A key went down (or repeated): arrows scroll a line, Page Up/Down and Space page, Home/End jump, plus, minus and zero zoom.
public bool KeyDown(InputKey key, InputModifiers modifiers)
The key.
The modifier keys held (Shift with Space pages back; Ctrl or Cmd is accepted with the zoom keys).
true when the key was handled, so the shell stops the platform's default action.Spec #33 viewer capability 14.