1/*
2 * Copyright (C) 2005, 2006, 2007 Apple Inc.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1.  Redistributions of source code must retain the above copyright
9 *     notice, this list of conditions and the following disclaimer.
10 * 2.  Redistributions in binary form must reproduce the above copyright
11 *     notice, this list of conditions and the following disclaimer in the
12 *     documentation and/or other materials provided with the distribution.
13 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
14 *     its contributors may be used to endorse or promote products derived
15 *     from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include "config.h"
30#include "StringTruncator.h"
31
32#include "Font.h"
33#include "TextBreakIterator.h"
34#include "TextRun.h"
35#include <wtf/Assertions.h>
36#include <wtf/Vector.h>
37#include <wtf/unicode/CharacterNames.h>
38
39namespace WebCore {
40
41#define STRING_BUFFER_SIZE 2048
42
43typedef unsigned TruncationFunction(const String&, unsigned length, unsigned keepCount, UChar* buffer);
44
45static inline int textBreakAtOrPreceding(TextBreakIterator* it, int offset)
46{
47    if (isTextBreak(it, offset))
48        return offset;
49
50    int result = textBreakPreceding(it, offset);
51    return result == TextBreakDone ? 0 : result;
52}
53
54static inline int boundedTextBreakFollowing(TextBreakIterator* it, int offset, int length)
55{
56    int result = textBreakFollowing(it, offset);
57    return result == TextBreakDone ? length : result;
58}
59
60static unsigned centerTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer)
61{
62    ASSERT(keepCount < length);
63    ASSERT(keepCount < STRING_BUFFER_SIZE);
64
65    unsigned omitStart = (keepCount + 1) / 2;
66    TextBreakIterator* it = characterBreakIterator(string.characters(), length);
67    unsigned omitEnd = boundedTextBreakFollowing(it, omitStart + (length - keepCount) - 1, length);
68    omitStart = textBreakAtOrPreceding(it, omitStart);
69
70    unsigned truncatedLength = omitStart + 1 + (length - omitEnd);
71    ASSERT(truncatedLength <= length);
72
73    memcpy(buffer, string.characters(), sizeof(UChar) * omitStart);
74    buffer[omitStart] = horizontalEllipsis;
75    memcpy(&buffer[omitStart + 1], &string.characters()[omitEnd], sizeof(UChar) * (length - omitEnd));
76
77    return truncatedLength;
78}
79
80static unsigned rightTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer)
81{
82    ASSERT(keepCount < length);
83    ASSERT(keepCount < STRING_BUFFER_SIZE);
84
85    TextBreakIterator* it = characterBreakIterator(string.characters(), length);
86    unsigned keepLength = textBreakAtOrPreceding(it, keepCount);
87    unsigned truncatedLength = keepLength + 1;
88
89    memcpy(buffer, string.characters(), sizeof(UChar) * keepLength);
90    buffer[keepLength] = horizontalEllipsis;
91
92    return truncatedLength;
93}
94
95static float stringWidth(const Font& renderer, const UChar* characters, unsigned length)
96{
97    TextRun run(characters, length);
98    return renderer.width(run);
99}
100
101static String truncateString(const String& string, float maxWidth, const Font& font, TruncationFunction truncateToBuffer)
102{
103    if (string.isEmpty())
104        return string;
105
106    ASSERT(maxWidth >= 0);
107
108    float currentEllipsisWidth = stringWidth(font, &horizontalEllipsis, 1);
109
110    UChar stringBuffer[STRING_BUFFER_SIZE];
111    unsigned truncatedLength;
112    unsigned keepCount;
113    unsigned length = string.length();
114
115    if (length > STRING_BUFFER_SIZE) {
116        keepCount = STRING_BUFFER_SIZE - 1; // need 1 character for the ellipsis
117        truncatedLength = centerTruncateToBuffer(string, length, keepCount, stringBuffer);
118    } else {
119        keepCount = length;
120        memcpy(stringBuffer, string.characters(), sizeof(UChar) * length);
121        truncatedLength = length;
122    }
123
124    float width = stringWidth(font, stringBuffer, truncatedLength);
125    if (width <= maxWidth)
126        return string;
127
128    unsigned keepCountForLargestKnownToFit = 0;
129    float widthForLargestKnownToFit = currentEllipsisWidth;
130
131    unsigned keepCountForSmallestKnownToNotFit = keepCount;
132    float widthForSmallestKnownToNotFit = width;
133
134    if (currentEllipsisWidth >= maxWidth) {
135        keepCountForLargestKnownToFit = 1;
136        keepCountForSmallestKnownToNotFit = 2;
137    }
138
139    while (keepCountForLargestKnownToFit + 1 < keepCountForSmallestKnownToNotFit) {
140        ASSERT(widthForLargestKnownToFit <= maxWidth);
141        ASSERT(widthForSmallestKnownToNotFit > maxWidth);
142
143        float ratio = (keepCountForSmallestKnownToNotFit - keepCountForLargestKnownToFit)
144            / (widthForSmallestKnownToNotFit - widthForLargestKnownToFit);
145        keepCount = static_cast<unsigned>(maxWidth * ratio);
146
147        if (keepCount <= keepCountForLargestKnownToFit) {
148            keepCount = keepCountForLargestKnownToFit + 1;
149        } else if (keepCount >= keepCountForSmallestKnownToNotFit) {
150            keepCount = keepCountForSmallestKnownToNotFit - 1;
151        }
152
153        ASSERT(keepCount < length);
154        ASSERT(keepCount > 0);
155        ASSERT(keepCount < keepCountForSmallestKnownToNotFit);
156        ASSERT(keepCount > keepCountForLargestKnownToFit);
157
158        truncatedLength = truncateToBuffer(string, length, keepCount, stringBuffer);
159
160        width = stringWidth(font, stringBuffer, truncatedLength);
161        if (width <= maxWidth) {
162            keepCountForLargestKnownToFit = keepCount;
163            widthForLargestKnownToFit = width;
164        } else {
165            keepCountForSmallestKnownToNotFit = keepCount;
166            widthForSmallestKnownToNotFit = width;
167        }
168    }
169
170    if (keepCountForLargestKnownToFit == 0) {
171        keepCountForLargestKnownToFit = 1;
172    }
173
174    if (keepCount != keepCountForLargestKnownToFit) {
175        keepCount = keepCountForLargestKnownToFit;
176        truncatedLength = truncateToBuffer(string, length, keepCount, stringBuffer);
177    }
178
179    return String(stringBuffer, truncatedLength);
180}
181
182String StringTruncator::centerTruncate(const String& string, float maxWidth, const Font& font)
183{
184    return truncateString(string, maxWidth, font, centerTruncateToBuffer);
185}
186
187String StringTruncator::rightTruncate(const String& string, float maxWidth, const Font& font)
188{
189    return truncateString(string, maxWidth, font, rightTruncateToBuffer);
190}
191
192float StringTruncator::width(const String& string, const Font& font)
193{
194    return stringWidth(font, string.characters(), string.length());
195}
196
197} // namespace WebCore
198