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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/206641">206641</a></dd>
<dt>Author</dt> <dd>antti@apple.com</dd>
<dt>Date</dt> <dd>2016-09-30 10:00:22 -0700 (Fri, 30 Sep 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Remove "rem" unit optimization for document element font size changes
https://bugs.webkit.org/show_bug.cgi?id=162778
Reviewed by Alex Christensen.
We awkwardly track from the parser level if any stylesheet in a document uses any rem units. This is only used to minimally
optimize a case where document element's (<html>) font size changes dynamically.
In practice such changes are rare. Browsing around I couldn't find a single case where this optimization got used.
Even if it was used it would be of low value as a full style resolution is likely to happen anyway (as font inherits)
and the only thing really saved is that we don't need to invalidate the matched properties cache.
* css/CSSGrammar.y.in:
* css/StyleSheetContents.cpp:
(WebCore::StyleSheetContents::StyleSheetContents):
* css/StyleSheetContents.h:
* dom/AuthorStyleSheets.cpp:
(WebCore::AuthorStyleSheets::updateActiveStyleSheets):
* dom/AuthorStyleSheets.h:
(WebCore::AuthorStyleSheets::usesRemUnits): Deleted.
(WebCore::AuthorStyleSheets::setUsesRemUnit): Deleted.
* dom/Document.cpp:
(WebCore::Document::recalcStyle):
(WebCore::Document::updateBaseURL):
* style/StyleTreeResolver.cpp:
(WebCore::Style::TreeResolver::resolveElement):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorecssCSSGrammaryin">trunk/Source/WebCore/css/CSSGrammar.y.in</a></li>
<li><a href="#trunkSourceWebCorecssStyleSheetContentscpp">trunk/Source/WebCore/css/StyleSheetContents.cpp</a></li>
<li><a href="#trunkSourceWebCorecssStyleSheetContentsh">trunk/Source/WebCore/css/StyleSheetContents.h</a></li>
<li><a href="#trunkSourceWebCoredomAuthorStyleSheetscpp">trunk/Source/WebCore/dom/AuthorStyleSheets.cpp</a></li>
<li><a href="#trunkSourceWebCoredomAuthorStyleSheetsh">trunk/Source/WebCore/dom/AuthorStyleSheets.h</a></li>
<li><a href="#trunkSourceWebCoredomDocumentcpp">trunk/Source/WebCore/dom/Document.cpp</a></li>
<li><a href="#trunkSourceWebCorestyleStyleTreeResolvercpp">trunk/Source/WebCore/style/StyleTreeResolver.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (206640 => 206641)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog 2016-09-30 16:59:24 UTC (rev 206640)
+++ trunk/Source/WebCore/ChangeLog 2016-09-30 17:00:22 UTC (rev 206641)
</span><span class="lines">@@ -1,3 +1,32 @@
</span><ins>+2016-09-30 Antti Koivisto <antti@apple.com>
+
+ Remove "rem" unit optimization for document element font size changes
+ https://bugs.webkit.org/show_bug.cgi?id=162778
+
+ Reviewed by Alex Christensen.
+
+ We awkwardly track from the parser level if any stylesheet in a document uses any rem units. This is only used to minimally
+ optimize a case where document element's (<html>) font size changes dynamically.
+
+ In practice such changes are rare. Browsing around I couldn't find a single case where this optimization got used.
+ Even if it was used it would be of low value as a full style resolution is likely to happen anyway (as font inherits)
+ and the only thing really saved is that we don't need to invalidate the matched properties cache.
+
+ * css/CSSGrammar.y.in:
+ * css/StyleSheetContents.cpp:
+ (WebCore::StyleSheetContents::StyleSheetContents):
+ * css/StyleSheetContents.h:
+ * dom/AuthorStyleSheets.cpp:
+ (WebCore::AuthorStyleSheets::updateActiveStyleSheets):
+ * dom/AuthorStyleSheets.h:
+ (WebCore::AuthorStyleSheets::usesRemUnits): Deleted.
+ (WebCore::AuthorStyleSheets::setUsesRemUnit): Deleted.
+ * dom/Document.cpp:
+ (WebCore::Document::recalcStyle):
+ (WebCore::Document::updateBaseURL):
+ * style/StyleTreeResolver.cpp:
+ (WebCore::Style::TreeResolver::resolveElement):
+
</ins><span class="cx"> 2016-09-30 Zalan Bujtas <zalan@apple.com>
</span><span class="cx">
</span><span class="cx"> RenderLayer::clipRects may return nullptr.
</span></span></pre></div>
<a id="trunkSourceWebCorecssCSSGrammaryin"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/CSSGrammar.y.in (206640 => 206641)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/CSSGrammar.y.in 2016-09-30 16:59:24 UTC (rev 206640)
+++ trunk/Source/WebCore/css/CSSGrammar.y.in 2016-09-30 17:00:22 UTC (rev 206641)
</span><span class="lines">@@ -1728,8 +1728,6 @@
</span><span class="cx"> $$.id = CSSValueInvalid;
</span><span class="cx"> $$.fValue = $1;
</span><span class="cx"> $$.unit = CSSPrimitiveValue::CSS_REMS;
</span><del>- if (parser->m_styleSheet)
- parser->m_styleSheet->parserSetUsesRemUnits();
</del><span class="cx"> }
</span><span class="cx"> | CHS { $$.id = CSSValueInvalid; $$.fValue = $1; $$.unit = CSSPrimitiveValue::CSS_CHS; }
</span><span class="cx"> | VW { $$.id = CSSValueInvalid; $$.fValue = $1; $$.unit = CSSPrimitiveValue::CSS_VW; }
</span></span></pre></div>
<a id="trunkSourceWebCorecssStyleSheetContentscpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/StyleSheetContents.cpp (206640 => 206641)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/StyleSheetContents.cpp 2016-09-30 16:59:24 UTC (rev 206640)
+++ trunk/Source/WebCore/css/StyleSheetContents.cpp 2016-09-30 17:00:22 UTC (rev 206641)
</span><span class="lines">@@ -67,7 +67,6 @@
</span><span class="cx"> , m_isUserStyleSheet(ownerRule && ownerRule->parentStyleSheet() && ownerRule->parentStyleSheet()->isUserStyleSheet())
</span><span class="cx"> , m_hasSyntacticallyValidCSSHeader(true)
</span><span class="cx"> , m_didLoadErrorOccur(false)
</span><del>- , m_usesRemUnits(false)
</del><span class="cx"> , m_usesStyleBasedEditability(false)
</span><span class="cx"> , m_isMutable(false)
</span><span class="cx"> , m_isInMemoryCache(false)
</span><span class="lines">@@ -88,7 +87,6 @@
</span><span class="cx"> , m_isUserStyleSheet(o.m_isUserStyleSheet)
</span><span class="cx"> , m_hasSyntacticallyValidCSSHeader(o.m_hasSyntacticallyValidCSSHeader)
</span><span class="cx"> , m_didLoadErrorOccur(false)
</span><del>- , m_usesRemUnits(o.m_usesRemUnits)
</del><span class="cx"> , m_usesStyleBasedEditability(o.m_usesStyleBasedEditability)
</span><span class="cx"> , m_isMutable(false)
</span><span class="cx"> , m_isInMemoryCache(false)
</span></span></pre></div>
<a id="trunkSourceWebCorecssStyleSheetContentsh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/css/StyleSheetContents.h (206640 => 206641)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/css/StyleSheetContents.h 2016-09-30 16:59:24 UTC (rev 206640)
+++ trunk/Source/WebCore/css/StyleSheetContents.h 2016-09-30 17:00:22 UTC (rev 206641)
</span><span class="lines">@@ -96,7 +96,6 @@
</span><span class="cx"> void parserAddNamespace(const AtomicString& prefix, const AtomicString& uri);
</span><span class="cx"> void parserAppendRule(Ref<StyleRuleBase>&&);
</span><span class="cx"> void parserSetEncodingFromCharsetRule(const String& encoding);
</span><del>- void parserSetUsesRemUnits() { m_usesRemUnits = true; }
</del><span class="cx"> void parserSetUsesStyleBasedEditability() { m_usesStyleBasedEditability = true; }
</span><span class="cx">
</span><span class="cx"> void clearRules();
</span><span class="lines">@@ -122,7 +121,6 @@
</span><span class="cx"> unsigned ruleCount() const;
</span><span class="cx"> StyleRuleBase* ruleAt(unsigned index) const;
</span><span class="cx">
</span><del>- bool usesRemUnits() const { return m_usesRemUnits; }
</del><span class="cx"> bool usesStyleBasedEditability() const { return m_usesStyleBasedEditability; }
</span><span class="cx">
</span><span class="cx"> unsigned estimatedSizeInBytes() const;
</span><span class="lines">@@ -166,7 +164,6 @@
</span><span class="cx"> bool m_isUserStyleSheet : 1;
</span><span class="cx"> bool m_hasSyntacticallyValidCSSHeader : 1;
</span><span class="cx"> bool m_didLoadErrorOccur : 1;
</span><del>- bool m_usesRemUnits : 1;
</del><span class="cx"> bool m_usesStyleBasedEditability : 1;
</span><span class="cx"> bool m_isMutable : 1;
</span><span class="cx"> bool m_isInMemoryCache : 1;
</span></span></pre></div>
<a id="trunkSourceWebCoredomAuthorStyleSheetscpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/dom/AuthorStyleSheets.cpp (206640 => 206641)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/dom/AuthorStyleSheets.cpp 2016-09-30 16:59:24 UTC (rev 206640)
+++ trunk/Source/WebCore/dom/AuthorStyleSheets.cpp 2016-09-30 17:00:22 UTC (rev 206641)
</span><span class="lines">@@ -330,8 +330,6 @@
</span><span class="cx"> InspectorInstrumentation::activeStyleSheetsUpdated(m_document);
</span><span class="cx">
</span><span class="cx"> for (const auto& sheet : m_activeStyleSheets) {
</span><del>- if (sheet->contents().usesRemUnits())
- m_usesRemUnits = true;
</del><span class="cx"> if (sheet->contents().usesStyleBasedEditability())
</span><span class="cx"> m_usesStyleBasedEditability = true;
</span><span class="cx"> }
</span></span></pre></div>
<a id="trunkSourceWebCoredomAuthorStyleSheetsh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/dom/AuthorStyleSheets.h (206640 => 206641)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/dom/AuthorStyleSheets.h 2016-09-30 16:59:24 UTC (rev 206640)
+++ trunk/Source/WebCore/dom/AuthorStyleSheets.h 2016-09-30 17:00:22 UTC (rev 206641)
</span><span class="lines">@@ -76,8 +76,6 @@
</span><span class="cx">
</span><span class="cx"> bool hasPendingSheets() const { return m_pendingStyleSheetCount > 0; }
</span><span class="cx">
</span><del>- bool usesRemUnits() const { return m_usesRemUnits; }
- void setUsesRemUnit(bool b) { m_usesRemUnits = b; }
</del><span class="cx"> bool usesStyleBasedEditability() { return m_usesStyleBasedEditability; }
</span><span class="cx">
</span><span class="cx"> bool activeStyleSheetsContains(const CSSStyleSheet*) const;
</span><span class="lines">@@ -131,7 +129,6 @@
</span><span class="cx"> String m_preferredStylesheetSetName;
</span><span class="cx"> String m_selectedStylesheetSetName;
</span><span class="cx">
</span><del>- bool m_usesRemUnits { false };
</del><span class="cx"> bool m_usesStyleBasedEditability { false };
</span><span class="cx"> };
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceWebCoredomDocumentcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/dom/Document.cpp (206640 => 206641)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/dom/Document.cpp 2016-09-30 16:59:24 UTC (rev 206640)
+++ trunk/Source/WebCore/dom/Document.cpp 2016-09-30 17:00:22 UTC (rev 206641)
</span><span class="lines">@@ -1866,12 +1866,6 @@
</span><span class="cx">
</span><span class="cx"> InspectorInstrumentationCookie cookie = InspectorInstrumentation::willRecalculateStyle(*this);
</span><span class="cx">
</span><del>- // FIXME: We never reset this flags.
- if (m_elementSheet && m_elementSheet->contents().usesRemUnits())
- authorStyleSheets().setUsesRemUnit(true);
- // We don't call setUsesStyleBasedEditability here because the whole point of the flag is to avoid style recalc.
- // i.e. updating the flag here would be too late.
-
</del><span class="cx"> m_inStyleRecalc = true;
</span><span class="cx"> bool updatedCompositingLayers = false;
</span><span class="cx"> {
</span><span class="lines">@@ -2972,12 +2966,9 @@
</span><span class="cx"> if (m_elementSheet) {
</span><span class="cx"> // Element sheet is silly. It never contains anything.
</span><span class="cx"> ASSERT(!m_elementSheet->contents().ruleCount());
</span><del>- bool usesRemUnits = m_elementSheet->contents().usesRemUnits();
</del><span class="cx"> bool usesStyleBasedEditability = m_elementSheet->contents().usesStyleBasedEditability();
</span><span class="cx"> m_elementSheet = CSSStyleSheet::createInline(*this, m_baseURL);
</span><span class="cx"> // FIXME: So we are not really the parser. The right fix is to eliminate the element sheet completely.
</span><del>- if (usesRemUnits)
- m_elementSheet->contents().parserSetUsesRemUnits();
</del><span class="cx"> if (usesStyleBasedEditability)
</span><span class="cx"> m_elementSheet->contents().parserSetUsesStyleBasedEditability();
</span><span class="cx"> }
</span></span></pre></div>
<a id="trunkSourceWebCorestyleStyleTreeResolvercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/style/StyleTreeResolver.cpp (206640 => 206641)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/style/StyleTreeResolver.cpp 2016-09-30 16:59:24 UTC (rev 206640)
+++ trunk/Source/WebCore/style/StyleTreeResolver.cpp 2016-09-30 17:00:22 UTC (rev 206641)
</span><span class="lines">@@ -214,10 +214,9 @@
</span><span class="cx"> m_documentElementStyle = RenderStyle::clonePtr(*update.style);
</span><span class="cx"> scope().styleResolver.setOverrideDocumentElementStyle(m_documentElementStyle.get());
</span><span class="cx">
</span><del>- // If "rem" units are used anywhere in the document, and if the document element's font size changes, then force font updating
- // all the way down the tree. This is simpler than having to maintain a cache of objects (and such font size changes should be rare anyway).
- if (m_document.authorStyleSheets().usesRemUnits() && update.change != NoChange && existingStyle && existingStyle->fontSize() != update.style->fontSize()) {
- // Cached RenderStyles may depend on the rem units.
</del><ins>+ if (update.change != NoChange && existingStyle && existingStyle->fontSize() != update.style->fontSize()) {
+ // "rem" units are relative to the document element's font size so we need to recompute everything.
+ // In practice this is rare.
</ins><span class="cx"> scope().styleResolver.invalidateMatchedPropertiesCache();
</span><span class="cx"> update.change = Force;
</span><span class="cx"> }
</span></span></pre>
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