third_party/WebKit/Source/core/frame/TopControls.cpp

   1 // Copyright 2015 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 "config.h"
   6 #include "TopControls.h"
   7
   8 #include "core/frame/FrameHost.h"
   9 #include "core/page/ChromeClient.h"
  10 #include "platform/geometry/FloatSize.h"
  11 #include <algorithm> // for std::min and std::max
  12
  13 namespace blink {
  14
  15 TopControls::TopControls(const FrameHost& frameHost)
  16     : m_frameHost(&frameHost)
  17     , m_height(0)
  18     , m_shownRatio(0)
  19     , m_baselineContentOffset(0)
  20     , m_accumulatedScrollDelta(0)
  21     , m_shrinkViewport(false)
  22     , m_permittedState(WebTopControlsBoth)
  23 {
  24 }
  25
  26 TopControls::~TopControls()
  27 {
  28 }
  29
  30 DEFINE_TRACE(TopControls)
  31 {
  32     visitor->trace(m_frameHost);
  33 }
  34
  35 void TopControls::scrollBegin()
  36 {
  37     resetBaseline();
  38 }
  39
  40 FloatSize TopControls::scrollBy(FloatSize pendingDelta)
  41 {
  42     if ((m_permittedState == WebTopControlsShown && pendingDelta.height() < 0) || (m_permittedState == WebTopControlsHidden && pendingDelta.height() > 0))
  43         return pendingDelta;
  44
  45     if (m_height == 0)
  46         return pendingDelta;
  47
  48     float oldOffset = contentOffset();
  49     float pageScale = m_frameHost->visualViewport().scale();
  50
  51     // Update accumulated vertical scroll and apply it to top controls
  52     // Compute scroll delta in viewport space by applying page scale
  53     m_accumulatedScrollDelta += pendingDelta.height() * pageScale;
  54
  55     float newContentOffset = m_baselineContentOffset + m_accumulatedScrollDelta;
  56
  57     setShownRatio(newContentOffset / m_height);
  58
  59     // Reset baseline when controls are fully visible
  60     if (m_shownRatio == 1)
  61         resetBaseline();
  62
  63     // Clamp and use the expected content offset so that we don't return
  64     // spurrious remaining scrolls due to the imprecision of the shownRatio.
  65     newContentOffset = std::min(newContentOffset, m_height);
  66     newContentOffset = std::max(newContentOffset, 0.f);
  67
  68     FloatSize appliedDelta(0, (newContentOffset - oldOffset) / pageScale);
  69     return pendingDelta - appliedDelta;
  70 }
  71
  72 void TopControls::resetBaseline()
  73 {
  74     m_accumulatedScrollDelta = 0;
  75     m_baselineContentOffset = contentOffset();
  76 }
  77
  78 float TopControls::layoutHeight()
  79 {
  80     return m_shrinkViewport ? m_height : 0;
  81 }
  82
  83 float TopControls::contentOffset()
  84 {
  85     return m_shownRatio * m_height;
  86 }
  87
  88 void TopControls::setShownRatio(float shownRatio)
  89 {
  90     shownRatio = std::min(shownRatio, 1.f);
  91     shownRatio = std::max(shownRatio, 0.f);
  92
  93     if (m_shownRatio == shownRatio)
  94         return;
  95
  96     m_shownRatio = shownRatio;
  97     m_frameHost->chromeClient().didUpdateTopControls();
  98 }
  99
 100 void TopControls::updateConstraints(WebTopControlsState constraints)
 101 {
 102     m_permittedState = constraints;
 103 }
 104
 105 void TopControls::setHeight(float height, bool shrinkViewport)
 106 {
 107     if (m_height == height && m_shrinkViewport == shrinkViewport)
 108         return;
 109
 110     m_height = height;
 111     m_shrinkViewport = shrinkViewport;
 112     m_frameHost->chromeClient().didUpdateTopControls();
 113 }
 114
 115 } // namespace blink