Pointer and Keyboard Input

Detailed Description

Platform input enters the Application event loop and is targeted into the connected visual hierarchy. Pointer, touch, and scroll input are directed by hit testing, while keyboard input is directed by focus. The Screen or a workspace finds the widget below the pointer. These are two targeting models, not two event loops. Every Widget is a Responder. A responder handles an event by returning true; returning false continues delivery through the responder chain. Mouse and touch positions are converted to each responder's local coordinates before its handler runs.

Hit testing selects the frontmost eligible widget below the pointer. Widget::setCapture() temporarily overrides hit testing and directs pointer input to the capturing widget until it releases capture. Forms sends a LeaveEvent before an EnterEvent when the pointer target changes. A MouseEvent reports movement and button state, a TouchEvent reports an individual touch and pressure, and a ScrollEvent reports the scroll axis and delta.

A Form is the focus root for its content tree. A focused control receives key input, subject to the form's interaction rules: an active control is considered first, then registered shortcuts, Alt mnemonics, and Tab focus traversal, followed by the focused control and responder chain. A control can take part in that focus set; pointer and touch presses on a control typically request focus. A KeyEvent carries a Key, press or release action, and optional Unicode text. Controls register their focus policy, action key, shortcut, and mnemonic through their public APIs.

InputMethod is the extension point for platform or custom text entry. It begins a session for a control, retains only a non-owning receiver, and sends KeyEvent objects to that receiver. Ordinary controls use the method installed on the application, which always provides a default method; derive an input method only to implement a text-entry interface.

Classes
class	EnterEvent
	Pointer entered a widget. More...
class	FocusEvent
	Reports that a widget gained or lost focus. More...
class	Form
	View that hosts one content control. More...
class	InputMethod
	Extension for platform or custom text entry. More...
class	DefaultInputMethod
	Provides the application-owned default input method. More...
class	Key
	Key code and modifiers. More...
class	KeyEvent
	Key press or release. More...
class	LeaveEvent
	Pointer left a widget. More...
class	MouseButton
	Mouse button identity. More...
class	MouseState
	Pressed or released state of the mouse buttons. More...
class	MouseEvent
	Pointer movement or button change. More...
class	Responder
	Object that handles input or forwards it. More...
class	ScrollEvent
	Scroll or wheel movement. More...
class	TouchEvent
	Touch press, move, or release. More...
class	Widget
	Common type of every visual Forms object. More...