(LayerImpl* layer) {
  34   LayerImpl::PushPropertiesTo(layer);
  35   DCHECK(layer->ToScrollbarLayer());
  36   layer->ToScrollbarLayer()->set_is_overlay_scrollbar(is_overlay_scrollbar_);
  37   PushScrollClipPropertiesTo(layer);
  38 }
  39
  40 void ScrollbarLayerImplBase::PushScrollClipPropertiesTo(LayerImpl* layer) {
  41   DCHECK(layer->ToScrollbarLayer());
  42   layer->ToScrollbarLayer()->SetScrollLayerById(ScrollLayerId());
  43   layer->ToScrollbarLayer()->SetClipLayerById(ClipLayerId());
  44 }
  45
  46 ScrollbarLayerImplBase* ScrollbarLayerImplBase::ToScrollbarLayer() {
  47   return this;
  48 }
  49
  50 void ScrollbarLayerImplBase::SetScrollLayerById(int id) {
  51   LayerImpl* scroll_layer = layer_tree_impl()->LayerById(id);
  52   if (scroll_layer_ == scroll_layer)
  53     return;
  54
  55   if (scroll_layer_)
  56     scroll_layer_->RemoveScrollbar(this);
  57   scroll_layer_ = scroll_layer;
  58   if (scroll_layer_)
  59     scroll_layer_->AddScrollbar(this);
  60 }
  61
  62 void ScrollbarLayerImplBase::SetClipLayerById(int id) {
  63   LayerImpl* clip_layer = layer_tree_impl()->LayerById(id);
  64   if (clip_layer_ == clip_layer)
  65     return;
  66
  67   if (clip_layer_)
  68     clip_layer_->RemoveScrollbar(this);
  69   clip_layer_ = clip_layer;
  70   if (clip_layer_)
  71     clip_layer_->AddScrollbar(this);
  72 }
  73
  74 gfx::Rect ScrollbarLayerImplBase::ScrollbarLayerRectToContentRect(
  75     const gfx::RectF& layer_rect) const {
  76   // Don't intersect with the bounds as in LayerRectToContentRect() because
  77   // layer_rect here might be in coordinates of the containing layer.
  78   gfx::RectF content_rect = gfx::ScaleRect(layer_rect,
  79       contents_scale_x(),
  80       contents_scale_y());
  81   return gfx::ToEnclosingRect(content_rect);
  82 }
  83
  84 void ScrollbarLayerImplBase::SetCurrentPos(float current_pos) {
  85   if (current_pos_ == current_pos)
  86     return;
  87   current_pos_ = current_pos;
  88   NoteLayerPropertyChanged();
  89 }
  90
  91 void ScrollbarLayerImplBase::SetMaximum(int maximum) {
  92   if (maximum_ == maximum)
  93     return;
  94   maximum_ = maximum;
  95   NoteLayerPropertyChanged();
  96 }
  97
  98 void ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
  99   if (vertical_adjust_ == vertical_adjust)
 100     return;
 101   vertical_adjust_ = vertical_adjust;
 102   NoteLayerPropertyChanged();
 103 }
 104
 105 void ScrollbarLayerImplBase::SetVisibleToTotalLengthRatio(float ratio) {
 106   if (!IsThumbResizable())
 107     return;
 108
 109   if (visible_to_total_length_ratio_ == ratio)
 110     return;
 111   visible_to_total_length_ratio_ = ratio;
 112   NoteLayerPropertyChanged();
 113 }
 114
 115 void ScrollbarLayerImplBase::SetThumbThicknessScaleFactor(float factor) {
 116   if (thumb_thickness_scale_factor_ == factor)
 117     return;
 118   thumb_thickness_scale_factor_ = factor;
 119   NoteLayerPropertyChanged();
 120 }
 121
 122 gfx::Rect ScrollbarLayerImplBase::ComputeThumbQuadRect() const {
 123   // Thumb extent is the length of the thumb in the scrolling direction, thumb
 124   // thickness is in the perpendicular direction. Here's an example of a
 125   // horizontal scrollbar - inputs are above the scrollbar, computed values
 126   // below:
 127   //
 128   //    |<------------------- track_length_ ------------------->|
 129   //
 130   // |--| <-- start_offset
 131   //
 132   // +--+----------------------------+------------------+-------+--+
 133   // |<||                            |##################|       ||>|
 134   // +--+----------------------------+------------------+-------+--+
 135   //
 136   //                                 |<- thumb_length ->|
 137   //
 138   // |<------- thumb_offset -------->|
 139   //
 140   // For painted, scrollbars, the length is fixed. For solid color scrollbars we
 141   // have to compute it. The ratio of the thumb's length to the track's length
 142   // is the same as that of the visible viewport to the total viewport, unless
 143   // that would make the thumb's length less than its thickness.
 144   //
 145   // vertical_adjust_ is used when the layer geometry from the main thread is
 146   // not in sync with what the user sees. For instance on Android scrolling the
 147   // top bar controls out of view reveals more of the page content. We want the
 148   // root layer scrollbars to reflect what the user sees even if we haven't
 149   // received new layer geometry from the main thread.  If the user has scrolled
 150   // down by 50px and the initial viewport size was 950px the geometry would
 151   // look something like this:
 152   //
 153   // vertical_adjust_ = 50, scroll position 0, visible ratios 99%
 154   // Layer geometry:             Desired thumb positions:
 155   // +--------------------+-+   +----------------------+   <-- 0px
 156   // |                    |v|   |                     #|
 157   // |                    |e|   |                     #|
 158   // |                    |r|   |                     #|
 159   // |                    |t|   |                     #|
 160   // |                    |i|   |                     #|
 161   // |                    |c|   |                     #|
 162   // |                    |a|   |                     #|
 163   // |                    |l|   |                     #|
 164   // |                    | |   |                     #|
 165   // |                    |l|   |                     #|
 166   // |                    |a|   |                     #|
 167   // |                    |y|   |                     #|
 168   // |                    |e|   |                     #|
 169   // |                    |r|   |                     #|
 170   // +--------------------+-+   |                     #|
 171   // | horizontal  layer  | |   |                     #|
 172   // +--------------------+-+   |                     #|  <-- 950px
 173   // |                      |   |                     #|
 174   // |                      |   |##################### |
 175   // +----------------------+   +----------------------+  <-- 1000px
 176   //
 177   // The layer geometry is set up for a 950px tall viewport, but the user can
 178   // actually see down to 1000px. Thus we have to move the quad for the
 179   // horizontal scrollbar down by the vertical_adjust_ factor and lay the
 180   // vertical thumb out on a track lengthed by the vertical_adjust_ factor. This
 181   // means the quads may extend outside the layer's bounds.
 182
 183   // With the length known, we can compute the thumb's position.
 184   float track_length = TrackLength();
 185   int thumb_length = ThumbLength();
 186   int thumb_thickness = ThumbThickness();
 187
 188   // With the length known, we can compute the thumb's position.
 189   float clamped_current_pos =
 190       std::min(std::max(current_pos_, 0.f), static_cast<float>(maximum_));
 191   float ratio = clamped_current_pos / maximum_;
 192   float max_offset = track_length - thumb_length;
 193   int thumb_offset = static_cast<int>(ratio * max_offset) + TrackStart();
 194
 195   float thumb_thickness_adjustment =
 196       thumb_thickness * (1.f - thumb_thickness_scale_factor_);
 197
 198   gfx::RectF thumb_rect;
 199   if (orientation_ == HORIZONTAL) {
 200     thumb_rect = gfx::RectF(thumb_offset,
 201                             vertical_adjust_ + thumb_thickness_adjustment,
 202                             thumb_length,
 203                             thumb_thickness - thumb_thickness_adjustment);
 204   } else {
 205     thumb_rect = gfx::RectF(
 206         is_left_side_vertical_scrollbar_
 207             ? bounds().width() - thumb_thickness
 208             : thumb_thickness_adjustment,
 209         thumb_offset,
 210         thumb_thickness - thumb_thickness_adjustment,
 211         thumb_length);
 212   }
 213
 214   return ScrollbarLayerRectToContentRect(thumb_rect);
 215 }
 216
 217 void ScrollbarLayerImplBase::ScrollbarParametersDidChange() {
 218   if (!clip_layer_ || !scroll_layer_)
 219     return;
 220
 221   scroll_layer_->SetScrollbarPosition(this, clip_layer_);
 222 }
 223
 224 }  // namespace cc