macos - Change OSX keyboard layout("input source") programmatically via terminal or AppleScript?

Question

I am currently switching input sources by running a GUI AppleScript through Alfred, and the GUI script can sometime take up to 1s to complete the change. It gets quite annoying at times.

I have come across Determine OS X keyboard layout (“input source”) in the terminal/a script. And I want to know since we can find out the current input source if there's a way to change input source programatically? I'd tried overwriting the com.apple.HIToolbox.plist but it does not change the input.

(I do realise there's mapping shortcut to input sources available in the system preference, however I prefer mapping keywords with Alfred)

Answer 1

You can do it using the Text Input Services API:

NSArray* sources = CFBridgingRelease(TISCreateInputSourceList((__bridge CFDictionaryRef)@{ (__bridge NSString*)kTISPropertyInputSourceID : @"com.apple.keylayout.French" }, FALSE));
TISInputSourceRef source = (__bridge TISInputSourceRef)sources[0];
OSStatus status = TISSelectInputSource(source);
if (status != noErr)
    /* handle error */;

The dictionary in the first line can use other properties for other criteria for picking an input source.

There's also NSTextInputContext. It has a selectedKeyboardInputSource which can be set to an input source ID to select a different input source. The issue there is that you need an instance of NSTextInputContext to work with and one of those exists only when you have a key window with a text view as its first responder.