Custom link style

GoDiagram (6 and previous)
1

I have the following code, to add some arrow heads to my links
if (myArrowPosition == ArrowPositionEnum.Multiple )
{
int num = this.PointsCount;
if (num < 2) return;
for (int i = 0; i < num-1; i++)
{
PointF a2, m2;
CalculateArrowPoints(GetPoint(i), GetPoint(i+1), out a2, out m2);
CalculateArrowhead(a2, m2, true, myPoly);
DrawArrowhead(g, view, new Pen(System.Drawing.Color.Red), new SolidBrush(System.Drawing.Color.Red), true, 0, 0, myPoly);
}

}
The problem is that my customer wants some gap/space after each arrow, so that the link will look more like multiple arrows, more than just a single link with multiple arrowheads .
what we have now : ----->------>
what we need : -----> ------>

2

It might be easiest to draw over a little bit of the stroke with a Pen that is the same color as the background, just before you call DrawArrowhead.

3

that’s exactly what I am trying right now, but i have a problem: I do not know which direction the link goes, so I don’t know where exactly to draw

4

Well, the link has to go from GetPoint(i+1) to GetPoint(i+2), assuming that segment exists (i.e. i+2 < num).

5

it seemed to work fine, but then I saw the app crasses. After searching this forum a little I found :

walter
Admin Group



Joined: 19 May 2003
Posts: 2402
Posted: 01 September 2005 at 8:14pm | IP Logged
Implementations of the GoObject.Paint method must NOT modify any objects, neither in the document nor in the view.
6

Is your code above part of an override of GoObject.Paint?
Do you modify any GoObjects in that method? I would think not, in which case there is some other failure. Please see what is causing the exception. What is the exception, anyway?

7

forget about it. found the problem.
it is not because I’m using the paint method, it is because I called
DrawArrowhead method after
ToArrowStyle = GoStrokeArrowheadStyle.Circle.
seems like the last param of DrawArrowhead isnt’t ok. will fix this.

8

It is in the paint method of a link object