src/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   float active_opacity = layer->opacity();
  35   LayerImpl::PushPropertiesTo(layer);
  36   layer->SetOpacity(active_opacity);
  37   DCHECK(layer->ToScrollbarLayer());
  38   layer->ToScrollbarLayer()->set_is_overlay_scrollbar(is_overlay_scrollbar_);
  39   PushScrollClipPropertiesTo(layer);
  40 }
  41
  42 void ScrollbarLayerImplBase::PushScrollClipPropertiesTo(LayerImpl* layer) {
  43   DCHECK(layer->ToScrollbarLayer());
  44   layer->ToScrollbarLayer()->SetScrollLayerAndClipLayerByIds(ScrollLayerId(),
  45                                                              ClipLayerId());
  46 }
  47
  48 ScrollbarLayerImplBase* ScrollbarLayerImplBase::ToScrollbarLayer() {
  49   return this;
  50 }
  51
  52 namespace {
  53
  54 typedef void (LayerImpl::*ScrollbarRegistrationOperation)(
  55     ScrollbarLayerImplBase*);
  56
  57 void RegisterScrollbarWithLayers(ScrollbarLayerImplBase* scrollbar,
  58                                  LayerImpl* container_layer,
  59                                  LayerImpl* scroll_layer,
  60                                  ScrollbarRegistrationOperation operation) {
  61   if (!container_layer || !scroll_layer)
  62     return;
  63
  64   DCHECK(scrollbar);
  65
  66   // Scrollbars must be notifed of changes to their scroll and container layers
  67   // and all scrollable layers in between.
  68   for (LayerImpl* current_layer = scroll_layer;
  69        current_layer && current_layer != container_layer->parent();
  70        current_layer = current_layer->parent()) {
  71     // TODO(wjmaclean) We shouldn't need to exempt the scroll_layer from the
  72     // scrollable() test below. https://crbug.com/367858.
  73     if (current_layer->scrollable() || current_layer == container_layer ||
  74         current_layer == scroll_layer)
  75       (current_layer->*operation)(scrollbar);
  76   }
  77 }
  78 }  // namespace
  79
  80 void ScrollbarLayerImplBase::SetScrollLayerAndClipLayerByIds(
  81     int scroll_layer_id,
  82     int clip_layer_id) {
  83   LayerImpl* scroll_layer = layer_tree_impl()->LayerById(scroll_layer_id);
  84   LayerImpl* clip_layer = layer_tree_impl()->LayerById(clip_layer_id);
  85   if (scroll_layer_ == scroll_layer && clip_layer_ == clip_layer)
  86     return;
  87
  88   RegisterScrollbarWithLayers(
  89       this, clip_layer_, scroll_layer_, &LayerImpl::RemoveScrollbar);
  90   scroll_layer_ = scroll_layer;
  91   clip_layer_ = clip_layer;
  92   RegisterScrollbarWithLayers(
  93       this, clip_layer_, scroll_layer_, &LayerImpl::AddScrollbar);
  94
  95   ScrollbarParametersDidChange();
  96 }
  97
  98 gfx::Rect ScrollbarLayerImplBase::ScrollbarLayerRectToContentRect(
  99     const gfx::RectF& layer_rect) const {
 100   // Don't intersect with the bounds as in LayerRectToContentRect() because
 101   // layer_rect here might be in coordinates of the containing layer.
 102   gfx::RectF content_rect = gfx::ScaleRect(layer_rect,
 103       contents_scale_x(),
 104       contents_scale_y());
 105   return gfx::ToEnclosingRect(content_rect);
 106 }
 107
 108 bool ScrollbarLayerImplBase::SetCurrentPos(float current_pos) {
 109   if (current_pos_ == current_pos)
 110     return false;
 111   current_pos_ = current_pos;
 112   NoteLayerPropertyChanged();
 113   return true;
 114 }
 115
 116 bool ScrollbarLayerImplBase::SetMaximum(int maximum) {
 117   if (maximum_ == maximum)
 118     return false;
 119   maximum_ = maximum;
 120   NoteLayerPropertyChanged();
 121   return true;
 122 }
 123
 124 bool ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
 125   if (vertical_adjust_ == vertical_adjust)
 126     return false;
 127   vertical_adjust_ = vertical_adjust;
 128   NoteLayerPropertyChanged();
 129   return true;
 130 }
 131
 132 bool ScrollbarLayerImplBase::SetVisibleToTotalLengthRatio(float ratio) {
 133   if (!IsThumbResizable())
 134     return false;
 135
 136   if (visible_to_total_length_ratio_ == ratio)
 137     return false;
 138   visible_to_total_length_ratio_ = ratio;
 139   NoteLayerPropertyChanged();
 140   return true;
 141 }
 142
 143 bool ScrollbarLayerImplBase::SetThumbThicknessScaleFactor(float factor) {
 144   if (thumb_thickness_scale_factor_ == factor)
 145     return false;
 146   thumb_thickness_scale_factor_ = factor;
 147   NoteLayerPropertyChanged();
 148   return true;
 149 }
 150
 151 gfx::Rect ScrollbarLayerImplBase::ComputeThumbQuadRect() const {
 152   // Thumb extent is the length of the thumb in the scrolling direction, thumb
 153   // thickness is in the perpendicular direction. Here's an example of a
 154   // horizontal scrollbar - inputs are above the scrollbar, computed values
 155   // below:
 156   //
 157   //    |<------------------- track_length_ ------------------->|
 158   //
 159   // |--| <-- start_offset
 160   //
 161   // +--+----------------------------+------------------+-------+--+
 162   // |<||                            |##################|       ||>|
 163   // +--+----------------------------+------------------+-------+--+
 164   //
 165   //                                 |<- thumb_length ->|
 166   //
 167   // |<------- thumb_offset -------->|
 168   //
 169   // For painted, scrollbars, the length is fixed. For solid color scrollbars we
 170   // have to compute it. The ratio of the thumb's length to the track's length
 171   // is the same as that of the visible viewport to the total viewport, unless
 172   // that would make the thumb's length less than its thickness.
 173   //
 174   // vertical_adjust_ is used when the layer geometry from the main thread is
 175   // not in sync with what the user sees. For instance on Android scrolling the
 176   // top bar controls out of view reveals more of the page content. We want the
 177   // root layer scrollbars to reflect what the user sees even if we haven't
 178   // received new layer geometry from the main thread.  If the user has scrolled
 179   // down by 50px and the initial viewport size was 950px the geometry would
 180   // look something like this:
 181   //
 182   // vertical_adjust_ = 50, scroll position 0, visible ratios 99%
 183   // Layer geometry:             Desired thumb positions:
 184   // +--------------------+-+   +----------------------+   <-- 0px
 185   // |                    |v|   |                     #|
 186   // |                    |e|   |                     #|
 187   // |                    |r|   |                     #|
 188   // |                    |t|   |                     #|
 189   // |                    |i|   |                     #|
 190   // |                    |c|   |                     #|
 191   // |                    |a|   |                     #|
 192   // |                    |l|   |                     #|
 193   // |                    | |   |                     #|
 194   // |                    |l|   |                     #|
 195   // |                    |a|   |                     #|
 196   // |                    |y|   |                     #|
 197   // |                    |e|   |                     #|
 198   // |                    |r|   |                     #|
 199   // +--------------------+-+   |                     #|
 200   // | horizontal  layer  | |   |                     #|
 201   // +--------------------+-+   |                     #|  <-- 950px
 202   // |                      |   |                     #|
 203   // |                      |   |##################### |
 204   // +----------------------+   +----------------------+  <-- 1000px
 205   //
 206   // The layer geometry is set up for a 950px tall viewport, but the user can
 207   // actually see down to 1000px. Thus we have to move the quad for the
 208   // horizontal scrollbar down by the vertical_adjust_ factor and lay the
 209   // vertical thumb out on a track lengthed by the vertical_adjust_ factor. This
 210   // means the quads may extend outside the layer's bounds.
 211
 212   // With the length known, we can compute the thumb's position.
 213   float track_length = TrackLength();
 214   int thumb_length = ThumbLength();
 215   int thumb_thickness = ThumbThickness();
 216
 217   // With the length known, we can compute the thumb's position.
 218   float clamped_current_pos =
 219       std::min(std::max(current_pos_, 0.f), static_cast<float>(maximum_));
 220
 221   int thumb_offset = TrackStart();
 222   if (maximum_ > 0) {
 223     float ratio = clamped_current_pos / maximum_;
 224     float max_offset = track_length - thumb_length;
 225     thumb_offset += static_cast<int>(ratio * max_offset);
 226   }
 227
 228   float thumb_thickness_adjustment =
 229       thumb_thickness * (1.f - thumb_thickness_scale_factor_);
 230
 231   gfx::RectF thumb_rect;
 232   if (orientation_ == HORIZONTAL) {
 233     thumb_rect = gfx::RectF(thumb_offset,
 234                             vertical_adjust_ + thumb_thickness_adjustment,
 235                             thumb_length,
 236                             thumb_thickness - thumb_thickness_adjustment);
 237   } else {
 238     thumb_rect = gfx::RectF(
 239         is_left_side_vertical_scrollbar_
 240             ? bounds().width() - thumb_thickness
 241             : thumb_thickness_adjustment,
 242         thumb_offset,
 243         thumb_thickness - thumb_thickness_adjustment,
 244         thumb_length);
 245   }
 246
 247   return ScrollbarLayerRectToContentRect(thumb_rect);
 248 }
 249
 250 void ScrollbarLayerImplBase::ScrollbarParametersDidChange() {
 251   if (!clip_layer_ || !scroll_layer_)
 252     return;
 253
 254   scroll_layer_->SetScrollbarPosition(this, clip_layer_);
 255 }
 256
 257 }  // namespace cc