You could simply create a layout where the space key produces an underscore. It cannot do everything the raw XML format can, but is much easier to use for simple changes like what you are suggesting. Ukelele is an application from SIL that can help you generate custom layouts in a more user‐friendly manner. macOS lets you create custom keyboard layouts (in addition to the hundreds that come preinstalled). However, if you play by the operating system’s rules and do things its way, it is easy enough to get your keyboard to work like that. You would be able to listen to every password as it is typed in.) (Think about the security vulnerabilities if the operating system let arbitrary applications silently intercept keyboard input destined for other applications. It would certainly not result in an application that would be allowed on the App Store. It requires a level of integration with the operating system that is highly unusual. Well it is not likely a good first time Swift project.

Custom keyboard ios swift github