In Compose Multiplatform for desktop, you can manage keyboard events by setting up event handlers in two different scopes:
Event handlers based on the focused element.
Event handlers in the window scope.
Events in a focused component
This approach implies that pressing a key on a keyboard triggers event handlers for the currently focused component.
A typical scenario is to define keyboard handlers for active controls like TextField. To intercept a key event before it triggers the default action, you can use both the onKeyEvent and onPreviewKeyEvent modifiers. With the onKeyEvent modifier, you can handle an individual keystroke, while onPreviewKeyEvent is preferable for defining shortcuts.
The following sample demonstrates TextField interactions with different actions depending on which key is pressed while you hold Ctrl:
To define keyboard event handlers that are always active within the current window, use the onPreviewKeyEvent and onKeyEvent parameters, available for the Window, singleWindowApplication, and Dialog functions. They differ in how the event is dispatched when it is not consumed: onPreviewKeyEvent dispatches the event to its first child, and onKeyEvent dispatches the event to the composable's parent. Typically, onPreviewKeyEvent is preferred for intercepting events, as it allows implementing even screen-wide keyboard shortcuts.
The following sample demonstrates window interactions such as closing a pop-up dialog by pressing Escape and changing the window content by pressing the Ctrl+Shift+C shortcut:
