[vtkusers] Labels for Plots in vtkChart?

[Joseph Melnyk]

OK, thanks Marcus.  I had considered the route of deriving from vtkPlot as well, since I'd want the labels to be associated with plots and not managed separately.  We'll see...






-----Original Message-----
From: Marcus D. Hanwell [mailto:marcus.hanwell at kitware.com] 
Sent: Monday, April 20, 2015 1:09 PM
To: Joseph Melnyk
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] Labels for Plots in vtkChart?

On Mon, Apr 20, 2015 at 12:51 PM, Joseph Melnyk <JMelnyk at pile.com> wrote:
> Is there a facility to add a label to a plot in vtkChart?  For 
> example, have a specific value in the plot be labeled to indicate it’s 
> special, or label the first value in the plot with the plot’s name?  
> From my understanding, nothing like this currently exists, and I’m 
> exploring how difficult it would be to adapt what’s currently there.  
> It seems it may be possible to create something from vtkBlockItem or 
> vtkTooltipItem to be “labels” but some scene coordinate translation 
> would need to be done and vtkChartXY mouse events would need to move 
> the objects around manually when the chart is zoomed/panned, etc…
>
This does not exist, the axes can have custom labels on them, i.e. set
5 to be Sun, 6 to be Moon, add numbers at other locations. It wouldn't be too hard, I would derive from vtkPlot, or possibly vtkPlotPoints, and add the code to render a label at the side of the selected points.

You can see how the tooltip item works, and that is certainly another fairly easy way of doing it (vtkChartXY has the code, you could add a tooltip item to the scene).

Hope that helps, it has been a while since I wrote some of this stuff but I would probably try to reuse the tooltip item as you suggested.

Marcus