Draw line on a form

[bona]

Hi guys,

Please explain me how can I find whether any drawn line on the form crossed or not Image box. Line has started coordinates X, Y when mouse button pressed and final coordinates X, Y when it was released. And Image – say small circle with coordinates X, Y and also width ~ 15 pixels. I appreciate any help.

[plenderj]

You want to check if a line intersects a rectangle is it ?
Well in java I had to do something similar.
This code might help (its easily ported) ;

	private static boolean isCross(myVertex lne1, myVertex lne2) {
		boolean toReturn = false;    
		double dx1 = lne1.x2 - lne1.x1;
		double dy1 = lne1.y2 - lne1.y1;
		double dx2 = lne2.x2 - lne2.x1;
		double dy2 = lne2.y2 - lne2.y1;
		double n = 0.0;
		double s = 0.0;
		
		if ((dx2 * dy1) - (dy2 * dx1) != 0) {
			n = (dx1 * (lne2.y1 - lne1.y1) + dy1 * (lne1.x1 - lne2.x1)) / (dx2 * dy1 - dy2 * dx1);
			s = (dx2 * (lne1.y1 - lne2.y1) + dy2 * (lne2.x1 - lne1.x1)) / (dy2 * dx1 - dx2 * dy1);
			toReturn = ((s >= 0) && (s <= 1) && (n >= 0) && (n <= 1));
		}

		return toReturn;		
	}

class myVertex {
	int x1;
	int y1;
	int x2;
	int y2;
}

[bona]

Thanks a lot, plenderj. It just what I needed. I have tried it tonight and it worked fine.