Title: [287525] trunk/Source/WebCore
- Revision
- 287525
- Author
- [email protected]
- Date
- 2022-01-02 16:49:30 -0800 (Sun, 02 Jan 2022)
Log Message
[LFC][IFC] Add ASSERT(middle >= left && middle < right) to TextUtil::breakWord
https://bugs.webkit.org/show_bug.cgi?id=234801
Reviewed by Antti Koivisto.
Before adding support for surrogate pairs, the implicit integral flooring guaranteed that
(left + right) / 2 always produced a middle point where left >= middle and middle < right.
With introducing surrogate pair support, the middle point may end up being equal to the right position.
(when the (left + right) / 2 falls right in the middle of a surrogate pair, we advance the index
to the _end_ of the pair (and later we adjust it by calling U16_SET_CP_START)).
In this patch, we revert this behavior back so that the middle point is always < right.
We also make sure that left/right/middle are all fall on cluster boundary by calling nextUserPerceivedCharacterIndex.
This patch is also in preparation for introducing grapheme cluster support.
* layout/formattingContexts/inline/text/TextUtil.cpp:
(WebCore::Layout::TextUtil::breakWord):
Modified Paths
Diff
Modified: trunk/Source/WebCore/ChangeLog (287524 => 287525)
--- trunk/Source/WebCore/ChangeLog 2022-01-02 23:42:27 UTC (rev 287524)
+++ trunk/Source/WebCore/ChangeLog 2022-01-03 00:49:30 UTC (rev 287525)
@@ -1,3 +1,23 @@
+2022-01-02 Alan Bujtas <[email protected]>
+
+ [LFC][IFC] Add ASSERT(middle >= left && middle < right) to TextUtil::breakWord
+ https://bugs.webkit.org/show_bug.cgi?id=234801
+
+ Reviewed by Antti Koivisto.
+
+ Before adding support for surrogate pairs, the implicit integral flooring guaranteed that
+ (left + right) / 2 always produced a middle point where left >= middle and middle < right.
+ With introducing surrogate pair support, the middle point may end up being equal to the right position.
+ (when the (left + right) / 2 falls right in the middle of a surrogate pair, we advance the index
+ to the _end_ of the pair (and later we adjust it by calling U16_SET_CP_START)).
+
+ In this patch, we revert this behavior back so that the middle point is always < right.
+ We also make sure that left/right/middle are all fall on cluster boundary by calling nextUserPerceivedCharacterIndex.
+ This patch is also in preparation for introducing grapheme cluster support.
+
+ * layout/formattingContexts/inline/text/TextUtil.cpp:
+ (WebCore::Layout::TextUtil::breakWord):
+
2022-01-02 Antoine Quint <[email protected]>
[Web Animations] getKeyframes() should handle multiple keyframes for the same offset
Modified: trunk/Source/WebCore/layout/formattingContexts/inline/text/TextUtil.cpp (287524 => 287525)
--- trunk/Source/WebCore/layout/formattingContexts/inline/text/TextUtil.cpp 2022-01-02 23:42:27 UTC (rev 287524)
+++ trunk/Source/WebCore/layout/formattingContexts/inline/text/TextUtil.cpp 2022-01-03 00:49:30 UTC (rev 287525)
@@ -151,13 +151,20 @@
ASSERT(length);
auto text = inlineTextBox.content();
- auto surrogatePairAwareIndex = [&] (auto index) {
- // We should never break in the middle of a surrogate pair. They are considered one joint entity.
- auto offset = index + 1;
- U16_SET_CP_LIMIT(text, 0, offset, text.length());
+ auto userPerceivedCharacterBoundaryAlignedIndex = [&] (auto index) {
+ if (text.is8Bit())
+ return index;
+ auto alignedStartIndex = index;
+ U16_SET_CP_START(text, startPosition, alignedStartIndex);
+ ASSERT(alignedStartIndex >= startPosition);
+ return alignedStartIndex;
+ };
- // Returns the index at trail.
- return offset - 1;
+ auto nextUserPerceivedCharacterIndex = [&] (auto index) {
+ if (text.is8Bit())
+ return index + 1;
+ U16_FWD_1(text, index, length);
+ return index;
};
auto left = startPosition;
@@ -165,22 +172,21 @@
// Adjust the range so that we can pick a reasonable midpoint.
auto averageCharacterWidth = InlineLayoutUnit { textWidth / length };
unsigned offset = toLayoutUnit(2 * availableWidth / averageCharacterWidth).toUnsigned();
- auto right = surrogatePairAwareIndex(std::min<unsigned>(left + offset, (startPosition + length - 1)));
+ auto right = userPerceivedCharacterBoundaryAlignedIndex(std::min<unsigned>(left + offset, (startPosition + length - 1)));
// Preserve the left width for the final split position so that we don't need to remeasure the left side again.
auto leftSideWidth = InlineLayoutUnit { 0 };
while (left < right) {
- auto middle = surrogatePairAwareIndex((left + right) / 2);
- auto width = TextUtil::width(inlineTextBox, fontCascade, startPosition, middle + 1, contentLogicalLeft);
+ auto middle = userPerceivedCharacterBoundaryAlignedIndex((left + right) / 2);
+ ASSERT(middle >= left && middle < right);
+ auto endOfMiddleCharacter = nextUserPerceivedCharacterIndex(middle);
+ auto width = TextUtil::width(inlineTextBox, fontCascade, startPosition, endOfMiddleCharacter, contentLogicalLeft);
if (width < availableWidth) {
- left = middle + 1;
+ left = endOfMiddleCharacter;
leftSideWidth = width;
- } else if (width > availableWidth) {
- // When the substring does not fit, the right side is supposed to be the start of the surrogate pair if applicable, unless startPosition falls between surrogate pair.
+ } else if (width > availableWidth)
right = middle;
- U16_SET_CP_START(text, 0, right);
- ASSERT(right >= startPosition);
- } else {
- right = middle + 1;
+ else {
+ right = endOfMiddleCharacter;
leftSideWidth = width;
break;
}
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