ax_platform_node_delegate.h

Go to the documentation of this file.

// Copyright 2014 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_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_
#define UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_
 
#include <cstdint>
#include <map>
#include <memory>
#include <new>
#include <ostream>
#include <set>
#include <string>
#include <utility>
#include <vector>
 
#include "ax/ax_clipping_behavior.h"
#include "ax/ax_coordinate_system.h"
#include "ax/ax_enums.h"
#include "ax/ax_export.h"
#include "ax/ax_node_position.h"
#include "ax/ax_offscreen_result.h"
#include "ax/ax_position.h"
#include "ax/ax_tree.h"
#include "ax/ax_tree_id.h"
#include "ax_unique_id.h"
#include "base/macros.h"
#include "gfx/geometry/rect.h"
#include "gfx/native_widget_types.h"
 
namespace ui {
 
struct AXActionData;
struct AXNodeData;
struct AXTreeData;
class AXPlatformNode;
 
using TextAttribute = std::pair<std::string, std::string>;
using TextAttributeList = std::vector<TextAttribute>;
 
// A TextAttributeMap is a map between the text offset in UTF-16 characters in
// the node hypertext and the TextAttributeList that starts at that location.
// An empty TextAttributeList signifies a return to the default node
// TextAttributeList.
using TextAttributeMap = std::map<int, TextAttributeList>;
 
// An object that wants to be accessible should derive from this class.
// AXPlatformNode subclasses use this interface to query all of the information
// about the object in order to implement native accessibility APIs.
//
// Note that AXPlatformNode has support for accessibility trees where some
// of the objects in the tree are not implemented using AXPlatformNode.
// For example, you may have a native window with platform-native widgets
// in it, but in that window you have custom controls that use AXPlatformNode
// to provide accessibility. That's why GetParent, ChildAtIndex, HitTestSync,
// and GetFocus all return a gfx::NativeViewAccessible - so you can return a
// native accessible if necessary, and AXPlatformNode::GetNativeViewAccessible
// otherwise.
class AX_EXPORT AXPlatformNodeDelegate {
 public:
  virtual ~AXPlatformNodeDelegate() = default;
 
  // Get the accessibility data that should be exposed for this node.
  // Virtually all of the information is obtained from this structure
  // (role, state, name, cursor position, etc.) - the rest of this interface
  // is mostly to implement support for walking the accessibility tree.
  virtual const AXNodeData& GetData() const = 0;
 
  // Get the accessibility tree data for this node.
  virtual const AXTreeData& GetTreeData() const = 0;
 
  // Returns the text of this node and all descendant nodes; including text
  // found in embedded objects.
  //
  // Only text displayed on screen is included. Text from ARIA and HTML
  // attributes that is either not displayed on screen, or outside this node,
  // e.g. aria-label and HTML title, is not returned.
  virtual std::u16string GetInnerText() const = 0;
 
  // Get the unignored selection from the tree
  virtual const AXTree::Selection GetUnignoredSelection() const = 0;
 
  // Creates a text position rooted at this object.
  virtual AXNodePosition::AXPositionInstance CreateTextPositionAt(
      int offset) const = 0;
 
  // Get the accessibility node for the NSWindow the node is contained in. This
  // method is only meaningful on macOS.
  virtual gfx::NativeViewAccessible GetNSWindow() = 0;
 
  // Get the node for this delegate, which may be an AXPlatformNode or it may
  // be a native accessible object implemented by another class.
  virtual gfx::NativeViewAccessible GetNativeViewAccessible() = 0;
 
  // Get the parent of the node, which may be an AXPlatformNode or it may
  // be a native accessible object implemented by another class.
  virtual gfx::NativeViewAccessible GetParent() = 0;
 
  // Get the index in parent. Typically this is the AXNode's index_in_parent_.
  // This should return -1 if the index in parent is unknown.
  virtual int GetIndexInParent() = 0;
 
  // Get the number of children of this node.
  virtual int GetChildCount() const = 0;
 
  // Get the child of a node given a 0-based index.
  virtual gfx::NativeViewAccessible ChildAtIndex(int index) = 0;
 
  // Returns true if it has a modal dialog.
  virtual bool HasModalDialog() const = 0;
 
  // Gets the first child of a node, or nullptr if no children exist.
  virtual gfx::NativeViewAccessible GetFirstChild() = 0;
 
  // Gets the last child of a node, or nullptr if no children exist.
  virtual gfx::NativeViewAccessible GetLastChild() = 0;
 
  // Gets the next sibling of a given node, or nullptr if no such node exists.
  virtual gfx::NativeViewAccessible GetNextSibling() = 0;
 
  // Gets the previous sibling of a given node, or nullptr if no such node
  // exists.
  virtual gfx::NativeViewAccessible GetPreviousSibling() = 0;
 
  // Returns true if an ancestor of this node (not including itself) is a
  // leaf node, meaning that this node is not actually exposed to any
  // platform's accessibility layer.
  virtual bool IsChildOfLeaf() const = 0;
 
  // Returns true if this current node is editable and the root editable node is
  // a plain text field.
  virtual bool IsChildOfPlainTextField() const = 0;
 
  // Returns true if this is a leaf node, meaning all its
  // children should not be exposed to any platform's native accessibility
  // layer.
  virtual bool IsLeaf() const = 0;
 
  // Returns true if this is a top-level browser window that doesn't have a
  // parent accessible node, or its parent is the application accessible node on
  // platforms that have one.
  virtual bool IsToplevelBrowserWindow() = 0;
 
  // If this object is exposed to the platform's accessibility layer, returns
  // this object. Otherwise, returns the platform leaf under which this object
  // is found.
  virtual gfx::NativeViewAccessible GetClosestPlatformObject() const = 0;
 
  class ChildIterator {
   public:
    virtual ~ChildIterator() = default;
    virtual bool operator==(const ChildIterator& rhs) const = 0;
    virtual bool operator!=(const ChildIterator& rhs) const = 0;
    virtual void operator++() = 0;
    virtual void operator++(int) = 0;
    virtual void operator--() = 0;
    virtual void operator--(int) = 0;
    virtual gfx::NativeViewAccessible GetNativeViewAccessible() const = 0;
    virtual int GetIndexInParent() const = 0;
    virtual AXPlatformNodeDelegate& operator*() const = 0;
    virtual AXPlatformNodeDelegate* operator->() const = 0;
  };
  virtual std::unique_ptr<AXPlatformNodeDelegate::ChildIterator>
  ChildrenBegin() = 0;
  virtual std::unique_ptr<AXPlatformNodeDelegate::ChildIterator>
  ChildrenEnd() = 0;
 
  // Returns the accessible name for the node.
  virtual std::string GetName() const = 0;
 
  // Returns the text of this node and represent the text of descendant nodes
  // with a special character in place of every embedded object. This represents
  // the concept of text in ATK and IA2 APIs.
  virtual std::u16string GetHypertext() const = 0;
 
  // Set the selection in the hypertext of this node. Depending on the
  // implementation, this may mean the new selection will span multiple nodes.
  virtual bool SetHypertextSelection(int start_offset, int end_offset) = 0;
 
  // Compute the text attributes map for the node associated with this
  // delegate, given a set of default text attributes that apply to the entire
  // node. A text attribute map associates a list of text attributes with a
  // given hypertext offset in this node.
  virtual TextAttributeMap ComputeTextAttributeMap(
      const TextAttributeList& default_attributes) const = 0;
 
  // Get the inherited font family name for text attributes. We need this
  // because inheritance works differently between the different delegate
  // implementations.
  virtual std::string GetInheritedFontFamilyName() const = 0;
 
  // Return the bounds of this node in the coordinate system indicated. If the
  // clipping behavior is set to clipped, clipping is applied. If an offscreen
  // result address is provided, it will be populated depending on whether the
  // returned bounding box is onscreen or offscreen.
  virtual gfx::Rect GetBoundsRect(
      const AXCoordinateSystem coordinate_system,
      const AXClippingBehavior clipping_behavior,
      AXOffscreenResult* offscreen_result = nullptr) const = 0;
 
  virtual gfx::Rect GetClippedScreenBoundsRect(
      AXOffscreenResult* offscreen_result = nullptr) const = 0;
 
  // Return the bounds of the text range given by text offsets relative to
  // GetHypertext in the coordinate system indicated. If the clipping behavior
  // is set to clipped, clipping is applied. If an offscreen result address is
  // provided, it will be populated depending on whether the returned bounding
  // box is onscreen or offscreen.
  virtual gfx::Rect GetHypertextRangeBoundsRect(
      const int start_offset,
      const int end_offset,
      const AXCoordinateSystem coordinate_system,
      const AXClippingBehavior clipping_behavior,
      AXOffscreenResult* offscreen_result = nullptr) const = 0;
 
  // Return the bounds of the text range given by text offsets relative to
  // GetInnerText in the coordinate system indicated. If the clipping behavior
  // is set to clipped, clipping is applied. If an offscreen result address is
  // provided, it will be populated depending on whether the returned bounding
  // box is onscreen or offscreen.
  virtual gfx::Rect GetInnerTextRangeBoundsRect(
      const int start_offset,
      const int end_offset,
      const AXCoordinateSystem coordinate_system,
      const AXClippingBehavior clipping_behavior,
      AXOffscreenResult* offscreen_result = nullptr) const = 0;
 
  // Do a *synchronous* hit test of the given location in global screen physical
  // pixel coordinates, and the node within this node's subtree (inclusive)
  // that's hit, if any.
  //
  // If the result is anything other than this object or NULL, it will be
  // hit tested again recursively - that allows hit testing to work across
  // implementation classes. It's okay to take advantage of this and return
  // only an immediate child and not the deepest descendant.
  //
  // This function is mainly used by accessibility debugging software.
  // Platforms with touch accessibility use a different asynchronous interface.
  virtual gfx::NativeViewAccessible HitTestSync(
      int screen_physical_pixel_x,
      int screen_physical_pixel_y) const = 0;
 
  // Return the node within this node's subtree (inclusive) that currently has
  // focus, or return nullptr if this subtree is not connected to the top
  // document through its ancestry chain.
  virtual gfx::NativeViewAccessible GetFocus() = 0;
 
  // Get whether this node is offscreen.
  virtual bool IsOffscreen() const = 0;
 
  // Get whether this node is a minimized window.
  virtual bool IsMinimized() const = 0;
 
  // See AXNode::IsText().
  virtual bool IsText() const = 0;
 
  // Get whether this node is in web content.
  virtual bool IsWebContent() const = 0;
 
  // Returns true if the caret or selection is visible on this object.
  virtual bool HasVisibleCaretOrSelection() const = 0;
 
  // Get another node from this same tree.
  virtual AXPlatformNode* GetFromNodeID(int32_t id) = 0;
 
  // Get a node from a different tree using a tree ID and node ID.
  // Note that this is only guaranteed to work if the other tree is of the
  // same type, i.e. it won't work between web and views or vice-versa.
  virtual AXPlatformNode* GetFromTreeIDAndNodeID(const ui::AXTreeID& ax_tree_id,
                                                 int32_t id) = 0;
 
  // Given a node ID attribute (one where IsNodeIdIntAttribute is true), return
  // a target nodes for which this delegate's node has that relationship
  // attribute or NULL if there is no such relationship.
  virtual AXPlatformNode* GetTargetNodeForRelation(
      ax::mojom::IntAttribute attr) = 0;
 
  // Given a node ID attribute (one where IsNodeIdIntListAttribute is true),
  // return a vector of all target nodes for which this delegate's node has that
  // relationship attribute.
  virtual std::vector<AXPlatformNode*> GetTargetNodesForRelation(
      ax::mojom::IntListAttribute attr) = 0;
 
  // Given a node ID attribute (one where IsNodeIdIntAttribute is true), return
  // a set of all source nodes that have that relationship attribute between
  // them and this delegate's node.
  virtual std::set<AXPlatformNode*> GetReverseRelations(
      ax::mojom::IntAttribute attr) = 0;
 
  // Given a node ID list attribute (one where IsNodeIdIntListAttribute is
  // true), return a set of all source nodes that have that relationship
  // attribute between them and this delegate's node.
  virtual std::set<AXPlatformNode*> GetReverseRelations(
      ax::mojom::IntListAttribute attr) = 0;
 
  // Return the string representation of the unique ID assigned by the author,
  // otherwise return an empty string. The author ID must be persistent across
  // any instance of the application, regardless of locale. The author ID should
  // be unique among sibling accessibility nodes and is best if unique across
  // the application, however, not meeting this requirement is non-fatal.
  virtual std::u16string GetAuthorUniqueId() const = 0;
 
  virtual const AXUniqueId& GetUniqueId() const = 0;
 
  // Finds the previous or next offset from the provided offset, that matches
  // the provided boundary type.
  //
  // This method finds text boundaries in the text used for platform text APIs.
  // Implementations may use side-channel data such as line or word indices to
  // produce appropriate results. It may optionally return no value, indicating
  // that the delegate does not have all the information required to calculate
  // this value and it is the responsibility of the AXPlatformNode itself to
  // calculate it.
  virtual std::optional<int> FindTextBoundary(
      ax::mojom::TextBoundary boundary,
      int offset,
      ax::mojom::MoveDirection direction,
      ax::mojom::TextAffinity affinity) const = 0;
 
  // Return a vector of all the descendants of this delegate's node. This method
  // is only meaningful for Windows UIA.
  virtual const std::vector<gfx::NativeViewAccessible> GetUIADescendants()
      const = 0;
 
  // Return a string representing the language code.
  //
  // For web content, this will consider the language declared in the DOM, and
  // may eventually attempt to automatically detect the language from the text.
  //
  // This language code will be BCP 47.
  //
  // Returns empty string if no appropriate language was found or if this node
  // uses the default interface language.
  virtual std::string GetLanguage() const = 0;
 
  //
  // Tables. All of these should be called on a node that's a table-like
  // role, otherwise they return nullopt.
  //
  virtual bool IsTable() const = 0;
  virtual std::optional<int> GetTableColCount() const = 0;
  virtual std::optional<int> GetTableRowCount() const = 0;
  virtual std::optional<int> GetTableAriaColCount() const = 0;
  virtual std::optional<int> GetTableAriaRowCount() const = 0;
  virtual std::optional<int> GetTableCellCount() const = 0;
  virtual std::optional<bool> GetTableHasColumnOrRowHeaderNode() const = 0;
  virtual std::vector<int32_t> GetColHeaderNodeIds() const = 0;
  virtual std::vector<int32_t> GetColHeaderNodeIds(int col_index) const = 0;
  virtual std::vector<int32_t> GetRowHeaderNodeIds() const = 0;
  virtual std::vector<int32_t> GetRowHeaderNodeIds(int row_index) const = 0;
  virtual AXPlatformNode* GetTableCaption() const = 0;
 
  // Table row-like nodes.
  virtual bool IsTableRow() const = 0;
  virtual std::optional<int> GetTableRowRowIndex() const = 0;
 
  // Table cell-like nodes.
  virtual bool IsTableCellOrHeader() const = 0;
  virtual std::optional<int> GetTableCellIndex() const = 0;
  virtual std::optional<int> GetTableCellColIndex() const = 0;
  virtual std::optional<int> GetTableCellRowIndex() const = 0;
  virtual std::optional<int> GetTableCellColSpan() const = 0;
  virtual std::optional<int> GetTableCellRowSpan() const = 0;
  virtual std::optional<int> GetTableCellAriaColIndex() const = 0;
  virtual std::optional<int> GetTableCellAriaRowIndex() const = 0;
  virtual std::optional<int32_t> GetCellId(int row_index,
                                           int col_index) const = 0;
  virtual std::optional<int32_t> CellIndexToId(int cell_index) const = 0;
 
  // Helper methods to check if a cell is an ARIA-1.1+ 'cell' or 'gridcell'
  virtual bool IsCellOrHeaderOfARIATable() const = 0;
  virtual bool IsCellOrHeaderOfARIAGrid() const = 0;
 
  // Ordered-set-like and item-like nodes.
  virtual bool IsOrderedSetItem() const = 0;
  virtual bool IsOrderedSet() const = 0;
  virtual std::optional<int> GetPosInSet() const = 0;
  virtual std::optional<int> GetSetSize() const = 0;
 
  //
  // Events.
  //
 
  // Return the platform-native GUI object that should be used as a target
  // for accessibility events.
  virtual gfx::AcceleratedWidget GetTargetForNativeAccessibilityEvent() = 0;
 
  //
  // Actions.
  //
 
  // Perform an accessibility action, switching on the ax::mojom::Action
  // provided in |data|.
  virtual bool AccessibilityPerformAction(const AXActionData& data) = 0;
 
  //
  // Localized strings.
  //
 
  virtual std::u16string GetLocalizedRoleDescriptionForUnlabeledImage()
      const = 0;
  virtual std::u16string GetLocalizedStringForImageAnnotationStatus(
      ax::mojom::ImageAnnotationStatus status) const = 0;
  virtual std::u16string GetLocalizedStringForLandmarkType() const = 0;
  virtual std::u16string GetLocalizedStringForRoleDescription() const = 0;
  virtual std::u16string GetStyleNameAttributeAsLocalizedString() const = 0;
 
  //
  // Testing.
  //
 
  // Accessibility objects can have the "hot tracked" state set when
  // the mouse is hovering over them, but this makes tests flaky because
  // the test behaves differently when the mouse happens to be over an
  // element. The default value should be false if not in testing mode.
  virtual bool ShouldIgnoreHoveredStateForTesting() = 0;
 
  // If this object is exposed to the platform's accessibility layer, returns
  // this object. Otherwise, returns the platform leaf or lowest unignored
  // ancestor under which this object is found.
  //
  // (An ignored node means that the node should not be exposed to platform
  // APIs: See `IsIgnored`.)
  virtual gfx::NativeViewAccessible GetLowestPlatformAncestor() const = 0;
 
  // Creates a string representation of this delegate's data.
  std::string ToString() { return GetData().ToString(); }
 
  // Returns a string representation of the subtree of delegates rooted at this
  // delegate.
  std::string SubtreeToString() { return SubtreeToStringHelper(0u); }
 
  friend std::ostream& operator<<(std::ostream& stream,
                                  AXPlatformNodeDelegate& delegate) {
    return stream << delegate.ToString();
  }
 
 protected:
  AXPlatformNodeDelegate() = default;
 
  virtual std::string SubtreeToStringHelper(size_t level) = 0;
 
 private:
  BASE_DISALLOW_COPY_AND_ASSIGN(AXPlatformNodeDelegate);
};
 
}  // namespace ui
 
#endif  // UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_