How to determine the keyboard layout for another process (Windows)?

Question

I'm working on a program that needs to record and play back keystrokes. The main process runs as a service, so it needs a configuration program to record the keystrokes.

The problem comes when the system default keyboard layout is (say) English, and the user's keyboard layout of the moment is (say) German. The user enters a 'ü' character into the configuration interface, which is duly recorded and stored.

Now the user runs Notepad and tries to play the keystroke back, which is done by a child of the service. When transforming input to pass to SendInput, we call VkKeyScan, which then tells us there's no way to reproduce that character on this keyboard (remember the default keyboard layout is English).

What I'd really like to do is sync the keyboard layouts of the service and the current foreground application, so the service can reproduce any character the user can with their keyboard. GetKeyboardLayout only works in the current process. This has to run on both 32- and 64-bit, so a message hook is... not preferred :).

Answer 1

To retrieve the keyboard layout for the foreground window:

GetKeyboardLayout(GetWindowThreadProcessId(GetForegroundWindow(), NULL))

It sounds like you're recording characters instead of keystrokes. Instead of sending keystrokes when replaying, can you use SendMessage to send WM_CHAR messages with the recorded characters instead of generating keystrokes?