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      1 /*
      2  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
      3  * Portions Copyright (c) 2011 Motorola Mobility, Inc.  All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      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  *
     14  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     15  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     17  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     18  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     19  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     20  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     21  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     22  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     24  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     25  */
     26 
     27 #include "config.h"
     28 #include "core/editing/VisiblePosition.h"
     29 
     30 #include "bindings/core/v8/ExceptionState.h"
     31 #include "core/HTMLNames.h"
     32 #include "core/dom/Document.h"
     33 #include "core/dom/Range.h"
     34 #include "core/dom/Text.h"
     35 #include "core/editing/VisibleUnits.h"
     36 #include "core/editing/htmlediting.h"
     37 #include "core/html/HTMLElement.h"
     38 #include "core/rendering/RenderBlock.h"
     39 #include "core/rendering/RootInlineBox.h"
     40 #include "platform/geometry/FloatQuad.h"
     41 #include "wtf/text/CString.h"
     42 
     43 #ifndef NDEBUG
     44 #include <stdio.h>
     45 #endif
     46 
     47 namespace blink {
     48 
     49 using namespace HTMLNames;
     50 
     51 VisiblePosition::VisiblePosition(const Position &pos, EAffinity affinity)
     52 {
     53     init(pos, affinity);
     54 }
     55 
     56 VisiblePosition::VisiblePosition(const PositionWithAffinity& positionWithAffinity)
     57 {
     58     init(positionWithAffinity.position(), positionWithAffinity.affinity());
     59 }
     60 
     61 void VisiblePosition::init(const Position& position, EAffinity affinity)
     62 {
     63     m_affinity = affinity;
     64 
     65     m_deepPosition = canonicalPosition(position);
     66 
     67     // When not at a line wrap, make sure to end up with DOWNSTREAM affinity.
     68     if (m_affinity == UPSTREAM && (isNull() || inSameLine(VisiblePosition(position, DOWNSTREAM), *this)))
     69         m_affinity = DOWNSTREAM;
     70 }
     71 
     72 VisiblePosition VisiblePosition::next(EditingBoundaryCrossingRule rule) const
     73 {
     74     VisiblePosition next(nextVisuallyDistinctCandidate(m_deepPosition), m_affinity);
     75 
     76     switch (rule) {
     77     case CanCrossEditingBoundary:
     78         return next;
     79     case CannotCrossEditingBoundary:
     80         return honorEditingBoundaryAtOrAfter(next);
     81     case CanSkipOverEditingBoundary:
     82         return skipToEndOfEditingBoundary(next);
     83     }
     84     ASSERT_NOT_REACHED();
     85     return honorEditingBoundaryAtOrAfter(next);
     86 }
     87 
     88 VisiblePosition VisiblePosition::previous(EditingBoundaryCrossingRule rule) const
     89 {
     90     Position pos = previousVisuallyDistinctCandidate(m_deepPosition);
     91 
     92     // return null visible position if there is no previous visible position
     93     if (pos.atStartOfTree())
     94         return VisiblePosition();
     95 
     96     VisiblePosition prev = VisiblePosition(pos, DOWNSTREAM);
     97     ASSERT(prev != *this);
     98 
     99 #if ENABLE(ASSERT)
    100     // we should always be able to make the affinity DOWNSTREAM, because going previous from an
    101     // UPSTREAM position can never yield another UPSTREAM position (unless line wrap length is 0!).
    102     if (prev.isNotNull() && m_affinity == UPSTREAM) {
    103         VisiblePosition temp = prev;
    104         temp.setAffinity(UPSTREAM);
    105         ASSERT(inSameLine(temp, prev));
    106     }
    107 #endif
    108 
    109     switch (rule) {
    110     case CanCrossEditingBoundary:
    111         return prev;
    112     case CannotCrossEditingBoundary:
    113         return honorEditingBoundaryAtOrBefore(prev);
    114     case CanSkipOverEditingBoundary:
    115         return skipToStartOfEditingBoundary(prev);
    116     }
    117 
    118     ASSERT_NOT_REACHED();
    119     return honorEditingBoundaryAtOrBefore(prev);
    120 }
    121 
    122 Position VisiblePosition::leftVisuallyDistinctCandidate() const
    123 {
    124     Position p = m_deepPosition;
    125     if (p.isNull())
    126         return Position();
    127 
    128     Position downstreamStart = p.downstream();
    129     TextDirection primaryDirection = p.primaryDirection();
    130 
    131     while (true) {
    132         InlineBox* box;
    133         int offset;
    134         p.getInlineBoxAndOffset(m_affinity, primaryDirection, box, offset);
    135         if (!box)
    136             return primaryDirection == LTR ? previousVisuallyDistinctCandidate(m_deepPosition) : nextVisuallyDistinctCandidate(m_deepPosition);
    137 
    138         RenderObject* renderer = &box->renderer();
    139 
    140         while (true) {
    141             if ((renderer->isReplaced() || renderer->isBR()) && offset == box->caretRightmostOffset())
    142                 return box->isLeftToRightDirection() ? previousVisuallyDistinctCandidate(m_deepPosition) : nextVisuallyDistinctCandidate(m_deepPosition);
    143 
    144             if (!renderer->node()) {
    145                 box = box->prevLeafChild();
    146                 if (!box)
    147                     return primaryDirection == LTR ? previousVisuallyDistinctCandidate(m_deepPosition) : nextVisuallyDistinctCandidate(m_deepPosition);
    148                 renderer = &box->renderer();
    149                 offset = box->caretRightmostOffset();
    150                 continue;
    151             }
    152 
    153             offset = box->isLeftToRightDirection() ? renderer->previousOffset(offset) : renderer->nextOffset(offset);
    154 
    155             int caretMinOffset = box->caretMinOffset();
    156             int caretMaxOffset = box->caretMaxOffset();
    157 
    158             if (offset > caretMinOffset && offset < caretMaxOffset)
    159                 break;
    160 
    161             if (box->isLeftToRightDirection() ? offset < caretMinOffset : offset > caretMaxOffset) {
    162                 // Overshot to the left.
    163                 InlineBox* prevBox = box->prevLeafChildIgnoringLineBreak();
    164                 if (!prevBox) {
    165                     Position positionOnLeft = primaryDirection == LTR ? previousVisuallyDistinctCandidate(m_deepPosition) : nextVisuallyDistinctCandidate(m_deepPosition);
    166                     if (positionOnLeft.isNull())
    167                         return Position();
    168 
    169                     InlineBox* boxOnLeft;
    170                     int offsetOnLeft;
    171                     positionOnLeft.getInlineBoxAndOffset(m_affinity, primaryDirection, boxOnLeft, offsetOnLeft);
    172                     if (boxOnLeft && boxOnLeft->root() == box->root())
    173                         return Position();
    174                     return positionOnLeft;
    175                 }
    176 
    177                 // Reposition at the other logical position corresponding to our edge's visual position and go for another round.
    178                 box = prevBox;
    179                 renderer = &box->renderer();
    180                 offset = prevBox->caretRightmostOffset();
    181                 continue;
    182             }
    183 
    184             ASSERT(offset == box->caretLeftmostOffset());
    185 
    186             unsigned char level = box->bidiLevel();
    187             InlineBox* prevBox = box->prevLeafChild();
    188 
    189             if (box->direction() == primaryDirection) {
    190                 if (!prevBox) {
    191                     InlineBox* logicalStart = 0;
    192                     if (primaryDirection == LTR ? box->root().getLogicalStartBoxWithNode(logicalStart) : box->root().getLogicalEndBoxWithNode(logicalStart)) {
    193                         box = logicalStart;
    194                         renderer = &box->renderer();
    195                         offset = primaryDirection == LTR ? box->caretMinOffset() : box->caretMaxOffset();
    196                     }
    197                     break;
    198                 }
    199                 if (prevBox->bidiLevel() >= level)
    200                     break;
    201 
    202                 level = prevBox->bidiLevel();
    203 
    204                 InlineBox* nextBox = box;
    205                 do {
    206                     nextBox = nextBox->nextLeafChild();
    207                 } while (nextBox && nextBox->bidiLevel() > level);
    208 
    209                 if (nextBox && nextBox->bidiLevel() == level)
    210                     break;
    211 
    212                 box = prevBox;
    213                 renderer = &box->renderer();
    214                 offset = box->caretRightmostOffset();
    215                 if (box->direction() == primaryDirection)
    216                     break;
    217                 continue;
    218             }
    219 
    220             while (prevBox && !prevBox->renderer().node())
    221                 prevBox = prevBox->prevLeafChild();
    222 
    223             if (prevBox) {
    224                 box = prevBox;
    225                 renderer = &box->renderer();
    226                 offset = box->caretRightmostOffset();
    227                 if (box->bidiLevel() > level) {
    228                     do {
    229                         prevBox = prevBox->prevLeafChild();
    230                     } while (prevBox && prevBox->bidiLevel() > level);
    231 
    232                     if (!prevBox || prevBox->bidiLevel() < level)
    233                         continue;
    234                 }
    235             } else {
    236                 // Trailing edge of a secondary run. Set to the leading edge of the entire run.
    237                 while (true) {
    238                     while (InlineBox* nextBox = box->nextLeafChild()) {
    239                         if (nextBox->bidiLevel() < level)
    240                             break;
    241                         box = nextBox;
    242                     }
    243                     if (box->bidiLevel() == level)
    244                         break;
    245                     level = box->bidiLevel();
    246                     while (InlineBox* prevBox = box->prevLeafChild()) {
    247                         if (prevBox->bidiLevel() < level)
    248                             break;
    249                         box = prevBox;
    250                     }
    251                     if (box->bidiLevel() == level)
    252                         break;
    253                     level = box->bidiLevel();
    254                 }
    255                 renderer = &box->renderer();
    256                 offset = primaryDirection == LTR ? box->caretMinOffset() : box->caretMaxOffset();
    257             }
    258             break;
    259         }
    260 
    261         p = createLegacyEditingPosition(renderer->node(), offset);
    262 
    263         if ((p.isCandidate() && p.downstream() != downstreamStart) || p.atStartOfTree() || p.atEndOfTree())
    264             return p;
    265 
    266         ASSERT(p != m_deepPosition);
    267     }
    268 }
    269 
    270 VisiblePosition VisiblePosition::left(bool stayInEditableContent) const
    271 {
    272     Position pos = leftVisuallyDistinctCandidate();
    273     // FIXME: Why can't we move left from the last position in a tree?
    274     if (pos.atStartOfTree() || pos.atEndOfTree())
    275         return VisiblePosition();
    276 
    277     VisiblePosition left = VisiblePosition(pos, DOWNSTREAM);
    278     ASSERT(left != *this);
    279 
    280     if (!stayInEditableContent)
    281         return left;
    282 
    283     // FIXME: This may need to do something different from "before".
    284     return honorEditingBoundaryAtOrBefore(left);
    285 }
    286 
    287 Position VisiblePosition::rightVisuallyDistinctCandidate() const
    288 {
    289     Position p = m_deepPosition;
    290     if (p.isNull())
    291         return Position();
    292 
    293     Position downstreamStart = p.downstream();
    294     TextDirection primaryDirection = p.primaryDirection();
    295 
    296     while (true) {
    297         InlineBox* box;
    298         int offset;
    299         p.getInlineBoxAndOffset(m_affinity, primaryDirection, box, offset);
    300         if (!box)
    301             return primaryDirection == LTR ? nextVisuallyDistinctCandidate(m_deepPosition) : previousVisuallyDistinctCandidate(m_deepPosition);
    302 
    303         RenderObject* renderer = &box->renderer();
    304 
    305         while (true) {
    306             if ((renderer->isReplaced() || renderer->isBR()) && offset == box->caretLeftmostOffset())
    307                 return box->isLeftToRightDirection() ? nextVisuallyDistinctCandidate(m_deepPosition) : previousVisuallyDistinctCandidate(m_deepPosition);
    308 
    309             if (!renderer->node()) {
    310                 box = box->nextLeafChild();
    311                 if (!box)
    312                     return primaryDirection == LTR ? nextVisuallyDistinctCandidate(m_deepPosition) : previousVisuallyDistinctCandidate(m_deepPosition);
    313                 renderer = &box->renderer();
    314                 offset = box->caretLeftmostOffset();
    315                 continue;
    316             }
    317 
    318             offset = box->isLeftToRightDirection() ? renderer->nextOffset(offset) : renderer->previousOffset(offset);
    319 
    320             int caretMinOffset = box->caretMinOffset();
    321             int caretMaxOffset = box->caretMaxOffset();
    322 
    323             if (offset > caretMinOffset && offset < caretMaxOffset)
    324                 break;
    325 
    326             if (box->isLeftToRightDirection() ? offset > caretMaxOffset : offset < caretMinOffset) {
    327                 // Overshot to the right.
    328                 InlineBox* nextBox = box->nextLeafChildIgnoringLineBreak();
    329                 if (!nextBox) {
    330                     Position positionOnRight = primaryDirection == LTR ? nextVisuallyDistinctCandidate(m_deepPosition) : previousVisuallyDistinctCandidate(m_deepPosition);
    331                     if (positionOnRight.isNull())
    332                         return Position();
    333 
    334                     InlineBox* boxOnRight;
    335                     int offsetOnRight;
    336                     positionOnRight.getInlineBoxAndOffset(m_affinity, primaryDirection, boxOnRight, offsetOnRight);
    337                     if (boxOnRight && boxOnRight->root() == box->root())
    338                         return Position();
    339                     return positionOnRight;
    340                 }
    341 
    342                 // Reposition at the other logical position corresponding to our edge's visual position and go for another round.
    343                 box = nextBox;
    344                 renderer = &box->renderer();
    345                 offset = nextBox->caretLeftmostOffset();
    346                 continue;
    347             }
    348 
    349             ASSERT(offset == box->caretRightmostOffset());
    350 
    351             unsigned char level = box->bidiLevel();
    352             InlineBox* nextBox = box->nextLeafChild();
    353 
    354             if (box->direction() == primaryDirection) {
    355                 if (!nextBox) {
    356                     InlineBox* logicalEnd = 0;
    357                     if (primaryDirection == LTR ? box->root().getLogicalEndBoxWithNode(logicalEnd) : box->root().getLogicalStartBoxWithNode(logicalEnd)) {
    358                         box = logicalEnd;
    359                         renderer = &box->renderer();
    360                         offset = primaryDirection == LTR ? box->caretMaxOffset() : box->caretMinOffset();
    361                     }
    362                     break;
    363                 }
    364 
    365                 if (nextBox->bidiLevel() >= level)
    366                     break;
    367 
    368                 level = nextBox->bidiLevel();
    369 
    370                 InlineBox* prevBox = box;
    371                 do {
    372                     prevBox = prevBox->prevLeafChild();
    373                 } while (prevBox && prevBox->bidiLevel() > level);
    374 
    375                 if (prevBox && prevBox->bidiLevel() == level)   // For example, abc FED 123 ^ CBA
    376                     break;
    377 
    378                 // For example, abc 123 ^ CBA or 123 ^ CBA abc
    379                 box = nextBox;
    380                 renderer = &box->renderer();
    381                 offset = box->caretLeftmostOffset();
    382                 if (box->direction() == primaryDirection)
    383                     break;
    384                 continue;
    385             }
    386 
    387             while (nextBox && !nextBox->renderer().node())
    388                 nextBox = nextBox->nextLeafChild();
    389 
    390             if (nextBox) {
    391                 box = nextBox;
    392                 renderer = &box->renderer();
    393                 offset = box->caretLeftmostOffset();
    394 
    395                 if (box->bidiLevel() > level) {
    396                     do {
    397                         nextBox = nextBox->nextLeafChild();
    398                     } while (nextBox && nextBox->bidiLevel() > level);
    399 
    400                     if (!nextBox || nextBox->bidiLevel() < level)
    401                         continue;
    402                 }
    403             } else {
    404                 // Trailing edge of a secondary run. Set to the leading edge of the entire run.
    405                 while (true) {
    406                     while (InlineBox* prevBox = box->prevLeafChild()) {
    407                         if (prevBox->bidiLevel() < level)
    408                             break;
    409                         box = prevBox;
    410                     }
    411                     if (box->bidiLevel() == level)
    412                         break;
    413                     level = box->bidiLevel();
    414                     while (InlineBox* nextBox = box->nextLeafChild()) {
    415                         if (nextBox->bidiLevel() < level)
    416                             break;
    417                         box = nextBox;
    418                     }
    419                     if (box->bidiLevel() == level)
    420                         break;
    421                     level = box->bidiLevel();
    422                 }
    423                 renderer = &box->renderer();
    424                 offset = primaryDirection == LTR ? box->caretMaxOffset() : box->caretMinOffset();
    425             }
    426             break;
    427         }
    428 
    429         p = createLegacyEditingPosition(renderer->node(), offset);
    430 
    431         if ((p.isCandidate() && p.downstream() != downstreamStart) || p.atStartOfTree() || p.atEndOfTree())
    432             return p;
    433 
    434         ASSERT(p != m_deepPosition);
    435     }
    436 }
    437 
    438 VisiblePosition VisiblePosition::right(bool stayInEditableContent) const
    439 {
    440     Position pos = rightVisuallyDistinctCandidate();
    441     // FIXME: Why can't we move left from the last position in a tree?
    442     if (pos.atStartOfTree() || pos.atEndOfTree())
    443         return VisiblePosition();
    444 
    445     VisiblePosition right = VisiblePosition(pos, DOWNSTREAM);
    446     ASSERT(right != *this);
    447 
    448     if (!stayInEditableContent)
    449         return right;
    450 
    451     // FIXME: This may need to do something different from "after".
    452     return honorEditingBoundaryAtOrAfter(right);
    453 }
    454 
    455 VisiblePosition VisiblePosition::honorEditingBoundaryAtOrBefore(const VisiblePosition &pos) const
    456 {
    457     if (pos.isNull())
    458         return pos;
    459 
    460     ContainerNode* highestRoot = highestEditableRoot(deepEquivalent());
    461 
    462     // Return empty position if pos is not somewhere inside the editable region containing this position
    463     if (highestRoot && !pos.deepEquivalent().deprecatedNode()->isDescendantOf(highestRoot))
    464         return VisiblePosition();
    465 
    466     // Return pos itself if the two are from the very same editable region, or both are non-editable
    467     // FIXME: In the non-editable case, just because the new position is non-editable doesn't mean movement
    468     // to it is allowed.  VisibleSelection::adjustForEditableContent has this problem too.
    469     if (highestEditableRoot(pos.deepEquivalent()) == highestRoot)
    470         return pos;
    471 
    472     // Return empty position if this position is non-editable, but pos is editable
    473     // FIXME: Move to the previous non-editable region.
    474     if (!highestRoot)
    475         return VisiblePosition();
    476 
    477     // Return the last position before pos that is in the same editable region as this position
    478     return lastEditableVisiblePositionBeforePositionInRoot(pos.deepEquivalent(), highestRoot);
    479 }
    480 
    481 VisiblePosition VisiblePosition::honorEditingBoundaryAtOrAfter(const VisiblePosition &pos) const
    482 {
    483     if (pos.isNull())
    484         return pos;
    485 
    486     ContainerNode* highestRoot = highestEditableRoot(deepEquivalent());
    487 
    488     // Return empty position if pos is not somewhere inside the editable region containing this position
    489     if (highestRoot && !pos.deepEquivalent().deprecatedNode()->isDescendantOf(highestRoot))
    490         return VisiblePosition();
    491 
    492     // Return pos itself if the two are from the very same editable region, or both are non-editable
    493     // FIXME: In the non-editable case, just because the new position is non-editable doesn't mean movement
    494     // to it is allowed.  VisibleSelection::adjustForEditableContent has this problem too.
    495     if (highestEditableRoot(pos.deepEquivalent()) == highestRoot)
    496         return pos;
    497 
    498     // Return empty position if this position is non-editable, but pos is editable
    499     // FIXME: Move to the next non-editable region.
    500     if (!highestRoot)
    501         return VisiblePosition();
    502 
    503     // Return the next position after pos that is in the same editable region as this position
    504     return firstEditableVisiblePositionAfterPositionInRoot(pos.deepEquivalent(), highestRoot);
    505 }
    506 
    507 VisiblePosition VisiblePosition::skipToStartOfEditingBoundary(const VisiblePosition &pos) const
    508 {
    509     if (pos.isNull())
    510         return pos;
    511 
    512     ContainerNode* highestRoot = highestEditableRoot(deepEquivalent());
    513     ContainerNode* highestRootOfPos = highestEditableRoot(pos.deepEquivalent());
    514 
    515     // Return pos itself if the two are from the very same editable region, or both are non-editable.
    516     if (highestRootOfPos == highestRoot)
    517         return pos;
    518 
    519     // If |pos| has an editable root, skip to the start
    520     if (highestRootOfPos)
    521         return VisiblePosition(previousVisuallyDistinctCandidate(Position(highestRootOfPos, Position::PositionIsBeforeAnchor).parentAnchoredEquivalent()));
    522 
    523     // That must mean that |pos| is not editable. Return the last position before pos that is in the same editable region as this position
    524     return lastEditableVisiblePositionBeforePositionInRoot(pos.deepEquivalent(), highestRoot);
    525 }
    526 
    527 VisiblePosition VisiblePosition::skipToEndOfEditingBoundary(const VisiblePosition &pos) const
    528 {
    529     if (pos.isNull())
    530         return pos;
    531 
    532     ContainerNode* highestRoot = highestEditableRoot(deepEquivalent());
    533     ContainerNode* highestRootOfPos = highestEditableRoot(pos.deepEquivalent());
    534 
    535     // Return pos itself if the two are from the very same editable region, or both are non-editable.
    536     if (highestRootOfPos == highestRoot)
    537         return pos;
    538 
    539     // If |pos| has an editable root, skip to the end
    540     if (highestRootOfPos)
    541         return VisiblePosition(Position(highestRootOfPos, Position::PositionIsAfterAnchor).parentAnchoredEquivalent());
    542 
    543     // That must mean that |pos| is not editable. Return the next position after pos that is in the same editable region as this position
    544     return firstEditableVisiblePositionAfterPositionInRoot(pos.deepEquivalent(), highestRoot);
    545 }
    546 
    547 static Position canonicalizeCandidate(const Position& candidate)
    548 {
    549     if (candidate.isNull())
    550         return Position();
    551     ASSERT(candidate.isCandidate());
    552     Position upstream = candidate.upstream();
    553     if (upstream.isCandidate())
    554         return upstream;
    555     return candidate;
    556 }
    557 
    558 Position VisiblePosition::canonicalPosition(const Position& passedPosition)
    559 {
    560     // The updateLayout call below can do so much that even the position passed
    561     // in to us might get changed as a side effect. Specifically, there are code
    562     // paths that pass selection endpoints, and updateLayout can change the selection.
    563     Position position = passedPosition;
    564 
    565     // FIXME (9535):  Canonicalizing to the leftmost candidate means that if we're at a line wrap, we will
    566     // ask renderers to paint downstream carets for other renderers.
    567     // To fix this, we need to either a) add code to all paintCarets to pass the responsibility off to
    568     // the appropriate renderer for VisiblePosition's like these, or b) canonicalize to the rightmost candidate
    569     // unless the affinity is upstream.
    570     if (position.isNull())
    571         return Position();
    572 
    573     ASSERT(position.document());
    574     position.document()->updateLayoutIgnorePendingStylesheets();
    575 
    576     Node* node = position.containerNode();
    577 
    578     Position candidate = position.upstream();
    579     if (candidate.isCandidate())
    580         return candidate;
    581     candidate = position.downstream();
    582     if (candidate.isCandidate())
    583         return candidate;
    584 
    585     // When neither upstream or downstream gets us to a candidate (upstream/downstream won't leave
    586     // blocks or enter new ones), we search forward and backward until we find one.
    587     Position next = canonicalizeCandidate(nextCandidate(position));
    588     Position prev = canonicalizeCandidate(previousCandidate(position));
    589     Node* nextNode = next.deprecatedNode();
    590     Node* prevNode = prev.deprecatedNode();
    591 
    592     // The new position must be in the same editable element. Enforce that first.
    593     // Unless the descent is from a non-editable html element to an editable body.
    594     if (isHTMLHtmlElement(node) && !node->hasEditableStyle() && node->document().body() && node->document().body()->hasEditableStyle())
    595         return next.isNotNull() ? next : prev;
    596 
    597     Element* editingRoot = editableRootForPosition(position);
    598 
    599     // If the html element is editable, descending into its body will look like a descent
    600     // from non-editable to editable content since rootEditableElement() always stops at the body.
    601     if (isHTMLHtmlElement(editingRoot) || position.deprecatedNode()->isDocumentNode())
    602         return next.isNotNull() ? next : prev;
    603 
    604     bool prevIsInSameEditableElement = prevNode && editableRootForPosition(prev) == editingRoot;
    605     bool nextIsInSameEditableElement = nextNode && editableRootForPosition(next) == editingRoot;
    606     if (prevIsInSameEditableElement && !nextIsInSameEditableElement)
    607         return prev;
    608 
    609     if (nextIsInSameEditableElement && !prevIsInSameEditableElement)
    610         return next;
    611 
    612     if (!nextIsInSameEditableElement && !prevIsInSameEditableElement)
    613         return Position();
    614 
    615     // The new position should be in the same block flow element. Favor that.
    616     Element* originalBlock = node ? enclosingBlockFlowElement(*node) : 0;
    617     bool nextIsOutsideOriginalBlock = !nextNode->isDescendantOf(originalBlock) && nextNode != originalBlock;
    618     bool prevIsOutsideOriginalBlock = !prevNode->isDescendantOf(originalBlock) && prevNode != originalBlock;
    619     if (nextIsOutsideOriginalBlock && !prevIsOutsideOriginalBlock)
    620         return prev;
    621 
    622     return next;
    623 }
    624 
    625 UChar32 VisiblePosition::characterAfter() const
    626 {
    627     // We canonicalize to the first of two equivalent candidates, but the second of the two candidates
    628     // is the one that will be inside the text node containing the character after this visible position.
    629     Position pos = m_deepPosition.downstream();
    630     if (!pos.containerNode() || !pos.containerNode()->isTextNode())
    631         return 0;
    632     switch (pos.anchorType()) {
    633     case Position::PositionIsAfterChildren:
    634     case Position::PositionIsAfterAnchor:
    635     case Position::PositionIsBeforeAnchor:
    636     case Position::PositionIsBeforeChildren:
    637         return 0;
    638     case Position::PositionIsOffsetInAnchor:
    639         break;
    640     }
    641     unsigned offset = static_cast<unsigned>(pos.offsetInContainerNode());
    642     Text* textNode = pos.containerText();
    643     unsigned length = textNode->length();
    644     if (offset >= length)
    645         return 0;
    646 
    647     return textNode->data().characterStartingAt(offset);
    648 }
    649 
    650 LayoutRect VisiblePosition::localCaretRect(RenderObject*& renderer) const
    651 {
    652     PositionWithAffinity positionWithAffinity(m_deepPosition, m_affinity);
    653     return localCaretRectOfPosition(positionWithAffinity, renderer);
    654 }
    655 
    656 IntRect VisiblePosition::absoluteCaretBounds() const
    657 {
    658     RenderObject* renderer;
    659     LayoutRect localRect = localCaretRect(renderer);
    660     if (localRect.isEmpty() || !renderer)
    661         return IntRect();
    662 
    663     return renderer->localToAbsoluteQuad(FloatRect(localRect)).enclosingBoundingBox();
    664 }
    665 
    666 int VisiblePosition::lineDirectionPointForBlockDirectionNavigation() const
    667 {
    668     RenderObject* renderer;
    669     LayoutRect localRect = localCaretRect(renderer);
    670     if (localRect.isEmpty() || !renderer)
    671         return 0;
    672 
    673     // This ignores transforms on purpose, for now. Vertical navigation is done
    674     // without consulting transforms, so that 'up' in transformed text is 'up'
    675     // relative to the text, not absolute 'up'.
    676     FloatPoint caretPoint = renderer->localToAbsolute(localRect.location());
    677     RenderObject* containingBlock = renderer->containingBlock();
    678     if (!containingBlock)
    679         containingBlock = renderer; // Just use ourselves to determine the writing mode if we have no containing block.
    680     return containingBlock->isHorizontalWritingMode() ? caretPoint.x() : caretPoint.y();
    681 }
    682 
    683 #ifndef NDEBUG
    684 
    685 void VisiblePosition::debugPosition(const char* msg) const
    686 {
    687     if (isNull())
    688         fprintf(stderr, "Position [%s]: null\n", msg);
    689     else {
    690         fprintf(stderr, "Position [%s]: %s, ", msg, m_deepPosition.deprecatedNode()->nodeName().utf8().data());
    691         m_deepPosition.showAnchorTypeAndOffset();
    692     }
    693 }
    694 
    695 void VisiblePosition::formatForDebugger(char* buffer, unsigned length) const
    696 {
    697     m_deepPosition.formatForDebugger(buffer, length);
    698 }
    699 
    700 void VisiblePosition::showTreeForThis() const
    701 {
    702     m_deepPosition.showTreeForThis();
    703 }
    704 
    705 #endif
    706 
    707 PassRefPtrWillBeRawPtr<Range> makeRange(const VisiblePosition &start, const VisiblePosition &end)
    708 {
    709     if (start.isNull() || end.isNull())
    710         return nullptr;
    711 
    712     Position s = start.deepEquivalent().parentAnchoredEquivalent();
    713     Position e = end.deepEquivalent().parentAnchoredEquivalent();
    714     if (s.isNull() || e.isNull())
    715         return nullptr;
    716 
    717     return Range::create(s.containerNode()->document(), s.containerNode(), s.offsetInContainerNode(), e.containerNode(), e.offsetInContainerNode());
    718 }
    719 
    720 VisiblePosition startVisiblePosition(const Range *r, EAffinity affinity)
    721 {
    722     return VisiblePosition(r->startPosition(), affinity);
    723 }
    724 
    725 bool setStart(Range *r, const VisiblePosition &visiblePosition)
    726 {
    727     if (!r)
    728         return false;
    729     Position p = visiblePosition.deepEquivalent().parentAnchoredEquivalent();
    730     TrackExceptionState exceptionState;
    731     r->setStart(p.containerNode(), p.offsetInContainerNode(), exceptionState);
    732     return !exceptionState.hadException();
    733 }
    734 
    735 bool setEnd(Range *r, const VisiblePosition &visiblePosition)
    736 {
    737     if (!r)
    738         return false;
    739     Position p = visiblePosition.deepEquivalent().parentAnchoredEquivalent();
    740     TrackExceptionState exceptionState;
    741     r->setEnd(p.containerNode(), p.offsetInContainerNode(), exceptionState);
    742     return !exceptionState.hadException();
    743 }
    744 
    745 Element* enclosingBlockFlowElement(const VisiblePosition& visiblePosition)
    746 {
    747     if (visiblePosition.isNull())
    748         return 0;
    749 
    750     return enclosingBlockFlowElement(*visiblePosition.deepEquivalent().deprecatedNode());
    751 }
    752 
    753 bool isFirstVisiblePositionInNode(const VisiblePosition& visiblePosition, const ContainerNode* node)
    754 {
    755     if (visiblePosition.isNull())
    756         return false;
    757 
    758     if (!visiblePosition.deepEquivalent().containerNode()->isDescendantOf(node))
    759         return false;
    760 
    761     VisiblePosition previous = visiblePosition.previous();
    762     return previous.isNull() || !previous.deepEquivalent().deprecatedNode()->isDescendantOf(node);
    763 }
    764 
    765 bool isLastVisiblePositionInNode(const VisiblePosition& visiblePosition, const ContainerNode* node)
    766 {
    767     if (visiblePosition.isNull())
    768         return false;
    769 
    770     if (!visiblePosition.deepEquivalent().containerNode()->isDescendantOf(node))
    771         return false;
    772 
    773     VisiblePosition next = visiblePosition.next();
    774     return next.isNull() || !next.deepEquivalent().deprecatedNode()->isDescendantOf(node);
    775 }
    776 
    777 void VisiblePosition::trace(Visitor* visitor)
    778 {
    779     visitor->trace(m_deepPosition);
    780 }
    781 
    782 }  // namespace blink
    783 
    784 #ifndef NDEBUG
    785 
    786 void showTree(const blink::VisiblePosition* vpos)
    787 {
    788     if (vpos)
    789         vpos->showTreeForThis();
    790 }
    791 
    792 void showTree(const blink::VisiblePosition& vpos)
    793 {
    794     vpos.showTreeForThis();
    795 }
    796 
    797 #endif
    798