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Commit 8b9992b2 authored by Nektarios Paisios's avatar Nektarios Paisios Committed by Commit Bot
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Switched AXPosition in Blink to use Layout NG offset mapping 

AXPosition now uses the deprecated text iterator class for translating DOM offsets to text offsets, and
for calculating text lengths with all uncompressed white space removed.
A text offset in the accessibility tree might not have the same value as the DOM offset for an
equivalent position in the DOM tree, because the DOM may have extra white space that should be collapsed.
This patch switches to using the NGOffsetMapping class in Layout NG for all such calculations.

AX-Relnotes: n/a.

R=dmazzoni@chromium.org, aleventhal@chromium.org

Bug: 1008031
Change-Id: I6953355e83b0953ffa341207bbdde0249cd1b74f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2384471
Commit-Queue: Nektarios Paisios <nektar@chromium.org>
Reviewed-by: default avatarDominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803471}
parent c8c5abba
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Showing with 121 additions and 46 deletions
third_party/blink/renderer/modules/accessibility/ax_position.cc
View file @ 8b9992b2
......@@ -9,12 +9,10 @@
#include "third_party/blink/renderer/core/dom/document.h"
#include "third_party/blink/renderer/core/dom/node.h"
#include "third_party/blink/renderer/core/dom/node_traversal.h"
#include "third_party/blink/renderer/core/editing/ephemeral_range.h"
#include "third_party/blink/renderer/core/editing/iterators/character_iterator.h"
#include "third_party/blink/renderer/core/editing/iterators/text_iterator.h"
#include "third_party/blink/renderer/core/editing/iterators/text_iterator_behavior.h"
#include "third_party/blink/renderer/core/editing/position.h"
#include "third_party/blink/renderer/core/editing/position_with_affinity.h"
#include "third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.h"
#include "third_party/blink/renderer/core/layout/ng/inline/ng_offset_mapping.h"
#include "third_party/blink/renderer/modules/accessibility/ax_layout_object.h"
#include "third_party/blink/renderer/modules/accessibility/ax_object.h"
#include "third_party/blink/renderer/modules/accessibility/ax_object_cache_impl.h"
......@@ -240,15 +238,37 @@ const AXPosition AXPosition::FromPosition(
AXPosition ax_position(*container);
// Convert from a DOM offset that may have uncompressed white space to a
// character offset.
// TODO(nektar): Use LayoutNG offset mapping instead of
// |TextIterator|.
TextIteratorBehavior::Builder iterator_builder;
const TextIteratorBehavior text_iterator_behavior =
iterator_builder.SetDoesNotEmitSpaceBeyondRangeEnd(true).Build();
const auto first_position = Position::FirstPositionInNode(*container_node);
int offset = TextIterator::RangeLength(
first_position, parent_anchored_position, text_iterator_behavior);
ax_position.text_offset_or_child_index_ = offset;
LayoutBlockFlow* formatting_context =
NGOffsetMapping::GetInlineFormattingContextOf(
*container_node->GetLayoutObject());
const NGOffsetMapping* container_offset_mapping =
formatting_context ? NGInlineNode::GetOffsetMapping(formatting_context)
: nullptr;
if (!container_offset_mapping) {
// We are unable to compute the text offset in the accessibility tree that
// corresponds to the DOM offset. We do the next best thing by returning
// either the first or the last AX position in |container| based on the
// |adjustment_behavior|.
switch (adjustment_behavior) {
case AXPositionAdjustmentBehavior::kMoveRight:
return CreateLastPositionInObject(*container, adjustment_behavior);
case AXPositionAdjustmentBehavior::kMoveLeft:
return CreateFirstPositionInObject(*container, adjustment_behavior);
}
}
// We can now compute the text offset that corresponds to the given DOM
// position from the beginning of our formatting context. We also need to
// subtract the text offset of our |container| from the beginning of the
// same formatting context.
int container_offset = container->TextOffsetInFormattingContext(0);
int text_offset =
int{container_offset_mapping
->GetTextContentOffset(parent_anchored_position)
.value_or(static_cast<unsigned int>(container_offset))} -
container_offset;
DCHECK_GE(text_offset, 0);
ax_position.text_offset_or_child_index_ = text_offset;
ax_position.affinity_ = affinity;
#if DCHECK_IS_ON()
String failure_reason;
......@@ -392,10 +412,13 @@ int AXPosition::MaxTextOffset() const {
return 0;
}
// TODO(nektar): Make AXObject::TextLength() public and use throughout this
// method.
if (container_object_->IsNativeTextControl())
return container_object_->StringValue().length();
if (container_object_->IsAXInlineTextBox() || !container_object_->GetNode()) {
const Node* container_node = container_object_->GetNode();
if (container_object_->IsAXInlineTextBox() || !container_node) {
// 1. The |Node| associated with an inline text box contains all the text in
// the static text object parent, whilst the inline text box might contain
// only part of it.
......@@ -405,16 +428,20 @@ int AXPosition::MaxTextOffset() const {
return container_object_->ComputedName().length();
}
// TODO(nektar): Use LayoutNG offset mapping instead of |TextIterator|.
TextIteratorBehavior::Builder iterator_builder;
const TextIteratorBehavior text_iterator_behavior =
iterator_builder.SetDoesNotEmitSpaceBeyondRangeEnd(true).Build();
const auto first_position =
Position::FirstPositionInNode(*container_object_->GetNode());
const auto last_position =
Position::LastPositionInNode(*container_object_->GetNode());
return TextIterator::RangeLength(first_position, last_position,
text_iterator_behavior);
LayoutBlockFlow* formatting_context =
NGOffsetMapping::GetInlineFormattingContextOf(
*container_node->GetLayoutObject());
const NGOffsetMapping* container_offset_mapping =
formatting_context ? NGInlineNode::GetOffsetMapping(formatting_context)
: nullptr;
if (!container_offset_mapping)
return container_object_->ComputedName().length();
const base::span<const NGOffsetMappingUnit> mapping_units =
container_offset_mapping->GetMappingUnitsForNode(*container_node);
if (mapping_units.empty())
return container_object_->ComputedName().length();
return int{mapping_units.back().TextContentEnd() -
mapping_units.front().TextContentStart()};
}
TextAffinity AXPosition::Affinity() const {
......@@ -688,7 +715,7 @@ const AXPosition AXPosition::AsValidDOMPosition(
// positions are also considered to be virtual since they don't have an
// associated DOM node.
// More Explaination:
// In more detail:
// If the child after a tree position doesn't have an associated node in the
// DOM tree, we adjust to the next or previous position because a
// corresponding child node will not be found in the DOM tree. We need a
......@@ -826,20 +853,60 @@ const PositionWithAffinity AXPosition::ToPositionWithAffinity(
affinity_);
}
// TODO(nektar): Use LayoutNG offset mapping instead of |TextIterator|.
TextIteratorBehavior::Builder iterator_builder;
const TextIteratorBehavior text_iterator_behavior =
iterator_builder.SetDoesNotEmitSpaceBeyondRangeEnd(true).Build();
const auto first_position = Position::FirstPositionInNode(*container_node);
const auto last_position = Position::LastPositionInNode(*container_node);
CharacterIterator character_iterator(first_position, last_position,
text_iterator_behavior);
unsigned text_offset_in_container =
adjusted_position.container_object_->TextOffsetInContainer(
// Convert from a text offset, which may have white space collapsed, to a DOM
// offset which should have uncompressed white space.
LayoutBlockFlow* formatting_context =
NGOffsetMapping::GetInlineFormattingContextOf(
*container_node->GetLayoutObject());
const NGOffsetMapping* container_offset_mapping =
formatting_context ? NGInlineNode::GetOffsetMapping(formatting_context)
: nullptr;
if (!container_offset_mapping) {
// We are unable to compute the text offset in the accessibility tree that
// corresponds to the DOM offset. We do the next best thing by returning
// either the first or the last DOM position in |container_node| based on
// the |adjustment_behavior|.
switch (adjustment_behavior) {
case AXPositionAdjustmentBehavior::kMoveRight:
return PositionWithAffinity(
Position::LastPositionInNode(*container_node), affinity_);
case AXPositionAdjustmentBehavior::kMoveLeft:
return PositionWithAffinity(
Position::FirstPositionInNode(*container_node), affinity_);
}
}
int text_offset_in_formatting_context =
adjusted_position.container_object_->TextOffsetInFormattingContext(
adjusted_position.TextOffset());
const EphemeralRange range = character_iterator.CalculateCharacterSubrange(
0, text_offset_in_container);
return PositionWithAffinity(range.EndPosition(), affinity_);
DCHECK_GE(text_offset_in_formatting_context, 0);
// An "after text" position in the accessibility tree should map to a text
// position in the DOM tree that is after the DOM node's text, but before any
// collapsed white space at the node's end. In all other cases, the text
// offset in the accessibility tree should be translated to a DOM offset that
// is after any collapsed white space. For example, look at the inline text
// box with the word "Hello" and observe how the white space in the DOM, both
// before and after the word, is mapped from the equivalent accessibility
// position.
//
// AX text position in "InlineTextBox" name="Hello", 0
// DOM position #text " Hello "@offsetInAnchor[3]
// AX text position in "InlineTextBox" name="Hello", 5
// DOM position #text " Hello "@offsetInAnchor[8]
Position dom_position =
adjusted_position.TextOffset() < adjusted_position.MaxTextOffset()
? container_offset_mapping->GetLastPosition(
static_cast<unsigned int>(text_offset_in_formatting_context))
: container_offset_mapping->GetFirstPosition(
static_cast<unsigned int>(text_offset_in_formatting_context));
// When there is no uncompressed white space at the end of our
// |container_node|, and this is an "after text" position, we might get back
// the NULL position if this is the last node in the DOM.
if (dom_position.IsNull())
dom_position = Position::LastPositionInNode(*container_node);
return PositionWithAffinity(dom_position, affinity_);
}
const Position AXPosition::ToPosition(
......
third_party/blink/renderer/modules/accessibility/ax_position_test.cc
View file @ 8b9992b2
......@@ -1681,10 +1681,15 @@ TEST_F(AccessibilityTest, PositionInInvalidMapLayout) {
TEST_P(ParameterizedAccessibilityTest,
ToPositionWithAffinityWithMultipleInlineTextBoxes) {
// This test expects the starting offset of the last InlineTextBox object to
// equate the sum of the previous inline text boxes' length, without the
// collapsed white-spaces.
//
// "&#10" is a Line Feed ("\n").
SetBodyInnerHTML(
R"HTML(<style>p { white-space: pre-line; }</style>
<p id="paragraph">Hello &#10; world</p>)HTML");
const Node* text = GetElementById("paragraph")->firstChild();
ASSERT_NE(nullptr, text);
ASSERT_TRUE(text->IsTextNode());
......@@ -1695,16 +1700,19 @@ TEST_P(ParameterizedAccessibilityTest,
ASSERT_EQ(ax::mojom::Role::kStaticText, ax_static_text->RoleValue());
ax_static_text->LoadInlineTextBoxes();
ASSERT_EQ(3, ax_static_text->ChildCountIncludingIgnored());
ASSERT_EQ(3, ax_static_text->UnignoredChildCount());
// This test expects the starting offset of the last InlineTextBox object to
// equates the sum of the previous inline text boxes length, without the
// collapsed white-spaces.
const auto ax_position = AXPosition::CreatePositionBeforeObject(
*(ax_static_text->LastChildIncludingIgnored()));
// The last inline text box should be:
// "InlineTextBox" name="world"
const AXObject* ax_last_inline_box =
ax_static_text->LastChildIncludingIgnored();
const auto ax_position =
AXPosition::CreatePositionBeforeObject(*ax_last_inline_box);
const auto position = ax_position.ToPositionWithAffinity();
EXPECT_EQ(LayoutNGEnabled() ? 7 : 6,
position.GetPosition().OffsetInContainerNode());
// The resulting DOM position should be:
// DOM position #text "Hello \n world"@offsetInAnchor[8]
ASSERT_TRUE(position.GetPosition().IsOffsetInAnchor());
EXPECT_EQ(8, position.GetPosition().OffsetInContainerNode());
}
} // namespace test
......
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