Class TouchDevice

A touch device represents input typically performed by fingers or a stylus. Touch devices support simultaneous presence of multiple touchpoints (performed by multiple fingers). Each touchpoint is captured by four axes and one button. The button state (pressed or not pressed) signals the presence of the respective axis. Two positional axes for each touchpoint reveal the position in X/Y screen space and two velocity axes represent the current velocity along X and Y.

In Addition to tracking individual touchpoints, this device also tracks the simultaneous movements of the first two active touchpoints and generates derived information, like two-point-move, pinch or rotate.

Constructors

TouchDevice(IInputDeviceImp)

Initializes a new instance of the TouchDevice class.

Declaration

public TouchDevice(IInputDeviceImp inpDeviceImp)

Parameters

Type	Name	Description
IInputDeviceImp	inpDeviceImp	The "driver".

Properties

ActiveTouchpoints

Retrieves the number of currently active touchpoints (e.g. the number of fingers currently touching the screen).

Declaration

public int ActiveTouchpoints { get; }

Property Value

Type	Description
System.Int32	The number of active touchpoints.

TwoPoint

Gets a value indicating whether two touchpoints are active.

Declaration

public bool TwoPoint { get; }

Property Value

Type	Description
System.Boolean	`true` if currently two touchpoints are active; otherwise, `false`.

TwoPointAngle

Gets the angle of a line between the first two active touchpoints measured from the positive screen x-axis. Use this value if you want to implement rotation-like actions based on the current absolute angle.

Declaration

public float TwoPointAngle { get; }

Property Value

Type	Description
System.Single	The angle value in radians. Ranges between -PI and PI. An angle of zero denotes the positive x-axis.

TwoPointAngleVel

Gets the angular velocity of a line between the first two active touchpoints measured from the positive screen x-axis. Use this value if you want to implement rotation-like actions based on the current rotation speed of the first two touchpoints.

Declaration

public float TwoPointAngleVel { get; }

Property Value

Type	Description
System.Single	The angular velocity of the rotation movement of the first two touchpoints. Positive values mean counter-clockwise rotation, negative values mean clockwise rotation.

TwoPointDistance

Gets the distance between the first two touchpoints. Use this value if you want to implement pinch-like actions based on the current absolute distance.

Declaration

public float TwoPointDistance { get; }

Property Value

Type	Description
System.Single	The distance between the first two active touchpoints, or zero, if no two touchpoints are active.

TwoPointDistanceVel

Gets velocity of the distance between the first two touchpoints. Use this value if you want to implement pinch-like actions based on the current speed of the distance.

Declaration

public float TwoPointDistanceVel { get; }

Property Value

Type	Description
System.Single	The distance velocity. Positive values mean fingers move away from each others (Zoom-In), negative values mean fingers approach each others (Zoom-Out).

TwoPointGesture

Gets a value indicating the TwoPointAction currently performed with the highest intensity.

Declaration

public TwoPointAction TwoPointGesture { get; }

Property Value

Type	Description
TwoPointAction	The double touch action currently performed by the user with the highest intensity.

Remarks

Two moving touchpoints on the screen can be interpreted in various ways. It's up to the application to interpret the two individual changes in position as Move , as a Rotate or as a Pinch . Use this method to retrieve a symbolic value which of these three possibilities is currently performed with the highest intensity. Applications should sensibly decide whether to allow to change their behavior during a two-point-gesture (as long as TwoPoint holds true) or to check this value only initially whenever a two-point gesture starts, or do something in-between. As a practice: Investigate how the Google Earth mobile app handles this question!

TwoPointMidPoint

Gets midpoint between the first two active touch points. Use this value if you want to implement two-finger movement-like actions based on the current averaged absolute position of the first two touchpoints

Declaration

public float2 TwoPointMidPoint { get; }

Property Value

Type	Description
float2	The midpoint (halfway between) touchpoint 0 and touchpoint 1.

TwoPointMidPointVel

Gets speed of the midpoint between the first two active touch points. Use this value if you want to implement two-finger movement-like actions based on the current averaged speed of the first two touchpoints.

Declaration

public float2 TwoPointMidPointVel { get; }

Property Value

Type	Description
float2	The two-dimensional speed vector of the midpoint between touchpoint 0 and touchpoint 1.

Methods

GetPosition(TouchPoints)

Returns the current position of the given touchpoint. The returned values are only valid if GetTouchActive(TouchPoints) holds true for the same touchpoint.

Declaration

public float2 GetPosition(TouchPoints touch)

Parameters

Type	Name	Description
TouchPoints	touch	The touchpoint.

Returns

Type	Description
float2	The X/Y position of the given touchpoint.

GetTouchActive(TouchPoints)

Returns a value signaling if the given touchpoint is currently active (if something hits the screen).

Declaration

public bool GetTouchActive(TouchPoints touch)

Parameters

Type	Name	Description
TouchPoints	touch	The touchpoint to check.

Returns

Type	Description
System.Boolean	true if this touch is active (a finger is on the screen), otherwise false.

GetVelocity(TouchPoints)

Retrieves the current velocity (in pixels per second) of the given touch point. The returned values are only valid if GetTouchActive(TouchPoints) holds true for the same touchpoint.

Declaration

public float2 GetVelocity(TouchPoints touch)

Parameters

Type	Name	Description
TouchPoints	touch	The touchpoint.

Returns

Type	Description
float2	The two-dimensional velocity of the touchpoint.

RegisterTtpAngleAxis()

Registers a new (Two-) touch point angle and returns the id.

Declaration

protected int RegisterTtpAngleAxis()

Returns

Type	Description
System.Int32	The id of the newly registered angle axis.

RegisterTtpDistanceAxis()

Registers a new (Two-) touch point distance and returns its id.

Declaration

protected int RegisterTtpDistanceAxis()

Returns

Type	Description
System.Int32	The id of the newly registered distance.

RegisterTtpMidpointAxis(Int32, Int32, Int32, Int32, AxisDirection, String)

Registers a new (Two-) touch point midpoint and returns its id.

Declaration

protected int RegisterTtpMidpointAxis(int axId0, int axId1, int axIdMin, int axIdMax, AxisDirection dir, string name)

Parameters

Type	Name	Description
System.Int32	axId0	The first point.
System.Int32	axId1	The second point.
System.Int32	axIdMin	The minimum value of the chosen axis.
System.Int32	axIdMax	The maximum value of the chosen axis.
AxisDirection	dir	The direction of the axis.
System.String	name	The name of the axis.

Returns

Type	Description
System.Int32	The id of the registered midpoint.