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/layers/layer.h"
9 #include "ui/gfx/rect_conversions.h"
10
11 namespace cc {
12
ScrollbarLayerImplBase(LayerTreeImpl * tree_impl,int id,ScrollbarOrientation orientation,bool is_left_side_vertical_scrollbar)13 ScrollbarLayerImplBase::ScrollbarLayerImplBase(
14 LayerTreeImpl* tree_impl,
15 int id,
16 ScrollbarOrientation orientation,
17 bool is_left_side_vertical_scrollbar)
18 : LayerImpl(tree_impl, id),
19 scroll_layer_id_(Layer::INVALID_ID),
20 is_overlay_scrollbar_(false),
21 thumb_thickness_scale_factor_(1.f),
22 current_pos_(0.f),
23 maximum_(0),
24 orientation_(orientation),
25 is_left_side_vertical_scrollbar_(is_left_side_vertical_scrollbar),
26 vertical_adjust_(0.f),
27 visible_to_total_length_ratio_(1.f) {}
28
PushPropertiesTo(LayerImpl * layer)29 void ScrollbarLayerImplBase::PushPropertiesTo(LayerImpl* layer) {
30 LayerImpl::PushPropertiesTo(layer);
31 }
32
ToScrollbarLayer()33 ScrollbarLayerImplBase* ScrollbarLayerImplBase::ToScrollbarLayer() {
34 return this;
35 }
36
ScrollbarLayerRectToContentRect(gfx::RectF layer_rect) const37 gfx::Rect ScrollbarLayerImplBase::ScrollbarLayerRectToContentRect(
38 gfx::RectF layer_rect) const {
39 // Don't intersect with the bounds as in LayerRectToContentRect() because
40 // layer_rect here might be in coordinates of the containing layer.
41 gfx::RectF content_rect = gfx::ScaleRect(layer_rect,
42 contents_scale_x(),
43 contents_scale_y());
44 return gfx::ToEnclosingRect(content_rect);
45 }
46
SetCurrentPos(float current_pos)47 void ScrollbarLayerImplBase::SetCurrentPos(float current_pos) {
48 if (current_pos_ == current_pos)
49 return;
50 current_pos_ = current_pos;
51 NoteLayerPropertyChanged();
52 }
53
SetMaximum(int maximum)54 void ScrollbarLayerImplBase::SetMaximum(int maximum) {
55 if (maximum_ == maximum)
56 return;
57 maximum_ = maximum;
58 NoteLayerPropertyChanged();
59 }
60
SetVerticalAdjust(float vertical_adjust)61 void ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
62 if (vertical_adjust_ == vertical_adjust)
63 return;
64 vertical_adjust_ = vertical_adjust;
65 NoteLayerPropertyChanged();
66 }
67
SetVisibleToTotalLengthRatio(float ratio)68 void ScrollbarLayerImplBase::SetVisibleToTotalLengthRatio(float ratio) {
69 if (visible_to_total_length_ratio_ == ratio)
70 return;
71 visible_to_total_length_ratio_ = ratio;
72 NoteLayerPropertyChanged();
73 }
74
SetThumbThicknessScaleFactor(float factor)75 void ScrollbarLayerImplBase::SetThumbThicknessScaleFactor(float factor) {
76 if (thumb_thickness_scale_factor_ == factor)
77 return;
78 thumb_thickness_scale_factor_ = factor;
79 NoteLayerPropertyChanged();
80 }
81
ComputeThumbQuadRect() const82 gfx::Rect ScrollbarLayerImplBase::ComputeThumbQuadRect() const {
83 // Thumb extent is the length of the thumb in the scrolling direction, thumb
84 // thickness is in the perpendicular direction. Here's an example of a
85 // horizontal scrollbar - inputs are above the scrollbar, computed values
86 // below:
87 //
88 // |<------------------- track_length_ ------------------->|
89 //
90 // |--| <-- start_offset
91 //
92 // +--+----------------------------+------------------+-------+--+
93 // |<|| |##################| ||>|
94 // +--+----------------------------+------------------+-------+--+
95 //
96 // |<- thumb_length ->|
97 //
98 // |<------- thumb_offset -------->|
99 //
100 // For painted, scrollbars, the length is fixed. For solid color scrollbars we
101 // have to compute it. The ratio of the thumb's length to the track's length
102 // is the same as that of the visible viewport to the total viewport, unless
103 // that would make the thumb's length less than its thickness.
104 //
105 // vertical_adjust_ is used when the layer geometry from the main thread is
106 // not in sync with what the user sees. For instance on Android scrolling the
107 // top bar controls out of view reveals more of the page content. We want the
108 // root layer scrollbars to reflect what the user sees even if we haven't
109 // received new layer geometry from the main thread. If the user has scrolled
110 // down by 50px and the initial viewport size was 950px the geometry would
111 // look something like this:
112 //
113 // vertical_adjust_ = 50, scroll position 0, visible ratios 99%
114 // Layer geometry: Desired thumb positions:
115 // +--------------------+-+ +----------------------+ <-- 0px
116 // | |v| | #|
117 // | |e| | #|
118 // | |r| | #|
119 // | |t| | #|
120 // | |i| | #|
121 // | |c| | #|
122 // | |a| | #|
123 // | |l| | #|
124 // | | | | #|
125 // | |l| | #|
126 // | |a| | #|
127 // | |y| | #|
128 // | |e| | #|
129 // | |r| | #|
130 // +--------------------+-+ | #|
131 // | horizontal layer | | | #|
132 // +--------------------+-+ | #| <-- 950px
133 // | | | #|
134 // | | |##################### |
135 // +----------------------+ +----------------------+ <-- 1000px
136 //
137 // The layer geometry is set up for a 950px tall viewport, but the user can
138 // actually see down to 1000px. Thus we have to move the quad for the
139 // horizontal scrollbar down by the vertical_adjust_ factor and lay the
140 // vertical thumb out on a track lengthed by the vertical_adjust_ factor. This
141 // means the quads may extend outside the layer's bounds.
142
143 // With the length known, we can compute the thumb's position.
144 float track_length = TrackLength();
145 int thumb_length = ThumbLength();
146 int thumb_thickness = ThumbThickness();
147
148 // With the length known, we can compute the thumb's position.
149 float clamped_current_pos =
150 std::min(std::max(current_pos_, 0.f), static_cast<float>(maximum_));
151 float ratio = clamped_current_pos / maximum_;
152 float max_offset = track_length - thumb_length;
153 int thumb_offset = static_cast<int>(ratio * max_offset) + TrackStart();
154
155 float thumb_thickness_adjustment =
156 thumb_thickness * (1.f - thumb_thickness_scale_factor_);
157
158 gfx::RectF thumb_rect;
159 if (orientation_ == HORIZONTAL) {
160 thumb_rect = gfx::RectF(thumb_offset,
161 vertical_adjust_ + thumb_thickness_adjustment,
162 thumb_length,
163 thumb_thickness - thumb_thickness_adjustment);
164 } else {
165 thumb_rect = gfx::RectF(
166 is_left_side_vertical_scrollbar_
167 ? bounds().width() - thumb_thickness
168 : thumb_thickness_adjustment,
169 thumb_offset,
170 thumb_thickness - thumb_thickness_adjustment,
171 thumb_length);
172 }
173
174 return ScrollbarLayerRectToContentRect(thumb_rect);
175 }
176
177 } // namespace cc
178