File: khtml_caret_p.h

package info (click to toggle)
khtml 5.54.0-1
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 18,940 kB
  • sloc: cpp: 206,281; java: 4,060; ansic: 2,829; perl: 2,313; yacc: 1,497; python: 339; sh: 141; xml: 37; makefile: 7
file content (1272 lines) | stat: -rw-r--r-- 38,060 bytes parent folder | download | duplicates (2)
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
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
/* This file is part of the KDE project
 *
 * Copyright (C) 2003-2004 Leo Savernik <l.savernik@aon.at>
 *
 * 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.
 */

#ifndef KHTML_CARET_P_H
#define KHTML_CARET_P_H

#include "rendering/render_table.h"

#define DEBUG_CARETMODE 0

class QFontMetrics;

namespace DOM
{
class NodeImpl;
class ElementImpl;
}

namespace khtml
{

/** caret advance policy.
 *
 * Used to determine which elements are taken into account when the caret is
 * advanced. Later policies pose refinements of all former
 * policies.
 * @param LeafsOnly advance from leave render object to leaf render object
 *  (It will allow outside flow positions if a flow wouldn't be reachable
 *  otherwise).
 * @param IndicatedFlows place caret also at the beginning/end of flows
 *  that have at least one visible border at any side.
 *  (It will allow not indicated flow positions if a flow wouldn't
 *  be reachable otherwise).
 * @param VisibleFlows place caret also at the beginning/end of any flow
 *  that has a renderer.
 */
enum CaretAdvancePolicy {
    LeafsOnly, IndicatedFlows, VisibleFlows
};

/** contextual information about the caret which is related to the view.
 * An object of this class is only instantiated when it is needed.
 */
struct CaretViewContext {
    int freqTimerId;        // caret blink frequency timer id
    int x, y;           // caret position in viewport coordinates
    // (y specifies the top, not the baseline)
    int width;          // width of caret in pixels
    int height;         // height of caret in pixels
    bool visible;       // true if currently visible.
    bool displayed;     // true if caret is to be displayed at all.
    bool caretMoved;        // set to true once caret has been moved in page
    // how to display the caret when view is not focused
    KHTMLPart::CaretDisplayPolicy displayNonFocused;

    /** For natural traversal of lines, the original x position is saved, and
     * the actual x is set to the first character whose x position is
     * greater than origX.
     *
     * origX is reset to x whenever the caret is moved horizontally or placed
     * by the mouse.
     */
    int origX;

    bool keyReleasePending; // true if keypress under caret mode awaits
    // corresponding release event
    CaretViewContext() : freqTimerId(-1), x(0), y(0), width(1), height(16),
        visible(true), displayed(false), caretMoved(false),
        displayNonFocused(KHTMLPart::CaretInvisible), origX(0),
        keyReleasePending(false)
    {}
};

class LinearDocument;

/**
 * Stores objects of a certain type, and calls delete on each of them
 * when this data structure is destroyed.
 *
 * As this structure merely consists of a vector of pointers, all objects
 * allocated can be traversed as seen fit.
 *
 * @author Leo Savernik
 * @internal
 */
template<class T> class MassDeleter : public QVector<T *>
{
public:
    MassDeleter(size_t reserved = 1)
    {
        this->reserve(reserved);
    }
    ~MassDeleter()
    {
        typename QVector<T *>::Iterator nd = this->end();
        for (typename QVector<T *>::Iterator it = this->begin(); it != nd; ++it) {
            delete *it;
        }
    }
};

class CaretBoxLine;

/**
 * Represents a rectangular box within which the caret is located.
 *
 * The caret box serves as a wrapper for inline boxes of all kind. It either
 * wraps an InlineBox, InlineTextBox, or InlineFlowBox, or if no such boxes
 * exist for a certain context, it contains the relevant information directly.
 *
 * This class will be constructed whenever a caret position has to be described.
 * @author Leo Savernik
 * @internal
 */
class CaretBox
{
protected:
    InlineBox *_box;      // associated inline box if available.
    short _w;         // width of box in pixels
    int _h;           // height of box in pixels
    int _x;           // x coordinate relative to containing block
    int _y;           // y coordinate relative to containing block
    RenderBox *cb;        // containing block
    bool _outside: 1;     // true when representing the outside of the element
    bool outside_end: 1;      // at ending outside of element rather than at beginning
    // 29 bits unused

public:
    /** empty constructor for later assignment */
    CaretBox() {}
    /** initializes the caret box from the given inline box */
    CaretBox(InlineBox *ibox, bool outside, bool outsideEnd) : _box(ibox),
        _w((short)ibox->width()), _h(ibox->height()), _x(ibox->xPos()),
        _y(ibox->yPos()), cb(0), _outside(outside), outside_end(outsideEnd)
    {
        RenderObject *r = ibox->object();
        if (r) {
            cb = r->containingBlock();
        }
    }
    /** initializes the caret box from scratch */
    CaretBox(int x, int y, int w, int h, RenderBox *cb, bool outside, bool outsideEnd) :
        _box(0), _w((short)w), _h(h), _x(x), _y(y), cb(cb), _outside(outside),
        outside_end(outsideEnd)
    {}

    int width() const
    {
        return _w;
    }
    int height() const
    {
        return _h;
    }
    int xPos() const
    {
        return _x;
    }
    int yPos() const
    {
        return _y;
    }
    RenderBox *enclosingObject() const
    {
        return cb;
    }
    InlineBox *inlineBox() const
    {
        return _box;
    }

    /** returns the containing block of this caret box. If the caret box
     * resembles a block itself, its containing block is returned.
     */
    RenderBlock *containingBlock() const
    {
        return _box ? static_cast<RenderBlock *>(cb) : cb->containingBlock();
    }

    /** returns the replaced render object if this caret box represents one,
     * 0 otherwise.
     */

    /** returns true if this caret box represents an inline element, or text box,
     * otherwise false.
     */
    bool isInline() const
    {
        return _box;
    }
    /** returns true if this caret box represents an inline text box.
     */
    bool isInlineTextBox() const
    {
        return _box && _box->isInlineTextBox();
    }
    /** returns true if this caret box represents a line break
     */
    bool isLineBreak() const
    {
        return _box && _box->object() && _box->object()->isBR();
    }
    /** returns true when this caret box represents an ouside position of an
     * element.
     */
    bool isOutside() const
    {
        return _outside;
    }
    /** returns the position at which the outside is targeted at.
     *
     * This method's return value is meaningless if isOutside() is not true.
     * @return true if the outside end is meant, false if the outside beginning
     *    is meant.
     */
    bool isOutsideEnd() const
    {
        return outside_end;
    }
    /** returns the associated render object. */
    RenderObject *object() const
    {
        return _box ? _box->object() : cb;
    }

    /** returns the minimum offset for this caret box.
     */
    long minOffset() const
    {
        return _box && !isLineBreak() ? _box->minOffset() : 0;
    }
    /** returns the maximum offset for this caret box.
     */
    long maxOffset() const
    {
        return _box && !isLineBreak() ? _box->maxOffset() : 0;
    }

#if DEBUG_CARETMODE > 0
    void dump(QTextStream &ts, const QString &ind) const;
#endif

    friend class CaretBoxLine;
};

typedef MassDeleter<CaretBox> CaretBoxDeleter;

/**
 * Iterates over the elements of a caret box line.
 *
 * @author Leo Savernik
 * @internal
 */
class CaretBoxIterator
{
protected:
    CaretBoxLine *cbl;        // associated caret box line
    int index;            // current index

public:
    // Let standard constructor/copy constructor/destructor/assignment operator
    // be defined by the compiler. They do exactly what we want.
    CaretBoxIterator()
        : cbl(0), index(0)
    {
    }

    bool operator ==(const CaretBoxIterator &it) const
    {
        return cbl == it.cbl && index == it.index;
    }

    bool operator !=(const CaretBoxIterator &it) const
    {
        return !operator ==(it);
    }

    /** returns the current caret box.
     * @return current caret box
     */
    CaretBox *data() const;
    /** shortcut for \c data
     * @return current caret box
     */
    CaretBox *operator *() const
    {
        return data();
    }

    /** increments the iterator to point to the next caret box.
     */
    CaretBoxIterator &operator ++()
    {
        index++;
        return *this;
    }
    /** decrements the iterator to point to the previous caret box.
     */
    CaretBoxIterator &operator --()
    {
        index--;
        return *this;
    }

    friend class CaretBoxLine;
    friend class EditableCaretBoxIterator;
};

/**
 * Resembles a line consisting of caret boxes.
 *
 * To the contrary of InlineFlowBoxes which are nested as needed to map the
 * DOM to the rendered representation, it is sufficient for caret navigation
 * to provide a linear list of unnested caret boxes.
 *
 * \code
 * Example: The document fragment <p>a <i><b>c</b> f</i> g</p> will be
 * represented by three caret box lines which each one consists of caret boxes
 * as follows:
 * CaretBoxLine 1:
 *   CaretBox(cb=<p>, _box=0, _outside=true, outside_end=false)
 * CaretBoxLine 2:
 *   CaretBox(cb=<p>, _box=InlineTextBox("a "), _outside=false)
 *   CaretBox(cb=<p>, _box=InlineFlowBox(<i>), _outside=true, outside_end=false)
 *   CaretBox(cb=<p>, _box=InlineFlowBox(<b>), _outside=true, outside_end=false)
 *   CaretBox(cb=<p>, _box=InlineTextBox("c"), _outside=false)
 *   CaretBox(cb=<p>, _box=InlineFlowBox(<b>), _outside=true, outside_end=true)
 *   CaretBox(cb=<p>, _box=InlineTextBox(" f"), _outside=false)
 *   CaretBox(cb=<p>, _box=InlineFlowBox(<i>), _outside=true, outside_end=true)
 *   CaretBox(cb=<p>, _box=InlineTextBox(" g"), _outside=true, outside_end=true)
 * CaretBoxLine 3:
 *   CaretBox(cb=<p>, _box=0, _outside=true, outside_end=true)
 * \endcode
 */
class CaretBoxLine
{
protected:
    CaretBoxDeleter caret_boxes;
    // base flow box which caret boxes have been constructed for
    InlineFlowBox *basefb;

    CaretBoxLine() : caret_boxes(8), basefb(0) {}
    CaretBoxLine(InlineFlowBox *basefb) : caret_boxes(8), basefb(basefb) {}
public:
#if DEBUG_CARETMODE > 3
    ~CaretBoxLine()
    {
        qCDebug(KHTML_LOG) << "called";
    }
#endif

    CaretBoxIterator begin()
    {
        CaretBoxIterator it;
        it.cbl = this;
        it.index = 0;
        return it;
    }
    CaretBoxIterator end()
    {
        CaretBoxIterator it;
        it.cbl = this;
        it.index = caret_boxes.size();
        return it;
    }
    CaretBoxIterator preBegin()
    {
        CaretBoxIterator it;
        it.cbl = this;
        it.index = -1;
        return it;
    }
    CaretBoxIterator preEnd()
    {
        CaretBoxIterator it;
        it.cbl = this;
        it.index = caret_boxes.size() - 1;
        return it;
    }

    /** returns the base inline flow box which the caret boxes of this
     * caret box line have been constructed from.
     *
     * This is generally a root line box, but may be an inline flow box when the
     * base is restricted to an inline element.
     */
    InlineFlowBox *baseFlowBox() const
    {
        return basefb;
    }

    /** returns the containing block */
    RenderBlock *containingBlock() const
    {
        return caret_boxes[0]->containingBlock();
    }
    /** returns the enclosing object */
    RenderBox *enclosingObject() const
    {
        return caret_boxes[0]->enclosingObject();
    }

    /** returns whether this caret box line is outside.
     * @return true if this caret box represents an outside position of this
     *    line box' containing block, false otherwise.
     */
    bool isOutside() const
    {
        const CaretBox *cbox = caret_boxes[0];
        return !cbox->isInline() && cbox->isOutside();
    }

    /** returns whether this caret box line is at the outside end.
     *
     * The result cannot be relied upon unless isOutside() returns true.
     */
    bool isOutsideEnd() const
    {
        return caret_boxes[0]->isOutsideEnd();
    }

    /** constructs a new caret box line out of the given inline flow box
     * @param deleter deleter which handles alloc+dealloc of the object
     * @param baseFlowBox basic flow box which to create a caret line box from
     * @param seekBox seek this box within the constructed line
     * @param seekOutside denoting whether position is outside of seekBox
     * @param seekOutsideEnd whether at the outside end of seekBox
     * @param iter returns an iterator that corresponds to seekBox. If no suitable
     *    caret box exists, it will return end()
     * @param seekObject seek this render object within the constructed line.
     *    It will only be regarded if \c seekBox is 0. \c iter will then point
     *    to the first caret box whose render object matches.
     */
    static CaretBoxLine *constructCaretBoxLine(MassDeleter<CaretBoxLine> *deleter,
            InlineFlowBox *baseFlowBox, InlineBox *seekBox, bool seekOutside,
            bool seekOutsideEnd, CaretBoxIterator &iter,
            RenderObject *seekObject = 0) /*KHTML_NO_EXPORT*/;

    /** constructs a new caret box line for the given render block.
     * @param deleter deleter which handles alloc+dealloc of the object
     * @param cb render block or render replaced
     * @param outside true when line is to be constructed outside
     * @param outsideEnd true when the ending outside is meant
     * @param iter returns the iterator to the caret box representing the given
     *    position for \c cb
     */
    static CaretBoxLine *constructCaretBoxLine(MassDeleter<CaretBoxLine> *deleter,
            RenderBox *cb, bool outside, bool outsideEnd, CaretBoxIterator &iter) /*KHTML_NO_EXPORT*/;

#if DEBUG_CARETMODE > 0
    void dump(QTextStream &ts, const QString &ind) const;
    QString information() const
    {
        QString result;
        QTextStream ts(&result, QIODevice::WriteOnly);
        dump(ts, QString());
        return result;
    }
#endif

protected:
    /** contains the seek parameters */
    struct SeekBoxParams {
        InlineBox *box;
        bool outside;
        bool outsideEnd;
        bool found;
        RenderObject *r;    // if box is 0, seek for equal render objects instead
        CaretBoxIterator &it;

        SeekBoxParams(InlineBox *box, bool outside, bool outsideEnd, RenderObject *obj, CaretBoxIterator &it)
            : box(box), outside(outside), outsideEnd(outsideEnd), found(false), r(obj), it(it)
        {}

        /** compares whether this seek box matches the given specification */
        bool equalsBox(const InlineBox *box, bool outside, bool outsideEnd) const
        {
            return (this->box && this->box == box
                    || this->r == box->object())
                   && this->outside == outside
                   && (!this->outside || this->outsideEnd == outsideEnd);
        }
        /** compares whether this seek box matches the given caret box */
        bool operator ==(const CaretBox *cbox) const
        {
            return equalsBox(cbox->inlineBox(), cbox->isOutside(), cbox->isOutsideEnd());
        }
        /** checks whether this box matches the given iterator.
         *
         * On success, it sets \c found, and assigns the iterator to \c it.
         * @return true on match
         */
        bool check(const CaretBoxIterator &chit)
        {
            if (*this == *chit) {
                Q_ASSERT(!found);
                found = true;
                it = chit;
            }
            return found;
        }
    };

    /** recursively converts the given inline box into caret boxes and adds them
     * to this caret box line.
     *
     * It will additionally look for the caret box specified in SeekBoxParams.
     */
    void addConvertedInlineBox(InlineBox *, SeekBoxParams &) /*KHTML_NO_EXPORT*/;

    /** creates and adds the edge of a generic inline box
     * @param box inline box
     * @param fm font metrics of inline box
     * @param left true to add left edge, false to add right edge
     * @param rtl true if direction is rtl
     */
    void addCreatedInlineBoxEdge(InlineBox *box, const QFontMetrics &fm,
                                 bool left, bool rtl) /*KHTML_NO_EXPORT*/;
    /** creates and adds the edge of an inline flow box
     * @param flowBox inline flow box
     * @param fm font metrics of inline flow box
     * @param left true to add left edge, false to add right edge
     * @param rtl true if direction is rtl
     */
    void addCreatedFlowBoxEdge(InlineFlowBox *flowBox, const QFontMetrics &fm,
                               bool left, bool rtl) /*KHTML_NO_EXPORT*/;
    /** creates and adds the inside of an inline flow box
     * @param flowBox inline flow box
     * @param fm font metrics of inline flow box
     */
    void addCreatedFlowBoxInside(InlineFlowBox *flowBox, const QFontMetrics &fm) /*KHTML_NO_EXPORT*/;

    friend class CaretBoxIterator;
};

typedef MassDeleter<CaretBoxLine> CaretBoxLineDeleter;

inline CaretBox *CaretBoxIterator::data() const
{
    return cbl->caret_boxes[index];
}

/**
 * Iterates through the lines of a document.
 *
 * The line iterator becomes invalid when the associated LinearDocument object
 * is destroyed.
 * @internal
 * @author Leo Savernik
 */
class LineIterator
{
protected:
    LinearDocument *lines;    // associated document
    CaretBoxLine *cbl;        // current caret box line

    static CaretBoxIterator currentBox;   // current inline box
    static long currentOffset;

    // Note: cbl == 0 indicates a position beyond the beginning or the
    // end of a document.

    /** Default constructor, only for internal use
     */
    LineIterator() {}

    /** Initializes a new iterator.
     *
     * Note: This constructor neither cares about the correctness of @p node
     * nor about @p offset. It is the responsibility of the caller to ensure
     * that both point to valid places.
     */
    LineIterator(LinearDocument *l, DOM::NodeImpl *node, long offset);

public:
    /** dereferences current caret box line.
     *
     * @returns the caret line box or 0 if end of document
     */
    CaretBoxLine *operator *() const
    {
        return cbl;
    }

    /** returns the associated linear document
     */
    LinearDocument *linearDocument() const
    {
        return lines;
    }

    /** seek next line
     *
     * Guaranteed to crash if beyond beginning/end of document.
     */
    LineIterator &operator ++()
    {
        advance(false);
        return *this;
    }

    /** seek previous line.
     *
     * Guaranteed to crash if beyond beginning/end of document.
     */
    LineIterator &operator --()
    {
        advance(true);
        return *this;
    }

    /** compares two iterators. The comparator actually works only for
     * comparing arbitrary iterators to begin() and end().
     */
    bool operator ==(const LineIterator &it) const
    {
        return lines == it.lines && cbl == it.cbl;
    }

    /** compares two iterators
     */
    bool operator !=(const LineIterator &it) const
    {
        return !operator ==(it);
    }

    /** Returns whether this line represents the outside end of the containing
     * block.
     *
     * This result can only be relied on when isOutside is true.
     */
    bool isOutsideEnd()
    {
        return cbl->isOutsideEnd();
    }

    /** Tells whether the offset is meant to be outside or inside the
     * containing block.
     */
    bool isOutside() const
    {
        return cbl->isOutside();
    }

    /** advances to the line to come.
     * @param toBegin true, move to previous line, false, move to next line.
     */
    void advance(bool toBegin);

    /** Whenever a new line iterator is created, it gets a caret box created.
     * For memory reasons, it's saved in a static instance,
     * thus making this function not thread-safe.
     *
     * This value can only be trusted immediately after having instantiated
     * a line iterator or one of its derivatives.
     * @return an iterator onto the corresponing caret box within the
     *    line represented by the last instantiation of a line iterator,
     *    or 0 if there was none.
     */
    static CaretBoxIterator &currentCaretBox()
    {
        return currentBox;
    }

    /** Whenever a new line iterator is created, it calculates a modified offset
     * that is to be used with respect to the current render object.
     * This offset can be queried with this function.
     *
     * This value can only be trusted immediately after having instantiated
     * a line iterator or one of its derivatives.
     * @return the modified offset.
     */
    static long currentModifiedOffset()
    {
        return currentOffset;
    }

protected:
    /** seeks next block.
     */
    void nextBlock();
    /** seeks previous block.
     */
    void prevBlock();

    friend class CaretBoxIterator;
    friend class EditableLineIterator;
    friend class EditableCaretBoxIterator;
    friend class EditableCharacterIterator;
    friend class LinearDocument;
};

/**
 * Represents the whole document in terms of lines.
 *
 * SGML documents are trees. But for navigation, this representation is
 * not practical. Therefore this class serves as a helper to represent the
 * document as a linear list of lines. Its usage somewhat resembles STL
 * semantics like begin and end as well as iterators.
 *
 * The lines itself are represented as caret line boxes.
 *
 * LinearDocument instances are not meant to be kept over the lifetime of their
 * associated document, but constructed from (node, offset) pairs whenever line
 * traversal is needed. This is because the underlying InlineFlowBox objects
 * may be destroyed and recreated (e. g. by resizing the window, adding/removing
 * elements).
 *
 * @author Leo Savernik
 * @internal
 */
class LinearDocument
{
public:
    typedef LineIterator Iterator;

    /**
     * Creates a new instance, and initializes it to the line specified by
     * the parameters below.
     *
     * Creation will fail if @p node is invisible or defect.
     * @param part part within which everything is taking place.
     * @param node document node with which to start
     * @param offset zero-based offset within this node.
     * @param advancePolicy caret advance policy
     * @param baseElem base element which the caret must not advance beyond
     *    (0 means whole document). The base element will be ignored if it
     *    cannot serve as a base (to see if this is the case, check whether
     *    LinearDocument::baseFlow()->element() != base)
     */
    LinearDocument(KHTMLPart *part, DOM::NodeImpl *node, long offset,
                   CaretAdvancePolicy advancePolicy, DOM::ElementImpl *baseElem);

    virtual ~LinearDocument();

    /**
     * Tells whether this list contains any lines.
     *
     * @returns @p true if this document contains lines, @p false otherwise. Note
     *    that an empty document contains at least one line, so this method
     *    only returns @p false if the document could not be initialised for
     *    some reason.
     */
    bool isValid() const      // FIXME: not yet impl'd
    {
        return true;
    }

    /**
     * Returns the count of lines.
     *
     * Warning: This function is expensive. Call it once and cache the value.
     *
     * FIXME: It's not implemented yet (and maybe never will)
     */
    int count() const;

    /**
     * Returns a line iterator containing the current position as its starting
     * value.
     */
    Iterator current();

    /**
     * Returns a line iterator pointing right after the end of the document.
     */
    const Iterator &end() const
    {
        return _end;
    }

    /**
     * Returns a line iterator pointing to the very last line of the document.
     */
    Iterator preEnd();

    /**
     * Returns a line iterator pointing to the very first line of the document.
     */
    Iterator begin();

    /**
     * Returns a line iterator pointing just before the very first line of the
     * document (this is somewhat an emulation of reverse iterators).
     */
    const Iterator &preBegin() const
    {
        return _preBegin;
    }

    /**
     * Returns the current caret advance policy
     */
    CaretAdvancePolicy advancePolicy() const
    {
        return advPol;
    }

    /**
     * Returns the base render object which the caret must not advance beyond.
     *
     * Note that HTML documents are usually restricted to the body element.
     *
     * @return the base render object or 0 if the whole document is valid.
     */
    RenderObject *baseObject() const
    {
        return base;
    }

protected:
    void initPreBeginIterator();
    void initEndIterator();

protected:
    CaretBoxLineDeleter cblDeleter;   // mass deleter for caret box lines
    DOM::NodeImpl *node;
    long offset;

    Iterator _preBegin;
    Iterator _end;

    KHTMLPart *m_part;
    CaretAdvancePolicy advPol;
    RenderObject *base;

    friend class LineIterator;
    friend class EditableLineIterator;
    friend class ErgonomicEditableLineIterator;
    friend class CaretBoxIterator;
    friend class EditableCaretBoxIterator;
    friend class EditableCharacterIterator;
};

/**
 * Iterates over the editable inner elements of a caret line box.
 *
 * The incrementor will traverse all caret boxes according to the associated
 * linear document's caret advance policy. In contrast to \c CaretBoxIterator
 * this iterator only regards caret boxes which are editable.
 *
 * @author Leo Savernik
 * @internal
 */
class EditableCaretBoxIterator : public CaretBoxIterator
{
    KHTMLPart *m_part;
    bool adjacent;
    CaretAdvancePolicy advpol;    // caret advance policy

public:
    /** initializes a new iterator from the given line iterator,
     * beginning with the given caret box iterator, if specified
     */
    EditableCaretBoxIterator(LineIterator &lit, bool fromEnd = false,
                             CaretBoxIterator *it = 0)
        : CaretBoxIterator(it ? *it : (fromEnd ? (*lit)->end() : (*lit)->preBegin())),
          m_part(lit.lines->m_part), adjacent(false),
          advpol(lit.lines->advancePolicy())
    {
        if (!it) {
            if (fromEnd) {
                --*this;
            } else {
                ++*this;
            }
        }
    }

    /** empty constructor. Use only to copy another iterator into this one.
     */
    EditableCaretBoxIterator() {}

    /** returns @p true when the current caret box is adjacent to the
     * previously iterated caret box, i. e. no intervening caret boxes.
     */
    bool isAdjacent() const
    {
        return adjacent;
    }

    /** increments the iterator to point to the next editable caret box.
     */
    EditableCaretBoxIterator &operator ++()
    {
        advance(false);
        return *this;
    }

    /** decrements the iterator to point to the previous editable caret box.
     */
    EditableCaretBoxIterator &operator --()
    {
        advance(true);
        return *this;
    }

    /** advances to the editable caret box to come
     * @param toBegin true, move towards beginning, false, move towards end.
     */
    void advance(bool toBegin);

protected:
    /** finds out if the given box is editable.
     * @param boxit iterator to given caret box
     * @param fromEnd true when advancing towards the beginning
     * @return @p true if box is editable
     */
    bool isEditable(const CaretBoxIterator &boxit, bool fromEnd);
};

/**
 * Iterates through the editable lines of a document.
 *
 * This iterator, opposing to @p LineIterator, only regards editable lines.
 * Additionally, this iterator enforces the caret advance policy.
 *
 * The iterator can be compared to normal LineIterators, especially to
 * @ref LinearDocument::preBegin and @ref LinearDocument::end
 *
 * The line iterator becomes invalid when the associated LinearDocument object
 * is destroyed.
 * @internal
 * @author Leo Savernik
 */
class EditableLineIterator : public LineIterator
{
public:
    /** Initializes a new iterator.
     *
     * The iterator is set to the first following editable line or to the
     * end if no editable line follows.
     * @param it a line iterator to initialize this from
     * @param fromEnd @p true, traverse towards the beginning in search of an
     *    editable line
     */
    EditableLineIterator(const LineIterator &it, bool fromEnd = false)
        : LineIterator(it)
    {
        if (!cbl) {
            return;
        }
        if (!isEditable(*this)) {
            advance(fromEnd);
        }
    }

    /** empty constructor.
     *
     * Only use if you want to copy another iterator onto it later.
     */
    EditableLineIterator() {}

    /** seek next line
     *
     * Guaranteed to crash if beyond beginning/end of document.
     */
    EditableLineIterator &operator ++()
    {
        advance(false);
        return *this;
    }

    /** seek previous line.
     *
     * Guaranteed to crash if beyond beginning/end of document.
     */
    EditableLineIterator &operator --()
    {
        advance(true);
        return *this;
    }

    /** advances to the line to come.
     * @param toBegin true, move to previous line, false, move to next line.
     */
    void advance(bool toBegin);

protected:
    /** finds out if the current line is editable.
     *
     * @param it check caret box line iterator points to
     * @return @p true if line is editable
     */
    bool isEditable(LineIterator &it)
    {
        EditableCaretBoxIterator fbit = it;
        return fbit != (*it)->end();
    }

};

/** Represents a render table as a linear list of rows.
 *
 * This iterator abstracts from table sections and treats tables as a linear
 * representation of all rows they contain.
 * @author Leo Savernik
 * @internal
 */
class TableRowIterator
{
protected:
    TableSectionIterator sec; // current section
    int index;            // index of row within section
public:
    /** Constructs a new iterator.
     * @param table table to iterate through.
     * @param fromEnd @p true to iterate towards the beginning
     * @param row pointer to row to start with, 0 starts at the first/last
     *    row.
     */
    TableRowIterator(RenderTable *table, bool fromEnd = false,
                     RenderTableSection::RowStruct *row = 0);

    /** Constructs a new iterator.
     * @param section table section to begin with
     * @param index index within table section
     */
    TableRowIterator(RenderTableSection *section, int index)
        : sec(section), index(index)
    {}

    /** empty constructor. This must be assigned another iterator before it is
     * useable.
     */
    TableRowIterator() {}

    /** returns the current table row.
     * @return the row or 0 if the end of the table has been reached.
     */
    RenderTableSection::RowStruct *operator *()
    {
        if (!*sec) {
            return 0;
        }
        return &(*sec)->grid[index];
    }

    /** advances to the next row
     */
    TableRowIterator &operator ++();

    /** advances to the previous row
     */
    TableRowIterator &operator --();

protected:
};

/** Iterates through the editable lines of a document, in a topological order.
 *
 * The differences between this and the EditableLineIterator lies in the way
 * lines are inquired. While the latter steps through the lines in document
 * order, the former takes into consideration ergonomics.
 *
 * This is especially useful for tables. EditableLineIterator traverses all
 * table cells from left to right, top to bottom, while this one will
 * actually snap to the cell in the right position, and traverse only
 * upwards/downwards, thus providing a more intuitive navigation.
 *
 * @author Leo Savernik
 * @internal
 */
class ErgonomicEditableLineIterator : public EditableLineIterator
{
protected:
    int xCoor;        // x-coordinate to determine cell position
public:
    /** Initializes a new ergonomic editable line iterator from the given one.
     * @param it line iterator
     * @param x absolute x-coordinate for cell determination
     */
    ErgonomicEditableLineIterator(const LineIterator &it, int x)
        : EditableLineIterator(it), xCoor(x) {}

    /** Constructs an uninitialized iterator which must be assigned a line iterator before
     * it can be used.
     */
    ErgonomicEditableLineIterator() {}

    /** seek next line.
     *
     * The next line will be one that is visually situated below this line.
     */
    ErgonomicEditableLineIterator &operator ++();

    /** seek previous line.
     *
     * The previous line will be one that is visually situated above this line.
     */
    ErgonomicEditableLineIterator &operator --();

protected:
    /** determines the topologically next render object.
     * @param oldCell table cell the original object was under.
     * @param newObject object to determine whether and which transition
     *    between cells is to be handled. It does not have to be an object in the correct
     *    topological cell, a simple delivery from an editable line iterator suffices.
     * @param toBegin if @p true, iterate towards the beginning
     */
    void determineTopologicalElement(RenderTableCell *oldCell,
                                     RenderObject *newObject, bool toBegin);

    /** initializes the iterator to point to the first previous/following editable
     * line.
     * @param newBlock take this as base block.
     * @param toBegin @p true, iterate towards beginning.
     */
    void calcAndStoreNewLine(RenderBlock *newBlock, bool toBegin);

};

/**
 * Provides iterating through the document in terms of characters. Only the
 * editable characters are regarded.
 *
 * This iterator represents the document, which is structured as a tree itself,
 * as a linear stream of characters.
 */
class EditableCharacterIterator
{
protected:
    EditableLineIterator _it;
    EditableCaretBoxIterator ebit;
    long _offset;     // offset within current caret box.
    int _char;
    bool _end: 1;     // true when end of document has been reached

public:

    /** empty constructor.
     *
     * Only use if you want to assign another iterator as no fields will
     * be initialized.
     */
    EditableCharacterIterator() {}

    /** constructs a new iterator from the given linear document.
     *
     * @param ld linear representation of document.
     */
    EditableCharacterIterator(LinearDocument *ld)
        : _it(ld->current()),
          ebit(_it, false, &_it.currentCaretBox()),
          _offset(_it.currentModifiedOffset()), _char(-1), _end(false)
    {
        // ### temporary fix for illegal nodes
        if (_it == ld->end()) {
            _end = true;
            return;
        }
        initFirstChar();
    }

    /** returns the current character, or -1 if not on a text node, or beyond
     * the end.
     */
    int chr() const
    {
        return _char;
    }

    /** returns the current character as a unicode symbol, substituting
     * a blank for a non-text node.
     */
    QChar operator *() const
    {
        return QChar(_char >= 0 ? _char : ' ');
    }

    /** returns true when the end of the document has been reached.
     */
    bool isEnd() const
    {
        return _end;
    }
    /** returns the current offset
     */
    long offset() const
    {
        return _offset;
    }
    /** returns the current render object.
     */
    RenderObject *renderer() const
    {
        return (*ebit)->object();
    }
    /** returns the current caret box.
     *
     * Will crash if beyond end.
     */
    CaretBox *caretBox() const
    {
        return *ebit;
    }
    /** returns the current inline box.
     *
     * May be 0 if the current element has none, or if the end has been reached.
     * Therefore, do *not* use this to test for the end condition, use node()
     * instead.
     */
    InlineBox *inlineBox() const
    {
        return (*ebit)->inlineBox();
    }
    /** returns whether the current line box represents the outside of its
     * render object.
     */
//  bool boxIsOutside() const { return _it.isOutside(); }

    /** moves to the next editable character.
     */
    EditableCharacterIterator &operator ++();

    /** moves to the previous editable character.
     */
    EditableCharacterIterator &operator --();

protected:
    /** initializes the _char member by reading the character at the current
     * offset, peeking ahead as necessary.
     */
    void initFirstChar();
    /** reads ahead the next node and updates the data structures accordingly
     */
    void peekNext()
    {
        EditableCaretBoxIterator copy = ebit;
        ++copy;
        if (copy == (*_it)->end()) {
            _char = -1;
            return;
        }

        CaretBox *box = *copy;
        InlineBox *b = box->inlineBox();
        if (b && !box->isOutside() && b->isInlineTextBox()) {
            _char = static_cast<RenderText *>(b->object())->str->s[b->minOffset()].unicode();
        } else {
            _char = -1;
        }
    }
    /** reads ahead the previous node and updates the data structures accordingly
     */
    void peekPrev()
    {
        --ebit;
    }

};

}/*namespace khtml*/

#endif