Implements OnAccessibilityEvent, which translates events from the AXTree
into Windows MSAA event notifications.
This also eliminates the UIA root object lookup in response to
WM_GETOBJECT, since our initial implementation, like Chromium's default
implementation, is based on MSAA.
Issue: https://github.com/flutter/flutter/issues/77838
When building Flutter engine using the --no-prebuilt-dart-sdk flag, we
need to be able to check out a version of Dart SDK source without a
built version available from the Dart SDK builders.
The 'download_dart_sdk' variable in DEPS is true by default, but
can be overridden when creating a gclient solution or running
gclient sync.
`AXPlatformNodeDelegate` provides a default implementation of
`GetUniqueId()` which returns the same value (1) for all nodes.
`AXPlatformNodeWin` relies on a unique ID being returned from this
method in its `GetTargetFromChildID` method.
In the world MSAA accessibility, each `HWND` may have a root
`IAccessible` object associated with it. Events are fired by calling the
`NotifyWinEvent` Win32 call and specifying:
1. The `HWND` (in our case, the one associated with our `WindowWin32`)
2. The target object (`OBJID_CLIENT` for the root `IAccessible`
associated with that `HWND`)
3. A child identifier that uniquely identifies the target node in the
tree
This child identifier can be one of:
* `CHILDID_SELF` for events targeting the root `IAccessible`.
* A positive integer that specifies the index of a direct child of the
root.
* A negative integer which, when negated, specifies the unique ID of a
child within the tree.
On receipt of an accessibility event, `AXPlatformWin` (our `IAccessible`
implementation) looks up the target `IAccessible` from the child ID
specified on the event using its `GetTargetFromChildID` method and
delegates the appropriate method call to that object.
So, why is this implemented on our `AXPlatformNodeDelegate` subclass and
not on `AXPlatformNodeWin` itself? Because the implementation of
`AXPlatformNode::GetUniqueId()` delegates this lookup to the node
delegate.
As background, `AXUniqueId` automatically assigns itself a
globally-unique value in its constructor; it tracks all used values in
an internal static pool.
Issue: https://github.com/flutter/flutter/issues/77838
Dart VM flags are passed to Flutter via an fml::CommandLine::Option that
looks something like:
{"dart-flags, "--max_profile_depth 1,--trace_service"}
We perform a prefix match to handle cases where Dart VM options take
arguments.
Adding the comment since in a recent review I found myself wondering why
we're using a prefix match to begin with. While the original author had
forgotten, the good news is, he wrote a test that covers this exact
case. This comment just removes one level of indirection for future
readers.
Implements DispatchAccessibilityAction: a pass-through method that
forwards to the engine, which calls through the Embedder API back to the
framework.
Issue: https://github.com/flutter/flutter/issues/77838
In download_dart_sdk.py, we previously ran curl with the --verbose flag
when the --verbose flag was passed to the script. This generates vast
quantities of output that is unlikely to be valuable except if we're
attempting to debug a curl download issue. In such a case we could
perhaps pass a separate --verbose-download flag as well.
Issue: https://github.com/flutter/flutter/issues/94492
