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ax_position.h
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ax_position.h
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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_ACCESSIBILITY_AX_POSITION_H_
#define UI_ACCESSIBILITY_AX_POSITION_H_
#include <math.h>
#include <stdint.h>
#include <functional>
#include <memory>
#include <ostream>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>
#include "base/containers/stack.h"
#include "base/i18n/break_iterator.h"
#include "base/optional.h"
#include "base/stl_util.h"
#include "base/strings/string16.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/utf_string_conversions.h"
#include "ui/accessibility/ax_enum_util.h"
#include "ui/accessibility/ax_enums.mojom.h"
#include "ui/accessibility/ax_node.h"
#include "ui/accessibility/ax_node_text_styles.h"
#include "ui/accessibility/ax_role_properties.h"
#include "ui/accessibility/ax_tree_id.h"
#include "ui/gfx/utf16_indexing.h"
namespace ui {
// Defines the type of position in the accessibility tree.
// A tree position is used when referring to a specific child of a node in the
// accessibility tree.
// A text position is used when referring to a specific character of text inside
// a particular node.
// A null position is used to signify that the provided data is invalid or that
// a boundary has been reached.
enum class AXPositionKind { NULL_POSITION, TREE_POSITION, TEXT_POSITION };
// Defines how creating the next or previous position should behave whenever we
// are at or are crossing a boundary, such as at the start of an anchor, a word
// or a line.
enum class AXBoundaryBehavior {
CrossBoundary,
StopAtAnchorBoundary,
StopIfAlreadyAtBoundary,
StopAtLastAnchorBoundary
};
// Describes in further detail what type of boundary a current position is on.
// For complex boundaries such as format boundaries, it can be useful to know
// why a particular boundary was chosen.
enum class AXBoundaryType {
// Not at a unit boundary.
kNone,
// At a unit boundary (e.g. a format boundary).
kUnitBoundary,
// At the start of a document.
kDocumentStart,
// At the end of a document.
kDocumentEnd
};
// When converting to an unignored position, determines how to adjust the new
// position in order to make it valid, either moving backward or forward in
// the accessibility tree.
enum class AXPositionAdjustmentBehavior { kMoveBackward, kMoveForward };
// Specifies how AXPosition::ExpandToEnclosingTextBoundary behaves.
//
// As an example, imagine we have the text "hello world" and a position before
// the space character. We want to expand to the surrounding word boundary.
// Since we are right at the end of the first word, we could either expand to
// the left first, find the start of the first word and then use that to find
// the corresponding word end, resulting in the word "Hello". Another
// possibility is to expand to the right first, find the end of the next word
// and use that as our starting point to find the previous word start, resulting
// in the word "world".
enum class AXRangeExpandBehavior {
// Expands to the left boundary first and then uses that position as the
// starting point to find the boundary to the right.
kLeftFirst,
// Expands to the right boundary first and then uses that position as the
// starting point to find the boundary to the left.
kRightFirst
};
// Some platforms require empty objects to be represented by a replacement
// character in order for text navigation to work correctly. This enum controls
// whether a replacement character will be exposed for such objects.
//
// When an embedded object is replaced by a real character, the expectations
// are the same with this character as with other ordinary characters.
// For example, with UIA on Windows, we need to be able to navigate inside and
// outside of this character as if it was an ordinary character, using the
// AXPlatformNodeTextRangeProvider methods. Since an embedded object character
// is the only character in a node, we also treat this character as a word.
enum class AXEmbeddedObjectBehavior {
kExposeCharacter,
kSuppressCharacter,
};
// Controls whether embedded objects are represented by a replacement
// character. This is initialized to a per-platform default but can be
// overridden for testing.
AX_EXPORT extern AXEmbeddedObjectBehavior g_ax_embedded_object_behavior;
// Forward declarations.
template <class AXPositionType, class AXNodeType>
class AXPosition;
template <class AXPositionType>
class AXRange;
template <class AXPositionType, class AXNodeType>
bool operator==(const AXPosition<AXPositionType, AXNodeType>& first,
const AXPosition<AXPositionType, AXNodeType>& second);
template <class AXPositionType, class AXNodeType>
bool operator!=(const AXPosition<AXPositionType, AXNodeType>& first,
const AXPosition<AXPositionType, AXNodeType>& second);
// A position in the accessibility tree.
//
// This class could either represent a tree position or a text position.
// Tree positions point to either a child of a specific node or at the end of a
// node (i.e. an "after children" position).
// Text positions point to either a character offset in the text inside a
// particular node including text from all its children, or to the end of the
// node's text, (i.e. an "after text" position).
// On tree positions that have a leaf node as their anchor, we also need to
// distinguish between "before text" and "after text" positions. To do this, if
// the child index is 0 and the anchor is a leaf node, then it's an "after text"
// position. If the child index is |BEFORE_TEXT| and the anchor is a leaf node,
// then this is a "before text" position.
// It doesn't make sense to have a "before text" position on a text position,
// because it is identical to setting its offset to the first character.
//
// To avoid re-computing either the text offset or the child index when
// converting between the two types of positions, both values are saved after
// the first conversion.
//
// This class template uses static polymorphism in order to allow sub-classes to
// be created from the base class without the base class knowing the type of the
// sub-class in advance.
// The template argument |AXPositionType| should always be set to the type of
// any class that inherits from this template, making this a
// "curiously recursive template".
//
// This class can be copied using the |Clone| method. It is designed to be
// immutable.
template <class AXPositionType, class AXNodeType>
class AXPosition {
public:
using AXPositionInstance =
std::unique_ptr<AXPosition<AXPositionType, AXNodeType>>;
using AXRangeType = AXRange<AXPosition<AXPositionType, AXNodeType>>;
using BoundaryConditionPredicate =
base::RepeatingCallback<bool(const AXPositionInstance&)>;
using BoundaryTextOffsetsFunc =
base::RepeatingCallback<std::vector<int32_t>(const AXPositionInstance&)>;
static const int BEFORE_TEXT = -1;
static const int INVALID_INDEX = -2;
static const int INVALID_OFFSET = -1;
// Replacement character used to represent an empty object. See
// AXEmbeddedObjectBehavior for more information.
//
// Duplicate of AXPlatformNodeBase::kEmbeddedCharacter because we don't want
// to include platform specific code in here.
static constexpr base::char16 kEmbeddedCharacter = L'\xfffc';
static AXPositionInstance CreateNullPosition() {
AXPositionInstance new_position(new AXPositionType());
new_position->Initialize(
AXPositionKind::NULL_POSITION, AXTreeIDUnknown(), AXNode::kInvalidAXID,
INVALID_INDEX, INVALID_OFFSET, ax::mojom::TextAffinity::kDownstream);
return new_position;
}
static AXPositionInstance CreateTreePosition(AXTreeID tree_id,
AXNode::AXID anchor_id,
int child_index) {
AXPositionInstance new_position(new AXPositionType());
new_position->Initialize(AXPositionKind::TREE_POSITION, tree_id, anchor_id,
child_index, INVALID_OFFSET,
ax::mojom::TextAffinity::kDownstream);
return new_position;
}
static AXPositionInstance CreateTextPosition(
AXTreeID tree_id,
AXNode::AXID anchor_id,
int text_offset,
ax::mojom::TextAffinity affinity) {
AXPositionInstance new_position(new AXPositionType());
new_position->Initialize(AXPositionKind::TEXT_POSITION, tree_id, anchor_id,
INVALID_INDEX, text_offset, affinity);
return new_position;
}
virtual ~AXPosition() = default;
// Implemented based on the copy and swap idiom.
AXPosition& operator=(const AXPosition& other) {
AXPositionInstance clone = other.Clone();
swap(*clone);
return *this;
}
virtual AXPositionInstance Clone() const = 0;
// A serialization of a position as POD. Not for sharing on disk or sharing
// across thread or process boundaries, just for passing a position to an
// API that works with positions as opaque objects.
struct SerializedPosition {
AXPositionKind kind;
AXNode::AXID anchor_id;
int child_index;
int text_offset;
ax::mojom::TextAffinity affinity;
char tree_id[33];
};
static_assert(std::is_trivially_copyable<SerializedPosition>::value,
"SerializedPosition must be POD");
SerializedPosition Serialize() {
SerializedPosition result;
result.kind = kind_;
// A tree ID can be serialized as a 32-byte string.
std::string tree_id_string = tree_id_.ToString();
DCHECK_LE(tree_id_string.size(), 32U);
strncpy(result.tree_id, tree_id_string.c_str(), 32);
result.tree_id[32] = 0;
result.anchor_id = anchor_id_;
result.child_index = child_index_;
result.text_offset = text_offset_;
result.affinity = affinity_;
return result;
}
static AXPositionInstance Unserialize(
const SerializedPosition& serialization) {
AXPositionInstance new_position(new AXPositionType());
new_position->Initialize(serialization.kind,
ui::AXTreeID::FromString(serialization.tree_id),
serialization.anchor_id, serialization.child_index,
serialization.text_offset, serialization.affinity);
return new_position;
}
std::string ToString() const {
std::string str;
switch (kind_) {
case AXPositionKind::NULL_POSITION:
return "NullPosition";
case AXPositionKind::TREE_POSITION: {
std::string str_child_index;
if (child_index_ == BEFORE_TEXT) {
str_child_index = "before_text";
} else if (child_index_ == INVALID_INDEX) {
str_child_index = "invalid";
} else {
str_child_index = base::NumberToString(child_index_);
}
str = "TreePosition tree_id=" + tree_id_.ToString() +
" anchor_id=" + base::NumberToString(anchor_id_) +
" child_index=" + str_child_index;
break;
}
case AXPositionKind::TEXT_POSITION: {
std::string str_text_offset;
if (text_offset_ == INVALID_OFFSET) {
str_text_offset = "invalid";
} else {
str_text_offset = base::NumberToString(text_offset_);
}
str = "TextPosition anchor_id=" + base::NumberToString(anchor_id_) +
" text_offset=" + str_text_offset + " affinity=" +
ui::ToString(static_cast<ax::mojom::TextAffinity>(affinity_));
break;
}
}
if (!IsTextPosition() || text_offset_ > MaxTextOffset())
return str;
base::string16 text = GetText();
DCHECK_GE(text_offset_, 0);
int max_text_offset = MaxTextOffset();
DCHECK_LE(text_offset_, max_text_offset);
base::string16 annotated_text;
if (text_offset_ == max_text_offset) {
annotated_text = text + base::WideToUTF16(L"<>");
} else {
annotated_text = text.substr(0, text_offset_) + base::WideToUTF16(L"<") +
text[text_offset_] + base::WideToUTF16(L">") +
text.substr(text_offset_ + 1);
}
return str + " annotated_text=" + base::UTF16ToUTF8(annotated_text);
}
AXTreeID tree_id() const { return tree_id_; }
AXNode::AXID anchor_id() const { return anchor_id_; }
AXNodeType* GetAnchor() const {
if (tree_id_ == AXTreeIDUnknown() || anchor_id_ == AXNode::kInvalidAXID)
return nullptr;
return GetNodeInTree(tree_id_, anchor_id_);
}
AXPositionKind kind() const { return kind_; }
int child_index() const { return child_index_; }
int text_offset() const { return text_offset_; }
ax::mojom::TextAffinity affinity() const { return affinity_; }
bool IsIgnored() const {
if (IsNullPosition())
return false;
DCHECK(GetAnchor());
// If this position is anchored to an ignored node, then consider this
// position to be ignored.
if (GetAnchor()->IsIgnored())
return true;
switch (kind_) {
case AXPositionKind::NULL_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TREE_POSITION: {
// If this is a "before text" or an "after text" tree position, it's
// pointing to the anchor itself, which we've determined to be
// unignored.
DCHECK(!IsLeaf() || child_index_ == BEFORE_TEXT || child_index_ == 0)
<< "\"Before text\" and \"after text\" tree positions are only "
"valid on leaf nodes.";
if (child_index_ == BEFORE_TEXT || IsLeaf())
return false;
// If this position is an "after children" position, consider the
// position to be ignored if the last child is ignored. This is because
// the last child will not be visible in the unignored tree. If the
// position is not adjusted, the resulting position would erroneously
// point before the second child in the unignored subtree rooted at the
// last child.
//
// 1 kRootWebArea
// ++2 kGenericContainer ignored
// ++++3 kStaticText "Line 1."
// ++++4 kStaticText "Line 2."
//
// Tree position anchor=kGenericContainer, child_index=1.
//
// Alternatively, if there is a node at the position pointed to by
// "child_index_", i.e. this position is neither a leaf position nor an
// "after children" position, consider this tree position to be ignored
// if the child node is ignored.
int adjusted_child_index = child_index_ != AnchorChildCount()
? child_index_
: child_index_ - 1;
AXPositionInstance child_position =
CreateChildPositionAt(adjusted_child_index);
DCHECK(child_position && !child_position->IsNullPosition());
return child_position->GetAnchor()->IsIgnored();
}
case AXPositionKind::TEXT_POSITION:
// If the corresponding leaf position is ignored, the current text
// offset will point to ignored text. Therefore, consider this position
// to be ignored.
if (!IsLeaf())
return AsLeafTreePosition()->IsIgnored();
return false;
}
}
bool IsNullPosition() const {
return kind_ == AXPositionKind::NULL_POSITION || !GetAnchor();
}
bool IsTreePosition() const {
return GetAnchor() && kind_ == AXPositionKind::TREE_POSITION;
}
bool IsLeafTreePosition() const { return IsTreePosition() && IsLeaf(); }
bool IsTextPosition() const {
return GetAnchor() && kind_ == AXPositionKind::TEXT_POSITION;
}
bool IsLeafTextPosition() const { return IsTextPosition() && IsLeaf(); }
bool IsLeaf() const {
if (IsNullPosition())
return false;
return !AnchorChildCount() || IsEmptyObjectReplacedByCharacter();
}
// Returns true if this is a valid position, e.g. the child_index_ or
// text_offset_ is within a valid range.
bool IsValid() const {
switch (kind_) {
case AXPositionKind::NULL_POSITION:
return tree_id_ == AXTreeIDUnknown() &&
anchor_id_ == AXNode::kInvalidAXID &&
child_index_ == INVALID_INDEX &&
text_offset_ == INVALID_OFFSET &&
affinity_ == ax::mojom::TextAffinity::kDownstream;
case AXPositionKind::TREE_POSITION:
return GetAnchor() &&
(child_index_ == BEFORE_TEXT ||
(child_index_ >= 0 && child_index_ <= AnchorChildCount())) &&
!IsInDescendantOfEmptyObject();
case AXPositionKind::TEXT_POSITION:
if (!GetAnchor() || IsInDescendantOfEmptyObject())
return false;
// For performance reasons we skip any validation of the text offset
// that involves retrieving the anchor's text, if the offset is set to
// 0, because 0 is frequently used and always valid regardless of the
// actual text.
return text_offset_ == 0 ||
(text_offset_ > 0 && text_offset_ <= MaxTextOffset());
}
}
// TODO(nektar): Update logic of AtStartOfAnchor() for text_offset_ == 0 and
// fix related bug.
bool AtStartOfAnchor() const {
if (!GetAnchor())
return false;
switch (kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
if (text_offset_ > 0)
return false;
if (!IsLeaf() || text_offset_ == 0)
return child_index_ == 0;
return child_index_ == BEFORE_TEXT;
case AXPositionKind::TEXT_POSITION:
return text_offset_ == 0;
}
}
bool AtEndOfAnchor() const {
if (!GetAnchor())
return false;
switch (kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
return child_index_ == AnchorChildCount();
case AXPositionKind::TEXT_POSITION:
return text_offset_ == MaxTextOffset();
}
}
bool AtStartOfWord() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION: {
const std::vector<int32_t> word_starts =
text_position->GetWordStartOffsets();
return base::Contains(word_starts,
int32_t{text_position->text_offset_});
}
}
}
bool AtEndOfWord() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION: {
const std::vector<int32_t> word_ends =
text_position->GetWordEndOffsets();
return base::Contains(word_ends, int32_t{text_position->text_offset_});
}
}
}
bool AtStartOfLine() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION:
// We treat a position after some white space that is not connected to
// any node after it via "next on line ID", to be equivalent to a
// position before the next line, and therefore as being at start of
// line.
//
// We assume that white space, including but not limited to hard line
// breaks, might be used to separate lines. For example, an inline text
// box with just a single space character inside it can be used to
// represent a soft line break. If an inline text box containing white
// space separates two lines, it should always be connected to the first
// line via "kPreviousOnLineId". This is guaranteed by the renderer. If
// there are multiple line breaks separating the two lines, then only
// the first line break is connected to the first line via
// "kPreviousOnLineId".
//
// Sometimes there might be an inline text box with a single space in it
// at the end of a text field. We should not mark positions that are at
// the end of text fields, or in general at the end of their anchor, as
// being at the start of line, except when that anchor is an inline text
// box that is in the middle of a text span. Note that in most but not
// all cases, the parent of an inline text box is a static text object,
// whose end signifies the end of the text span. One exception is line
// breaks.
if (text_position->AtEndOfAnchor() &&
!text_position->AtEndOfTextSpan() &&
text_position->IsInWhiteSpace() &&
GetNextOnLineID(text_position->anchor_id_) ==
AXNode::kInvalidAXID) {
return true;
}
return GetPreviousOnLineID(text_position->anchor_id_) ==
AXNode::kInvalidAXID &&
text_position->AtStartOfAnchor();
}
}
bool AtEndOfLine() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION:
// Text positions on objects with no text should not be considered at
// end of line because the empty position may share a text offset with
// a non-empty text position in which case the end of line iterators
// must move to the line end of the non-empty content. Specified next
// line IDs are ignored.
if (!text_position->MaxTextOffset())
return false;
// If affinity has been used to specify whether the caret is at the end
// of a line or at the start of the next one, this should have been
// reflected in the leaf text position we got via "AsLeafTextPosition".
// If affinity had been set to upstream, the leaf text position should
// be pointing to the end of the inline text box that ends the first
// line. If it had been set to downstream, the leaf text position should
// be pointing to the start of the inline text box that starts the
// second line.
//
// In other cases, we assume that white space, including but not limited
// to hard line breaks, might be used to separate lines. For example, an
// inline text box with just a single space character inside it can be
// used to represent a soft line break. If an inline text box containing
// white space separates two lines, it should always be connected to the
// first line via "kPreviousOnLineId". This is guaranteed by the
// renderer. If there are multiple line breaks separating the two lines,
// then only the first line break is connected to the first line via
// "kPreviousOnLineId".
//
// We don't treat a position that is at the start of white space that is
// on a line by itself as being at the end of the line. This is in order
// to enable screen readers to recognize and announce blank lines
// correctly. However, we do treat positions at the start of white space
// that end a line of text as being at the end of that line. We also
// treat positions at the end of white space that is on a line by
// itself, i.e. on a blank line, as being at the end of that line.
//
// Sometimes there might be an inline text box with a single space in it
// at the end of a text field. We should mark positions that are at the
// end of text fields, or in general at the end of an anchor with no
// "kNextOnLineId", as being at end of line, except when that anchor is
// an inline text box that is in the middle of a text span. Note that
// in most but not all cases, the parent of an inline text box is a
// static text object, whose end signifies the end of the text span. One
// exception is line breaks.
if (GetNextOnLineID(text_position->anchor_id_) ==
AXNode::kInvalidAXID) {
return (!text_position->AtEndOfTextSpan() &&
text_position->IsInWhiteSpace() &&
GetPreviousOnLineID(text_position->anchor_id_) !=
AXNode::kInvalidAXID)
? text_position->AtStartOfAnchor()
: text_position->AtEndOfAnchor();
}
// The current anchor might be followed by a soft line break.
return text_position->AtEndOfAnchor() &&
text_position->CreateNextLeafTextPosition()->AtEndOfLine();
}
}
// |AtStartOfParagraph| is asymmetric from |AtEndOfParagraph| because of
// trailing whitespace collapse rules.
// The start of a paragraph should be a leaf text position (or equivalent),
// either at the start of the document, or at the start of the next leaf text
// position from the one representing the end of the previous paragraph.
// A position |AsLeafTextPosition| is the start of a paragraph if all of the
// following are true :
// 1. The current leaf text position must be an unignored position at
// the start of an anchor.
// 2. The current position is not whitespace only, unless it is also
// the first leaf text position within the document.
// 3. Either (a) the current leaf text position is the first leaf text
// position in the document, or (b) there are no line breaking
// objects between it and the previous non-whitespace leaf text
// position.
bool AtStartOfParagraph() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION: {
// 1. The current leaf text position must be an unignored position at
// the start of an anchor.
if (text_position->IsIgnored() || !text_position->AtStartOfAnchor())
return false;
// 2. The current position is not whitespace only, unless it is also
// the first leaf text position within the document.
if (text_position->IsInWhiteSpace()) {
return text_position->CreatePreviousLeafTextPosition()
->IsNullPosition();
}
// 3. Either (a) the current leaf text position is the first leaf text
// position in the document, or (b) there are no line breaking
// objects between it and the previous non-whitespace leaf text
// position.
//
// Search for the previous text position within the current paragraph,
// using the paragraph boundary abort predicate.
// If a valid position was found, then this position cannot be
// the start of a paragraph.
// This will return a null position when an anchor movement would
// cross a paragraph boundary, or the start of document was reached.
bool crossed_line_breaking_object_token = false;
const AbortMovePredicate abort_move_predicate =
base::BindRepeating(&AbortMoveAtParagraphBoundary,
std::ref(crossed_line_breaking_object_token));
AXPositionInstance previous_text_position = text_position->Clone();
do {
previous_text_position =
previous_text_position->CreatePreviousTextAnchorPosition(
abort_move_predicate);
// If the previous position is whitespace, then continue searching
// until a non-whitespace leaf text position is found within the
// current paragraph because whitespace is supposed to be collapsed.
// There's a chance that |CreatePreviousTextAnchorPosition| will
// return whitespace that should be appended to a previous paragraph
// rather than separating two pieces of the current paragraph.
} while (previous_text_position->IsInWhiteSpace() ||
previous_text_position->IsIgnored());
return previous_text_position->IsNullPosition();
}
}
}
// |AtEndOfParagraph| is asymmetric from |AtStartOfParagraph| because of
// trailing whitespace collapse rules.
// The end of a paragraph should be a leaf text position (or equivalent),
// either at the end of the document, or at the end of the previous leaf text
// position from the one representing the start of the next paragraph.
// A position |AsLeafTextPosition| is the end of a paragraph if all of the
// following are true :
// 1. The current leaf text position must be an unignored position at
// the end of an anchor.
// 2. Either (a) the current leaf text position is the last leaf text
// position in the document, or (b) there are no line breaking
// objects between it and the next leaf text position except when
// the next leaf text position is whitespace only since whitespace
// must be collapsed.
// 3. If there is a next leaf text position then it must not be
// whitespace only.
// 4. If there is a next leaf text position and it is not whitespace
// only, it must also be the start of a paragraph for the current
// position to be the end of a paragraph.
bool AtEndOfParagraph() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION: {
// 1. The current leaf text position must be an unignored position at
// the end of an anchor.
if (text_position->IsIgnored() || !text_position->AtEndOfAnchor())
return false;
// 2. Either (a) the current leaf text position is the last leaf text
// position in the document, or (b) there are no line breaking
// objects between it and the next leaf text position except when
// the next leaf text position is whitespace only since whitespace
// must be collapsed.
//
// Search for the next text position within the current paragraph,
// using the paragraph boundary abort predicate.
// If a null position was found, then this position must be the end of
// a paragraph.
// |CreateNextTextAnchorPosition| + |AbortMoveAtParagraphBoundary|
// will return a null position when an anchor movement would
// cross a paragraph boundary and there is no doubt that it is the end
// of a paragraph, or the end of document was reached.
// There are some fringe cases related to whitespace collapse that
// cannot be handled easily with only |AbortMoveAtParagraphBoundary|.
bool crossed_line_breaking_object_token = false;
const AbortMovePredicate abort_move_predicate =
base::BindRepeating(&AbortMoveAtParagraphBoundary,
std::ref(crossed_line_breaking_object_token));
AXPositionInstance next_text_position = text_position->Clone();
do {
next_text_position = next_text_position->CreateNextTextAnchorPosition(
abort_move_predicate);
} while (next_text_position->IsIgnored());
if (next_text_position->IsNullPosition())
return true;
// 3. If there is a next leaf text position then it must not be
// whitespace only.
if (next_text_position->IsInWhiteSpace())
return false;
// 4. If there is a next leaf text position and it is not whitespace
// only, it must also be the start of a paragraph for the current
// position to be the end of a paragraph.
//
// Consider the following example :
// ++{1} kStaticText "First Paragraph"
// ++++{2} kInlineTextBox "First Paragraph"
// ++{3} kStaticText "\n Second Paragraph"
// ++++{4} kInlineTextBox "\n" kIsLineBreakingObject
// ++++{5} kInlineTextBox " "
// ++++{6} kInlineTextBox "Second Paragraph"
// A position at the end of {5} is the end of a paragraph, because
// the first paragraph must collapse trailing whitespace and contain
// leaf text anchors {2, 4, 5}. The second paragraph is only {6}.
return next_text_position->CreatePositionAtStartOfAnchor()
->AtStartOfParagraph();
}
}
}
bool AtStartOfPage() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION: {
if (!text_position->AtStartOfAnchor())
return false;
// Search for the previous text position within the current page,
// using the page boundary abort predicate.
// If a valid position was found, then this position cannot be
// the start of a page.
// This will return a null position when an anchor movement would
// cross a page boundary, or the start of document was reached.
AXPositionInstance previous_text_position =
text_position->CreatePreviousTextAnchorPosition(
base::BindRepeating(&AbortMoveAtPageBoundary));
return previous_text_position->IsNullPosition();
}
}
}
bool AtEndOfPage() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION: {
if (!text_position->AtEndOfAnchor())
return false;
// Search for the next text position within the current page,
// using the page boundary abort predicate.
// If a valid position was found, then this position cannot be
// the end of a page.
// This will return a null position when an anchor movement would
// cross a page boundary, or the end of document was reached.
AXPositionInstance next_text_position =
text_position->CreateNextTextAnchorPosition(
base::BindRepeating(&AbortMoveAtPageBoundary));
return next_text_position->IsNullPosition();
}
}
}
bool AtStartOfAXTree() const {
if (IsNullPosition())
return false;
if (AtStartOfAnchor()) {
AXPositionInstance previous_anchor = CreatePreviousAnchorPosition();
// Consider the start of the document as the start of an AXTree.
if (previous_anchor->IsNullPosition())
return true;
else
return previous_anchor->tree_id() != tree_id();
}
return false;
}
bool AtEndOfAXTree() const {
if (IsNullPosition())
return false;
if (AtEndOfAnchor()) {
AXPositionInstance next_anchor = CreateNextAnchorPosition();
// Consider the end of the document as the end of an AXTree.
if (next_anchor->IsNullPosition())
return true;
else
return next_anchor->tree_id() != tree_id();
}
return false;
}
AXBoundaryType GetFormatStartBoundaryType() const {
// Since formats are stored on text anchors, the start of a format boundary
// must be at the start of an anchor.
if (IsNullPosition() || !AtStartOfAnchor())
return AXBoundaryType::kNone;
// Treat the first iterable node as a format boundary.
if (CreatePreviousLeafTreePosition()->IsNullPosition())
return AXBoundaryType::kDocumentStart;
// Ignored positions cannot be format boundaries.
if (IsIgnored())
return AXBoundaryType::kNone;
// Iterate over anchors until a format boundary is found. This will return a
// null position upon crossing a boundary. Make sure the previous position
// is not on an ignored node.
AXPositionInstance previous_position = Clone();
do {
previous_position = previous_position->CreatePreviousLeafTreePosition(
base::BindRepeating(&AbortMoveAtFormatBoundary));
} while (previous_position->IsIgnored());
if (previous_position->IsNullPosition())
return AXBoundaryType::kUnitBoundary;
return AXBoundaryType::kNone;
}
bool AtStartOfFormat() const {
return GetFormatStartBoundaryType() != AXBoundaryType::kNone;
}
AXBoundaryType GetFormatEndBoundaryType() const {
// Since formats are stored on text anchors, the end of a format break must
// be at the end of an anchor.
if (IsNullPosition() || !AtEndOfAnchor())
return AXBoundaryType::kNone;
// Treat the last iterable node as a format boundary
if (CreateNextLeafTreePosition()->IsNullPosition())
return AXBoundaryType::kDocumentEnd;
// Ignored positions cannot be format boundaries.
if (IsIgnored())
return AXBoundaryType::kNone;
// Iterate over anchors until a format boundary is found. This will return a
// null position upon crossing a boundary. Make sure the next position is
// not on an ignored node.
AXPositionInstance next_position = Clone();
do {
next_position = next_position->CreateNextLeafTreePosition(
base::BindRepeating(&AbortMoveAtFormatBoundary));
} while (next_position->IsIgnored());
if (next_position->IsNullPosition())
return AXBoundaryType::kUnitBoundary;
return AXBoundaryType::kNone;
}
bool AtEndOfFormat() const {
return GetFormatEndBoundaryType() != AXBoundaryType::kNone;
}
bool AtStartOfInlineBlock() const {
AXPositionInstance text_position = AsLeafTextPosition();
switch (text_position->kind_) {
case AXPositionKind::NULL_POSITION:
return false;
case AXPositionKind::TREE_POSITION:
NOTREACHED();
return false;
case AXPositionKind::TEXT_POSITION: {
if (text_position->AtStartOfAnchor()) {
AXPositionInstance previous_position =
text_position->CreatePreviousLeafTreePosition();
// Check that this position is not the start of the first anchor.
if (!previous_position->IsNullPosition()) {
previous_position = text_position->CreatePreviousLeafTreePosition(
base::BindRepeating(&AbortMoveAtStartOfInlineBlock));
// If we get a null position here it means we have crossed an inline
// block's start, thus this position is located at such start.
if (previous_position->IsNullPosition())
return true;
}
}
if (text_position->AtEndOfAnchor()) {
AXPositionInstance next_position =
text_position->CreateNextLeafTreePosition();
// Check that this position is not the end of the last anchor.
if (!next_position->IsNullPosition()) {
next_position = text_position->CreateNextLeafTreePosition(
base::BindRepeating(&AbortMoveAtStartOfInlineBlock));
// If we get a null position here it means we have crossed an inline
// block's start, thus this position is located at such start.
if (next_position->IsNullPosition())
return true;
}
}
return false;
}
}
}
bool AtStartOfDocument() const {
if (IsNullPosition())
return false;
return IsDocument(GetAnchorRole()) && AtStartOfAnchor();
}
bool AtEndOfDocument() const {
if (IsNullPosition())
return false;
return AtLastNodeInTree() && AtEndOfAnchor();
}
bool AtLastNodeInTree() const {
if (IsNullPosition())
return false;
// Avoid a potentionally expensive MaxTextOffset call by only using tree
// positions. The only thing that matters is whether our anchor_id_ is at
// the last anchor of the document, so we're free to ignore text_offset_.
AXPositionInstance tree_position =
CreateTreePosition(tree_id_, anchor_id_, 0);
return tree_position->CreateNextAnchorPosition()->IsNullPosition();
}
// This method finds the lowest common AXNodeType of |this| and |second|.
AXNodeType* LowestCommonAnchor(const AXPosition& second) const {
if (IsNullPosition() || second.IsNullPosition())
return nullptr;
if (GetAnchor() == second.GetAnchor())
return GetAnchor();
base::stack<AXNodeType*> our_ancestors = GetAncestorAnchors();
base::stack<AXNodeType*> other_ancestors = second.GetAncestorAnchors();