summaryrefslogtreecommitdiffstats
path: root/src/gui/image/qicon.cpp
blob: 0799ea71d0a0d085660e52ed4b66aa8ff1a7290f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the QtGui module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qicon.h"
#include "qiconengine.h"
#include "qiconengineplugin.h"
#include "private/qfactoryloader_p.h"
#include "qapplication.h"
#include "qstyleoption.h"
#include "qpainter.h"
#include "qfileinfo.h"
#include "qstyle.h"
#include "qpixmapcache.h"
#include "qvariant.h"
#include "qdebug.h"

#ifdef Q_WS_MAC
#include <private/qt_mac_p.h>
#include <Carbon/Carbon.h>
#endif

QT_BEGIN_NAMESPACE

/*!
    \enum QIcon::Mode

    This enum type describes the mode for which a pixmap is intended
    to be used. The currently defined modes are:

    \value Normal
         Display the pixmap when the user is
        not interacting with the icon, but the
        functionality represented by the icon is available.
    \value Disabled
         Display the pixmap when the
        functionality represented by the icon is not available.
    \value Active
         Display the pixmap when the
        functionality represented by the icon is available and
        the user is interacting with the icon, for example, moving the
        mouse over it or clicking it.
   \value Selected
        Display the pixmap when the item represented by the icon is
        selected.
*/

/*!
  \enum QIcon::State

  This enum describes the state for which a pixmap is intended to be
  used. The \e state can be:

  \value Off  Display the pixmap when the widget is in an "off" state
  \value On  Display the pixmap when the widget is in an "on" state
*/

static QBasicAtomicInt serialNumCounter = Q_BASIC_ATOMIC_INITIALIZER(1);

class QIconPrivate
{
public:
    QIconPrivate(): engine(0), ref(1), serialNum(serialNumCounter.fetchAndAddRelaxed(1)), detach_no(0), engine_version(2), v1RefCount(0) {}

    ~QIconPrivate() {
        if (engine_version == 1) {
            if (!v1RefCount->deref()) {
                delete engine;
                delete v1RefCount;
            }
        } else if (engine_version == 2) {
            delete engine;
        }
    }

    QIconEngine *engine;

    QAtomicInt ref;
    int serialNum;
    int detach_no;
    int engine_version;

    QAtomicInt *v1RefCount;
};


struct QPixmapIconEngineEntry
{
    QPixmapIconEngineEntry():mode(QIcon::Normal), state(QIcon::Off){}
    QPixmapIconEngineEntry(const QPixmap &pm, QIcon::Mode m = QIcon::Normal, QIcon::State s = QIcon::Off)
        :pixmap(pm), size(pm.size()), mode(m), state(s){}
    QPixmapIconEngineEntry(const QString &file, const QSize &sz = QSize(), QIcon::Mode m = QIcon::Normal, QIcon::State s = QIcon::Off)
        :fileName(file), size(sz), mode(m), state(s){}
    QPixmap pixmap;
    QString fileName;
    QSize size;
    QIcon::Mode mode;
    QIcon::State state;
    bool isNull() const {return (fileName.isEmpty() && pixmap.isNull()); }
};

class QPixmapIconEngine : public QIconEngineV2 {
public:
    QPixmapIconEngine();
    QPixmapIconEngine(const QPixmapIconEngine &);
    ~QPixmapIconEngine();
    void paint(QPainter *painter, const QRect &rect, QIcon::Mode mode, QIcon::State state);
    QPixmap pixmap(const QSize &size, QIcon::Mode mode, QIcon::State state);
    QPixmapIconEngineEntry *bestMatch(const QSize &size, QIcon::Mode mode, QIcon::State state, bool sizeOnly);
    QSize actualSize(const QSize &size, QIcon::Mode mode, QIcon::State state);
    void addPixmap(const QPixmap &pixmap, QIcon::Mode mode, QIcon::State state);
    void addFile(const QString &fileName, const QSize &size, QIcon::Mode mode, QIcon::State state);

    // v2 functions
    QString key() const;
    QIconEngineV2 *clone() const;
    bool read(QDataStream &in);
    bool write(QDataStream &out) const;
    void virtual_hook(int id, void *data);

private:
    QPixmapIconEngineEntry *tryMatch(const QSize &size, QIcon::Mode mode, QIcon::State state);
    QVector<QPixmapIconEngineEntry> pixmaps;

    friend QDataStream &operator<<(QDataStream &s, const QIcon &icon);
};

QPixmapIconEngine::QPixmapIconEngine()
{
}

QPixmapIconEngine::QPixmapIconEngine(const QPixmapIconEngine &other)
    : QIconEngineV2(other), pixmaps(other.pixmaps)
{
}

QPixmapIconEngine::~QPixmapIconEngine()
{
}

void QPixmapIconEngine::paint(QPainter *painter, const QRect &rect, QIcon::Mode mode, QIcon::State state)
{
    QSize pixmapSize = rect.size();
#if defined(Q_WS_MAC) && !defined(Q_WS_MAC64)
    pixmapSize *= (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_4) ? HIGetScaleFactor() : 1;
#endif
    painter->drawPixmap(rect, pixmap(pixmapSize, mode, state));
}

static inline int area(const QSize &s) { return s.width() * s.height(); }

// returns the smallest of the two that is still larger than or equal to size.
static QPixmapIconEngineEntry *bestSizeMatch( const QSize &size, QPixmapIconEngineEntry *pa, QPixmapIconEngineEntry *pb)
{
    int s = area(size);
    if (pa->size == QSize() && pa->pixmap.isNull()) {
        pa->pixmap = QPixmap(pa->fileName);
        pa->size = pa->pixmap.size();
    }
    int a = area(pa->size);
    if (pb->size == QSize() && pb->pixmap.isNull()) {
        pb->pixmap = QPixmap(pb->fileName);
        pb->size = pb->pixmap.size();
    }
    int b = area(pb->size);
    int res = a;
    if (qMin(a,b) >= s)
        res = qMin(a,b);
    else
        res = qMax(a,b);
    if (res == a)
        return pa;
    return pb;
}

QPixmapIconEngineEntry *QPixmapIconEngine::tryMatch(const QSize &size, QIcon::Mode mode, QIcon::State state)
{
    QPixmapIconEngineEntry *pe = 0;
    for (int i = 0; i < pixmaps.count(); ++i)
        if (pixmaps.at(i).mode == mode && pixmaps.at(i).state == state) {
            if (pe)
                pe = bestSizeMatch(size, &pixmaps[i], pe);
            else
                pe = &pixmaps[i];
        }
    return pe;
}


QPixmapIconEngineEntry *QPixmapIconEngine::bestMatch(const QSize &size, QIcon::Mode mode, QIcon::State state, bool sizeOnly)
{
    QPixmapIconEngineEntry *pe = tryMatch(size, mode, state);
    while (!pe){
        QIcon::State oppositeState = (state == QIcon::On) ? QIcon::Off : QIcon::On;
        if (mode == QIcon::Disabled || mode == QIcon::Selected) {
            QIcon::Mode oppositeMode = (mode == QIcon::Disabled) ? QIcon::Selected : QIcon::Disabled;
            if ((pe = tryMatch(size, QIcon::Normal, state)))
                break;
            if ((pe = tryMatch(size, QIcon::Active, state)))
                break;
            if ((pe = tryMatch(size, mode, oppositeState)))
                break;
            if ((pe = tryMatch(size, QIcon::Normal, oppositeState)))
                break;
            if ((pe = tryMatch(size, QIcon::Active, oppositeState)))
                break;
            if ((pe = tryMatch(size, oppositeMode, state)))
                break;
            if ((pe = tryMatch(size, oppositeMode, oppositeState)))
                break;
        } else {
            QIcon::Mode oppositeMode = (mode == QIcon::Normal) ? QIcon::Active : QIcon::Normal;
            if ((pe = tryMatch(size, oppositeMode, state)))
                break;
            if ((pe = tryMatch(size, mode, oppositeState)))
                break;
            if ((pe = tryMatch(size, oppositeMode, oppositeState)))
                break;
            if ((pe = tryMatch(size, QIcon::Disabled, state)))
                break;
            if ((pe = tryMatch(size, QIcon::Selected, state)))
                break;
            if ((pe = tryMatch(size, QIcon::Disabled, oppositeState)))
                break;
            if ((pe = tryMatch(size, QIcon::Selected, oppositeState)))
                break;
        }

        if (!pe)
            return pe;
    }

    if (sizeOnly ? (pe->size.isNull() || !pe->size.isValid()) : pe->pixmap.isNull()) {
        pe->pixmap = QPixmap(pe->fileName);
        if (!pe->pixmap.isNull())
            pe->size = pe->pixmap.size();
    }

    return pe;
}

QPixmap QPixmapIconEngine::pixmap(const QSize &size, QIcon::Mode mode, QIcon::State state)
{
    QPixmap pm;
    QPixmapIconEngineEntry *pe = bestMatch(size, mode, state, false);
    if (pe)
        pm = pe->pixmap;

    if (pm.isNull()) {
        int idx = pixmaps.count();
        while (--idx >= 0) {
            if (pe == &pixmaps[idx]) {
                pixmaps.remove(idx);
                break;
            }
        }
        if (pixmaps.isEmpty())
            return pm;
        else
            return pixmap(size, mode, state);
    }

    QSize actualSize = pm.size();
    if (!actualSize.isNull() && (actualSize.width() > size.width() || actualSize.height() > size.height()))
        actualSize.scale(size, Qt::KeepAspectRatio);

    QString key = QLatin1String("$qt_icon_")
                  + QString::number(pm.cacheKey())
                  + QString::number(pe->mode)
                  + QString::number(actualSize.width())
                  + QLatin1Char('_')
                  + QString::number(actualSize.height())
                  + QLatin1Char('_');


    if (mode == QIcon::Active) {
        if (QPixmapCache::find(key + QString::number(mode), pm))
            return pm; // horray
        if (QPixmapCache::find(key + QString::number(QIcon::Normal), pm)) {
            QStyleOption opt(0);
            opt.palette = QApplication::palette();
            QPixmap active = QApplication::style()->generatedIconPixmap(QIcon::Active, pm, &opt);
            if (pm.cacheKey() == active.cacheKey())
                return pm;
        }
    }

    if (!QPixmapCache::find(key + QString::number(mode), pm)) {
        if (pm.size() != actualSize)
            pm = pm.scaled(actualSize, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
        if (pe->mode != mode && mode != QIcon::Normal) {
            QStyleOption opt(0);
            opt.palette = QApplication::palette();
            QPixmap generated = QApplication::style()->generatedIconPixmap(mode, pm, &opt);
            if (!generated.isNull())
                pm = generated;
        }
        QPixmapCache::insert(key + QString::number(mode), pm);
    }
    return pm;
}

QSize QPixmapIconEngine::actualSize(const QSize &size, QIcon::Mode mode, QIcon::State state)
{
    QSize actualSize;
    if (QPixmapIconEngineEntry *pe = bestMatch(size, mode, state, true))
        actualSize = pe->size;

    if (actualSize.isNull())
        return actualSize;

    if (!actualSize.isNull() && (actualSize.width() > size.width() || actualSize.height() > size.height()))
        actualSize.scale(size, Qt::KeepAspectRatio);
    return actualSize;
}

void QPixmapIconEngine::addPixmap(const QPixmap &pixmap, QIcon::Mode mode, QIcon::State state)
{
    if (!pixmap.isNull()) {
        QPixmapIconEngineEntry *pe = tryMatch(pixmap.size(), mode, state);
        if(pe && pe->size == pixmap.size()) {
            pe->pixmap = pixmap;
            pe->fileName.clear();
        } else {
            pixmaps += QPixmapIconEngineEntry(pixmap, mode, state);
        }
    }
}

void QPixmapIconEngine::addFile(const QString &fileName, const QSize &_size, QIcon::Mode mode, QIcon::State state)
{
    if (!fileName.isEmpty()) {
        QSize size = _size;
        QPixmap pixmap;

        QString abs = fileName;
        if (fileName.at(0) != QLatin1Char(':'))
            abs = QFileInfo(fileName).absoluteFilePath();

        for (int i = 0; i < pixmaps.count(); ++i) {
            if (pixmaps.at(i).mode == mode && pixmaps.at(i).state == state) {
                QPixmapIconEngineEntry *pe = &pixmaps[i];
                if(size == QSize()) {
                    pixmap = QPixmap(abs);
                    size = pixmap.size();
                }
                if (pe->size == QSize() && pe->pixmap.isNull()) {
                    pe->pixmap = QPixmap(pe->fileName);
                    pe->size = pe->pixmap.size();
                }
                if(pe->size == size) {
                    pe->pixmap = pixmap;
                    pe->fileName = abs;
                    return;
                }
            }
        }
        QPixmapIconEngineEntry e(abs, size, mode, state);
        e.pixmap = pixmap;
        pixmaps += e;
    }
}

QString QPixmapIconEngine::key() const
{
    return QLatin1String("QPixmapIconEngine");
}

QIconEngineV2 *QPixmapIconEngine::clone() const
{
    return new QPixmapIconEngine(*this);
}

bool QPixmapIconEngine::read(QDataStream &in)
{
    int num_entries;
    QPixmap pm;
    QString fileName;
    QSize sz;
    uint mode;
    uint state;

    in >> num_entries;
    for (int i=0; i < num_entries; ++i) {
        if (in.atEnd()) {
            pixmaps.clear();
            return false;
        }
        in >> pm;
        in >> fileName;
        in >> sz;
        in >> mode;
        in >> state;
        if (pm.isNull()) {
            addFile(fileName, sz, QIcon::Mode(mode), QIcon::State(state));
        } else {
            QPixmapIconEngineEntry pe(fileName, sz, QIcon::Mode(mode), QIcon::State(state));
            pe.pixmap = pm;
            pixmaps += pe;
        }
    }
    return true;
}

bool QPixmapIconEngine::write(QDataStream &out) const
{
    int num_entries = pixmaps.size();
    out << num_entries;
    for (int i=0; i < num_entries; ++i) {
        if (pixmaps.at(i).pixmap.isNull())
            out << QPixmap(pixmaps.at(i).fileName);
        else
            out << pixmaps.at(i).pixmap;
        out << pixmaps.at(i).fileName;
        out << pixmaps.at(i).size;
        out << (uint) pixmaps.at(i).mode;
        out << (uint) pixmaps.at(i).state;
    }
    return true;
}

void QPixmapIconEngine::virtual_hook(int id, void *data)
{
    switch (id) {
    case QIconEngineV2::AvailableSizesHook: {
        QIconEngineV2::AvailableSizesArgument &arg =
            *reinterpret_cast<QIconEngineV2::AvailableSizesArgument*>(data);
        arg.sizes.clear();
        for (int i = 0; i < pixmaps.size(); ++i) {
            QPixmapIconEngineEntry &pe = pixmaps[i];
            if (pe.size == QSize() && pe.pixmap.isNull()) {
                pe.pixmap = QPixmap(pe.fileName);
                pe.size = pe.pixmap.size();
            }
            if (pe.mode == arg.mode && pe.state == arg.state && !pe.size.isEmpty())
                arg.sizes.push_back(pe.size);
        }
        break;
    }
    default:
        QIconEngineV2::virtual_hook(id, data);
    }
}

#if !defined (QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, loader,
    (QIconEngineFactoryInterface_iid, QLatin1String("/iconengines"), Qt::CaseInsensitive))
Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, loaderV2,
    (QIconEngineFactoryInterfaceV2_iid, QLatin1String("/iconengines"), Qt::CaseInsensitive))
#endif



/*!
  \class QIcon

  \brief The QIcon class provides scalable icons in different modes
  and states.

  \ingroup multimedia
  \ingroup shared
  \mainclass

  A QIcon can generate smaller, larger, active, and disabled pixmaps
  from the set of pixmaps it is given. Such pixmaps are used by Qt
  widgets to show an icon representing a particular action.

  The simplest use of QIcon is to create one from a QPixmap file or
  resource, and then use it, allowing Qt to work out all the required
  icon styles and sizes. For example:

  \snippet doc/src/snippets/code/src_gui_image_qicon.cpp 0

  To undo a QIcon, simply set a null icon in its place:

  \snippet doc/src/snippets/code/src_gui_image_qicon.cpp 1

  Use the QImageReader::supportedImageFormats() and
  QImageWriter::supportedImageFormats() functions to retrieve a
  complete list of the supported file formats.

  When you retrieve a pixmap using pixmap(QSize, Mode, State), and no
  pixmap for this given size, mode and state has been added with
  addFile() or addPixmap(), then QIcon will generate one on the
  fly. This pixmap generation happens in a QIconEngineV2. The default
  engine scales pixmaps down if required, but never up, and it uses
  the current style to calculate a disabled appearance. By using
  custom icon engines, you can customize every aspect of generated
  icons. With QIconEnginePluginV2 it is possible to register different
  icon engines for different file suffixes, making it possible for
  third parties to provide additional icon engines to those included
  with Qt.

  \note Since Qt 4.2, an icon engine that supports SVG is included.

  \section1 Making Classes that Use QIcon

  If you write your own widgets that have an option to set a small
  pixmap, consider allowing a QIcon to be set for that pixmap.  The
  Qt class QToolButton is an example of such a widget.

  Provide a method to set a QIcon, and when you draw the icon, choose
  whichever pixmap is appropriate for the current state of your widget.
  For example:
  \snippet doc/src/snippets/code/src_gui_image_qicon.cpp 2

  You might also make use of the \c Active mode, perhaps making your
  widget \c Active when the mouse is over the widget (see \l
  QWidget::enterEvent()), while the mouse is pressed pending the
  release that will activate the function, or when it is the currently
  selected item. If the widget can be toggled, the "On" mode might be
  used to draw a different icon.

  \img icon.png QIcon

  \sa {fowler}{GUI Design Handbook: Iconic Label}, {Icons Example}
*/


/*!
  Constructs a null icon.
*/
QIcon::QIcon()
    : d(0)
{
}

/*!
  Constructs an icon from a \a pixmap.
 */
QIcon::QIcon(const QPixmap &pixmap)
    :d(0)
{
    addPixmap(pixmap);
}

/*!
  Constructs a copy of \a other. This is very fast.
*/
QIcon::QIcon(const QIcon &other)
    :d(other.d)
{
    if (d)
        d->ref.ref();
}

/*!
    Constructs an icon from the file with the given \a fileName. The
    file will be loaded on demand.

    If \a fileName contains a relative path (e.g. the filename only)
    the relevant file must be found relative to the runtime working
    directory.

    The file name can be either refer to an actual file on disk or to
    one of the application's embedded resources.  See the
    \l{resources.html}{Resource System} overview for details on how to
    embed images and other resource files in the application's
    executable.

    Use the QImageReader::supportedImageFormats() and
    QImageWriter::supportedImageFormats() functions to retrieve a
    complete list of the supported file formats.
*/
QIcon::QIcon(const QString &fileName)
    : d(0)
{
    addFile(fileName);
}


/*!
    Creates an icon with a specific icon \a engine. The icon takes
    ownership of the engine.
*/
QIcon::QIcon(QIconEngine *engine)
    :d(new QIconPrivate)
{
    d->engine_version = 1;
    d->engine = engine;
    d->v1RefCount = new QAtomicInt(1);
}

/*!
    Creates an icon with a specific icon \a engine. The icon takes
    ownership of the engine.
*/
QIcon::QIcon(QIconEngineV2 *engine)
    :d(new QIconPrivate)
{
    d->engine_version = 2;
    d->engine = engine;
}

/*!
    Destroys the icon.
*/
QIcon::~QIcon()
{
    if (d && !d->ref.deref())
        delete d;
}

/*!
    Assigns the \a other icon to this icon and returns a reference to
    this icon.
*/
QIcon &QIcon::operator=(const QIcon &other)
{
    if (other.d)
        other.d->ref.ref();
    if (d && !d->ref.deref())
        delete d;
    d = other.d;
    return *this;
}

/*!
   Returns the icon as a QVariant.
*/
QIcon::operator QVariant() const
{
    return QVariant(QVariant::Icon, this);
}

/*! \obsolete

    Returns a number that identifies the contents of this
    QIcon object. Distinct QIcon objects can have
    the same serial number if they refer to the same contents
    (but they don't have to). Also, the serial number of
    a QIcon object may change during its lifetime.

    Use cacheKey() instead.

    A null icon always has a serial number of 0.

    Serial numbers are mostly useful in conjunction with caching.

    \sa QPixmap::serialNumber()
*/

int QIcon::serialNumber() const
{
    return d ? d->serialNum : 0;
}

/*!
    Returns a number that identifies the contents of this QIcon
    object. Distinct QIcon objects can have the same key if
    they refer to the same contents.
    \since 4.3

    The cacheKey() will change when the icon is altered via
    addPixmap() or addFile().

    Cache keys are mostly useful in conjunction with caching.

    \sa QPixmap::cacheKey()
*/
qint64 QIcon::cacheKey() const
{
    if (!d)
        return 0;
    return (((qint64) d->serialNum) << 32) | ((qint64) (d->detach_no));
}

/*!
  Returns a pixmap with the requested \a size, \a mode, and \a
  state, generating one if necessary. The pixmap might be smaller than
  requested, but never larger.

  \sa actualSize(), paint()
*/
QPixmap QIcon::pixmap(const QSize &size, Mode mode, State state) const
{
    if (!d)
        return QPixmap();
    return d->engine->pixmap(size, mode, state);
}

/*!
    \fn QPixmap QIcon::pixmap(int w, int h, Mode mode = Normal, State state = Off) const

    \overload

    Returns a pixmap of size QSize(\a w, \a h). The pixmap might be smaller than
    requested, but never larger.
*/

/*!
    \fn QPixmap QIcon::pixmap(int extent, Mode mode = Normal, State state = Off) const

    \overload

    Returns a pixmap of size QSize(\a extent, \a extent). The pixmap might be smaller
    than requested, but never larger.
*/

/*!  Returns the actual size of the icon for the requested \a size, \a
  mode, and \a state. The result might be smaller than requested, but
  never larger.

  \sa pixmap(), paint()
*/
QSize QIcon::actualSize(const QSize &size, Mode mode, State state) const
{
    if (!d)
        return QSize();
    return d->engine->actualSize(size, mode, state);
}


/*!
    Uses the \a painter to paint the icon with specified \a alignment,
    required \a mode, and \a state into the rectangle \a rect.

    \sa actualSize(), pixmap()
*/
void QIcon::paint(QPainter *painter, const QRect &rect, Qt::Alignment alignment, Mode mode, State state) const
{
    if (!d || !painter)
        return;
    QRect alignedRect = QStyle::alignedRect(painter->layoutDirection(), alignment, d->engine->actualSize(rect.size(), mode, state), rect);
    d->engine->paint(painter, alignedRect, mode, state);
}

/*!
    \fn void QIcon::paint(QPainter *painter, int x, int y, int w, int h, Qt::Alignment alignment,
                          Mode mode, State state) const

    \overload

    Paints the icon into the rectangle QRect(\a x, \a y, \a w, \a h).
*/

/*!
    Returns true if the icon is empty; otherwise returns false.

    An icon is empty if it has neither a pixmap nor a filename.

    Note: Even a non-null icon might not be able to create valid
    pixmaps, eg. if the file does not exist or cannot be read.
*/
bool QIcon::isNull() const
{
    return !d;
}

/*!\internal
 */
bool QIcon::isDetached() const
{
    return !d || d->ref == 1;
}

/*! \internal
 */
void QIcon::detach()
{
    if (d) {
        if (d->ref != 1) {
            QIconPrivate *x = new QIconPrivate;
            if (d->engine_version > 1) {
                QIconEngineV2 *engine = static_cast<QIconEngineV2 *>(d->engine);
                x->engine = engine->clone();
            } else {
                x->engine = d->engine;
                x->v1RefCount = d->v1RefCount;
                x->v1RefCount->ref();
            }
            x->engine_version = d->engine_version;
            if (!d->ref.deref())
                delete d;
            d = x;
        }
        ++d->detach_no;
    }
}

/*!
    Adds \a pixmap to the icon, as a specialization for \a mode and
    \a state.

    Custom icon engines are free to ignore additionally added
    pixmaps.

    \sa addFile()
*/
void QIcon::addPixmap(const QPixmap &pixmap, Mode mode, State state)
{
    if (pixmap.isNull())
        return;
    if (!d) {
        d = new QIconPrivate;
        d->engine = new QPixmapIconEngine;
    } else {
        detach();
    }
    d->engine->addPixmap(pixmap, mode, state);
}


/*!  Adds an image from the file with the given \a fileName to the
     icon, as a specialization for \a size, \a mode and \a state. The
     file will be loaded on demand. Note: custom icon engines are free
     to ignore additionally added pixmaps.

     If \a fileName contains a relative path (e.g. the filename only)
     the relevant file must be found relative to the runtime working
     directory.

    The file name can be either refer to an actual file on disk or to
    one of the application's embedded resources. See the
    \l{resources.html}{Resource System} overview for details on how to
    embed images and other resource files in the application's
    executable.

    Use the QImageReader::supportedImageFormats() and
    QImageWriter::supportedImageFormats() functions to retrieve a
    complete list of the supported file formats.

    Note: When you add a non-empty filename to a QIcon, the icon becomes
    non-null, even if the file doesn't exist or points to a corrupt file.

    \sa addPixmap()
 */
void QIcon::addFile(const QString &fileName, const QSize &size, Mode mode, State state)
{
    if (fileName.isEmpty())
        return;
    if (!d) {
#if !defined (QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
        QFileInfo info(fileName);
        QString suffix = info.suffix();
        if (!suffix.isEmpty()) {
            // first try version 2 engines..
            if (QIconEngineFactoryInterfaceV2 *factory = qobject_cast<QIconEngineFactoryInterfaceV2*>(loaderV2()->instance(suffix))) {
                if (QIconEngine *engine = factory->create(fileName)) {
                    d = new QIconPrivate;
                    d->engine = engine;
                }
            }
            // ..then fall back and try to load version 1 engines
            if (!d) {
                if (QIconEngineFactoryInterface *factory = qobject_cast<QIconEngineFactoryInterface*>(loader()->instance(suffix))) {
                    if (QIconEngine *engine = factory->create(fileName)) {
                        d = new QIconPrivate;
                        d->engine = engine;
                        d->engine_version = 1;
                        d->v1RefCount = new QAtomicInt(1);
                    }
                }
            }
        }
#endif
        // ...then fall back to the default engine
        if (!d) {
            d = new QIconPrivate;
            d->engine = new QPixmapIconEngine;
        }
    } else {
        detach();
    }
    d->engine->addFile(fileName, size, mode, state);
}

/*!
    \since 4.5

    Returns a list of available icon sizes for the specified \a mode and
    \a state.
*/
QList<QSize> QIcon::availableSizes(Mode mode, State state) const
{
    if (!d || !d->engine || d->engine_version < 2)
        return QList<QSize>();
    QIconEngineV2 *engine = static_cast<QIconEngineV2*>(d->engine);
    return engine->availableSizes(mode, state);
}

/*****************************************************************************
  QIcon stream functions
 *****************************************************************************/
#if !defined(QT_NO_DATASTREAM)
/*!
    \fn QDataStream &operator<<(QDataStream &stream, const QIcon &icon)
    \relates QIcon
    \since 4.2

    Writes the given \a icon to the given \a stream as a PNG
    image. If the icon contains more than one image, all images will
    be written to the stream. Note that writing the stream to a file
    will not produce a valid image file.
*/

QDataStream &operator<<(QDataStream &s, const QIcon &icon)
{
    if (s.version() >= QDataStream::Qt_4_3) {
        if (icon.isNull()) {
            s << QString();
        } else {
            if (icon.d->engine_version > 1) {
                QIconEngineV2 *engine = static_cast<QIconEngineV2 *>(icon.d->engine);
                s << engine->key();
                engine->write(s);
            } else {
                // not really supported
                qWarning("QIcon: Cannot stream QIconEngine. Use QIconEngineV2 instead.");
            }
        }
    } else if (s.version() == QDataStream::Qt_4_2) {
        if (icon.isNull()) {
            s << 0;
        } else {
            QPixmapIconEngine *engine = static_cast<QPixmapIconEngine *>(icon.d->engine);
            int num_entries = engine->pixmaps.size();
            s << num_entries;
            for (int i=0; i < num_entries; ++i) {
                s << engine->pixmaps.at(i).pixmap;
                s << engine->pixmaps.at(i).fileName;
                s << engine->pixmaps.at(i).size;
                s << (uint) engine->pixmaps.at(i).mode;
                s << (uint) engine->pixmaps.at(i).state;
            }
        }
    } else {
        s << QPixmap(icon.pixmap(22,22));
    }
    return s;
}

/*!
    \fn QDataStream &operator>>(QDataStream &stream, QIcon &icon)
    \relates QIcon
    \since 4.2

    Reads an image, or a set of images, from the given \a stream into
    the given \a icon.
*/

QDataStream &operator>>(QDataStream &s, QIcon &icon)
{
    if (s.version() >= QDataStream::Qt_4_3) {
        icon = QIcon();
        QString key;
        s >> key;
        if (key == QLatin1String("QPixmapIconEngine")) {
            icon.d = new QIconPrivate;
            QIconEngineV2 *engine = new QPixmapIconEngine;
            icon.d->engine = engine;
            engine->read(s);
#if !defined (QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
        } else if (QIconEngineFactoryInterfaceV2 *factory = qobject_cast<QIconEngineFactoryInterfaceV2*>(loaderV2()->instance(key))) {
            if (QIconEngineV2 *engine= factory->create()) {
                icon.d = new QIconPrivate;
                icon.d->engine = engine;
                engine->read(s);
            }
#endif
        }
    } else if (s.version() == QDataStream::Qt_4_2) {
        icon = QIcon();
        int num_entries;
        QPixmap pm;
        QString fileName;
        QSize sz;
        uint mode;
        uint state;

        s >> num_entries;
        for (int i=0; i < num_entries; ++i) {
            s >> pm;
            s >> fileName;
            s >> sz;
            s >> mode;
            s >> state;
            if (pm.isNull())
                icon.addFile(fileName, sz, QIcon::Mode(mode), QIcon::State(state));
            else
                icon.addPixmap(pm, QIcon::Mode(mode), QIcon::State(state));
        }
    } else {
        QPixmap pm;
        s >> pm;
        icon.addPixmap(pm);
    }
    return s;
}

#endif //QT_NO_DATASTREAM


#ifdef QT3_SUPPORT

static int widths[2] = { 22, 32 };
static int heights[2] = { 22, 32 };

static QSize pixmapSizeHelper(QIcon::Size which)
{
    int i = 0;
    if (which == QIcon::Large)
        i = 1;
    return QSize(widths[i], heights[i]);
}

/*!
    \enum QIcon::Size
    \compat

    \value Small  Use QStyle::pixelMetric(QStyle::PM_SmallIconSize) instead.
    \value Large  Use QStyle::pixelMetric(QStyle::PM_LargeIconSize) instead.
    \value Automatic  N/A.
*/

/*!
    Use pixmap(QSize(...), \a mode, \a state), where the first
    argument is an appropriate QSize instead of a \l Size value.

    \sa pixmapSize()
*/
QPixmap QIcon::pixmap(Size size, Mode mode, State state) const
{ return pixmap(pixmapSizeHelper(size), mode, state); }

/*!
    Use pixmap(QSize(...), mode, \a state), where the first argument
    is an appropriate QSize instead of a \l Size value, and the
    second argument is QIcon::Normal or QIcon::Disabled, depending on
    the value of \a enabled.

    \sa pixmapSize()
*/
QPixmap QIcon::pixmap(Size size, bool enabled, State state) const
{ return pixmap(pixmapSizeHelper(size), enabled ? Normal : Disabled, state); }

/*!
    Use one of the other pixmap() overloads.
*/
QPixmap QIcon::pixmap() const
{ return pixmap(pixmapSizeHelper(Small), Normal, Off); }

/*!
    The pixmap() function now takes a QSize instead of a QIcon::Size,
    so there is no need for this function in new code.
*/
void QIcon::setPixmapSize(Size which, const QSize &size)
{
    int i = 0;
    if (which == Large)
        i = 1;
    widths[i] = size.width();
    heights[i] = size.height();
}

/*!
    Use QStyle::pixelMetric() with QStyle::PM_SmallIconSize or
    QStyle::PM_LargeIconSize as the first argument, depending on \a
    which.
*/
QSize QIcon::pixmapSize(Size which)
{
    return pixmapSizeHelper(which);
}

/*!
    \fn void QIcon::reset(const QPixmap &pixmap, Size size)

    Use the constructor that takes a QPixmap and operator=().
*/

/*!
    \fn void QIcon::setPixmap(const QPixmap &pixmap, Size size, Mode mode, State state)

    Use addPixmap(\a pixmap, \a mode, \a state) instead. The \a size
    parameter is ignored.
*/

/*!
    \fn void QIcon::setPixmap(const QString &fileName, Size size, Mode mode, State state)

    Use addFile(\a fileName, \a mode, \a state) instead. The \a size
    parameter is ignored.
*/

#endif // QT3_SUPPORT

/*!
    \fn DataPtr &QIcon::data_ptr()
    \internal
*/

/*!
    \typedef QIcon::DataPtr
    \internal
*/

QT_END_NAMESPACE