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office-gobmx/include/svx/AccessibleShape.hxx
Michael Weghorn 206543c7be [API CHANGE] tdf#150683 a11y: Switch a11y child index to 64 bit 
With 16k column support in Calc enabled by default in

    commit 4c5f8ccf0a
    Date:   Tue Mar 8 12:44:49 2022 +0100

        change default Calc number of columns to 16384 (tdf#50916)

, the number of Calc cells in a spreadsheet is larger than
SAL_MAX_INT32, meaning that a 32-bit a11y child index is no more
enough and using it resulted in integer overflows in
methods handling corresponding Calc cells in the a11y layer.
This e.g. had the effect of the Orca and NVDA screen readers
not announcing focused or selected cells properly when their
a11y child index was out of the 32-bit integer range.

Switch the internal a11y child indices to 64 bit to
be able to handle this properly internally.

Since the platform APIs (at least AT-SPI on Linux and
IAccessible2 on Windows; from what I can see LO's macOS
a11y bridge doesn't directly expose the child index)
are still restricted to 32 bit, larger child indices
still cannot be exposed via the platform APIs.

As a consequence, use of the the IAccessible2 and
AT-SPI methods that use the child index remains
problematic in those cases where the child index
is larger. However, as an alternative to using the
AT-SPI Table interface and the IAccessibleTable/
IAccessibleTable2 interfaces with the child index
to retrieve information about a specific cell,
both AT-SPI and IAccessible2 also provide interfaces
to retrieve that information directly
from the cell object (TableCell interface for AT-SPI,
IAccessibleTableCell for IAccessible2).

Those interfaces are already implemented/exposed
for winaccessibility (s. `CAccTable`) and the
qt5/qt6/kf5 VCL plugins (s. the `QAccessibleTableCellInterface`
methods implemented in `QtAccessibleInterface`).
With the switch to 64-bit internal a11y child indices,
these now behave correctly for cells with a child
index that doesn't fit into 32 bit as well.

NVDA on Windows already uses the IAccessibleTableCell
interface and thus announcing focused cells works fine
with this change in place.

Orca on Linux currently doesn't make use of the AT-SPI
TableCell interface yet, but with a suggested change to
do so [1], announcement of selected cells works
with the qt6 VCL plugin with a current qtbase dev branch
as well - when combined with the suggested changes
to implement support for the AT-SPI TableCell interface
in Qt [2] [3] and the LO change based on that [4] and
a fix for a nullptr dereference [5].

The gtk3 VCL plugin doesn't expose the AT-SPI
TableCell interface yet, but once it does so
(via `AtkTableCell`), it also works with the
suggested Orca change [1] in place.
(Adding that is planned for an upcoming change,
works with a local WIP patch.)

For handling return values that are larger than what
platform APIs support, the following approach has
been chosen for now:

1) When the return value is for the count of
(selected) children, the maximum value N
supported by the platform API is returned.
(This is what `ScAccessibleTableBase::getAccessibleChildCount`
did previously.)
The first N elements can be accessed by their
actual (selection) indices.

2) When the return value is the child/cell index,
-2 is returned for objects whose index is greater
than the maximum value supported by the platform
API.
Using a non-negative value would mean that the
index would refer to *another* actually existing
child. A child index of -1 on the other hand
tends to be interpreted as "child is invalid" or
"object isn't actually a child of its (previous)
parent any more)". For the Orca case, this would
result in objects with a child index of -1
not being announced, as they are considered
"zombies" [6].

What's still somewhat problematic is the case where
more than 2^31 children are *selected*, since access
to those children still happens by the index into
the selection in the platform APIs, and not all
selected items are accessible this way.
(Screen readers usually just retrieve
the first and last element from the selection and
announce those.)

Orca already seems to apply different handling for the
case for fully selected rows and columns, so
"All cells selected" or "Columns ... to ... selected"
is announced just fine even if more than 2^31
cells are selected.

(Side note: While Microsoft User Interface
Automation - UIA - also uses 32-bit indices, it also
has specific methods in the ISelectionProvider2
interface that allow to explicitly retrieve the
first and last selected item,
`ISelectionProvider2::get_FirstSelectedItem` and
`ISelectionProvider2::get_LastSelectedItem`, but
we currently don't support UIA on Windows.)

Bound checks at the beginning of the methods from the
`XAccessibleContext`, `XAccessibleSelection` and
`XAccessibleTable` interfaces that take a child index
(or in helper methods called by those) should generally
already prevent too large indices from being passed to
the methods in the lower layer code that take smaller
integer types. Such bound checking has been
been added in various places where it wasn't present yet.
If there any remaining issues of this
kind that show after this commit, they can probably be
solved in a similar way (s.e.g. the change to
`AccessibleBrowseBox::getAccessibleChild` in this
commit).
A few asserts were also added at
places where my understanding is that values shouldn't
be larger than what is supported by a called method
anyway.

A test case will be added in a following change.

[1] https://gitlab.gnome.org/GNOME/orca/-/merge_requests/131
[2] https://codereview.qt-project.org/c/qt/qtbase/+/428566
[3] https://codereview.qt-project.org/c/qt/qtbase/+/428567
[4] https://gerrit.libreoffice.org/c/core/+/138750
[5] https://codereview.qt-project.org/c/qt/qtbase/+/430157
[6] 82c8542002/src/orca/script_utilities.py (L5155)

Change-Id: I3af590c988b0e6754fc72545918412f39e8fea07
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/139258
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
2022-09-02 15:47:37 +02:00

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.apache.org/licenses/LICENSE-2.0 .
*/
#ifndef INCLUDED_SVX_ACCESSIBLESHAPE_HXX
#define INCLUDED_SVX_ACCESSIBLESHAPE_HXX
#include <com/sun/star/accessibility/AccessibleScrollType.hpp>
#include <com/sun/star/accessibility/TextSegment.hpp>
#include <com/sun/star/accessibility/XAccessibleSelection.hpp>
#include <com/sun/star/accessibility/XAccessibleExtendedAttributes.hpp>
#include <com/sun/star/accessibility/XAccessibleGroupPosition.hpp>
#include <com/sun/star/accessibility/XAccessibleHypertext.hpp>
#include <com/sun/star/awt/Point.hpp>
#include <com/sun/star/awt/Rectangle.hpp>
#include <com/sun/star/awt/Size.hpp>
#include <com/sun/star/document/XShapeEventListener.hpp>
#include <com/sun/star/lang/EventObject.hpp>
#include <com/sun/star/uno/Any.hxx>
#include <com/sun/star/uno/Reference.hxx>
#include <com/sun/star/uno/Sequence.hxx>
#include <com/sun/star/uno/Type.hxx>
#include <com/sun/star/lang/XUnoTunnel.hpp>
#include <comphelper/servicehelper.hxx>
#include <editeng/AccessibleContextBase.hxx>
#include <editeng/AccessibleComponentBase.hxx>
#include <rtl/ustring.hxx>
#include <sal/types.h>
#include <svx/AccessibleShapeTreeInfo.hxx>
#include <svx/IAccessibleViewForwarderListener.hxx>
#include <svx/svxdllapi.h>
#include <memory>
namespace com::sun::star {
namespace accessibility { class XAccessible; }
namespace accessibility { class XAccessibleEventListener; }
namespace accessibility { class XAccessibleHyperlink; }
namespace accessibility { class XAccessibleRelationSet; }
namespace beans { struct PropertyValue; }
namespace document { struct EventObject; }
namespace drawing { class XShape; }
namespace uno { class XInterface; }
}
class SdrObject;
namespace accessibility {
class AccessibleShapeInfo;
class AccessibleTextHelper;
class ChildrenManager;
class IAccessibleParent;
/** This base class provides a base implementation for all shapes. For more
detailed documentation about the methods refer to the descriptions of
the implemented interfaces. These are, among others,
XAccessible, <type>XAccessibleContext</type>,
XAccessibleComponent and
XAccessibleExtendedComponent.
<p>The children of a shape can stem from two sources which, in case of
SVX and SD shapes, are mutually exclusive. This implementation,
however, handles both simultaneously to cope with future extensions or
shapes from other projects.
<ul>
<li>If this shape is a group shape, i.e. a
SvxShapeGroup or a <type>Svx3DSceneObject</type>, it
can have nested shapes.</li>
<li>If this shape is a descendant from SvxShapeText
then the text paragraphs are its children.</li>
</ul>
</p>
<p>Accessible shapes do not listen for disposing() calls of the UNO
shapes they make accessible. This is the task of their owner, usually a
container, who can then call dispose() at the accessible object.</p>
*/
class SVX_DLLPUBLIC AccessibleShape
: public AccessibleContextBase,
public AccessibleComponentBase,
public css::accessibility::XAccessibleSelection,
public css::accessibility::XAccessibleExtendedAttributes,
public css::accessibility::XAccessibleGroupPosition,
public css::accessibility::XAccessibleHypertext,
public IAccessibleViewForwarderListener,
public css::document::XShapeEventListener,
public css::lang::XUnoTunnel
{
public:
//===== internal ========================================================
/** Create a new accessible object that makes the given shape accessible.
@param rShapeInfo
This object contains all information specific to the new
accessible shape. That are e.g. the shape to be made accessible
and the accessible object that will become the parent of the new
object.
@param rShapeTreeInfo
Bundle of information passed to this shape and all of its descendants.
@attention
Always call the <member>init</member> method after creating a
new accessible shape. This is one way to overcome the potential
problem of registering the new object with e.g. event
broadcasters. That would delete the new object if a broadcaster
would not keep a strong reference to the new object.
*/
AccessibleShape (
const AccessibleShapeInfo& rShapeInfo,
const AccessibleShapeTreeInfo& rShapeTreeInfo);
//Solution: Overwrite the object's current name.
virtual OUString SAL_CALL getAccessibleName() override;
virtual OUString SAL_CALL getAccessibleDescription() override;
virtual css::uno::Reference< css::accessibility::XAccessibleRelationSet> SAL_CALL getAccessibleRelationSet() override;
//===== XAccessibleSelection ============================================
virtual void SAL_CALL selectAccessibleChild(
sal_Int64 nChildIndex ) override;
virtual sal_Bool SAL_CALL isAccessibleChildSelected(
sal_Int64 nChildIndex ) override;
virtual void SAL_CALL clearAccessibleSelection( ) override;
virtual void SAL_CALL selectAllAccessibleChildren( ) override;
virtual sal_Int64 SAL_CALL getSelectedAccessibleChildCount( ) override;
virtual css::uno::Reference< css::accessibility::XAccessible > SAL_CALL getSelectedAccessibleChild(
sal_Int64 nSelectedChildIndex ) override;
virtual void SAL_CALL deselectAccessibleChild(
sal_Int64 nSelectedChildIndex ) override;
// ====== XAccessibleExtendedAttributes =====================================
virtual css::uno::Any SAL_CALL getExtendedAttributes() override ;
/// Return this object's role.
virtual sal_Int16 SAL_CALL getAccessibleRole() override;
//===== XAccessibleGroupPosition =========================================
virtual css::uno::Sequence< sal_Int32 > SAL_CALL
getGroupPosition( const css::uno::Any& rAny ) override;
virtual OUString SAL_CALL getObjectLink( const css::uno::Any& accoject ) override;
/** The destructor releases its children manager and text engine if
still existent. These are responsible to send appropriate events.
*/
virtual ~AccessibleShape() override;
/** Initialize a new shape. See the documentation of the constructor
for the reason of this method's existence.
*/
virtual void Init();
/** Set the specified state. If the state is <const>FOCUSED</const>
then, additionally to the inherited functionality, the focus
listeners registered with the XAccessibleComponent
interface are called (if that state really changes).
@param aState
The state to turn on.
@return
The returned flag indicates whether the specified state has been
changed (<TRUE/>), i.e. it has formerly not been set.
*/
virtual bool SetState (sal_Int64 aState) override;
/** Reset the specified state. If the state is <const>FOCUSED</const>
then, additionally to the inherited functionality, the focus
listeners registered with the XAccessibleComponent
interface are called (if that state really changes).
@param aState
The state to turn off.
@return
The returned flag indicates whether the specified state has been
changed (<TRUE/>), i.e. it has formerly been set.
*/
virtual bool ResetState (sal_Int64 aState) override;
/** Return the state of the specified state. Take the
<const>FOCUSED</const> state from the accessible edit engine.
@param aState
The state for which to return its value.
@return
A value of <TRUE/> indicates that the state is set. A <FALSE/>
value indicates an unset state or the inability to access the
entity that manages the state set.
*/
bool GetState (sal_Int64 aState);
//===== XAccessibleContext ==============================================
/// Return the number of currently visible children.
virtual sal_Int64 SAL_CALL
getAccessibleChildCount() override;
/** Return the specified child.
@param nIndex
Index of the requested child.
@return
Reference of the requested child which is the accessible object
of a visible shape.
@throws IndexOutOfBoundsException
Throws an exception if the index is not valid.
*/
virtual css::uno::Reference<
css::accessibility::XAccessible> SAL_CALL
getAccessibleChild (sal_Int64 nIndex) override;
/// Return the set of current states.
virtual sal_Int64 SAL_CALL
getAccessibleStateSet() override;
/// Return this objects index among the parents children.
virtual sal_Int64 SAL_CALL
getAccessibleIndexInParent() override;
//===== XAccessibleComponent ============================================
virtual css::uno::Reference<
css::accessibility::XAccessible > SAL_CALL
getAccessibleAtPoint (const css::awt::Point& aPoint) override;
virtual css::awt::Rectangle SAL_CALL getBounds() override;
virtual css::awt::Point SAL_CALL getLocation() override;
virtual css::awt::Point SAL_CALL getLocationOnScreen() override;
virtual css::awt::Size SAL_CALL getSize() override;
virtual sal_Int32 SAL_CALL getForeground() override;
virtual sal_Int32 SAL_CALL getBackground() override;
//===== XAccessibleEventBroadcaster =====================================
/** This call is forwarded to a) the base class and b) to the
accessible edit engine if it is present.
@param rxListener
This listener is informed about accessibility events.
*/
virtual void SAL_CALL
addAccessibleEventListener (
const css::uno::Reference<
css::accessibility::XAccessibleEventListener >& rxListener) override;
/** This call is forwarded to a) the base class and b) to the
accessible edit engine if it is present.
@param rxListener
This listener will not be informed about accessibility events
anymore.
*/
virtual void SAL_CALL
removeAccessibleEventListener (
const css::uno::Reference<
css::accessibility::XAccessibleEventListener >& rxListener) override;
//===== XInterface ======================================================
virtual css::uno::Any SAL_CALL
queryInterface (const css::uno::Type & rType) override;
virtual void SAL_CALL
acquire()
noexcept override;
virtual void SAL_CALL
release()
noexcept override;
//===== XServiceInfo ====================================================
/** Returns an identifier for the implementation of this object.
*/
virtual OUString SAL_CALL
getImplementationName() override;
virtual css::uno::Sequence< OUString> SAL_CALL
getSupportedServiceNames() override;
//===== XTypeProvider ===================================================
virtual css::uno::Sequence< css::uno::Type> SAL_CALL
getTypes() override;
//===== IAccessibleViewForwarderListener ================================
virtual void ViewForwarderChanged() override;
/** Listen for disposing events of the model. The accessible shape
remains functional when this happens.
*/
void disposing (const css::lang::EventObject& Source);
//===== document::XShapeEventListener ========================================
virtual void SAL_CALL
notifyShapeEvent (const css::document::EventObject& rEventObject) override;
//===== XUnoTunnel ========================================================
UNO3_GETIMPLEMENTATION_DECL(AccessibleShape)
//===== XAccessibleHypertext ========================================================
virtual sal_Int32 SAL_CALL getHyperLinkCount() override;
virtual css::uno::Reference< css::accessibility::XAccessibleHyperlink >
SAL_CALL getHyperLink( sal_Int32 nLinkIndex ) override;
virtual sal_Int32 SAL_CALL getHyperLinkIndex( sal_Int32 nCharIndex ) override;
//===== XAccessibleText ==================================================
virtual sal_Int32 SAL_CALL getCaretPosition( ) override;
virtual sal_Bool SAL_CALL setCaretPosition( sal_Int32 nIndex ) override;
virtual sal_Unicode SAL_CALL getCharacter( sal_Int32 nIndex ) override;//Shen Zhen Jie changed sal_Unicode to sal_uInt32; change back to sal_Unicode
virtual css::uno::Sequence< css::beans::PropertyValue > SAL_CALL getCharacterAttributes( sal_Int32 nIndex, const css::uno::Sequence< OUString >& aRequestedAttributes ) override;
virtual css::awt::Rectangle SAL_CALL getCharacterBounds( sal_Int32 nIndex ) override;
virtual sal_Int32 SAL_CALL getCharacterCount( ) override;
virtual sal_Int32 SAL_CALL getIndexAtPoint( const css::awt::Point& aPoint ) override;
virtual OUString SAL_CALL getSelectedText( ) override;
virtual sal_Int32 SAL_CALL getSelectionStart( ) override;
virtual sal_Int32 SAL_CALL getSelectionEnd( ) override;
virtual sal_Bool SAL_CALL setSelection( sal_Int32 nStartIndex, sal_Int32 nEndIndex ) override;
virtual OUString SAL_CALL getText( ) override;
virtual OUString SAL_CALL getTextRange( sal_Int32 nStartIndex, sal_Int32 nEndIndex ) override;
virtual css::accessibility::TextSegment SAL_CALL getTextAtIndex( sal_Int32 nIndex, sal_Int16 aTextType ) override;
virtual css::accessibility::TextSegment SAL_CALL getTextBeforeIndex( sal_Int32 nIndex, sal_Int16 aTextType ) override;
virtual css::accessibility::TextSegment SAL_CALL getTextBehindIndex( sal_Int32 nIndex, sal_Int16 aTextType ) override;
virtual sal_Bool SAL_CALL copyText( sal_Int32 nStartIndex, sal_Int32 nEndIndex ) override;
virtual sal_Bool SAL_CALL scrollSubstringTo( sal_Int32 nStartIndex, sal_Int32 nEndIndex, css::accessibility::AccessibleScrollType aScrollType) override;
//===== Misc ========================================================
const css::uno::Reference< css::drawing::XShape >&
GetXShape() const { return mxShape; }
/** set the index _nIndex at the accessible shape
@param _nIndex
The new index in parent.
*/
void setIndexInParent(sal_Int32 _nIndex) { m_nIndexInParent = _nIndex; }
protected:
/// Children manager. May be empty if there are no children.
std::unique_ptr<ChildrenManager> mpChildrenManager;
/// Reference to the actual shape.
css::uno::Reference<
css::drawing::XShape> mxShape;
/** Bundle of information passed to all shapes in a document tree.
*/
AccessibleShapeTreeInfo maShapeTreeInfo;
/** the index in parent.
*/
sal_Int32 m_nIndexInParent;
/** The accessible text engine. May be NULL if it can not be created.
*/
std::unique_ptr<AccessibleTextHelper> mpText;
/** This object can be used to modify the child list of our parent.
*/
IAccessibleParent* mpParent;
/** This object can be removed when we have an extra interface to ask if the shape is selected
*/
SdrObject* m_pShape;
/** This method is called from the component helper base class while
disposing.
*/
virtual void SAL_CALL disposing() override;
/** Create a base name string that contains the accessible name.
@throws css::uno::RuntimeException
*/
virtual OUString
CreateAccessibleBaseName();
/** Create a unique name string that contains the accessible name. The
name consists of the base name and the index.
*/
virtual OUString
CreateAccessibleName() override;
/// @throws css::uno::RuntimeException
OUString
GetFullAccessibleName(AccessibleShape *shape);
virtual OUString GetStyle() const;
/** Update the <const>OPAQUE</const> and <const>SELECTED</const> state.
*/
void UpdateStates();
private:
AccessibleShape (const AccessibleShape&) = delete;
AccessibleShape& operator= (const AccessibleShape&) = delete;
//Old accessible name
OUString aAccName;
/** Call this method when the title, name, or description of the mxShape
member (may) have been changed.
This method adapts the name and description members of the
AccessibleContextBase base class.
*/
void UpdateNameAndDescription();
};
} // end of namespace accessibility
#endif
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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