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