Source/WebCore/platform/graphics/StringTruncator.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2005, 2006, 2007, 2014 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
  *     documentation and/or other materials provided with the distribution.
  * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
  *     its contributors may be used to endorse or promote products derived
  *     from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "StringTruncator.h"

 #include "FontCascade.h"
 #include <wtf/text/TextBreakIterator.h>
 #include "TextRun.h"
 #include <unicode/ubrk.h>
 #include <wtf/Assertions.h>
 #include <wtf/Vector.h>
 #include <wtf/text/StringView.h>
 #include <wtf/unicode/CharacterNames.h>

 namespace WebCore {

 #define STRING_BUFFER_SIZE 2048

 typedef unsigned TruncationFunction(const String&, unsigned length, unsigned keepCount, UChar* buffer, bool shouldInsertEllipsis);

 static inline int textBreakAtOrPreceding(UBreakIterator* it, int offset)
 {
     if (ubrk_isBoundary(it, offset))
         return offset;

     int result = ubrk_preceding(it, offset);
     return result == UBRK_DONE ? 0 : result;
 }

 static inline int boundedTextBreakFollowing(UBreakIterator* it, int offset, int length)
 {
     int result = ubrk_following(it, offset);
     return result == UBRK_DONE ? length : result;
 }

 static unsigned centerTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool shouldInsertEllipsis)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(keepCount < length);
     ASSERT_WITH_SECURITY_IMPLICATION(keepCount < STRING_BUFFER_SIZE);

     unsigned omitStart = (keepCount + 1) / 2;
     NonSharedCharacterBreakIterator it(StringView(string).left(length));
     unsigned omitEnd = boundedTextBreakFollowing(it, omitStart + (length - keepCount) - 1, length);
     omitStart = textBreakAtOrPreceding(it, omitStart);

 #if PLATFORM(IOS_FAMILY)
     // FIXME: We should guard this code behind an editing behavior. Then we can remove the PLATFORM(IOS_FAMILY)-guard.
     // Or just turn it on for all platforms. It seems like good behavior everywhere. Might be better to generalize
     // it to handle all whitespace, not just "space".

     // Strip single character before ellipsis character, when that character is preceded by a space
     if (omitStart > 1 && string[omitStart - 1] != space && omitStart > 2 && string[omitStart - 2] == space)
         --omitStart;

     // Strip whitespace before and after the ellipsis character
     while (omitStart > 1 && string[omitStart - 1] == space)
         --omitStart;

     // Strip single character after ellipsis character, when that character is followed by a space
     if ((length - omitEnd) > 1 && string[omitEnd] != space && (length - omitEnd) > 2 && string[omitEnd + 1] == space)
         ++omitEnd;

     while ((length - omitEnd) > 1 && string[omitEnd] == space)
         ++omitEnd;
 #endif

     unsigned truncatedLength = omitStart + shouldInsertEllipsis + (length - omitEnd);
     ASSERT(truncatedLength <= length);

     StringView(string).left(omitStart).getCharactersWithUpconvert(buffer);
     if (shouldInsertEllipsis)
         buffer[omitStart++] = horizontalEllipsis;
     StringView(string).substring(omitEnd, length - omitEnd).getCharactersWithUpconvert(&buffer[omitStart]);
     return truncatedLength;
 }

 static unsigned rightTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool shouldInsertEllipsis)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(keepCount < length);
     ASSERT_WITH_SECURITY_IMPLICATION(keepCount < STRING_BUFFER_SIZE);

 #if PLATFORM(IOS_FAMILY)
     // FIXME: We should guard this code behind an editing behavior. Then we can remove the PLATFORM(IOS_FAMILY)-guard.
     // Or just turn it on for all platforms. It seems like good behavior everywhere. Might be better to generalize
     // it to handle all whitespace, not just "space".

     // Strip single character before ellipsis character, when that character is preceded by a space
     if (keepCount > 1 && string[keepCount - 1] != space && keepCount > 2 && string[keepCount - 2] == space)
         --keepCount;

     // Strip whitespace before the ellipsis character
     while (keepCount > 1 && string[keepCount - 1] == space)
         --keepCount;
 #endif

     NonSharedCharacterBreakIterator it(StringView(string).left(length));
     unsigned keepLength = textBreakAtOrPreceding(it, keepCount);
     unsigned truncatedLength = shouldInsertEllipsis ? keepLength + 1 : keepLength;

     StringView(string).left(keepLength).getCharactersWithUpconvert(buffer);
     if (shouldInsertEllipsis)
         buffer[keepLength] = horizontalEllipsis;

     return truncatedLength;
 }

 static unsigned rightClipToCharacterBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool)
 {
     ASSERT(keepCount < length);
     ASSERT(keepCount < STRING_BUFFER_SIZE);

     NonSharedCharacterBreakIterator it(StringView(string).left(length));
     unsigned keepLength = textBreakAtOrPreceding(it, keepCount);
     StringView(string).left(keepLength).getCharactersWithUpconvert(buffer);

     return keepLength;
 }

 static unsigned rightClipToWordBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool)
 {
     ASSERT(keepCount < length);
     ASSERT(keepCount < STRING_BUFFER_SIZE);

     UBreakIterator* it = wordBreakIterator(StringView(string).left(length));
     unsigned keepLength = textBreakAtOrPreceding(it, keepCount);
     StringView(string).left(keepLength).getCharactersWithUpconvert(buffer);

 #if PLATFORM(IOS_FAMILY)
     // FIXME: We should guard this code behind an editing behavior. Then we can remove the PLATFORM(IOS_FAMILY)-guard.
     // Or just turn it on for all platforms. It seems like good behavior everywhere. Might be better to generalize
     // it to handle all whitespace, not just "space".

     // Motivated by <rdar://problem/7439327> truncation should not include a trailing space
     while (keepLength && string[keepLength - 1] == space)
         --keepLength;
 #endif

     return keepLength;
 }

 static unsigned leftTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool shouldInsertEllipsis)
 {
     ASSERT(keepCount < length);
     ASSERT(keepCount < STRING_BUFFER_SIZE);

     unsigned startIndex = length - keepCount;

     NonSharedCharacterBreakIterator it(string);
     unsigned adjustedStartIndex = startIndex;
     boundedTextBreakFollowing(it, startIndex, length - startIndex);

     // Strip single character after ellipsis character, when that character is preceded by a space
     if (adjustedStartIndex < length && string[adjustedStartIndex] != space
         && adjustedStartIndex < length - 1 && string[adjustedStartIndex + 1] == space)
         ++adjustedStartIndex;

     // Strip whitespace after the ellipsis character
     while (adjustedStartIndex < length && string[adjustedStartIndex] == space)
         ++adjustedStartIndex;

     if (shouldInsertEllipsis) {
         buffer[0] = horizontalEllipsis;
         StringView(string).substring(adjustedStartIndex, length - adjustedStartIndex + 1).getCharactersWithUpconvert(&buffer[1]);
         return length - adjustedStartIndex + 1;
     }
     StringView(string).substring(adjustedStartIndex, length - adjustedStartIndex + 1).getCharactersWithUpconvert(&buffer[0]);
     return length - adjustedStartIndex;
 }

 static float stringWidth(const FontCascade& renderer, const UChar* characters, unsigned length)
 {
     TextRun run(StringView(characters, length));
     return renderer.width(run);
 }

 static String truncateString(const String& string, float maxWidth, const FontCascade& font, TruncationFunction truncateToBuffer, float* resultWidth = nullptr, bool shouldInsertEllipsis = true,  float customTruncationElementWidth = 0, bool alwaysTruncate = false)
 {
     if (string.isEmpty())
         return string;

     if (resultWidth)
         *resultWidth = 0;

     ASSERT(maxWidth >= 0);

     float currentEllipsisWidth = shouldInsertEllipsis ? stringWidth(font, &horizontalEllipsis, 1) : customTruncationElementWidth;

     UChar stringBuffer[STRING_BUFFER_SIZE];
     unsigned truncatedLength;
     unsigned keepCount;
     unsigned length = string.length();

     if (length > STRING_BUFFER_SIZE) {
         if (shouldInsertEllipsis)
             keepCount = STRING_BUFFER_SIZE - 1; // need 1 character for the ellipsis
         else
             keepCount = 0;
         truncatedLength = centerTruncateToBuffer(string, length, keepCount, stringBuffer, shouldInsertEllipsis);
     } else {
         keepCount = length;
         StringView(string).getCharactersWithUpconvert(stringBuffer);
         truncatedLength = length;
     }

     float width = stringWidth(font, stringBuffer, truncatedLength);
     if (!shouldInsertEllipsis && alwaysTruncate)
         width += customTruncationElementWidth;
     if ((width - maxWidth) < 0.0001) { // Ignore rounding errors.
         if (resultWidth)
             *resultWidth = width;
         return string;
     }

     unsigned keepCountForLargestKnownToFit = 0;
     float widthForLargestKnownToFit = currentEllipsisWidth;

     unsigned keepCountForSmallestKnownToNotFit = keepCount;
     float widthForSmallestKnownToNotFit = width;

     if (currentEllipsisWidth >= maxWidth) {
         keepCountForLargestKnownToFit = 1;
         keepCountForSmallestKnownToNotFit = 2;
     }

     while (keepCountForLargestKnownToFit + 1 < keepCountForSmallestKnownToNotFit) {
         ASSERT_WITH_SECURITY_IMPLICATION(widthForLargestKnownToFit <= maxWidth);
         ASSERT_WITH_SECURITY_IMPLICATION(widthForSmallestKnownToNotFit > maxWidth);

         float ratio = (keepCountForSmallestKnownToNotFit - keepCountForLargestKnownToFit)
             / (widthForSmallestKnownToNotFit - widthForLargestKnownToFit);
         keepCount = static_cast<unsigned>(maxWidth * ratio);

         if (keepCount <= keepCountForLargestKnownToFit)
             keepCount = keepCountForLargestKnownToFit + 1;
         else if (keepCount >= keepCountForSmallestKnownToNotFit)
             keepCount = keepCountForSmallestKnownToNotFit - 1;

         ASSERT_WITH_SECURITY_IMPLICATION(keepCount < length);
         ASSERT(keepCount > 0);
         ASSERT_WITH_SECURITY_IMPLICATION(keepCount < keepCountForSmallestKnownToNotFit);
         ASSERT_WITH_SECURITY_IMPLICATION(keepCount > keepCountForLargestKnownToFit);

         truncatedLength = truncateToBuffer(string, length, keepCount, stringBuffer, shouldInsertEllipsis);

         width = stringWidth(font, stringBuffer, truncatedLength);
         if (!shouldInsertEllipsis)
             width += customTruncationElementWidth;
         if (width <= maxWidth) {
             keepCountForLargestKnownToFit = keepCount;
             widthForLargestKnownToFit = width;
             if (resultWidth)
                 *resultWidth = width;
         } else {
             keepCountForSmallestKnownToNotFit = keepCount;
             widthForSmallestKnownToNotFit = width;
         }
     }

     if (keepCountForLargestKnownToFit == 0) {
         keepCountForLargestKnownToFit = 1;
     }

     if (keepCount != keepCountForLargestKnownToFit) {
         keepCount = keepCountForLargestKnownToFit;
         truncatedLength = truncateToBuffer(string, length, keepCount, stringBuffer, shouldInsertEllipsis);
     }

     return String(stringBuffer, truncatedLength);
 }

 String StringTruncator::centerTruncate(const String& string, float maxWidth, const FontCascade& font)
 {
     return truncateString(string, maxWidth, font, centerTruncateToBuffer);
 }

 String StringTruncator::rightTruncate(const String& string, float maxWidth, const FontCascade& font)
 {
     return truncateString(string, maxWidth, font, rightTruncateToBuffer);
 }

 float StringTruncator::width(const String& string, const FontCascade& font)
 {
     return stringWidth(font, StringView(string).upconvertedCharacters(), string.length());
 }

 String StringTruncator::centerTruncate(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth)
 {
     return truncateString(string, maxWidth, font, centerTruncateToBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth);
 }

 String StringTruncator::rightTruncate(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth)
 {
     return truncateString(string, maxWidth, font, rightTruncateToBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth);
 }

 String StringTruncator::leftTruncate(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth)
 {
     return truncateString(string, maxWidth, font, leftTruncateToBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth);
 }

 String StringTruncator::rightClipToCharacter(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth)
 {
     return truncateString(string, maxWidth, font, rightClipToCharacterBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth);
 }

 String StringTruncator::rightClipToWord(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis,  float customTruncationElementWidth, bool alwaysTruncate)
 {
     return truncateString(string, maxWidth, font, rightClipToWordBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth, alwaysTruncate);
 }

 } // namespace WebCore
	/*
	* Copyright (C) 2005, 2006, 2007, 2014 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. Neither the name of Apple Inc. ("Apple") nor the names of
	* its contributors may be used to endorse or promote products derived
	* from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
	* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
	* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
	* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
	* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "StringTruncator.h"

	#include "FontCascade.h"
	#include <wtf/text/TextBreakIterator.h>
	#include "TextRun.h"
	#include <unicode/ubrk.h>
	#include <wtf/Assertions.h>
	#include <wtf/Vector.h>
	#include <wtf/text/StringView.h>
	#include <wtf/unicode/CharacterNames.h>

	namespace WebCore {

	#define STRING_BUFFER_SIZE 2048

	typedef unsigned TruncationFunction(const String&, unsigned length, unsigned keepCount, UChar* buffer, bool shouldInsertEllipsis);

	static inline int textBreakAtOrPreceding(UBreakIterator* it, int offset)
	{
	if (ubrk_isBoundary(it, offset))
	return offset;

	int result = ubrk_preceding(it, offset);
	return result == UBRK_DONE ? 0 : result;
	}

	static inline int boundedTextBreakFollowing(UBreakIterator* it, int offset, int length)
	{
	int result = ubrk_following(it, offset);
	return result == UBRK_DONE ? length : result;
	}

	static unsigned centerTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool shouldInsertEllipsis)
	{
	ASSERT_WITH_SECURITY_IMPLICATION(keepCount < length);
	ASSERT_WITH_SECURITY_IMPLICATION(keepCount < STRING_BUFFER_SIZE);

	unsigned omitStart = (keepCount + 1) / 2;
	NonSharedCharacterBreakIterator it(StringView(string).left(length));
	unsigned omitEnd = boundedTextBreakFollowing(it, omitStart + (length - keepCount) - 1, length);
	omitStart = textBreakAtOrPreceding(it, omitStart);

	#if PLATFORM(IOS_FAMILY)
	// FIXME: We should guard this code behind an editing behavior. Then we can remove the PLATFORM(IOS_FAMILY)-guard.
	// Or just turn it on for all platforms. It seems like good behavior everywhere. Might be better to generalize
	// it to handle all whitespace, not just "space".

	// Strip single character before ellipsis character, when that character is preceded by a space
	if (omitStart > 1 && string[omitStart - 1] != space && omitStart > 2 && string[omitStart - 2] == space)
	--omitStart;

	// Strip whitespace before and after the ellipsis character
	while (omitStart > 1 && string[omitStart - 1] == space)
	--omitStart;

	// Strip single character after ellipsis character, when that character is followed by a space
	if ((length - omitEnd) > 1 && string[omitEnd] != space && (length - omitEnd) > 2 && string[omitEnd + 1] == space)
	++omitEnd;

	while ((length - omitEnd) > 1 && string[omitEnd] == space)
	++omitEnd;
	#endif

	unsigned truncatedLength = omitStart + shouldInsertEllipsis + (length - omitEnd);
	ASSERT(truncatedLength <= length);

	StringView(string).left(omitStart).getCharactersWithUpconvert(buffer);
	if (shouldInsertEllipsis)
	buffer[omitStart++] = horizontalEllipsis;
	StringView(string).substring(omitEnd, length - omitEnd).getCharactersWithUpconvert(&buffer[omitStart]);
	return truncatedLength;
	}

	static unsigned rightTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool shouldInsertEllipsis)
	{
	ASSERT_WITH_SECURITY_IMPLICATION(keepCount < length);
	ASSERT_WITH_SECURITY_IMPLICATION(keepCount < STRING_BUFFER_SIZE);

	#if PLATFORM(IOS_FAMILY)
	// FIXME: We should guard this code behind an editing behavior. Then we can remove the PLATFORM(IOS_FAMILY)-guard.
	// Or just turn it on for all platforms. It seems like good behavior everywhere. Might be better to generalize
	// it to handle all whitespace, not just "space".

	// Strip single character before ellipsis character, when that character is preceded by a space
	if (keepCount > 1 && string[keepCount - 1] != space && keepCount > 2 && string[keepCount - 2] == space)
	--keepCount;

	// Strip whitespace before the ellipsis character
	while (keepCount > 1 && string[keepCount - 1] == space)
	--keepCount;
	#endif

	NonSharedCharacterBreakIterator it(StringView(string).left(length));
	unsigned keepLength = textBreakAtOrPreceding(it, keepCount);
	unsigned truncatedLength = shouldInsertEllipsis ? keepLength + 1 : keepLength;

	StringView(string).left(keepLength).getCharactersWithUpconvert(buffer);
	if (shouldInsertEllipsis)
	buffer[keepLength] = horizontalEllipsis;

	return truncatedLength;
	}

	static unsigned rightClipToCharacterBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool)
	{
	ASSERT(keepCount < length);
	ASSERT(keepCount < STRING_BUFFER_SIZE);

	NonSharedCharacterBreakIterator it(StringView(string).left(length));
	unsigned keepLength = textBreakAtOrPreceding(it, keepCount);
	StringView(string).left(keepLength).getCharactersWithUpconvert(buffer);

	return keepLength;
	}

	static unsigned rightClipToWordBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool)
	{
	ASSERT(keepCount < length);
	ASSERT(keepCount < STRING_BUFFER_SIZE);

	UBreakIterator* it = wordBreakIterator(StringView(string).left(length));
	unsigned keepLength = textBreakAtOrPreceding(it, keepCount);
	StringView(string).left(keepLength).getCharactersWithUpconvert(buffer);

	#if PLATFORM(IOS_FAMILY)
	// FIXME: We should guard this code behind an editing behavior. Then we can remove the PLATFORM(IOS_FAMILY)-guard.
	// Or just turn it on for all platforms. It seems like good behavior everywhere. Might be better to generalize
	// it to handle all whitespace, not just "space".

	// Motivated by <rdar://problem/7439327> truncation should not include a trailing space
	while (keepLength && string[keepLength - 1] == space)
	--keepLength;
	#endif

	return keepLength;
	}

	static unsigned leftTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer, bool shouldInsertEllipsis)
	{
	ASSERT(keepCount < length);
	ASSERT(keepCount < STRING_BUFFER_SIZE);

	unsigned startIndex = length - keepCount;

	NonSharedCharacterBreakIterator it(string);
	unsigned adjustedStartIndex = startIndex;
	boundedTextBreakFollowing(it, startIndex, length - startIndex);

	// Strip single character after ellipsis character, when that character is preceded by a space
	if (adjustedStartIndex < length && string[adjustedStartIndex] != space
	&& adjustedStartIndex < length - 1 && string[adjustedStartIndex + 1] == space)
	++adjustedStartIndex;

	// Strip whitespace after the ellipsis character
	while (adjustedStartIndex < length && string[adjustedStartIndex] == space)
	++adjustedStartIndex;

	if (shouldInsertEllipsis) {
	buffer[0] = horizontalEllipsis;
	StringView(string).substring(adjustedStartIndex, length - adjustedStartIndex + 1).getCharactersWithUpconvert(&buffer[1]);
	return length - adjustedStartIndex + 1;
	}
	StringView(string).substring(adjustedStartIndex, length - adjustedStartIndex + 1).getCharactersWithUpconvert(&buffer[0]);
	return length - adjustedStartIndex;
	}

	static float stringWidth(const FontCascade& renderer, const UChar* characters, unsigned length)
	{
	TextRun run(StringView(characters, length));
	return renderer.width(run);
	}

	static String truncateString(const String& string, float maxWidth, const FontCascade& font, TruncationFunction truncateToBuffer, float* resultWidth = nullptr, bool shouldInsertEllipsis = true, float customTruncationElementWidth = 0, bool alwaysTruncate = false)
	{
	if (string.isEmpty())
	return string;

	if (resultWidth)
	*resultWidth = 0;

	ASSERT(maxWidth >= 0);

	float currentEllipsisWidth = shouldInsertEllipsis ? stringWidth(font, &horizontalEllipsis, 1) : customTruncationElementWidth;

	UChar stringBuffer[STRING_BUFFER_SIZE];
	unsigned truncatedLength;
	unsigned keepCount;
	unsigned length = string.length();

	if (length > STRING_BUFFER_SIZE) {
	if (shouldInsertEllipsis)
	keepCount = STRING_BUFFER_SIZE - 1; // need 1 character for the ellipsis
	else
	keepCount = 0;
	truncatedLength = centerTruncateToBuffer(string, length, keepCount, stringBuffer, shouldInsertEllipsis);
	} else {
	keepCount = length;
	StringView(string).getCharactersWithUpconvert(stringBuffer);
	truncatedLength = length;
	}

	float width = stringWidth(font, stringBuffer, truncatedLength);
	if (!shouldInsertEllipsis && alwaysTruncate)
	width += customTruncationElementWidth;
	if ((width - maxWidth) < 0.0001) { // Ignore rounding errors.
	if (resultWidth)
	*resultWidth = width;
	return string;
	}

	unsigned keepCountForLargestKnownToFit = 0;
	float widthForLargestKnownToFit = currentEllipsisWidth;

	unsigned keepCountForSmallestKnownToNotFit = keepCount;
	float widthForSmallestKnownToNotFit = width;

	if (currentEllipsisWidth >= maxWidth) {
	keepCountForLargestKnownToFit = 1;
	keepCountForSmallestKnownToNotFit = 2;
	}

	while (keepCountForLargestKnownToFit + 1 < keepCountForSmallestKnownToNotFit) {
	ASSERT_WITH_SECURITY_IMPLICATION(widthForLargestKnownToFit <= maxWidth);
	ASSERT_WITH_SECURITY_IMPLICATION(widthForSmallestKnownToNotFit > maxWidth);

	float ratio = (keepCountForSmallestKnownToNotFit - keepCountForLargestKnownToFit)
	/ (widthForSmallestKnownToNotFit - widthForLargestKnownToFit);
	keepCount = static_cast<unsigned>(maxWidth * ratio);

	if (keepCount <= keepCountForLargestKnownToFit)
	keepCount = keepCountForLargestKnownToFit + 1;
	else if (keepCount >= keepCountForSmallestKnownToNotFit)
	keepCount = keepCountForSmallestKnownToNotFit - 1;

	ASSERT_WITH_SECURITY_IMPLICATION(keepCount < length);
	ASSERT(keepCount > 0);
	ASSERT_WITH_SECURITY_IMPLICATION(keepCount < keepCountForSmallestKnownToNotFit);
	ASSERT_WITH_SECURITY_IMPLICATION(keepCount > keepCountForLargestKnownToFit);

	truncatedLength = truncateToBuffer(string, length, keepCount, stringBuffer, shouldInsertEllipsis);

	width = stringWidth(font, stringBuffer, truncatedLength);
	if (!shouldInsertEllipsis)
	width += customTruncationElementWidth;
	if (width <= maxWidth) {
	keepCountForLargestKnownToFit = keepCount;
	widthForLargestKnownToFit = width;
	if (resultWidth)
	*resultWidth = width;
	} else {
	keepCountForSmallestKnownToNotFit = keepCount;
	widthForSmallestKnownToNotFit = width;
	}
	}

	if (keepCountForLargestKnownToFit == 0) {
	keepCountForLargestKnownToFit = 1;
	}

	if (keepCount != keepCountForLargestKnownToFit) {
	keepCount = keepCountForLargestKnownToFit;
	truncatedLength = truncateToBuffer(string, length, keepCount, stringBuffer, shouldInsertEllipsis);
	}

	return String(stringBuffer, truncatedLength);
	}

	String StringTruncator::centerTruncate(const String& string, float maxWidth, const FontCascade& font)
	{
	return truncateString(string, maxWidth, font, centerTruncateToBuffer);
	}

	String StringTruncator::rightTruncate(const String& string, float maxWidth, const FontCascade& font)
	{
	return truncateString(string, maxWidth, font, rightTruncateToBuffer);
	}

	float StringTruncator::width(const String& string, const FontCascade& font)
	{
	return stringWidth(font, StringView(string).upconvertedCharacters(), string.length());
	}

	String StringTruncator::centerTruncate(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth)
	{
	return truncateString(string, maxWidth, font, centerTruncateToBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth);
	}

	String StringTruncator::rightTruncate(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth)
	{
	return truncateString(string, maxWidth, font, rightTruncateToBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth);
	}

	String StringTruncator::leftTruncate(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth)
	{
	return truncateString(string, maxWidth, font, leftTruncateToBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth);
	}

	String StringTruncator::rightClipToCharacter(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth)
	{
	return truncateString(string, maxWidth, font, rightClipToCharacterBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth);
	}

	String StringTruncator::rightClipToWord(const String& string, float maxWidth, const FontCascade& font, float& resultWidth, bool shouldInsertEllipsis, float customTruncationElementWidth, bool alwaysTruncate)
	{
	return truncateString(string, maxWidth, font, rightClipToWordBuffer, &resultWidth, shouldInsertEllipsis, customTruncationElementWidth, alwaysTruncate);
	}

	} // namespace WebCore