[Lazarus] TAChart marks on mouseoverpoint

[Andrea Mauri]

> Well, there is only so much pixels on the chart.
> If you put enough marks, they will overlap sooner or later.
> Do you have some concrete proposal to reduce overlapping?
>
>   
Looking at TeeChart from Steema (an old version, Delphi 6 ;) ) I noticed 
two things.
1. Marks are drawn over the points (the serie) and not below.
2. There is "Clipped" property for Marks. If Clipped is true the marks 
behave as Marks on TAChart (they are visible only inside the Chart 
Axis). Otherwise if Clipped is False the marks are visible also outside 
the Chart Axis.
See image below.
3. An option could be that the marks can be dragged...

Another option I like in Steema Chart is the possibility to have Panel 
properties (BevelInner, BevelOuter...) But it is not a so important 
thing, actually I put the TAChart on a panel to do that.

> Since r21827 you can use TUserDrawnSeries for that.
> See demo/func/funcdemo project for an example.
>
>   
I will check it.
> For this you need to create your own series class by inheriting
> TCustomChartSeries, TChartSeries or TLineSeries and overriding Draw method.
> Do you mean to create something like
> http://www.steema.com/products/teechart/screenshots/infopoint3dpolaradar.htm ?
> If so, you are very welcome to contribute your code back to the TAChart ;-)
>
>   
Actually I just need to draw a Principal Component Analysis Loading 
Plot. That is not a polar chart, it is a simple scatter plot where as an 
option a unitary circle can be drawn and the rays from the center to the 
points can be drawn also.
Anyway I would like to contribute to the development of TAChart. Now I 
am just using it and trying to understand it looking at the source. I am 
a final user and I am not sure I have the capabilities to contribute on 
a development basis.. we'll see. :)
thanks,
andrea