Keyboard state tracking, modifier-aware key dispatch, and the responder chain for focus management.
The browser's native keyboard handling has two gaps that matter for an application framework. First, keydown and keyup events tell you which key was just pressed but not which other keys are already held — there is no built-in API for querying current keyboard state. Second, the DOM's focus model is element-level: it knows which element has focus, but has no concept of a focus chain through a view hierarchy, tab-order navigation between views, or a centralized way for views to declare whether they accept keyboard input. SvKeyboard and the responder chain address these: a singleton tracks live key state and generates modifier-aware method names (so views handle onShiftAKeyDown instead of parsing modifier flags), while SvResponderDomView layers a responder chain on top of DOM focus to manage keyboard routing through the view tree.
SvKeyboard is a singleton that tracks global keyboard state — which keys are currently pressed, modifier key status, and key code/name mapping.
When a key event fires, SvKeyboard generates a method name that includes active modifiers. For example, pressing Shift+A generates a call to onShiftAKeyDown(). This allows views to handle specific key combinations by simply implementing the named method.
The generated method names follow the pattern: on[Modifiers][KeyName]Key[Down|Up].
SvResponderDomView implements a responder chain for managing keyboard focus:
acceptsFirstResponder — Whether a view can receive keyboard focus.becomeFirstResponder() / releaseFirstResponder() — Acquire or release focus.nextKeyView — The next view in the tab order, enabling Tab-key navigation between focusable views.The responder chain ensures that keyboard events are routed to the focused view, and provides hooks (willBecomeFirstResponder) for views to prepare when receiving focus.