Source/WebCore/rendering/updating/RenderTreeBuilderFirstLetter.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003-2011, 2017 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */

 #include "config.h"
 #include "RenderTreeBuilderFirstLetter.h"

 #include "FontCascade.h"
 #include "RenderBlock.h"
 #include "RenderButton.h"
 #include "RenderInline.h"
 #include "RenderRubyRun.h"
 #include "RenderSVGText.h"
 #include "RenderStyle.h"
 #include "RenderTable.h"
 #include "RenderTextFragment.h"
 #include "RenderTreeBuilder.h"

 namespace WebCore {

 static RenderStyle styleForFirstLetter(const RenderBlock& firstLetterBlock, const RenderObject& firstLetterContainer)
 {
     auto* containerFirstLetterStyle = firstLetterBlock.getCachedPseudoStyle(FIRST_LETTER, &firstLetterContainer.firstLineStyle());
     // FIXME: There appears to be some path where we have a first letter renderer without first letter style.
     ASSERT(containerFirstLetterStyle);
     auto firstLetterStyle = RenderStyle::clone(containerFirstLetterStyle ? *containerFirstLetterStyle : firstLetterContainer.firstLineStyle());

     // If we have an initial letter drop that is >= 1, then we need to force floating to be on.
     if (firstLetterStyle.initialLetterDrop() >= 1 && !firstLetterStyle.isFloating())
         firstLetterStyle.setFloating(firstLetterStyle.isLeftToRightDirection() ? LeftFloat : RightFloat);

     // We have to compute the correct font-size for the first-letter if it has an initial letter height set.
     auto* paragraph = firstLetterContainer.isRenderBlockFlow() ? &firstLetterContainer : firstLetterContainer.containingBlock();
     if (firstLetterStyle.initialLetterHeight() >= 1 && firstLetterStyle.fontMetrics().hasCapHeight() && paragraph->style().fontMetrics().hasCapHeight()) {
         // FIXME: For ideographic baselines, we want to go from line edge to line edge. This is equivalent to (N-1)*line-height + the font height.
         // We don't yet support ideographic baselines.
         // For an N-line first-letter and for alphabetic baselines, the cap-height of the first letter needs to equal (N-1)*line-height of paragraph lines + cap-height of the paragraph
         // Mathematically we can't rely on font-size, since font().height() doesn't necessarily match. For reliability, the best approach is simply to
         // compare the final measured cap-heights of the two fonts in order to get to the closest possible value.
         firstLetterStyle.setLineBoxContain(LineBoxContainInitialLetter);
         int lineHeight = paragraph->style().computedLineHeight();

         // Set the font to be one line too big and then ratchet back to get to a precise fit. We can't just set the desired font size based off font height metrics
         // because many fonts bake ascent into the font metrics. Therefore we have to look at actual measured cap height values in order to know when we have a good fit.
         auto newFontDescription = firstLetterStyle.fontDescription();
         float capRatio = firstLetterStyle.fontMetrics().floatCapHeight() / firstLetterStyle.computedFontPixelSize();
         float startingFontSize = ((firstLetterStyle.initialLetterHeight() - 1) * lineHeight + paragraph->style().fontMetrics().capHeight()) / capRatio;
         newFontDescription.setSpecifiedSize(startingFontSize);
         newFontDescription.setComputedSize(startingFontSize);
         firstLetterStyle.setFontDescription(newFontDescription);
         firstLetterStyle.fontCascade().update(firstLetterStyle.fontCascade().fontSelector());

         int desiredCapHeight = (firstLetterStyle.initialLetterHeight() - 1) * lineHeight + paragraph->style().fontMetrics().capHeight();
         int actualCapHeight = firstLetterStyle.fontMetrics().capHeight();
         while (actualCapHeight > desiredCapHeight) {
             auto newFontDescription = firstLetterStyle.fontDescription();
             newFontDescription.setSpecifiedSize(newFontDescription.specifiedSize() - 1);
             newFontDescription.setComputedSize(newFontDescription.computedSize() -1);
             firstLetterStyle.setFontDescription(newFontDescription);
             firstLetterStyle.fontCascade().update(firstLetterStyle.fontCascade().fontSelector());
             actualCapHeight = firstLetterStyle.fontMetrics().capHeight();
         }
     }

     // Force inline display (except for floating first-letters).
     firstLetterStyle.setDisplay(firstLetterStyle.isFloating() ? BLOCK : INLINE);
     // CSS2 says first-letter can't be positioned.
     firstLetterStyle.setPosition(StaticPosition);
     return firstLetterStyle;
 }

 // CSS 2.1 http://www.w3.org/TR/CSS21/selector.html#first-letter
 // "Punctuation (i.e, characters defined in Unicode [UNICODE] in the "open" (Ps), "close" (Pe),
 // "initial" (Pi). "final" (Pf) and "other" (Po) punctuation classes), that precedes or follows the first letter should be included"
 static inline bool isPunctuationForFirstLetter(UChar32 c)
 {
     return U_GET_GC_MASK(c) & (U_GC_PS_MASK | U_GC_PE_MASK | U_GC_PI_MASK | U_GC_PF_MASK | U_GC_PO_MASK);
 }

 static inline bool shouldSkipForFirstLetter(UChar32 c)
 {
     return isSpaceOrNewline(c) || c == noBreakSpace || isPunctuationForFirstLetter(c);
 }

 static bool supportsFirstLetter(RenderBlock& block)
 {
     if (is<RenderButton>(block))
         return true;
     if (!is<RenderBlockFlow>(block))
         return false;
     if (is<RenderSVGText>(block))
         return false;
     if (is<RenderRubyRun>(block))
         return false;
     return block.canHaveGeneratedChildren();
 }

 RenderTreeBuilder::FirstLetter::FirstLetter(RenderTreeBuilder& builder)
     : m_builder(builder)
 {
 }

 void RenderTreeBuilder::FirstLetter::updateAfterDescendants(RenderBlock& block)
 {
     if (!block.style().hasPseudoStyle(FIRST_LETTER))
         return;
     if (!supportsFirstLetter(block))
         return;

     // FIXME: This should be refactored, firstLetterContainer is not needed.
     RenderObject* firstLetterRenderer;
     RenderElement* firstLetterContainer;
     block.getFirstLetter(firstLetterRenderer, firstLetterContainer);

     if (!firstLetterRenderer)
         return;

     // Other containers are handled when updating their renderers.
     if (&block != firstLetterContainer)
         return;

     // If the child already has style, then it has already been created, so we just want
     // to update it.
     if (firstLetterRenderer->parent()->style().styleType() == FIRST_LETTER) {
         updateStyle(block, *firstLetterRenderer);
         return;
     }

     if (!is<RenderText>(firstLetterRenderer))
         return;

     createRenderers(block, downcast<RenderText>(*firstLetterRenderer));
 }

 void RenderTreeBuilder::FirstLetter::cleanupOnDestroy(RenderTextFragment& textFragment)
 {
     if (!textFragment.firstLetter())
         return;
     m_builder.destroy(*textFragment.firstLetter());
 }

 void RenderTreeBuilder::FirstLetter::updateStyle(RenderBlock& firstLetterBlock, RenderObject& currentChild)
 {
     RenderElement* firstLetter = currentChild.parent();
     ASSERT(firstLetter->isFirstLetter());

     RenderElement* firstLetterContainer = firstLetter->parent();
     auto pseudoStyle = styleForFirstLetter(firstLetterBlock, *firstLetterContainer);
     ASSERT(firstLetter->isFloating() || firstLetter->isInline());

     if (Style::determineChange(firstLetter->style(), pseudoStyle) == Style::Detach) {
         // The first-letter renderer needs to be replaced. Create a new renderer of the right type.
         RenderPtr<RenderBoxModelObject> newFirstLetter;
         if (pseudoStyle.display() == INLINE)
             newFirstLetter = createRenderer<RenderInline>(firstLetterBlock.document(), WTFMove(pseudoStyle));
         else
             newFirstLetter = createRenderer<RenderBlockFlow>(firstLetterBlock.document(), WTFMove(pseudoStyle));
         newFirstLetter->initializeStyle();
         newFirstLetter->setIsFirstLetter();

         // Move the first letter into the new renderer.
         while (RenderObject* child = firstLetter->firstChild()) {
             if (is<RenderText>(*child))
                 downcast<RenderText>(*child).removeAndDestroyTextBoxes();
             auto toMove = m_builder.detach(*firstLetter, *child);
             m_builder.attach(*newFirstLetter, WTFMove(toMove));
         }

         RenderObject* nextSibling = firstLetter->nextSibling();
         if (RenderTextFragment* remainingText = downcast<RenderBoxModelObject>(*firstLetter).firstLetterRemainingText()) {
             ASSERT(remainingText->isAnonymous() || remainingText->textNode()->renderer() == remainingText);
             // Replace the old renderer with the new one.
             remainingText->setFirstLetter(*newFirstLetter);
             newFirstLetter->setFirstLetterRemainingText(*remainingText);
         }
         m_builder.destroy(*firstLetter);
         m_builder.attach(*firstLetterContainer, WTFMove(newFirstLetter), nextSibling);
         return;
     }

     firstLetter->setStyle(WTFMove(pseudoStyle));
 }

 void RenderTreeBuilder::FirstLetter::createRenderers(RenderBlock& firstLetterBlock, RenderText& currentTextChild)
 {
     RenderElement* firstLetterContainer = currentTextChild.parent();
     auto pseudoStyle = styleForFirstLetter(firstLetterBlock, *firstLetterContainer);
     RenderPtr<RenderBoxModelObject> newFirstLetter;
     if (pseudoStyle.display() == INLINE)
         newFirstLetter = createRenderer<RenderInline>(firstLetterBlock.document(), WTFMove(pseudoStyle));
     else
         newFirstLetter = createRenderer<RenderBlockFlow>(firstLetterBlock.document(), WTFMove(pseudoStyle));
     newFirstLetter->initializeStyle();
     newFirstLetter->setIsFirstLetter();

     auto& firstLetter = *newFirstLetter;
     m_builder.attach(*firstLetterContainer, WTFMove(newFirstLetter), &currentTextChild);

     // The original string is going to be either a generated content string or a DOM node's
     // string. We want the original string before it got transformed in case first-letter has
     // no text-transform or a different text-transform applied to it.
     String oldText = currentTextChild.originalText();
     ASSERT(!oldText.isNull());

     if (!oldText.isEmpty()) {
         unsigned length = 0;

         // Account for leading spaces and punctuation.
         while (length < oldText.length() && shouldSkipForFirstLetter(oldText.characterStartingAt(length)))
             length += numCodeUnitsInGraphemeClusters(StringView(oldText).substring(length), 1);

         // Account for first grapheme cluster.
         length += numCodeUnitsInGraphemeClusters(StringView(oldText).substring(length), 1);

         // Keep looking for whitespace and allowed punctuation, but avoid
         // accumulating just whitespace into the :first-letter.
         unsigned numCodeUnits = 0;
         for (unsigned scanLength = length; scanLength < oldText.length(); scanLength += numCodeUnits) {
             UChar32 c = oldText.characterStartingAt(scanLength);

             if (!shouldSkipForFirstLetter(c))
                 break;

             numCodeUnits = numCodeUnitsInGraphemeClusters(StringView(oldText).substring(scanLength), 1);

             if (isPunctuationForFirstLetter(c))
                 length = scanLength + numCodeUnits;
         }

         auto* textNode = currentTextChild.textNode();
         auto* beforeChild = currentTextChild.nextSibling();
         m_builder.destroy(currentTextChild);

         // Construct a text fragment for the text after the first letter.
         // This text fragment might be empty.
         RenderPtr<RenderTextFragment> newRemainingText;
         if (textNode) {
             newRemainingText = createRenderer<RenderTextFragment>(*textNode, oldText, length, oldText.length() - length);
             textNode->setRenderer(newRemainingText.get());
         } else
             newRemainingText = createRenderer<RenderTextFragment>(firstLetterBlock.document(), oldText, length, oldText.length() - length);

         RenderTextFragment& remainingText = *newRemainingText;
         m_builder.attach(*firstLetterContainer, WTFMove(newRemainingText), beforeChild);
         remainingText.setFirstLetter(firstLetter);
         firstLetter.setFirstLetterRemainingText(remainingText);

         // construct text fragment for the first letter
         auto letter = createRenderer<RenderTextFragment>(firstLetterBlock.document(), oldText, 0, length);

         m_builder.attach(firstLetter, WTFMove(letter));
     }
 }

 };
	/*
	* Copyright (C) 1999 Lars Knoll (knoll@kde.org)
	* (C) 1999 Antti Koivisto (koivisto@kde.org)
	* (C) 2007 David Smith (catfish.man@gmail.com)
	* Copyright (C) 2003-2011, 2017 Apple Inc. All rights reserved.
	* Copyright (C) Research In Motion Limited 2010. All rights reserved.
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Library General Public
	* License as published by the Free Software Foundation; either
	* version 2 of the License, or (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Library General Public License for more details.
	*
	* You should have received a copy of the GNU Library General Public License
	* along with this library; see the file COPYING.LIB. If not, write to
	* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
	* Boston, MA 02110-1301, USA.
	*/

	#include "config.h"
	#include "RenderTreeBuilderFirstLetter.h"

	#include "FontCascade.h"
	#include "RenderBlock.h"
	#include "RenderButton.h"
	#include "RenderInline.h"
	#include "RenderRubyRun.h"
	#include "RenderSVGText.h"
	#include "RenderStyle.h"
	#include "RenderTable.h"
	#include "RenderTextFragment.h"
	#include "RenderTreeBuilder.h"

	namespace WebCore {

	static RenderStyle styleForFirstLetter(const RenderBlock& firstLetterBlock, const RenderObject& firstLetterContainer)
	{
	auto* containerFirstLetterStyle = firstLetterBlock.getCachedPseudoStyle(FIRST_LETTER, &firstLetterContainer.firstLineStyle());
	// FIXME: There appears to be some path where we have a first letter renderer without first letter style.
	ASSERT(containerFirstLetterStyle);
	auto firstLetterStyle = RenderStyle::clone(containerFirstLetterStyle ? *containerFirstLetterStyle : firstLetterContainer.firstLineStyle());

	// If we have an initial letter drop that is >= 1, then we need to force floating to be on.
	if (firstLetterStyle.initialLetterDrop() >= 1 && !firstLetterStyle.isFloating())
	firstLetterStyle.setFloating(firstLetterStyle.isLeftToRightDirection() ? LeftFloat : RightFloat);

	// We have to compute the correct font-size for the first-letter if it has an initial letter height set.
	auto* paragraph = firstLetterContainer.isRenderBlockFlow() ? &firstLetterContainer : firstLetterContainer.containingBlock();
	if (firstLetterStyle.initialLetterHeight() >= 1 && firstLetterStyle.fontMetrics().hasCapHeight() && paragraph->style().fontMetrics().hasCapHeight()) {
	// FIXME: For ideographic baselines, we want to go from line edge to line edge. This is equivalent to (N-1)*line-height + the font height.
	// We don't yet support ideographic baselines.
	// For an N-line first-letter and for alphabetic baselines, the cap-height of the first letter needs to equal (N-1)*line-height of paragraph lines + cap-height of the paragraph
	// Mathematically we can't rely on font-size, since font().height() doesn't necessarily match. For reliability, the best approach is simply to
	// compare the final measured cap-heights of the two fonts in order to get to the closest possible value.
	firstLetterStyle.setLineBoxContain(LineBoxContainInitialLetter);
	int lineHeight = paragraph->style().computedLineHeight();

	// Set the font to be one line too big and then ratchet back to get to a precise fit. We can't just set the desired font size based off font height metrics
	// because many fonts bake ascent into the font metrics. Therefore we have to look at actual measured cap height values in order to know when we have a good fit.
	auto newFontDescription = firstLetterStyle.fontDescription();
	float capRatio = firstLetterStyle.fontMetrics().floatCapHeight() / firstLetterStyle.computedFontPixelSize();
	float startingFontSize = ((firstLetterStyle.initialLetterHeight() - 1) * lineHeight + paragraph->style().fontMetrics().capHeight()) / capRatio;
	newFontDescription.setSpecifiedSize(startingFontSize);
	newFontDescription.setComputedSize(startingFontSize);
	firstLetterStyle.setFontDescription(newFontDescription);
	firstLetterStyle.fontCascade().update(firstLetterStyle.fontCascade().fontSelector());

	int desiredCapHeight = (firstLetterStyle.initialLetterHeight() - 1) * lineHeight + paragraph->style().fontMetrics().capHeight();
	int actualCapHeight = firstLetterStyle.fontMetrics().capHeight();
	while (actualCapHeight > desiredCapHeight) {
	auto newFontDescription = firstLetterStyle.fontDescription();
	newFontDescription.setSpecifiedSize(newFontDescription.specifiedSize() - 1);
	newFontDescription.setComputedSize(newFontDescription.computedSize() -1);
	firstLetterStyle.setFontDescription(newFontDescription);
	firstLetterStyle.fontCascade().update(firstLetterStyle.fontCascade().fontSelector());
	actualCapHeight = firstLetterStyle.fontMetrics().capHeight();
	}
	}

	// Force inline display (except for floating first-letters).
	firstLetterStyle.setDisplay(firstLetterStyle.isFloating() ? BLOCK : INLINE);
	// CSS2 says first-letter can't be positioned.
	firstLetterStyle.setPosition(StaticPosition);
	return firstLetterStyle;
	}

	// CSS 2.1 http://www.w3.org/TR/CSS21/selector.html#first-letter
	// "Punctuation (i.e, characters defined in Unicode [UNICODE] in the "open" (Ps), "close" (Pe),
	// "initial" (Pi). "final" (Pf) and "other" (Po) punctuation classes), that precedes or follows the first letter should be included"
	static inline bool isPunctuationForFirstLetter(UChar32 c)
	{
	return U_GET_GC_MASK(c) & (U_GC_PS_MASK \| U_GC_PE_MASK \| U_GC_PI_MASK \| U_GC_PF_MASK \| U_GC_PO_MASK);
	}

	static inline bool shouldSkipForFirstLetter(UChar32 c)
	{
	return isSpaceOrNewline(c) \|\| c == noBreakSpace \|\| isPunctuationForFirstLetter(c);
	}

	static bool supportsFirstLetter(RenderBlock& block)
	{
	if (is<RenderButton>(block))
	return true;
	if (!is<RenderBlockFlow>(block))
	return false;
	if (is<RenderSVGText>(block))
	return false;
	if (is<RenderRubyRun>(block))
	return false;
	return block.canHaveGeneratedChildren();
	}

	RenderTreeBuilder::FirstLetter::FirstLetter(RenderTreeBuilder& builder)
	: m_builder(builder)
	{
	}

	void RenderTreeBuilder::FirstLetter::updateAfterDescendants(RenderBlock& block)
	{
	if (!block.style().hasPseudoStyle(FIRST_LETTER))
	return;
	if (!supportsFirstLetter(block))
	return;

	// FIXME: This should be refactored, firstLetterContainer is not needed.
	RenderObject* firstLetterRenderer;
	RenderElement* firstLetterContainer;
	block.getFirstLetter(firstLetterRenderer, firstLetterContainer);

	if (!firstLetterRenderer)
	return;

	// Other containers are handled when updating their renderers.
	if (&block != firstLetterContainer)
	return;

	// If the child already has style, then it has already been created, so we just want
	// to update it.
	if (firstLetterRenderer->parent()->style().styleType() == FIRST_LETTER) {
	updateStyle(block, *firstLetterRenderer);
	return;
	}

	if (!is<RenderText>(firstLetterRenderer))
	return;

	createRenderers(block, downcast<RenderText>(*firstLetterRenderer));
	}

	void RenderTreeBuilder::FirstLetter::cleanupOnDestroy(RenderTextFragment& textFragment)
	{
	if (!textFragment.firstLetter())
	return;
	m_builder.destroy(*textFragment.firstLetter());
	}

	void RenderTreeBuilder::FirstLetter::updateStyle(RenderBlock& firstLetterBlock, RenderObject& currentChild)
	{
	RenderElement* firstLetter = currentChild.parent();
	ASSERT(firstLetter->isFirstLetter());

	RenderElement* firstLetterContainer = firstLetter->parent();
	auto pseudoStyle = styleForFirstLetter(firstLetterBlock, *firstLetterContainer);
	ASSERT(firstLetter->isFloating() \|\| firstLetter->isInline());

	if (Style::determineChange(firstLetter->style(), pseudoStyle) == Style::Detach) {
	// The first-letter renderer needs to be replaced. Create a new renderer of the right type.
	RenderPtr<RenderBoxModelObject> newFirstLetter;
	if (pseudoStyle.display() == INLINE)
	newFirstLetter = createRenderer<RenderInline>(firstLetterBlock.document(), WTFMove(pseudoStyle));
	else
	newFirstLetter = createRenderer<RenderBlockFlow>(firstLetterBlock.document(), WTFMove(pseudoStyle));
	newFirstLetter->initializeStyle();
	newFirstLetter->setIsFirstLetter();

	// Move the first letter into the new renderer.
	while (RenderObject* child = firstLetter->firstChild()) {
	if (is<RenderText>(*child))
	downcast<RenderText>(*child).removeAndDestroyTextBoxes();
	auto toMove = m_builder.detach(firstLetter, child);
	m_builder.attach(*newFirstLetter, WTFMove(toMove));
	}

	RenderObject* nextSibling = firstLetter->nextSibling();
	if (RenderTextFragment* remainingText = downcast<RenderBoxModelObject>(*firstLetter).firstLetterRemainingText()) {
	ASSERT(remainingText->isAnonymous() \|\| remainingText->textNode()->renderer() == remainingText);
	// Replace the old renderer with the new one.
	remainingText->setFirstLetter(*newFirstLetter);
	newFirstLetter->setFirstLetterRemainingText(*remainingText);
	}
	m_builder.destroy(*firstLetter);
	m_builder.attach(*firstLetterContainer, WTFMove(newFirstLetter), nextSibling);
	return;
	}

	firstLetter->setStyle(WTFMove(pseudoStyle));
	}

	void RenderTreeBuilder::FirstLetter::createRenderers(RenderBlock& firstLetterBlock, RenderText& currentTextChild)
	{
	RenderElement* firstLetterContainer = currentTextChild.parent();
	auto pseudoStyle = styleForFirstLetter(firstLetterBlock, *firstLetterContainer);
	RenderPtr<RenderBoxModelObject> newFirstLetter;
	if (pseudoStyle.display() == INLINE)
	newFirstLetter = createRenderer<RenderInline>(firstLetterBlock.document(), WTFMove(pseudoStyle));
	else
	newFirstLetter = createRenderer<RenderBlockFlow>(firstLetterBlock.document(), WTFMove(pseudoStyle));
	newFirstLetter->initializeStyle();
	newFirstLetter->setIsFirstLetter();

	auto& firstLetter = *newFirstLetter;
	m_builder.attach(*firstLetterContainer, WTFMove(newFirstLetter), &currentTextChild);

	// The original string is going to be either a generated content string or a DOM node's
	// string. We want the original string before it got transformed in case first-letter has
	// no text-transform or a different text-transform applied to it.
	String oldText = currentTextChild.originalText();
	ASSERT(!oldText.isNull());

	if (!oldText.isEmpty()) {
	unsigned length = 0;

	// Account for leading spaces and punctuation.
	while (length < oldText.length() && shouldSkipForFirstLetter(oldText.characterStartingAt(length)))
	length += numCodeUnitsInGraphemeClusters(StringView(oldText).substring(length), 1);

	// Account for first grapheme cluster.
	length += numCodeUnitsInGraphemeClusters(StringView(oldText).substring(length), 1);

	// Keep looking for whitespace and allowed punctuation, but avoid
	// accumulating just whitespace into the :first-letter.
	unsigned numCodeUnits = 0;
	for (unsigned scanLength = length; scanLength < oldText.length(); scanLength += numCodeUnits) {
	UChar32 c = oldText.characterStartingAt(scanLength);

	if (!shouldSkipForFirstLetter(c))
	break;

	numCodeUnits = numCodeUnitsInGraphemeClusters(StringView(oldText).substring(scanLength), 1);

	if (isPunctuationForFirstLetter(c))
	length = scanLength + numCodeUnits;
	}

	auto* textNode = currentTextChild.textNode();
	auto* beforeChild = currentTextChild.nextSibling();
	m_builder.destroy(currentTextChild);

	// Construct a text fragment for the text after the first letter.
	// This text fragment might be empty.
	RenderPtr<RenderTextFragment> newRemainingText;
	if (textNode) {
	newRemainingText = createRenderer<RenderTextFragment>(*textNode, oldText, length, oldText.length() - length);
	textNode->setRenderer(newRemainingText.get());
	} else
	newRemainingText = createRenderer<RenderTextFragment>(firstLetterBlock.document(), oldText, length, oldText.length() - length);

	RenderTextFragment& remainingText = *newRemainingText;
	m_builder.attach(*firstLetterContainer, WTFMove(newRemainingText), beforeChild);
	remainingText.setFirstLetter(firstLetter);
	firstLetter.setFirstLetterRemainingText(remainingText);

	// construct text fragment for the first letter
	auto letter = createRenderer<RenderTextFragment>(firstLetterBlock.document(), oldText, 0, length);

	m_builder.attach(firstLetter, WTFMove(letter));
	}
	}

	};