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office-gobmx/accessibility/inc/extended/AccessibleBrowseBoxTableBase.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 .
*/
#pragma once
#include <extended/AccessibleBrowseBoxBase.hxx>
#include <cppuhelper/implbase1.hxx>
#include <com/sun/star/accessibility/XAccessibleTable.hpp>
namespace accessibility {
typedef ::cppu::ImplHelper1< css::accessibility::XAccessibleTable >
AccessibleBrowseBoxTableImplHelper;
/** The BrowseBox accessible table objects inherit from this base class. It
implements basic functionality for the XAccessibleTable interface.
BrowseBox table objects are: the data table, the column header bar and the
row header bar. */
class AccessibleBrowseBoxTableBase :
public BrowseBoxAccessibleElement,
public AccessibleBrowseBoxTableImplHelper
{
public:
/** Constructor sets specified name and description. If the constant of a
text is BBTEXT_NONE, the derived class has to set the text via
implSetName() and implSetDescription() (in Ctor) or later via
setAccessibleName() and setAccessibleDescription() (these methods
notify the listeners about the change).
@param rxParent XAccessible interface of the parent object.
@param rBrowseBox The BrowseBox control.
@param eObjType Type of BrowseBox object. */
AccessibleBrowseBoxTableBase(
const css::uno::Reference< css::accessibility::XAccessible >& rxParent,
::vcl::IAccessibleTableProvider& rBrowseBox,
AccessibleBrowseBoxObjType eObjType );
protected:
virtual ~AccessibleBrowseBoxTableBase() override = default;
public:
// XAccessibleContext
/** @return The count of visible children. */
virtual sal_Int64 SAL_CALL getAccessibleChildCount() override;
/** @return The role of this object (a table). */
virtual sal_Int16 SAL_CALL getAccessibleRole() override;
/* Derived classes have to implement:
- getAccessibleChild,
- getAccessibleIndexInParent. */
// XAccessibleComponent
/* Derived classes have to implement:
- getAccessibleAt,
- grabFocus. */
// XAccessibleTable
/** @return The number of used rows in the table (0 = empty table). */
virtual sal_Int32 SAL_CALL getAccessibleRowCount() override;
/** @return The number of used columns in the table (0 = empty table). */
virtual sal_Int32 SAL_CALL getAccessibleColumnCount() override;
/** @return The row extent of the specified cell (always 1). */
virtual sal_Int32 SAL_CALL
getAccessibleRowExtentAt( sal_Int32 nRow, sal_Int32 nColumn ) override;
/** @return The column extent of the specified cell (always 1). */
virtual sal_Int32 SAL_CALL
getAccessibleColumnExtentAt( sal_Int32 nRow, sal_Int32 nColumn ) override;
/** @return The caption cell of the table (not supported). */
virtual css::uno::Reference<
css::accessibility::XAccessible > SAL_CALL
getAccessibleCaption() override;
/** @return The summary object of the table (not supported). */
virtual css::uno::Reference<
css::accessibility::XAccessible > SAL_CALL
getAccessibleSummary() override;
/** @return The child index of the specified cell. */
virtual sal_Int64 SAL_CALL getAccessibleIndex( sal_Int32 nRow, sal_Int32 nColumn ) override;
/** @return The row index of the specified child cell. */
virtual sal_Int32 SAL_CALL getAccessibleRow( sal_Int64 nChildIndex ) override;
/** @return The column index of the specified child cell. */
virtual sal_Int32 SAL_CALL getAccessibleColumn( sal_Int64 nChildIndex ) override;
/* Derived classes have to implement:
- getAccessibleRowDescription,
- getAccessibleColumnDescription,
- getAccessibleRowHeaders,
- getAccessibleColumnHeaders,
- getSelectedAccessibleRows,
- getSelectedAccessibleColumns,
- isAccessibleRowSelected,
- isAccessibleColumnSelected,
- getAccessibleCellAt,
- isAccessibleSelected. */
// XInterface
/** Queries for a new interface. */
css::uno::Any SAL_CALL queryInterface( const css::uno::Type& rType ) override;
/** Acquires the object (calls acquire() on base class). */
virtual void SAL_CALL acquire() noexcept override;
/** Releases the object (calls release() on base class). */
virtual void SAL_CALL release() noexcept override;
// XTypeProvider
/** @return a sequence of possible types (received from base classes). */
virtual css::uno::Sequence< css::uno::Type > SAL_CALL getTypes() override;
/** @return a unique implementation ID. */
virtual css::uno::Sequence< sal_Int8 > SAL_CALL getImplementationId() override;
// XServiceInfo
/* Derived classes have to implement:
- getImplementationName */
protected:
// internal virtual methods
/** @attention This method requires locked mutex's and a living object.
@return The count of data rows without header bar. */
virtual sal_Int32 implGetRowCount() const;
/** @attention This method requires locked mutex's and a living object.
@return The count of data columns without "handle column". */
virtual sal_Int32 implGetColumnCount() const;
// internal helper methods
/** @return TRUE, if first BrowseBox column is the "handle column". */
bool implHasHandleColumn() const;
/** @attention This method requires locked mutex's and a living object.
@param nColumn
the position of the column in the Accessible world
@return
the position of the column in VCL the Accessible world
*/
sal_uInt16 implToVCLColumnPos( sal_Int32 nColumn ) const;
/** @attention This method requires locked mutex's and a living object.
@return The number of cells of the table. */
sal_Int64 implGetChildCount() const;
/** @attention This method requires locked mutex's and a living object.
@return The row index of the specified cell index. */
sal_Int32 implGetRow( sal_Int64 nChildIndex ) const;
/** @attention This method requires locked mutex's and a living object.
@return The column index of the specified cell index. */
sal_Int32 implGetColumn( sal_Int64 nChildIndex ) const;
/** @attention This method requires locked mutex's and a living object.
@return TRUE, if the specified row is selected. */
bool implIsRowSelected( sal_Int32 nRow ) const;
/** @attention This method requires locked mutex's and a living object.
@return TRUE, if the specified column is selected. */
bool implIsColumnSelected( sal_Int32 nColumn ) const;
/** Selects/deselects a row (tries to expand selection).
@attention This method requires locked mutex's and a living object.
@param nRow Row to select
@param bSelect TRUE = select, FALSE = deselect */
void implSelectRow( sal_Int32 nRow, bool bSelect );
/** Selects/deselects a column (tries to expand selection).
@attention This method requires locked mutex's and a living object.
@param nColumnPos column number to select
@param bSelect TRUE = select, FALSE = deselect */
void implSelectColumn( sal_Int32 nColumnPos, bool bSelect );
/** @attention This method requires locked mutex's and a living object.
@return The count of selected rows. */
sal_Int32 implGetSelectedRowCount() const;
/** @attention This method requires locked mutex's and a living object.
@return The count of selected columns. */
sal_Int32 implGetSelectedColumnCount() const;
/** Fills a sequence with sorted indexes of completely selected rows.
@attention This method requires locked mutex's and a living object.
@param rSeq Out-parameter that takes the sorted row index list. */
void implGetSelectedRows( css::uno::Sequence< sal_Int32 >& rSeq );
/** Fills a sequence with sorted indexes of completely selected columns.
@attention This method requires locked mutex's and a living object.
@param rSeq Out-parameter that takes the sorted column index list. */
void implGetSelectedColumns( css::uno::Sequence< sal_Int32 >& rSeq );
/** @attention This method requires locked mutex's and a living object.
@throws <type>IndexOutOfBoundsException</type>
If the specified row index is invalid. */
void ensureIsValidRow( sal_Int32 nRow );
/** @attention This method requires locked mutex's and a living object.
@throws <type>IndexOutOfBoundsException</type>
If the specified column index is invalid. */
void ensureIsValidColumn( sal_Int32 nColumn );
/** @attention This method requires locked mutex's and a living object.
@throws <type>IndexOutOfBoundsException</type>
If the specified cell address is invalid. */
void ensureIsValidAddress( sal_Int32 nRow, sal_Int32 nColumn );
/** @attention This method requires locked mutex's and a living object.
@throws <type>IndexOutOfBoundsException</type>
If the specified child index is invalid. */
void ensureIsValidIndex( sal_Int64 nChildIndex );
};
} // namespace accessibility
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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