Touch Zone Interface

This code was developed to allow for location-dependent input on a touch screen. Capacitive touch screens are sensitive to small position changes, but they have a margin of error for any given touch location from a large, blunt human finger. This interface allows a program to define a region of any given shape and size. Touch input methods can then detect the presence of touches and gestures within that region.

This example shows a good purpose for interfaces in place of class inheritance.

public interface IZone
{
    bool ContainsPoint(Vector2 point);
}
 
public class Vector2Zone: IZone
{
    public Vector2 position1;
    public Vector2 position2;
 
    public Vector2Zone(Vector2 pos1, Vector2 pos2)
    {
        position1 = pos1;
        position2 = pos2;
    }
 
    public bool ContainsPoint(Vector2 point)
    {
        if ((point.X >= Math.Min(position1.X, position2.X)) &&
            (point.X <= Math.Max(position1.X, position2.X)) &&
            (point.Y >= Math.Min(position1.Y, position2.Y)) &&
            (point.Y <= Math.Max(position1.Y, position2.Y)))
            return true;
        else
            return false;
    }    
}
 
public class CircleZone: IZone
{
    public float radius;
    public Vector2 center;
 
    public CircleZone(Vector2 center, float radius)
    {
        this.center = center;
        this.radius = radius;
    }
 
    public bool ContainsPoint(Vector2 point)
    {
        if (Vector2.DistanceSquared(center, point) <= (radius * radius))
            return true;
        else
            return false;
 
        //AKA return (Vector2.DistanceSquared(center, point) <= (radius * radius));
    }
}

The above code may be expanded or combined to define more complex shapes. Semicircles would be a combination of being inside a circle but not inside a rectangle. Rings would be a larger circle and not an inner circle.

This interface allows the design of input functions that disregard shape and location:

public bool IsLocationTouch(IZone zone)
{
    for (int i = 0; i < touchPanelCapabilities.MaximumTouchCount; i++)
    {
        if (IsLocationTouch(i,zone)) return true;
    }
    return false;
}
public bool IsLocationTouch(int touchNumber, IZone zone)
{
    return zone.ContainsPoint(touchPositions[touchNumber]);
}