Determine which control is closest to the mouse pointer

Question

In my C # application (.NET 2), I would like to determine which control is closed to the mouse.

I can come up with several ways to do this that won't work correctly. I could use a property Control.Location, but that just gives me top / left, and the mouse can be on the other side of the control. I could calculate the center point of the control, but the large controls would distort it (being near the edge of the control account as being next to the control).

So basically I have a bunch of rectangles on the canvas and a dot. I need to find the rectangle closest to the point.

(Ideally, I would like to know the distance between a point and a rectangle).

Any ideas?

Answer 1

You need to find the following:
 - Distance to the nearest corner
 - Distance to the nearest edge
 - (optional) Distance to the center

Basically, you want the smaller of these three values. Take a moment for the two controls to determine which is closer.

Start when you load the form, iterating over all the controls on the form and creating a collection of this class below.

, (. ). , . ContainsPoint(), ... , , ( ). , , , /, .

public class HitControl {

    public Control ThisControl;

    private Rectangle ControlBounds;
    private Point Center;

    public HitControl (Control FormControl) {
        ControlBounds = FormControl.Bounds;
        Center = new Point(ControlBounds.X + (ControlBounds.Width/2), ControlBounds.Y + (ControlBounds.Height/2));
    }

    //  Calculate the minimum distance from the left, right, and center
    public double DistanceFrom(Point TestPoint) {

        //  Note:  You don't need to consider control center points unless
        //  you plan to allow for controls placed over other controls... 
        //  Then you need to test the distance to the centers, as well, 
        //  and pick the shortest distance of to-edge, to-side, to-corner

        bool withinWidth = TestPoint.X > ControlBounds.X && TestPoint.X < ControlBounds.X + ControlBounds.Width;
        bool withinHeight = TestPoint.Y > ControlBounds.Y && TestPoint.Y < ControlBounds.Y + ControlBounds.Height;

        int EdgeLeftXDistance = Math.Abs(ControlBounds.X - TestPoint.X);
        int EdgeRightXDistance = Math.Abs(ControlBounds.X + ControlBounds.Width - TestPoint.X);

        int EdgeTopYDistance = Math.Abs(ControlBounds.Y - TestPoint.Y);
        int EdgeBottomYDistance = Math.Abs(ControlBounds.Y + ControlBounds.Height - TestPoint.Y);

        int EdgeXDistance = Math.Min(EdgeLeftXDistance, EdgeRightXDistance);
        int EdgeYDistance = Math.Min(EdgeTopYDistance, EdgeBottomYDistance);


        // Some points to consider for rectangle (100, 100, 100, 100):
        //  - (140, 90):  Distance to top edge
        //  - (105, 10):  Distance to top edge
        //  - (50, 50):   Distance to upper left corner
        //  - (250, 50):  Distance to upper right corner
        //  - (10, 105):  Distance to left edge
        //  - (140, 105):  Distance to top edge
        //  - (105, 140):  Distance to left edge
        //  - (290, 105):  Distance to right edge
        //  - (205, 150):  Distance to right edge
        //  ... and so forth


        //  You're within the control
        if (withinWidth && withinHeight) {
            return Math.Min(EdgeXDistance, EdgeYDistance);
        }

        //  You're above or below the control
        if (withinWidth) {
            return EdgeYDistance;
        }

        //  You're to the left or right of the control
        if (withinHeight) {
            return EdgeXDistance;
        }

        //  You're in one of the four outside corners around the control.
        //  Find the distance to the closest corner
        return Math.Sqrt(EdgeXDistance ^ 2 + EdgeYDistance ^ 2);


    }

    public bool ContainsPoint (Point TestPoint) {
        return ControlBounds.Contains(TestPoint);
    }


}



//  Initialize and use this collection
List<HitControl> hitControls = (from Control control in Controls
                                select new HitControl(control)).ToList();

Point testPoint = new Point(175, 619);
double distance;
double shortestDistance = 0;
HitControl closestControl = null;

foreach (HitControl hitControl in hitControls) {

    //  Optional... works so long as you don't have overlapping controls
    //  If you do, comment this block out
    if (hitControl.ContainsPoint(testPoint)) {
        closestControl = hitControl;
        break;
    }

    distance = hitControl.DistanceFrom(testPoint);
    if (shortestDistance == 0 || distance < shortestDistance) {
        shortestDistance = distance;
        closestControl = hitControl;
    }
}

if (closestControl != null) {
    Control foundControl = closestControl.ThisControl;
}

Answer 2

, rectangle. , . 4 , ( ) ( ), , .

Answer 3

:)

• : ?
• : ?

, , - , , .

Answer 4

, . :

double DistanceFrom(Rect r, Point p);

, , , , , .

.

EDIT:

, , , , - . :)

Answer 5

, : double DistanceFrom (Rect r, Point p);

But before that we need: double DistanceFrom (line r, point p); as well as double AngleBetweenPoints (point p1, point p2);