809409ca84
So far, there was an internal copy of the IAccessible2
IDL file added in 2013, and never updated since then
(except for cosmetic changes like formatting and typo
fixes), and therefore it e.g. doesn't have the
`IA2_ROLE_BLOCK_QUOTE` role needed for tdf#135586.
Drop the outdated internal copy and integrate an up to
date upstream version (current git master) instead.
Instead of duplicating things in an internal copy,
switch to using the usual mechanism for externals.
The IAccessible2 source contains separate .idl files
for the different interfaces, while the previous
interal copy was already the merged IDL file.
Call the IAccessible2 `./concatidl.sh` script to generate
the merged `ia2_api_all.idl`
(s. external/IAccessible2/ExternalProject_IAccessible2.mk)
and adapt the winaccessibility make files to use that
version instead of the internal copy.
(Add a dependency to the target that generates
`ia2_api_all.idl`.)
The tarball was generated from the master branch of the
IAccessible2 git repo [1] as of
commit 3d8c7f0b833453f761ded6b12d8be431507bfe0b (HEAD -> master, origin/master, origin/HEAD, mygithub/master)
Author: Michael Weghorn <m.weghorn@posteo.de>
Date: Fri Oct 13 04:16:03 2023 +0300
Update no longer working links (#26)
* Update link to Linux Foundation Trademark Policy
* Update link to Object Attributes specification
Signed-off-by: Michael Weghorn <m.weghorn@posteo.de>
using this command:
$ git archive -o ../IAccessible2-1.3+git20231013.3d8c7f0.tar.gz --prefix=IAccessible2-1.3+git20231013.3d8c7f0/ master
Andrea Gelmini's typo fixes have been upstreamed in [2].
[1] https://github.com/LinuxA11y/IAccessible2
[2] https://github.com/LinuxA11y/IAccessible2/pull/21
Change-Id: I9f19ff55694da5d3a9a8750be8de387cbf6da785
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/158427
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
|
||
|---|---|---|
| .. | ||
| inc | ||
| source | ||
| CustomTarget_ia2_idl.mk | ||
| Library_uacccom.mk | ||
| Library_winaccessibility.mk | ||
| Makefile | ||
| Module_winaccessibility.mk | ||
| README.md | ||
| WinResTarget_uacccom.mk | ||
Windows Accessibility Bridge
This code provides a bridge between our internal Accessibility
interfaces (implemented on all visible 'things' in the suite: eg.
windows, buttons, entry boxes etc.) - and the Windows MSAA /
IAccessible2 COM interfaces that are familiar to windows users and
Accessible Technologies (ATs) such as the NVDA screen reader.
The code breaks into three bits:
-
source/service/- the UNO service providing the accessibility bridge. It essentially listens to events from the LibreOffice core and creates and synchronises COM peers for our internal accessibility objects when events arrive.
-
source/UAccCom/- COM implementations of the
MSAA/IAccessible2interfaces to provide native peers for the accessibility code.
- COM implementations of the
-
source/UAccCOMIDL/- COM Interface Definition Language (IDL) for UAccCom.
Here is one way of visualising the code / control flow
VCL <-> UNO toolkit <-> UNO a11y <-> win a11y <-> COM / IAccessible2
vcl/ <-> toolkit/ <-> accessibility/ <-> winaccessibility/ <-> UAccCom/
Threading
It's possible that the UNO components are called from threads other
than the main thread, so they have to be synchronized. It would be nice
to put the component into a UNO apartment (and the COM components into STA)
but UNO would spawn a new thread for it so it's not possible.
The COM components also call into the same global AccObjectWinManager
as the UNO components do so both have to be synchronized in the same way.
So we use the SolarMutex for all synchronization since anything else
would be rather difficult to make work. Unfortunately there is a
pre-existing problem in vcl with Win32 Window creation and destruction
on non-main threads where a synchronous SendMessage is used while
the SolarMutex is locked that can cause deadlocks if the main thread is
waiting on the SolarMutex itself at that time and thus not handing the
Win32 message; this is easy to trigger with JunitTests but hopefully
not by actual end users.
Debugging / Playing with winaccessibility
If NVDA is running when soffice starts, IA2 should be automatically enabled and work as expected. In order to use 'accprobe' to debug it is necessary to override the check for whether an AT (like NVDA) is running; to do that use:
SAL_FORCE_IACCESSIBLE2=1 soffice.exe -writer
Then you can use accprobe to introspect the accessibility hierarchy remotely, checkout:
http://accessibility.linuxfoundation.org/a11yweb/util/accprobe/
But often it's more useful to look at NVDA's text output window.