layout/base/ScrollStyles.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/ScrollStyles.h"
   8 #include "nsStyleStruct.h"  // for nsStyleDisplay
   9
  10 namespace mozilla {
  11
  12 // https://drafts.csswg.org/css-overflow/#overflow-propagation
  13 // "If `visible` is applied to the viewport, it must be interpreted as `auto`.
  14 //  If `clip` is applied to the viewport, it must be interpreted as `hidden`."
  15 static StyleOverflow MapOverflowValueForViewportPropagation(
  16     StyleOverflow aOverflow) {
  17   switch (aOverflow) {
  18     case StyleOverflow::Visible:
  19       return StyleOverflow::Auto;
  20     case StyleOverflow::Clip:
  21       return StyleOverflow::Hidden;
  22     default:
  23       return aOverflow;
  24   }
  25 }
  26
  27 ScrollStyles::ScrollStyles(StyleOverflow aH, StyleOverflow aV)
  28     : mHorizontal(aH), mVertical(aV) {
  29   MOZ_ASSERT(mHorizontal == StyleOverflow::Auto ||
  30              mHorizontal == StyleOverflow::Hidden ||
  31              mHorizontal == StyleOverflow::Scroll);
  32   MOZ_ASSERT(mVertical == StyleOverflow::Auto ||
  33              mVertical == StyleOverflow::Hidden ||
  34              mVertical == StyleOverflow::Scroll);
  35 }
  36
  37 ScrollStyles::ScrollStyles(const nsStyleDisplay& aDisplay,
  38                            MapOverflowToValidScrollStyleTag)
  39     : ScrollStyles(
  40           MapOverflowValueForViewportPropagation(aDisplay.mOverflowX),
  41           MapOverflowValueForViewportPropagation(aDisplay.mOverflowY)) {}
  42
  43 bool ScrollStyles::IsHiddenInBothDirections() const {
  44   return mHorizontal == StyleOverflow::Hidden &&
  45          mVertical == StyleOverflow::Hidden;
  46 }
  47
  48 }  // namespace mozilla