layout/painting/DisplayItemClipChain.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 "DisplayItemClipChain.h"
   8
   9 #include "nsDisplayList.h"
  10
  11 namespace mozilla {
  12
  13 /* static */ const DisplayItemClip* DisplayItemClipChain::ClipForASR(
  14     const DisplayItemClipChain* aClipChain, const ActiveScrolledRoot* aASR) {
  15   while (aClipChain &&
  16          !ActiveScrolledRoot::IsAncestor(aClipChain->mASR, aASR)) {
  17     aClipChain = aClipChain->mParent;
  18   }
  19   return (aClipChain && aClipChain->mASR == aASR) ? &aClipChain->mClip
  20                                                   : nullptr;
  21 }
  22
  23 bool DisplayItemClipChain::Equal(const DisplayItemClipChain* aClip1,
  24                                  const DisplayItemClipChain* aClip2) {
  25   if (aClip1 == aClip2) {
  26     return true;
  27   }
  28
  29   if (!aClip1 || !aClip2) {
  30     return false;
  31   }
  32
  33   bool ret = aClip1->mASR == aClip2->mASR && aClip1->mClip == aClip2->mClip &&
  34              Equal(aClip1->mParent, aClip2->mParent);
  35   // Sanity check: if two clip chains are equal they must hash to the same
  36   // thing too, or Bad Things (TM) will happen.
  37   MOZ_ASSERT(!ret || (Hash(aClip1) == Hash(aClip2)));
  38   return ret;
  39 }
  40
  41 uint32_t DisplayItemClipChain::Hash(const DisplayItemClipChain* aClip) {
  42   if (!aClip) {
  43     return 0;
  44   }
  45
  46   // We include the number of rounded rects in the hash but not their contents.
  47   // This is to keep the hash fast, because most clips will not have rounded
  48   // rects and including them will slow down the hash in the common case. Note
  49   // that the ::Equal check still checks the rounded rect contents, so in case
  50   // of hash collisions the clip chains can still be distinguished using that.
  51   uint32_t hash = HashGeneric(aClip->mASR, aClip->mClip.GetRoundedRectCount());
  52   if (aClip->mClip.HasClip()) {
  53     const nsRect& rect = aClip->mClip.GetClipRect();
  54     // empty rects are considered equal in DisplayItemClipChain::Equal, even
  55     // though they may have different x and y coordinates. So make sure they
  56     // hash to the same thing in those cases too.
  57     if (!rect.IsEmpty()) {
  58       hash = AddToHash(hash, rect.x, rect.y, rect.width, rect.height);
  59     }
  60   }
  61
  62   return hash;
  63 }
  64
  65 /* static */
  66 nsCString DisplayItemClipChain::ToString(
  67     const DisplayItemClipChain* aClipChain) {
  68   nsAutoCString str;
  69   for (auto* sc = aClipChain; sc; sc = sc->mParent) {
  70     if (sc->mASR) {
  71       str.AppendPrintf("0x%p <%s> [0x%p]", sc, sc->mClip.ToString().get(),
  72                        sc->mASR->mScrollableFrame);
  73     } else {
  74       str.AppendPrintf("0x%p <%s> [root asr]", sc, sc->mClip.ToString().get());
  75     }
  76     if (sc->mParent) {
  77       str.AppendLiteral(", ");
  78     }
  79   }
  80   return std::move(str);
  81 }
  82
  83 bool DisplayItemClipChain::HasRoundedCorners() const {
  84   return mClip.GetRoundedRectCount() > 0 ||
  85          (mParent && mParent->HasRoundedCorners());
  86 }
  87
  88 }  // namespace mozilla