Pointer Events

A pointer is a device-independent representation of input devices (such as a mouse, pen,or point of contact on a touch surface). A pointer can point to a specific coordinate(or set of coordinates) on a contact surface such as a screen.

All pointers can generate several kinds of events

Event	Constant	Description
"pointer-down"	PointerDown	The pointer was pressed.
"pointer-up"	PointerUp	The pointer was released.
"pointer-move"	PointerMove	The pointer has been moved
"pointer-cancel"	PointerCancel	Pointer events aborted.
"pointer-out"	PointerOut	The pointer went out of bounds of the View, or went into the child View
"pointer-over"	PointerOver	The pointer is within the limits of View

The main event data listener has the following format:

func(View, PointerEvent)

where the second argument describes the parameters of the pointer. PointerEvent structure extends MouseEvent structureand has the following additional fields:

Field	Type	Description
PointerID	int	The unique identifier of the pointer that raised the event.
Width	float64	The width (X-axis value) in pixels of the pointer's contact geometry.
Height	float64	The height (Y-axis value) in pixels of the pointer's contact geometry.
Pressure	float64	Normalized gauge inlet pressure ranging from 0 to 1, where 0 and 1 represent the minimum and maximum pressure that the hardware is capable of detecting, respectively.
TangentialPressure	float64	Normalized gauge inlet tangential pressure (also known as cylinder pressure or cylinder voltage) ranges from -1 to 1, where 0 is the neutral position of the control.
TiltX	float64	The planar angle (in degrees, ranging from -90 to 90) between the Y – Z plane and the plane that contains both the pointer (such as a stylus) axis and the Y axis.
TiltY	float64	The planar angle (in degrees, ranging from -90 to 90) between the X – Z plane and the plane containing both the pointer (such as a stylus) axis and the X axis.
Twist	float64	Rotation of a pointer (for example, a stylus) clockwise around its main axis in degrees with a value in the range from 0 to 359.
PointerType	string	the type of device that triggered the event: "mouse", "pen", "touch", etc.
IsPrimary	bool	a pointer is the primary pointer of this type.

You can also use listeners in the following formats:

func(PointerEvent)
func(View)
func()

You can get lists of pointer event listeners using the functions:

func GetPointerDownListeners(view View, subviewID ...string) []func(View, PointerEvent)
func GetPointerUpListeners(view View, subviewID ...string) []func(View, PointerEvent)
func GetPointerMoveListeners(view View, subviewID ...string) []func(View, PointerEvent)
func GetPointerCancelListeners(view View, subviewID ...string) []func(View, PointerEvent)
func GetPointerOverListeners(view View, subviewID ...string) []func(View, PointerEvent)
func GetPointerOutListeners(view View, subviewID ...string) []func(View, PointerEvent)