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Diffstat (limited to 'winaccessibility')
| -rw-r--r-- | winaccessibility/README.md | 43 |
1 files changed, 22 insertions, 21 deletions
diff --git a/winaccessibility/README.md b/winaccessibility/README.md index 2f507beacc64..6abf34a37e16 100644 --- a/winaccessibility/README.md +++ b/winaccessibility/README.md @@ -1,61 +1,62 @@ -Windows Accessibility Bridge. +# 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 +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/ ++ `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 / IAccessible2 interfaces ++ `source/UAccCom/` + + COM implementations of the `MSAA` / `IAccessible2` interfaces to provide native peers for the accessibility code. -source/UAccCOMIDL/ ++ `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/ + VCL <-> UNO toolkit <-> UNO a11y <-> win a11y <-> COM / IAccessible2 -Threading + 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 +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 + +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 +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 +## 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 + 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... +<http://accessibility.linuxfoundation.org/a11yweb/util/accprobe/> +But often it's more useful to look at NVDA's text output window. |