Changeset 287809 in webkit

Timestamp:

Jan 8, 2022, 6:27:39 AM (5 years ago)

Author:

Alan Bujtas

Message:

[LFC][IFC] Implement TextUtil::breakWord for the complex font codepath using ubrk_next
​https://bugs.webkit.org/show_bug.cgi?id=234998

Reviewed by Antti Koivisto.

In order to use ubrk_preceding/ubrk_following with arbitrary position (binary search) inside a cluster with surrogate pairs we have to
implement some additional surrogate boundary checks (it would move the index to the beginning/end of the surrogate when it falls right
in the middle of it). In addition to that, ICU would still need to scan the content from the start to find the right index for
the boundary.
This new breakWord implementation simply iterates over the clusters by calling ubrk_next until the content overflows.

• layout/formattingContexts/inline/text/TextUtil.cpp:

(WebCore::Layout::TextUtil::breakWord):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/formattingContexts/inline/text/TextUtil.cpp (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2022-01-08  Alan Bujtas  <zalan@apple.com>
+
+        [LFC][IFC] Implement TextUtil::breakWord for the complex font codepath using ubrk_next
+        https://bugs.webkit.org/show_bug.cgi?id=234998
+
+        Reviewed by Antti Koivisto.
+
+        In order to use ubrk_preceding/ubrk_following with arbitrary position (binary search) inside a cluster with surrogate pairs we have to
+        implement some additional surrogate boundary checks (it would move the index to the beginning/end of the surrogate when it falls right
+        in the middle of it). In addition to that, ICU would still need to scan the content from the start to find the right index for
+        the boundary.
+        This new breakWord implementation simply iterates over the clusters by calling ubrk_next until the content overflows.
+
+        * layout/formattingContexts/inline/text/TextUtil.cpp:
+        (WebCore::Layout::TextUtil::breakWord):
+
 2022-01-07  Jean-Yves Avenard  <jya@apple.com>
 

trunk/Source/WebCore/layout/formattingContexts/inline/text/TextUtil.cpp

@@ -154 +154 @@
     ASSERT(length);
     auto text = inlineTextBox.content();
-    auto contentUsesSimpleFontCodePath = inlineTextBox.canUseSimpleFontCodePath();
-
-    auto graphemeClustersIterator = std::optional<NonSharedCharacterBreakIterator> { };
-    if (!contentUsesSimpleFontCodePath)
-        graphemeClustersIterator.emplace(text);
-
-    auto userPerceivedCharacterBoundaryAlignedIndex = [&] (auto index) -> size_t {
-        if (text.is8Bit())
-            return index;
-        if (contentUsesSimpleFontCodePath) {
-            auto alignedStartIndex = index;
-            U16_SET_CP_START(text, startPosition, alignedStartIndex);
-            ASSERT(alignedStartIndex >= startPosition);
-            return alignedStartIndex;
-        }
-        ASSERT(graphemeClustersIterator.has_value());
-        if (ubrk_isBoundary(*graphemeClustersIterator, index))
-            return index;
-        auto boundaryIndex = ubrk_preceding(*graphemeClustersIterator, index);
-        return boundaryIndex == UBRK_DONE ? startPosition : boundaryIndex;
-    };
-
-    auto nextUserPerceivedCharacterIndex = [&] (auto index) -> size_t {
-        if (text.is8Bit())
-            return index + 1;
-        if (contentUsesSimpleFontCodePath) {
-            U16_FWD_1(text, index, length);
-            return index;
-        }
-        ASSERT(graphemeClustersIterator.has_value());
-        auto nextPosition = ubrk_following(*graphemeClustersIterator, index);
-        return nextPosition == UBRK_DONE ? startPosition + length - 1 : nextPosition;
-    };
-
-    auto left = startPosition;
-    auto right = left + length - 1;
-    if (contentUsesSimpleFontCodePath) {
-        // Pathological case of (extremely)long string and narrow lines.
-        // Adjust the range so that we can pick a reasonable midpoint.
-        auto averageCharacterWidth = InlineLayoutUnit { textWidth / length };
-        size_t startOffset = 2 * availableWidth / averageCharacterWidth;
-        right = userPerceivedCharacterBoundaryAlignedIndex(std::min(left + startOffset, right));
-    }
-    // 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 = 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 = endOfMiddleCharacter;
-            leftSideWidth = width;
-        } else if (width > availableWidth)
-            right = middle;
-        else {
-            right = endOfMiddleCharacter;
-            leftSideWidth = width;
-            break;
-        }
-    }
-    RELEASE_ASSERT(right >= startPosition);
-    return { right - startPosition, leftSideWidth };
+
+    if (inlineTextBox.canUseSimpleFontCodePath()) {
+
+        auto findBreakingPositionInSimpleText = [&] {
+            auto userPerceivedCharacterBoundaryAlignedIndex = [&] (auto index) -> size_t {
+                if (text.is8Bit())
+                    return index;
+                auto alignedStartIndex = index;
+                U16_SET_CP_START(text, startPosition, alignedStartIndex);
+                ASSERT(alignedStartIndex >= startPosition);
+                return alignedStartIndex;
+            };
+
+            auto nextUserPerceivedCharacterIndex = [&] (auto index) -> size_t {
+                if (text.is8Bit())
+                    return index + 1;
+                U16_FWD_1(text, index, length);
+                return index;
+            };
+
+            auto left = startPosition;
+            auto right = left + length - 1;
+            // Pathological case of (extremely)long string and narrow lines.
+            // Adjust the range so that we can pick a reasonable midpoint.
+            auto averageCharacterWidth = InlineLayoutUnit { textWidth / length };
+            size_t startOffset = 2 * availableWidth / averageCharacterWidth;
+            right = userPerceivedCharacterBoundaryAlignedIndex(std::min(left + startOffset, right));
+            // 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 = 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 = endOfMiddleCharacter;
+                    leftSideWidth = width;
+                } else if (width > availableWidth)
+                    right = middle;
+                else {
+                    right = endOfMiddleCharacter;
+                    leftSideWidth = width;
+                    break;
+                }
+            }
+            RELEASE_ASSERT(right >= startPosition);
+            return TextUtil::WordBreakLeft { right - startPosition, leftSideWidth };
+        };
+        return findBreakingPositionInSimpleText();
+    }
+
+    auto graphemeClusterIterator = NonSharedCharacterBreakIterator { StringView { text }.substring(startPosition, length) };
+    auto leftSide = TextUtil::WordBreakLeft { };
+    for (auto clusterStartPosition = ubrk_next(graphemeClusterIterator); clusterStartPosition != UBRK_DONE; clusterStartPosition = ubrk_next(graphemeClusterIterator)) {
+        auto width = TextUtil::width(inlineTextBox, fontCascade, startPosition, startPosition + clusterStartPosition, contentLogicalLeft);
+        if (width > availableWidth)
+            return leftSide;
+        leftSide = { static_cast<size_t>(clusterStartPosition), width };
+    }
+    // This content is not supposed to fit availableWidth.
+    ASSERT_NOT_REACHED();
+    return { };
 }