The default implementation of GetUniqueId on ui::AXPlatformNodeDelegate
always returns ID 1. We had previously implemented this on the windows
platform node delegate, but for consistency's sake, and because the
default implementation is surprising, we're promoting this to the
FlutterPlatformNodeDelegate base class.
Issue: https://github.com/flutter/flutter/issues/77838
This enables unittests for the accessibility bridge in
common_cpp_unittests, when running on Windows. Previously, we only
tested on macOS.
Issue: https://github.com/flutter/flutter/issues/77838
TestAccessibilityBridgeDelegate::accessibility_events previously held
values of type ui::AXEventGenerator::TargetedEvent. TargetedEvent
contains an AXNode pointer and a const reference to a
ui::AXEventGenerator::EventParams object, and as such it's unsafe to
make or read copies of TargetedEvent values outside the scope of the
AccessibilityBridgeDelegate::OnAccessibilityEvent callback.
In this patch, we update the accessibility_events vector to simply hold
EventType values since this is the only part of the value we use in our
existing tests. If in future we need the full TargetedEvent, we'll need
to properly copy these values.
This patch also fixes a typo in the accessibility_events identifier and
converts an EXPECT_EQ to an ASSERT_EQ in a case where the following
test expectations are meaningless/could crash if the
accessibility_events size isn't as expected.
Issue: https://github.com/flutter/flutter/issues/77838
In the Win32 accessibility tree, each AXTree node has an associated
IAccessible object. In WindowWin32, our WM_GETOBJECT handler returns the
IAccessible associated with the root node of the tree (node 0). On other
platforms, we often add our root accessibility object as a subnode of
some existing accessibility object associated with the view. On Windows,
the root IAccessible _is_ the accessibility object associated with the
view (on Windows, and HWND).
In the previous implementation, AccessibleObjectFromWindow actually just
returns the root IAccessible object, which is equivalent to just
returning GetNativeViewAccessible. Instead, we just return null once we
hit the root of the tree.
Issue: https://github.com/flutter/flutter/issues/77838
On receipt of a FOCUS_CHANGED event from the AX tree, call
IAccessible::accFocus to tell screen readers to move the accessibility
focus to that node. This is in addition to setting the keyboard focus
via the EVENT_OBJECT_FOCUS event.
Issue: https://github.com/flutter/flutter/issues/77838
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
