Thank you very much for the explanations. I get your point, but still I don't understand how to solve the problem. Let's say that with the code above I draw a concave path. This is made of hundreds of tiny points next to each other. Shouldn't I be able to close it and fill it?
Unless you're paraphrasing your code, no. As you've posted your code on the forums, it takes exactly two points, the current one and the prior one, draws a stroke between them, and draws another stroke between them (with the close shape command) and then tries to fill in the shape with no area that lies between those two lines that lie perfectly on top of each other.
If you run all of that code repeatedly, you'll just end up drawing several 2-sided shapes.
What you probably want will look more like this:
Code:
// iVars:
CGPoint points[100];
int pointCount = 0; //Set this in init I think... I've been spending the last several weeks learning Java where iVars can be initialized when you declare them... I don't think that's allowed in Obj-C, is it?
- (void)touchMovesWithEvent:(NSEvent*)event {
// Code that converts the received event into a CGPoint newPoint should be typed here...
points[pointCount++] = newPoint;
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), points[0].x, points[0].y);
for (int i = 1; i < pointCount; i++)
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), points[i].x, points[i].y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextSetRGBFillColor(UIGraphicsGetCurrentContext(), 1.0, 0.4, 1.0, 1.0);
CGContextFillPath(UIGraphicsGetCurrentContext());
}
I haven't so much as tested it in any way (I didn't even write out some of the starting code) but what it should do is keep a running list of all your points that it adds to each time it detects another touch. It then draws a shape, starting at the first point, then going to each of the in between points, and then returning to the first point with the close shape command. It then fills the shape.
Some short comings of using my code exactly as it is:
- There's no way to start a second shape.
- Is filling in each partially finished shape a good idea? Maybe, maybe not... it seems to me if you tried doing a shape with any concave parts that this would mess it up.
- It's limited to 100 points in the shape. Beyond that, I think it'll crash... simply increasing this number may not be the best idea either, as that will cause it to potentially set aside unnecessary memory. Maybe find some way to optimize the code so that, for example, if there's a 180 degree angle at a point, it'll get rid of the point.
- The code is a bit of a mess, kind of on purpose, kind of because I'm too lazy to so much as start up Xcode or a text editor... IE, the for loop has no braces (which makes it a bit odd / maybe difficult to read / it's just begging to cause issues later on when you add more to the loop), the point increment occurs inside of the array index... personally, I like doing things like that but I don't see others do it very often... it kind of obscures your code which is bad for collaboration, but good for the TopCoder challenge round...
So, yeah, I leave those as exercises for you, because I basically gave wrote the code that answers your question, I think.
