title: Intersection between two lines in coordinates
body: <p>I can detect the intersection point of two lines, but if my line don't has the length of my screen, it detects the point, where it shouldn't be.</p>
  
  <p>Here a preview: <img src="https://i.stack.imgur.com/M1HkR.png" alt="Intersection">
  So, it shouldn't detect this intersection because the horizontal line isn't that long.</p>
  
  <p>Code:</p>
  
  <pre><code>- (NSMutableArray *) intersectWithLines:(CGPoint)startPoint andEnd:(CGPoint)endPoint {
      NSMutableArray *intersects = [[NSMutableArray alloc] init];
  
      for(GameLine *line in [_lineBackground getLines]) {
  
          double lineStartX = line.startPos.x;
          double lineStartY = line.startPos.y;
          double tempEndX = line.endPos.x;
          double tempEndY = line.endPos.y;
  
          double d = ((startPoint.x - endPoint.x)*(lineStartY - tempEndY)) - ((startPoint.y - endPoint.y) * (lineStartX - tempEndX));
  
          if(d != 0) {            
              double sX = ((lineStartX - tempEndX) * (startPoint.x * endPoint.y - startPoint.y * endPoint.x) - (startPoint.x - endPoint.x) * (lineStartX * tempEndY - lineStartY * tempEndX)) / d;
              double sY = ((lineStartY - tempEndY) * (startPoint.x * endPoint.y - startPoint.y * endPoint.x) - (startPoint.y - endPoint.y) * (lineStartX * tempEndY - lineStartY * tempEndX)) / d;
  
  
              if([self isValidCGPoint:CGPointMake(sX, sY)]) {
                  [intersects addObject:[NSValue valueWithCGPoint:CGPointMake(sX, sY)]];
              }            
          }
      }
  
      return intersects;
  }
  </code></pre>