"Martijn Mulder" <i@m> wrote in message
news:444292ab$0$22744$dbd4f001@news.wanadoo.nl...
> I want to know if the mouse is over (hitting) a line. Therefore I created
> a Region object that holds the line and use the IsVisible() method to test
> if the mouse hits the line. It doesn't work! In the little program below I
> create two Regions: one is square, the other is a line. Hit testing works
> on the square-Region, not on the line-Region.
>
> How can I do a hit-test over a line?
>
> //namespace HitTest
> namespace HitTest
> {
>
>
> //class Form
> class Form:System.Windows.Forms.Form
> {
>
>
>
> //two points that make up a line
> System.Drawing.Point point1=new System.Drawing.Point(0,0);
> System.Drawing.Point point2=new System.Drawing.Point(50,50);
>
>
>
>
> //a rectangle
> System.Drawing.Rectangle rectangle=new
> System.Drawing.Rectangle(50,50,100,100);
>
>
>
>
> //a line region
> System.Drawing.Region line;
>
>
>
>
> //a square region
> System.Drawing.Region square;
>
>
>
>
> //a brush
> System.Drawing.Brush brush=System.Drawing.Brushes.White;
>
>
>
>
> //constructor
> Form()
> {
>
>
> //set style for double buffered graphics
> SetStyle
> (
> System.Windows.Forms.ControlStyles.AllPaintingInWmPaint|
> System.Windows.Forms.ControlStyles.DoubleBuffer|
> System.Windows.Forms.ControlStyles.ResizeRedraw|
> System.Windows.Forms.ControlStyles.UserPaint,
> true
> );
>
>
> //get a GraphicsPath object
> System.Drawing.Drawing2D.GraphicsPath graphicspath=new
> System.Drawing.Drawing2D.GraphicsPath();
>
>
> //add a line to the graphicspath
> graphicspath.AddLine(point1,point2);
>
>
> //use the graphicspath to define the line-region
> line=new System.Drawing.Region(graphicspath);
>
>
> //use the rectangle to define the square-region
> square=new System.Drawing.Region(rectangle);
>
>
> //prepare for mouse-input
> MouseMove+=new System.Windows.Forms.MouseEventHandler(OnMouseMove);
>
>
> //prepare for paint
> Paint+=new System.Windows.Forms.PaintEventHandler(OnPaint);
>
> }
>
>
>
>
> //OnMouseMove
> void OnMouseMove(object a,System.Windows.Forms.MouseEventArgs b)
> {
>
> //use White brush
> brush=System.Drawing.Brushes.White;
>
> if(square.IsVisible(b.X,b.Y))
> {
>
> //use Red brush if mouse is over square
> brush=System.Drawing.Brushes.Red;
> }
>
> else if(line.IsVisible(b.X,b.Y))
> {
>
> //use Blue brush if mouse is over line
> brush=System.Drawing.Brushes.Blue;
> }
>
> //force redraw
> Invalidate();
> }
>
>
>
>
> //OnPaint
> void OnPaint(object a,System.Windows.Forms.PaintEventArgs b)
> {
> b.Graphics.DrawLine(System.Drawing.Pens.Black,point1,point2);
> b.Graphics.DrawRectangle(System.Drawing.Pens.Black,rectangle);
> b.Graphics.FillRegion(brush,square);
> }
>
>
>
>
> //Main
> public static void Main()
> {
> System.Windows.Forms.Application.Run(new Form());
> }
>
> }
> }
>
>
>
>

> This could be because the region is actually empty it has no area. I'd
> suggest using GrpahicsPaths. They support IsVisible and IsOutlineVisible
> methods. The latter is what you need to use for hittesting lines.