32-bit Java Accessibility on a 64-bit machine

Question

I have a 32-bit app that makes use of Java Accessibility (WindowsAccessBridge-32.dll, via the Java Access Bridge), and works perfectly on a 32-bit machine, but fails on an x64 m

Answer 1

It appears that the problem is in the type of AccessibilityContext:

[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("WindowsAccessBridge-32.dll", CallingConvention = CallingConvention.Cdecl)]
public extern static bool getAccessibleContextFromHWND(IntPtr hwnd, out Int32 vmID, out IntPtr acParent);

AccessibilityContext (acParent above), which I had incorrectly mapped as an IntPtr, is actually an Int32 when using the "legacy" WindowsAccessBridge.dll library (used under x86), and an Int64 when using the WOW64 WindowsAccessBridge-32.dll library.

So the upshot is, the code has to differ between x86 and WOW x64, and must be compiled separately for each. I do this by #define'ing WOW64 during x64 builds, always referencing the Int64 methods, and using "shim" methods on x86:

#if WOW64 // using x64

[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("WindowsAccessBridge-32.dll", CallingConvention = CallingConvention.Cdecl)]
public extern static bool getAccessibleContextFromHWND(IntPtr hwnd, out Int32 vmID, out Int64 acParent);

#else // using x86

[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("WindowsAccessBridge.dll", EntryPoint = "getAccessibleContextFromHWND", CallingConvention = CallingConvention.Cdecl)]
private extern static bool _getAccessibleContextFromHWND(IntPtr hwnd, out Int32 vmID, out Int32 acParent);

public static bool getAccessibleContextFromHWND(IntPtr hwnd, out Int32 vmID, out Int64 acParent)
{
  Int32 _acParent;

  bool retVal = _getAccessibleContextFromHWND(hwnd, out vmID, out _acParent);
  acParent = _acParent;

  return retVal;
}

#endif