OnKeyUp event

OnKeyUp is the standard VCL keyboard event exposed by TPdfView. The handler runs after Windows reports a WM_KEYUP / WM_SYSKEYUP message while the control has focus. Its event signature is procedure(Sender: TObject; var Key: Word; Shift: TShiftState) — Key is the virtual-key code (VK_ESCAPE, VK_NEXT, VK_PRIOR, …) and Shift reports modifier state at the point of release

OnKeyUp fires for every key — including non-character keys such as arrow keys and function keys — as long as TPdfView has keyboard focus. Set Key to zero inside the handler to consume the event so that it does not propagate further, for example to stop Tab moving focus while a form field is being edited

Use OnKeyUp for viewer shortcuts that should run on release rather than while a key is held — Page Down / Page Up for navigation, F3 for search-next, Escape to dismiss a selection. Continuous interactions such as panning or marquee selection are better driven from OnKeyDown because the OS repeats KeyDown but emits only one KeyUp for each physical release

• For character-producing keys the OS sends KeyDown, KeyPress, then KeyUp OnKeyUp is the only event guaranteed to fire exactly once for each key release
• Modifier-only releases (Ctrl, Shift, Alt) also fire OnKeyUp — check Key in [VK_CONTROL, VK_SHIFT, VK_MENU] if you want to ignore them
• When the embedded AcroForm widget consumes the key (an editable text field has focus), OnKeyUp may not fire — the form layer intercepts the message before it reaches the VCL handler