Question

I have implemented the following code in my CPTScatterPlotDelegate to display a callout bubble:

-(void)scatterPlot:(CPTScatterPlot *)plot plotSymbolWasSelectedAtRecordIndex:(NSUInteger)index
{
    CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)plot.plotSpace;
    CPTGraph *graph = plot.graph;
    int yIdent = ((NSString*)plot.identifier).intValue;

    NSNumber *yVal = [[_dataRange yForIndex:index] objectAtIndex:yIdent-1];
    NSNumber *xVal = [_dataRange xForIndex:index];
    double doublePrecisionPlotPoint[2];//[x,y]
    doublePrecisionPlotPoint[0] = xVal.doubleValue;
    doublePrecisionPlotPoint[1] = yVal.doubleValue;
    CGPoint touchedPoint = [graph.defaultPlotSpace plotAreaViewPointForDoublePrecisionPlotPoint:doublePrecisionPlotPoint];

    if(_annotation)
        [_annotation dismissCalloutAnimated:YES];
    _annotation = [[SMCalloutView alloc] init];
    //todo appropriate units
    _annotation.title = [NSString stringWithFormat:@"%.2f kg", yVal.doubleValue];
    [_annotation presentCalloutFromRect:CGRectMake(touchedPoint.x, touchedPoint.y, 1, 1) inView:_view constrainedToView:_view permittedArrowDirections:SMCalloutArrowDirectionAny animated:YES];
}

_dataRange is just a custom class holding my data and _annotation is the instance of my callout.

The problem is I cant’t get the position of the callout working properly. If I set _view to the ViewController.view I get the right callout but in the wrong place like this:

If I set _view to the CPTGraphHostingView instead I get the right point but the callout appears to be flipped like this:

How to I get the right plot point co-ordinates to display the callout?

Answer 1

You shouldn’t add any subviews to the hosting view—it uses a flip transform on iOS so Core Plot can share drawing code between iOS and the Mac.

Use the -convertPoint:toView: or -convertPoint:fromView: method to convert touchedPoint from the hosting view’s coordinate system to the ViewController.view coordinate system.