Changeset 254425 in webkit

Timestamp:

Jan 13, 2020 2:11:00 AM (4 years ago)

Author:

Antti Koivisto

Message:

[LFC][IFC] fast/text/fast-run-width-vs-slow-run-width.html is failing
​https://bugs.webkit.org/show_bug.cgi?id=206143

Reviewed by Zalan Bujtas.

The test is constructed so that the preferred width computation produces float value that maps exactly to LayoutUnit
(usually it gets ceiled up). This get converted back to float and the same input widths are substracted from
the total during inline layout. Due to nature of floating point arithmetic this ends up producing slightly
different result and the last word doesn't fit.

• layout/inlineformatting/InlineLineBreaker.cpp:

(WebCore::Layout::LineBreaker::tryWrappingInlineContent const):

When using floats, do an additional equality comparison that accepts values within scaled float epsilon as equal.

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/inlineformatting/InlineLineBreaker.cpp (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2020-01-13  Antti Koivisto  <antti@apple.com>
+
+        [LFC][IFC] fast/text/fast-run-width-vs-slow-run-width.html is failing
+        https://bugs.webkit.org/show_bug.cgi?id=206143
+
+        Reviewed by Zalan Bujtas.
+
+        The test is constructed so that the preferred width computation produces float value that maps exactly to LayoutUnit
+        (usually it gets ceiled up). This get converted back to float and the same input widths are substracted from
+        the total during inline layout. Due to nature of floating point arithmetic this ends up producing slightly
+        different result and the last word doesn't fit.
+
+        * layout/inlineformatting/InlineLineBreaker.cpp:
+        (WebCore::Layout::LineBreaker::tryWrappingInlineContent const):
+
+        When using floats, do an additional equality comparison that accepts values within scaled float epsilon as equal.
+
 2020-01-12  Zalan Bujtas  <zalan@apple.com>
 

trunk/Source/WebCore/layout/inlineformatting/InlineLineBreaker.cpp

@@ -131 +131 @@
     if (candidateContent.width() <= lineStatus.availableWidth)
         return { Result::Action::Keep };
+
+#if USE_FLOAT_AS_INLINE_LAYOUT_UNIT
+    // Preferred width computation sums up floats while line breaker substracts them. This can lead to epsilon-scale differences.
+    if (WTF::areEssentiallyEqual(candidateContent.width(), lineStatus.availableWidth))
+        return { Result::Action::Keep };
+#endif
+
     if (candidateContent.hasTrailingCollapsibleContent()) {
         ASSERT(candidateContent.hasTextContentOnly());