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   LayerImpl::PushPropertiesTo(layer);
  37   layer->SetOpacity(active_opacity);
  38   DCHECK(layer->ToScrollbarLayer());
  39   layer->ToScrollbarLayer()->set_is_overlay_scrollbar(is_overlay_scrollbar_);
  40   PushScrollClipPropertiesTo(layer);
  41 }
  42
  43 void ScrollbarLayerImplBase::PushScrollClipPropertiesTo(LayerImpl* layer) {
  44   DCHECK(layer->ToScrollbarLayer());
  45   layer->ToScrollbarLayer()->SetScrollLayerAndClipLayerByIds(ScrollLayerId(),
  46                                                              ClipLayerId());
  47 }
  48
  49 ScrollbarLayerImplBase* ScrollbarLayerImplBase::ToScrollbarLayer() {
  50   return this;
  51 }
  52
  53 namespace {
  54
  55 typedef void (LayerImpl::*ScrollbarRegistrationOperation)(
  56     ScrollbarLayerImplBase*);
  57
  58 void RegisterScrollbarWithLayers(ScrollbarLayerImplBase* scrollbar,
  59                                  LayerImpl* container_layer,
  60                                  LayerImpl* scroll_layer,
  61                                  ScrollbarRegistrationOperation operation) {
  62   if (!container_layer || !scroll_layer)
  63     return;
  64
  65   DCHECK(scrollbar);
  66
  67   // Scrollbars must be notifed of changes to their scroll and container layers
  68   // and all scrollable layers in between.
  69   for (LayerImpl* current_layer = scroll_layer;
  70        current_layer && current_layer != container_layer->parent();
  71        current_layer = current_layer->parent()) {
  72     // TODO(wjmaclean) We shouldn't need to exempt the scroll_layer from the
  73     // scrollable() test below. https://crbug.com/367858.
  74     if (current_layer->scrollable() || current_layer == container_layer ||
  75         current_layer == scroll_layer)
  76       (current_layer->*operation)(scrollbar);
  77   }
  78 }
  79 }  // namespace
  80
  81 void ScrollbarLayerImplBase::SetScrollLayerAndClipLayerByIds(
  82     int scroll_layer_id,
  83     int clip_layer_id) {
  84   LayerImpl* scroll_layer = layer_tree_impl()->LayerById(scroll_layer_id);
  85   LayerImpl* clip_layer = layer_tree_impl()->LayerById(clip_layer_id);
  86   if (scroll_layer_ == scroll_layer && clip_layer_ == clip_layer)
  87     return;
  88
  89   RegisterScrollbarWithLayers(
  90       this, clip_layer_, scroll_layer_, &LayerImpl::RemoveScrollbar);
  91   scroll_layer_ = scroll_layer;
  92   clip_layer_ = clip_layer;
  93   RegisterScrollbarWithLayers(
  94       this, clip_layer_, scroll_layer_, &LayerImpl::AddScrollbar);
  95
  96   ScrollbarParametersDidChange(false);
  97 }
  98
  99 gfx::Rect ScrollbarLayerImplBase::ScrollbarLayerRectToContentRect(
 100     const gfx::RectF& layer_rect) const {
 101   // Don't intersect with the bounds as in LayerRectToContentRect() because
 102   // layer_rect here might be in coordinates of the containing layer.
 103   gfx::RectF content_rect = gfx::ScaleRect(layer_rect,
 104       contents_scale_x(),
 105       contents_scale_y());
 106   return gfx::ToEnclosingRect(content_rect);
 107 }
 108
 109 bool ScrollbarLayerImplBase::SetCurrentPos(float current_pos) {
 110   if (current_pos_ == current_pos)
 111     return false;
 112   current_pos_ = current_pos;
 113   NoteLayerPropertyChanged();
 114   return true;
 115 }
 116
 117 bool ScrollbarLayerImplBase::SetMaximum(int maximum) {
 118   if (maximum_ == maximum)
 119     return false;
 120   maximum_ = maximum;
 121   NoteLayerPropertyChanged();
 122   return true;
 123 }
 124
 125 bool ScrollbarLayerImplBase::CanScrollOrientation() const {
 126   if (!scroll_layer_)
 127     return false;
 128   return scroll_layer_->user_scrollable(orientation()) && (0 < maximum());
 129 }
 130
 131 bool ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
 132   if (vertical_adjust_ == vertical_adjust)
 133     return false;
 134   vertical_adjust_ = vertical_adjust;
 135   NoteLayerPropertyChanged();
 136   return true;
 137 }
 138
 139 bool ScrollbarLayerImplBase::SetVisibleToTotalLengthRatio(float ratio) {
 140   if (!IsThumbResizable())
 141     return false;
 142
 143   if (visible_to_total_length_ratio_ == ratio)
 144     return false;
 145   visible_to_total_length_ratio_ = ratio;
 146   NoteLayerPropertyChanged();
 147   return true;
 148 }
 149
 150 bool ScrollbarLayerImplBase::SetThumbThicknessScaleFactor(float factor) {
 151   if (thumb_thickness_scale_factor_ == factor)
 152     return false;
 153   thumb_thickness_scale_factor_ = factor;
 154   NoteLayerPropertyChanged();
 155   return true;
 156 }
 157
 158 gfx::Rect ScrollbarLayerImplBase::ComputeThumbQuadRect() const {
 159   // Thumb extent is the length of the thumb in the scrolling direction, thumb
 160   // thickness is in the perpendicular direction. Here's an example of a
 161   // horizontal scrollbar - inputs are above the scrollbar, computed values
 162   // below:
 163   //
 164   //    |<------------------- track_length_ ------------------->|
 165   //
 166   // |--| <-- start_offset
 167   //
 168   // +--+----------------------------+------------------+-------+--+
 169   // |<||                            |##################|       ||>|
 170   // +--+----------------------------+------------------+-------+--+
 171   //
 172   //                                 |<- thumb_length ->|
 173   //
 174   // |<------- thumb_offset -------->|
 175   //
 176   // For painted, scrollbars, the length is fixed. For solid color scrollbars we
 177   // have to compute it. The ratio of the thumb's length to the track's length
 178   // is the same as that of the visible viewport to the total viewport, unless
 179   // that would make the thumb's length less than its thickness.
 180   //
 181   // vertical_adjust_ is used when the layer geometry from the main thread is
 182   // not in sync with what the user sees. For instance on Android scrolling the
 183   // top bar controls out of view reveals more of the page content. We want the
 184   // root layer scrollbars to reflect what the user sees even if we haven't
 185   // received new layer geometry from the main thread.  If the user has scrolled
 186   // down by 50px and the initial viewport size was 950px the geometry would
 187   // look something like this:
 188   //
 189   // vertical_adjust_ = 50, scroll position 0, visible ratios 99%
 190   // Layer geometry:             Desired thumb positions:
 191   // +--------------------+-+   +----------------------+   <-- 0px
 192   // |                    |v|   |                     #|
 193   // |                    |e|   |                     #|
 194   // |                    |r|   |                     #|
 195   // |                    |t|   |                     #|
 196   // |                    |i|   |                     #|
 197   // |                    |c|   |                     #|
 198   // |                    |a|   |                     #|
 199   // |                    |l|   |                     #|
 200   // |                    | |   |                     #|
 201   // |                    |l|   |                     #|
 202   // |                    |a|   |                     #|
 203   // |                    |y|   |                     #|
 204   // |                    |e|   |                     #|
 205   // |                    |r|   |                     #|
 206   // +--------------------+-+   |                     #|
 207   // | horizontal  layer  | |   |                     #|
 208   // +--------------------+-+   |                     #|  <-- 950px
 209   // |                      |   |                     #|
 210   // |                      |   |##################### |
 211   // +----------------------+   +----------------------+  <-- 1000px
 212   //
 213   // The layer geometry is set up for a 950px tall viewport, but the user can
 214   // actually see down to 1000px. Thus we have to move the quad for the
 215   // horizontal scrollbar down by the vertical_adjust_ factor and lay the
 216   // vertical thumb out on a track lengthed by the vertical_adjust_ factor. This
 217   // means the quads may extend outside the layer's bounds.
 218
 219   // With the length known, we can compute the thumb's position.
 220   float track_length = TrackLength();
 221   int thumb_length = ThumbLength();
 222   int thumb_thickness = ThumbThickness();
 223
 224   // With the length known, we can compute the thumb's position.
 225   float clamped_current_pos =
 226       std::min(std::max(current_pos_, 0.f), static_cast<float>(maximum_));
 227
 228   int thumb_offset = TrackStart();
 229   if (maximum_ > 0) {
 230     float ratio = clamped_current_pos / maximum_;
 231     float max_offset = track_length - thumb_length;
 232     thumb_offset += static_cast<int>(ratio * max_offset);
 233   }
 234
 235   float thumb_thickness_adjustment =
 236       thumb_thickness * (1.f - thumb_thickness_scale_factor_);
 237
 238   gfx::RectF thumb_rect;
 239   if (orientation_ == HORIZONTAL) {
 240     thumb_rect = gfx::RectF(thumb_offset,
 241                             vertical_adjust_ + thumb_thickness_adjustment,
 242                             thumb_length,
 243                             thumb_thickness - thumb_thickness_adjustment);
 244   } else {
 245     thumb_rect = gfx::RectF(
 246         is_left_side_vertical_scrollbar_
 247             ? bounds().width() - thumb_thickness
 248             : thumb_thickness_adjustment,
 249         thumb_offset,
 250         thumb_thickness - thumb_thickness_adjustment,
 251         thumb_length);
 252   }
 253
 254   return ScrollbarLayerRectToContentRect(thumb_rect);
 255 }
 256
 257 void ScrollbarLayerImplBase::ScrollbarParametersDidChange(bool on_resize) {
 258   if (!clip_layer_ || !scroll_layer_)
 259     return;
 260
 261   scroll_layer_->SetScrollbarPosition(this, clip_layer_, on_resize);
 262 }
 263
 264 }  // namespace cc