C# Create Snap To Grid Functionality

Question

I am trying to create some snap to grid functionality to be used at run time but I am having problems with the snapping part. I have successfully drawn a dotted grid on a panel but when I add a label control to the panel how to I snap the top, left corner of the label to the nearest dot?

Thanks

Answer 1

pos.x - pos.x % gridWidth should do it

Answer 2

Just use integers and division will just work for you:

int xSnap = (xMouse / gridWidth) * gridWidth;
int ySnap = (yMouse / gridHeight) * gridHeight;

Except of course the modulo solution is so much more elegant.

Answer 3

private enum SnapMode { Create, Move }
private Size gridSizeModeCreate = new Size(30, 30);
private Size gridSizeModeMove = new Size(15, 15);

private Point SnapCalculate(Point p, Size s)
{
    double snapX = p.X + ((Math.Round(p.X / s.Width) - p.X / s.Width) * s.Width);
    double snapY = p.Y + ((Math.Round(p.Y / s.Height) - p.Y / s.Height) * s.Height);
    return new Point(snapX, snapY);
}

private Point SnapToGrid(Point p, SnapMode mode)
{
    if (mode == SnapMode.Create)
        return SnapCalculate(p, gridSizeModeCreate);
    else if (mode == SnapMode.Move)
        return SnapCalculate(p, gridSizeModeMove);
    else
        return new Point(0, 0);
}

Answer 4

Here is a solution that rounds to the nearest grid point:

    public static readonly Size  Grid     = new Size( 16, 16 );
    public static readonly Size  HalfGrid = new Size( Grid.Width/2, Grid.Height/2 );

    // ~~~~ Round to nearest Grid point ~~~~
    public Point  SnapCalculate( Point p )
    {
        int     snapX = ( ( p.X + HalfGrid.Width  ) / Grid.Width  ) * Grid.Width;
        int     snapY = ( ( p.Y + HalfGrid.Height ) / Grid.Height ) * Grid.Height;

        return  new Point( snapX, snapY );
    }