Changeset 286101 in webkit

Timestamp:

Nov 21, 2021, 10:33:06 AM (5 years ago)

Author:

Alan Bujtas

Message:

[LFC][IFC] Cache measured width even if canUseSimplifiedTextMeasuring is false
​https://bugs.webkit.org/show_bug.cgi?id=233404

Reviewed by Antti Koivisto.

Just because some content goes through the non-simplified text measuring codepath, it does not
necessary mean we can't cache the measured value on the inline item (actually, we can cache these values just fine in most cases).

This is in preparation for being able to cache bidi content measured widths.

• layout/formattingContexts/inline/InlineItemsBuilder.cpp:

(WebCore::Layout::canCacheMeasuredWidthOnInlineTextItem):
(WebCore::Layout::InlineItemsBuilder::handleTextContent):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• layout/formattingContexts/inline/InlineItemsBuilder.cpp (modified) (5 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2021-11-21  Alan Bujtas  <zalan@apple.com>
+
+        [LFC][IFC] Cache measured width even if canUseSimplifiedTextMeasuring is false
+        https://bugs.webkit.org/show_bug.cgi?id=233404
+
+        Reviewed by Antti Koivisto.
+
+        Just because some content goes through the non-simplified text measuring codepath, it does not
+        necessary mean we can't cache the measured value on the inline item (actually, we can cache these values just fine in most cases).
+
+        This is in preparation for being able to cache bidi content measured widths.
+
+        * layout/formattingContexts/inline/InlineItemsBuilder.cpp:
+        (WebCore::Layout::canCacheMeasuredWidthOnInlineTextItem):
+        (WebCore::Layout::InlineItemsBuilder::handleTextContent):
+
 2021-11-21  Ziran Sun  <zsun@igalia.com>
 

trunk/Source/WebCore/layout/formattingContexts/inline/InlineItemsBuilder.cpp

@@ -350 +350 @@
 }
 
-static inline bool canCacheMeasuredWidthOnInlineTextItem(const InlineTextBox& inlineTextBox)
-{
-    // FIXME: Disable width caching for position dependent content only.
-    if (!inlineTextBox.canUseSimplifiedContentMeasuring())
+static inline bool canCacheMeasuredWidthOnInlineTextItem(const InlineTextBox& inlineTextBox, size_t start, size_t length, bool isWhitespace)
+{
+    // Do not cache when:
+    // 1. first-line style's unique font properties may produce non-matching width values.
+    // 2. position dependent content is present (preserved tab character atm).
+    if (inlineTextBox.style().fontCascade() != inlineTextBox.firstLineStyle().fontCascade())
         return false;
-    return inlineTextBox.style().fontCascade() == inlineTextBox.firstLineStyle().fontCascade();
+    if (!isWhitespace || !TextUtil::shouldPreserveSpacesAndTabs(inlineTextBox))
+        return true;
+    // FIXME: Currently we opt out of caching only when we see a preserved \t character (position dependent measured width).
+    auto textContent = inlineTextBox.content();
+    for (auto index = start; index < start + length; ++index) {
+        if (textContent[index] == tabCharacter)
+            return false;
+    }
+    return true;
 }
 
@@ -370 +380 @@
     auto& style = inlineTextBox.style();
     auto& fontCascade = style.fontCascade();
+    auto whiteSpaceWidth = std::optional<InlineLayoutUnit> { fontCascade.spaceWidth() };
     auto shouldPreserveSpacesAndTabs = TextUtil::shouldPreserveSpacesAndTabs(inlineTextBox);
     auto whitespaceContentIsTreatedAsSingleSpace = !shouldPreserveSpacesAndTabs;
@@ -376 +387 @@
     auto lineBreakIterator = LazyLineBreakIterator { text, style.computedLocale(), TextUtil::lineBreakIteratorMode(style.lineBreak()) };
     unsigned currentPosition = 0;
-
-    auto textWidth = [&](auto startPosition, auto length) -> std::optional<InlineLayoutUnit> {
-        // Delay content measuring until after bidi split.
-        if (hasSeenBidiContent() || !canCacheMeasuredWidthOnInlineTextItem(inlineTextBox))
-            return { };
-        return TextUtil::width(inlineTextBox, fontCascade, startPosition, startPosition + length, { });
-    };
 
     while (currentPosition < contentLength) {
@@ -404 +408 @@
             ASSERT(whitespaceContent->length);
             auto appendWhitespaceItem = [&] (auto startPosition, auto itemLength) {
-                auto simpleSingleWhitespaceContent = inlineTextBox.canUseSimplifiedContentMeasuring() && (itemLength == 1 || whitespaceContentIsTreatedAsSingleSpace);
-                auto width = simpleSingleWhitespaceContent ? std::make_optional(InlineLayoutUnit { fontCascade.spaceWidth() }) : textWidth(startPosition, itemLength);
+                auto width = [&]() -> std::optional<InlineLayoutUnit> {
+                    if (!canCacheMeasuredWidthOnInlineTextItem(inlineTextBox, startPosition, itemLength, true))
+                        return { };
+                    if (whitespaceContentIsTreatedAsSingleSpace || (itemLength == 1 && inlineTextBox.canUseSimplifiedContentMeasuring()))
+                        return whiteSpaceWidth;
+                    return TextUtil::width(inlineTextBox, fontCascade, startPosition, startPosition + itemLength, { });
+                }();
                 inlineItems.append(InlineTextItem::createWhitespaceItem(inlineTextBox, startPosition, itemLength, UBIDI_DEFAULT_LTR, whitespaceContent->isWordSeparator, width));
             };
@@ -438 +447 @@
             }
             ASSERT_IMPLIES(style.hyphens() == Hyphens::None, !hasTrailingSoftHyphen);
-            auto inlineItemLength = endPosition - startPosition;
-            inlineItems.append(InlineTextItem::createNonWhitespaceItem(inlineTextBox, startPosition, inlineItemLength, UBIDI_DEFAULT_LTR, hasTrailingSoftHyphen, textWidth(startPosition, inlineItemLength)));
+            auto length = endPosition - startPosition;
+            auto textWidth = [&]() -> std::optional<InlineLayoutUnit> {
+                // Delay non-whitespace content measuring until after bidi split.
+                if (hasSeenBidiContent() || !canCacheMeasuredWidthOnInlineTextItem(inlineTextBox, startPosition, length, false))
+                    return { };
+                return TextUtil::width(inlineTextBox, fontCascade, startPosition, endPosition, { });
+            }();
+            inlineItems.append(InlineTextItem::createNonWhitespaceItem(inlineTextBox, startPosition, length, UBIDI_DEFAULT_LTR, hasTrailingSoftHyphen, textWidth));
             currentPosition = endPosition;
-
             return true;
         };