Infinitely scrollable UIView for a graph - ios

Question

I'm relatively new to graphics. This block of code simply draws graph nodes and edges in a UIView. This code works fine for a small number of nodes, but takes a 10+ seconds to load when the number of nodes and edges exceeds 200 in a UIView that is equaly to the frame of the iPad. Am I drawing inefficiently? My goal is to create an 'infinite' scrollable/zoomable graph view where nodes and edges are loaded only when they become visible. I believe that UIView dimensions are limited, so inserting an extremely large UIView into a UIScrollView will not work.
Currently, I am creating a UIView that is slightly larger than the dimensions of the iPad and placing that within a UIScrollView. All nodes and edges are being rendered, even if they are not visible. This is most likely inefficient.
How can I minimize time drawing? How can I create an infinite scrollable/zoomable view?
Thanks
A sample of the drawing:
UIView Code:
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
//Set background
CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
CGContextFillRect(context, self.bounds);
//Translate the coordinate system relative to the minimum and maximum points in the graph
CGContextTranslateCTM(context, -graph.minX + MAP_BORDER_WIDTH, -graph.minY + MAP_BORDER_HEIGHT);
if (graph) {
//Draw all edges in graph
for (FNETEdge *edge in graph.edges) {
[self drawEdge:edge
inRect:rect];
}
//Draw all nodes in graph
for (FNETNode *node in graph.nodes) {
[self drawNode:node
inRect:rect];
}
}
CGContextRestoreGState(context);
}
- (void)drawNode:(FNETNode*)node inRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
//Get the size of the text
NSMutableAttributedString *text = node.getAttributedText;
CGSize maxTextSize = [text boundingRectWithSize:CGSizeMake(0, 0) options:NSStringDrawingUsesLineFragmentOrigin context:nil].size;
//Find the width and height of the node
CGFloat width = NODE_PADDING + node.icon.size.width + NODE_SPACING + maxTextSize.width + NODE_PADDING;
CGFloat height = node.icon.size.height > maxTextSize.height ? (NODE_PADDING + node.icon.size.height + NODE_PADDING) : (NODE_PADDING + maxTextSize.height + NODE_PADDING);
//Top left corner of the node
CGPoint topLeftPoint = CGPointMake(node.center.x - width/2, node.center.y - height/2);
//Inner and outer rectangles for node
CGRect outerNodeRect = CGRectMake(topLeftPoint.x, topLeftPoint.y, width, height);
CGRect innerNodeRect = CGRectMake(topLeftPoint.x + NODE_PADDING, topLeftPoint.y + NODE_PADDING, width - (2 * NODE_PADDING), height - (2 * NODE_PADDING));
//Find where we will draw the icon and the text
CGRect iconRect = CGRectMake(innerNodeRect.origin.x, topLeftPoint.y + (height - node.icon.size.height) / 2, node.icon.size.width, node.icon.size.height);
CGRect textRect = CGRectMake(innerNodeRect.origin.x + node.icon.size.width + NODE_SPACING, innerNodeRect.origin.y, maxTextSize.width, maxTextSize.height);
//Fill background
[[node getDeviceColor] setFill];
UIBezierPath *roundedRect = [UIBezierPath bezierPathWithRoundedRect:outerNodeRect cornerRadius:8];
[roundedRect fillWithBlendMode: kCGBlendModeNormal alpha:1.0f];
//Draw icon
[node.icon drawInRect:iconRect];
//Draw text
CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
[text drawWithRect:textRect options:NSStringDrawingUsesLineFragmentOrigin context:nil];
CGContextRestoreGState(context);
}
- (void)drawEdge:(FNETEdge*)edge inRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextSetLineCap(context, kCGLineCapSquare);
CGContextSetStrokeColorWithColor(context, [edge getSpeedColor].CGColor);
CGContextSetLineWidth(context, EDGE_LINE_WIDTH);
//Iterate through all points and connect the dots!
for (int i = 0; i < edge.points.count -1; i++) {
CGPoint startPoint = ((NSValue*)[edge.points objectAtIndex:i]).CGPointValue;
CGPoint endPoint = ((NSValue*)[edge.points objectAtIndex:i+1]).CGPointValue;
CGContextMoveToPoint(context, startPoint.x, startPoint.y);
CGContextAddLineToPoint(context, endPoint.x, endPoint.y);
}
CGContextStrokePath(context);
CGContextRestoreGState(context);
}