a11y: Add new QAccessibleSelectionInterface

This adds a new QAccessibleSelectionInterface
that implements support for handling selections,
both retrieving information about the current selection
as well as modifying the selection, thus providing
the necessary foundation for exposing selections
to assistive technology.

This is similar to AT-SPI's Selection interface [1],
but uses QAccessibleInterface pointers instead of
child indices as parameters for methods.

Bridging this newly introduced interface to AT-SPI
will be done in a follow-up change.

The concept for selection handling in Microsoft's
UI Automation looks similar, so bridging this to the
corresponding UIA interfaces ISelectionProvider [2],
ISelectionItemProvider [3] and ISelectionProvider2 [4]
should also be reasonably straightforward.

At this point, this is only meant to be used for
handling selection of direct children as is the
concept in AT-SPI's Selection and presumably
in UIA as well. (The ISelectionItemProvider and
ISelectionProvider doc speaks of "child controls
of containers" etc., but doesn't explicitly mention
that this is only for direct children or whether
grand children are also allowed.)

(The proposed API itself could
also be used to support selection of objects
that are no direct children, but the practical
use of that is unclear and it would make mapping/
bridging to platform a11y layers tricky.)

[5] demonstrates a sample implementation of the
QAccessibleSelectionInterface for the Qt-based
UI variants of LibreOffice (screencast that
shows the use of the interface attached to
QTBUG-105909).

This interface is marked \preliminary until:

1. There is a working a11y bridge for macOS/VoiceOver
2. There is a working a11y bridge for Windows/UI Automation
3. There is a working a11y bridge for linux/AT-SPI
4. There is at least one implementation (e.g. QAccessibleTable)
   that implements it successfully (second candidate:
   Qt Quick TableView [6])

[1] https://lazka.github.io/pgi-docs/Atspi-2.0/classes/Selection.html
[2] https://docs.microsoft.com/en-us/windows/win32/api/uiautomationcore/nn-uiautomationcore-iselectionprovider
[3] https://docs.microsoft.com/en-us/windows/win32/api/uiautomationcore/nn-uiautomationcore-iselectionitemprovider
[4] https://docs.microsoft.com/en-us/windows/win32/api/uiautomationcore/nn-uiautomationcore-iselectionprovider2
[5] https://gerrit.libreoffice.org/c/core/+/138750
[6] https://doc-snapshots.qt.io/qt6-dev/qml-qtquick-tableview.html

[ChangeLog][QtGui][QAccessibleSelectionInterface] Added new
preliminary QAccessibleSelectionInterface that can be used to expose
selections to assistive technology.

Task-number: QTBUG-105909
Change-Id: If77beacd94fa3eb663f0fbb2373f12382bab2ee3
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

0 files changed, 0 insertions, 0 deletions