summaryrefslogtreecommitdiffstats
path: root/layout/style/nsNthIndexCache.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'layout/style/nsNthIndexCache.cpp')
-rw-r--r--layout/style/nsNthIndexCache.cpp155
1 files changed, 155 insertions, 0 deletions
diff --git a/layout/style/nsNthIndexCache.cpp b/layout/style/nsNthIndexCache.cpp
new file mode 100644
index 000000000..970c070f2
--- /dev/null
+++ b/layout/style/nsNthIndexCache.cpp
@@ -0,0 +1,155 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * A class that computes and caches the indices used for :nth-* pseudo-class
+ * matching.
+ */
+
+#include "nsNthIndexCache.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/NodeInfoInlines.h"
+
+nsNthIndexCache::nsNthIndexCache()
+{
+}
+
+nsNthIndexCache::~nsNthIndexCache()
+{
+}
+
+void
+nsNthIndexCache::Reset()
+{
+ mCaches[0][0].clear();
+ mCaches[0][1].clear();
+ mCaches[1][0].clear();
+ mCaches[1][1].clear();
+}
+
+inline bool
+nsNthIndexCache::SiblingMatchesElement(nsIContent* aSibling, Element* aElement,
+ bool aIsOfType)
+{
+ return aSibling->IsElement() &&
+ (!aIsOfType ||
+ aSibling->NodeInfo()->NameAndNamespaceEquals(aElement->NodeInfo()));
+}
+
+inline bool
+nsNthIndexCache::IndexDeterminedFromPreviousSibling(nsIContent* aSibling,
+ Element* aChild,
+ bool aIsOfType,
+ bool aIsFromEnd,
+ const Cache& aCache,
+ int32_t& aResult)
+{
+ if (SiblingMatchesElement(aSibling, aChild, aIsOfType)) {
+ Cache::Ptr siblingEntry = aCache.lookup(aSibling);
+ if (siblingEntry) {
+ int32_t siblingIndex = siblingEntry->value();
+ NS_ASSERTION(siblingIndex != 0,
+ "How can a non-anonymous node have an anonymous sibling?");
+ if (siblingIndex > 0) {
+ // At this point, aResult is a count of how many elements matching
+ // aChild we have seen after aSibling, including aChild itself.
+ // |siblingIndex| is the index of aSibling.
+ // So if aIsFromEnd, we want |aResult = siblingIndex - aResult| and
+ // otherwise we want |aResult = siblingIndex + aResult|.
+ aResult = siblingIndex + aResult * (1 - 2 * aIsFromEnd);
+ return true;
+ }
+ }
+
+ ++aResult;
+ }
+
+ return false;
+}
+
+int32_t
+nsNthIndexCache::GetNthIndex(Element* aChild, bool aIsOfType,
+ bool aIsFromEnd, bool aCheckEdgeOnly)
+{
+ if (aChild->IsRootOfAnonymousSubtree()) {
+ return 0;
+ }
+
+ Cache& cache = mCaches[aIsOfType][aIsFromEnd];
+
+ if (!cache.initialized() && !cache.init()) {
+ // Give up and just don't match.
+ return 0;
+ }
+
+ Cache::AddPtr entry = cache.lookupForAdd(aChild);
+
+ // Default the value to -2 when adding
+ if (!entry && !cache.add(entry, aChild, -2)) {
+ // No good; don't match.
+ return 0;
+ }
+
+ int32_t& slot = entry->value();
+ if (slot != -2 && (slot != -1 || aCheckEdgeOnly)) {
+ return slot;
+ }
+
+ int32_t result = 1;
+ if (aCheckEdgeOnly) {
+ // The caller only cares whether or not the result is 1, so we can
+ // stop as soon as we see any other elements that match us.
+ if (aIsFromEnd) {
+ for (nsIContent *cur = aChild->GetNextSibling();
+ cur;
+ cur = cur->GetNextSibling()) {
+ if (SiblingMatchesElement(cur, aChild, aIsOfType)) {
+ result = -1;
+ break;
+ }
+ }
+ } else {
+ for (nsIContent *cur = aChild->GetPreviousSibling();
+ cur;
+ cur = cur->GetPreviousSibling()) {
+ if (SiblingMatchesElement(cur, aChild, aIsOfType)) {
+ result = -1;
+ break;
+ }
+ }
+ }
+ } else {
+ // In the common case, we already have a cached index for one of
+ // our previous siblings, so check that first.
+ for (nsIContent *cur = aChild->GetPreviousSibling();
+ cur;
+ cur = cur->GetPreviousSibling()) {
+ if (IndexDeterminedFromPreviousSibling(cur, aChild, aIsOfType,
+ aIsFromEnd, cache, result)) {
+ slot = result;
+ return result;
+ }
+ }
+
+ // Now if aIsFromEnd we lose: need to actually compute our index,
+ // since looking at previous siblings wouldn't have told us
+ // anything about it. Note that it doesn't make sense to do cache
+ // lookups on our following siblings, since chances are the cache
+ // is not primed for them.
+ if (aIsFromEnd) {
+ result = 1;
+ for (nsIContent *cur = aChild->GetNextSibling();
+ cur;
+ cur = cur->GetNextSibling()) {
+ if (SiblingMatchesElement(cur, aChild, aIsOfType)) {
+ ++result;
+ }
+ }
+ }
+ }
+
+ slot = result;
+ return result;
+}