class KeyboardEventHandler

The KeyboardEventHandler class encapsulates a keyboard event handler callback function.

class KeyboardEventHandler : public ListElement<KeyboardEventHandler>

KeyboardEventHandler(HandlerCallback *callback, void *cookie = nullptr);

callback	The callback function to invoke when a keyboard event occurs.
cookie	The cookie that is passed to the event callback function as its last parameter.

The KeyboardEventHandler class encapsulates a callback function that is invoked when a keyboard event occurs. Once an instance of the KeyboardEventHandler class has been constructed, it can be installed by calling the Engine::InstallKeyboardEventHandler function.

When a keyboard event occurs, the callback functions corresponding to all installed keyboard event handlers are invoked. The HandlerCallback type is defined as follows.

typedef bool HandlerCallback(const KeyboardEventData *eventData, void *cookie);

The eventType field of the KeyboardEventData structure specifies what type of keyboard event occurred and can be one of the following constants.

kEventKeyDown	A key was pressed. If a key is held down long enough to trigger auto-repeat, then this event is received each time a character is generated.
kEventKeyUp	A key was released.
kEventKeyCommand	A command key combination was pressed. This means the user held in the control key (under Windows) or the command key (under Mac OS) while pressing another key.

The keyCode field of the KeyboardEventData structure specifies either the Unicode value corresponding to the character that was involved in the event or one of the following values for special keys.

kKeyCodeEnter	The enter key (return key on the Mac).
kKeyCodeEscape	The escape key.
kKeyCodeTab	The tab key.
kKeyCodeLeftArrow	The left arrow key.
kKeyCodeRightArrow	The right arrow key.
kKeyCodeUpArrow	The up arrow key.
kKeyCodeDownArrow	The down arrow key.
kKeyCodePageUp	The page up key.
kKeyCodePageDown	The page down key.
kKeyCodeHome	The home key.
kKeyCodeEnd	The end key.
kKeyCodeDelete	The delete key.
kKeyCodeBackspace	The backspace key.
kKeyCodeF1	The F1 key.
kKeyCodeF2	The F2 key.
kKeyCodeF3	The F3 key.
kKeyCodeF4	The F4 key.
kKeyCodeF5	The F5 key.
kKeyCodeF6	The F6 key.
kKeyCodeF7	The F7 key.
kKeyCodeF8	The F8 key.
kKeyCodeF9	The F9 key.
kKeyCodeF10	The F10 key.
kKeyCodeF11	The F11 key.
kKeyCodeF12	The F12 key.

Special keys always have codes in the ranges [0x01, 0x1F] or [0x80, 0x9F], and keyboard event handlers should not attempt to handle codes in these ranges as ordinary characters.

The modifierKeys field specifies which modifier keys were held down when the event occurred. It can be zero or a combination (through logical OR) of the following values.

kModifierKeyShift	The Shift key was held down.
kModifierKeyControl	The Control key (Command key on the Mac) was held down.
kModifierKeyAlternate	The Alternate key (Option key on the Mac) was held down.

The cookie parameter is the value passed to the KeyboardEventHandler constructor.

The value returned by the callback function specifies whether the keyboard event was successfully handled. If the callback function returns true, then the keybaord event is considered handled, and no further keyboard event handlers will be called for the same event. If the callback function returns false, then the event is passed to the next keyboard event handler.

A keyboard event handler is uninstalled by destroying its associated class instance.

ListElement<KeyboardEventHandler>

Used internally to store all instances of KeyboardEventHandler in a list.