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.AllPaintingInWm Paint|
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,poin t1,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());
}
}
}
