Changeset 269384 in webkit

Timestamp:

Nov 4, 2020, 2:04:58 PM (6 years ago)

Author:

Antti Koivisto

Message:

REGRESSION (r257839): Miscomputed style due to computed 'rem' value in matched declaration cache
​https://bugs.webkit.org/show_bug.cgi?id=218561
<rdar://problem/70074191>

Reviewed by Zalan Bujtas.

Source/WebCore:

Test: fast/dom/focus-rem-style-update.html

Call to focus() causes computed style update for the element’s ancestor chain before the the document
has otherwise been styled (using the shortcut mechanism introduced in r257839). This style, which uses ‘rem’
unit and so depends on root element font size, gets cached in MatchedDeclarationsCache. The root font size
then changes but during the resulting style update we use this cached value, failing to re-resolve ‘rem’.

• style/StyleTreeResolver.cpp:

(WebCore::Style::TreeResolver::resolveElement):

Invalidate matched declarations cache also when there is no existing document element style.

LayoutTests:

• fast/dom/focus-rem-style-update-expected.html: Added.
• fast/dom/focus-rem-style-update.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/dom/focus-rem-style-update-expected.html (added)
• LayoutTests/fast/dom/focus-rem-style-update.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/style/StyleTreeResolver.cpp (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2020-11-04  Antti Koivisto  <antti@apple.com>
+
+        REGRESSION (r257839): Miscomputed style due to computed 'rem' value in matched declaration cache
+        https://bugs.webkit.org/show_bug.cgi?id=218561
+        <rdar://problem/70074191>
+
+        Reviewed by Zalan Bujtas.
+
+        * fast/dom/focus-rem-style-update-expected.html: Added.
+        * fast/dom/focus-rem-style-update.html: Added.
+
 2020-11-04  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2020-11-04  Antti Koivisto  <antti@apple.com>
+
+        REGRESSION (r257839): Miscomputed style due to computed 'rem' value in matched declaration cache
+        https://bugs.webkit.org/show_bug.cgi?id=218561
+        <rdar://problem/70074191>
+
+        Reviewed by Zalan Bujtas.
+
+        Test: fast/dom/focus-rem-style-update.html
+
+        Call to focus() causes computed style update for the element’s ancestor chain before the the document
+        has otherwise been styled (using the shortcut mechanism introduced in r257839). This style, which uses ‘rem’
+        unit and so depends on root element font size, gets cached in MatchedDeclarationsCache. The root font size
+        then changes but during the resulting style update we use this cached value, failing to re-resolve ‘rem’.
+
+        * style/StyleTreeResolver.cpp:
+        (WebCore::Style::TreeResolver::resolveElement):
+
+        Invalidate matched declarations cache also when there is no existing document element style.
+
 2020-11-04  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebCore/style/StyleTreeResolver.cpp

@@ -225 +225 @@
         scope().resolver.setOverrideDocumentElementStyle(m_documentElementStyle.get());
 
-        if (update.change != Change::None && existingStyle && existingStyle->computedFontPixelSize() != update.style->computedFontPixelSize()) {
+        if (!existingStyle || existingStyle->computedFontPixelSize() != update.style->computedFontPixelSize()) {
             // "rem" units are relative to the document element's font size so we need to recompute everything.
-            // In practice this is rare.
             scope().resolver.invalidateMatchedDeclarationsCache();
             descendantsToResolve = DescendantsToResolve::All;