Changeset 222588 in webkit

Timestamp:

Sep 27, 2017 5:25:59 PM (7 years ago)

Author:

mmaxfield@apple.com

Message:

Minimum font size may cause elements to have an infinite line-height
​https://bugs.webkit.org/show_bug.cgi?id=177573
<rdar://problem/34573792>

Reviewed by Dan Bernstein.

Source/WebCore:

When minimum font size is specified, we were trying to preserve the ratio of specified font-size
and specified line-height in order to boost the computed font size proportionately to the font-size
boost. However, this doesn't work when the specified font-size is 0, because the ratio between
line-height and font-size is infinite.

The most straightforward solution is just to make small font-sizes opt out of the line-height
adjustment because the result would be too big.

Test: fast/text/line-height-minimumFontSize-text-small-font-size.html

• css/StyleBuilderCustom.h:

(WebCore::computeLineHeightMultiplierDueToFontSize):
(WebCore::StyleBuilderCustom::applyValueLineHeight):

LayoutTests:

• fast/text/line-height-minimumFontSize-text-small-font-size-expected.txt: Added.
• fast/text/line-height-minimumFontSize-text-small-font-size.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/text/line-height-minimumFontSize-text-small-font-size-expected.txt (added)
• LayoutTests/fast/text/line-height-minimumFontSize-text-small-font-size.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/css/StyleBuilderCustom.h (modified) (2 diffs)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2017-09-27  Myles C. Maxfield  <mmaxfield@apple.com>
+
+        Minimum font size may cause elements to have an infinite line-height
+        https://bugs.webkit.org/show_bug.cgi?id=177573
+        <rdar://problem/34573792>
+
+        Reviewed by Dan Bernstein.
+
+        * fast/text/line-height-minimumFontSize-text-small-font-size-expected.txt: Added.
+        * fast/text/line-height-minimumFontSize-text-small-font-size.html: Added.
+
 2017-09-27  Matt Lewis  <jlewis3@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2017-09-27  Myles C. Maxfield  <mmaxfield@apple.com>
+
+        Minimum font size may cause elements to have an infinite line-height
+        https://bugs.webkit.org/show_bug.cgi?id=177573
+        <rdar://problem/34573792>
+
+        Reviewed by Dan Bernstein.
+
+        When minimum font size is specified, we were trying to preserve the ratio of specified font-size
+        and specified line-height in order to boost the computed font size proportionately to the font-size
+        boost. However, this doesn't work when the specified font-size is 0, because the ratio between
+        line-height and font-size is infinite.
+
+        The most straightforward solution is just to make small font-sizes opt out of the line-height
+        adjustment because the result would be too big.
+
+        Test: fast/text/line-height-minimumFontSize-text-small-font-size.html
+
+        * css/StyleBuilderCustom.h:
+        (WebCore::computeLineHeightMultiplierDueToFontSize):
+        (WebCore::StyleBuilderCustom::applyValueLineHeight):
+
 2017-09-27  Alex Christensen  <achristensen@webkit.org>
 

trunk/Source/WebCore/css/StyleBuilderCustom.h

@@ -671 +671 @@
         if (minimumFontSize > 0) {
             auto specifiedFontSize = computeBaseSpecifiedFontSize(document, style, percentageAutosizingEnabled);
-            if (specifiedFontSize < minimumFontSize) {
+            // Small font sizes cause a preposterously large (near infinity) line-height. Add a fuzz-factor of 1px which opts out of
+            // boosted line-height.
+            if (specifiedFontSize < minimumFontSize && specifiedFontSize >= 1) {
                 // FIXME: There are two settings which are relevant here: minimum font size, and minimum logical font size (as
                 // well as things like the zoom property, text zoom on the page, and text autosizing). The minimum logical font
@@ -707 +709 @@
         if (multiplier == 1)
             computedLineHeight = lineHeight.value();
-        else {
-            std::optional<Length> lineHeight = StyleBuilderConverter::convertLineHeight(styleResolver, value, multiplier);
-            ASSERT(static_cast<bool>(lineHeight));
-            computedLineHeight = lineHeight.value();
-        }
+        else
+            computedLineHeight = StyleBuilderConverter::convertLineHeight(styleResolver, value, multiplier).value();
     }