CorePlot plot hit testing

Question

I have a question about CorePlot. My question is: I've drawn a curve. Next task is: curve selection. I've added the handler:

But that does not work. Any ideas? Thanks.

- (BOOL)npvCurveContainPoint:(CGPoint)point
{
    if ([[graph allPlots] count] == 0) {
         return NO;
    }
    CPTPlot* plot = [graph plotAtIndex:0];
    BOOL xContains = [[plot plotRangeForCoordinate:CPTCoordinateX] containsDouble:point.x];
    BOOL yContains = [[plot plotRangeForCoordinate:CPTCoordinateY] containsDouble:point.y];
    if (xContains && yContains) {
        return YES;
    }
    return NO;
}

#pragma mark - Plot Space Delegate Methods
- (BOOL)plotSpace:(CPTPlotSpace*)space shouldHandlePointingDeviceDownEvent:(id)event atPoint:(CGPoint)point
{
    CGPoint pointInPlotArea = [graph convertPoint:point fromLayer:graph.plotAreaFrame];
    if ([self npvCurveContainPoint:pointInPlotArea]) {
        NSLog(@"Curve is selected!!!");
    }
    return NO;
}

Answer 1

I'm not sure exactly what you're trying to test, but you're mixing coordinate systems. The point passed to the plot space delegate method is in the view coordinates of the plot area layer. You convert it to the coordinate system of the entire graph layer and then test the point against the plot space data coordinates.

The plot space defines the mapping between the data and the plot area on screen. The location of the xRange corresponds to the left hand edge of the plot area and its end point (location + length) corresponds to the right hand edge. Similarly, the location of the yRange corresponds to the bottom edge of the plot area and its end point corresponds to the top edge. Note the plot ranges can have negative lengths, which means that the data coordinate of the end point can be less than the starting location.