Core Plot range change performance - ios

Question

I need to resize my plot using pinch recognizers, its allowed to resize "width" and "height" separately in small areas at left and bottom.
Also my plot is inside of UIScrollView to scroll it horizontally
This is my Y-axis pinch code:
- (void)yAxisPinchPerformed:(UIPinchGestureRecognizer *)pinchRecognizer
{
CGFloat recognizerScale = pinchRecognizer.scale;
CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)_graph.defaultPlotSpace;
switch (pinchRecognizer.state) {
case UIGestureRecognizerStateBegan:
{
_savedRange = plotSpace.yRange;
}
break;
case UIGestureRecognizerStateChanged:
{
CGFloat scaledRange = recognizerScale * _savedRange;
[plotSpace setYRange:scaledRange];
}
break;
default:
break;
}
}
works good, but really slow on devices, probably because it redraws the whole plot (it's wide and inside UIScrollView), not only visible area;
my plot contains maximum 100 bars with gradient fill. I tried to turn off filling but it helped just a little;
now i have these improvements:
- (void)yAxisPinchPerformed:(UIPinchGestureRecognizer *)pinchRecognizer
{
CGFloat recognizerScale = pinchRecognizer.scale;
switch (pinchRecognizer.state) {
case UIGestureRecognizerStateBegan:
{
// UIImageView *_imageView;
[_imageView setImage:_graph.imageOfLayer];
[_imageView setHidden:NO];
// CGRect initialFrame is frame of graph container
[_imageView setFrame:initialFrame];
_savedHeigth = _imageView.frame.size.height;
}
break;
case UIGestureRecognizerStateChanged:
{
CGFloat scaledHeight = recognizerScale * _savedHeight;
CGRect imageFrame = _imageView.frame;
imageFrame.size.height = scaledHeight;
[_imageView setFrame:imageFrame];
}
break;
case UIGestureRecognizerStateEnded:
CGFloat scaledRange = calculateRangeFromHeights(...);
CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)_graph.defaultPlotSpace;
[plotSpace setYRange:scaledRange];
[_imageView setHidden:YES];
break;
default:
break;
}
}
I get image of plot layer and perform scaling of UIImageView, it's super faster. But when i decrease Y-scale i have only part of graph, it's cutted at the top.
Is it possible to scale Core Plot graph smoothly and real-time?

Answer 1

Core Plot has no way to know how much of the graph is visible inside your scroll view. I would remove the scroll view and rely on the built-in Core Plot scrolling. If that's not feasible, you could determine which bars are visible and only show the visible bars. Modify your datasource to return data only for the visible bars and reload the data whenever the set of visible bars changes.