mirror of
https://github.com/flutter/flutter.git
synced 2026-02-20 02:29:02 +08:00
9d6070dd18
Windows does not provide a system notification the embedder can subscribe to to determine when a screen reader or other assistive technology that requires the semantics tree has been enabled. [1] In the absence of such a notification, we watch for queries for the IAccessible COM object representing the root node of the semantics tree, and on receipt of such queries we enable the semantics tree. For the time being, we assume that if accessiblity is enabled, it will be enabled for the duration of the application lifetime. In a future patch we can optimise this by adopting the approach taken by Chromium, which is to disable semantics if we haven't received a query within some reasonable timeout. This patch enables Flutter's semantics tree; a follow-up patch wires in the AccessibilityBridge which maintains the AXTree of COM objects that is the Windows representation of the Flutter SemanticsTree. Issue: https://github.com/flutter/flutter/issues/77838 [1]: https://docs.microsoft.com/en-us/windows/win32/winauto/screen-reader-parameter