Data-point hints for TAChart?
lazarus / 55-TAChart

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dkjMusic · 2011-10-07 17:35

Is there a simple means whereby I can hover over a data point and
display a hint with, e.g., the literature reference for that point?

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wp · 2011-10-07 17:57

These are the steps needed for your effect:

- When adding the data to the series pass the literature reference for
each point in the text parameter, e.g.
Code: [Select]    Chart1LineSeries1.AddXY(x,y,ReferenceText, clRed); 

- Add a ChartToolset to the form, and after doubleclicking on it, add
a DataPointToolHit

- Assign the ChartToolset to the corresponding Chart's property

- Write a handler for the DataPointToolHint.OnHint event:
Code: [Select]procedure
TForm1.ChartToolset1DataPointHintTool1Hint(ATool: TDataPointHintTool;
  const APoint: TPoint; var AHint: String);
begin
  AHint :=
TChartSeries(ATool.Series).Source.Item[ATool.PointIndex]^.Text;
end;

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dkjMusic · 2011-10-07 20:58

Quote from: wp on October 07, 2011, 07:57:01 pmThese are the steps
needed for your effect:

- When adding the data to the series pass the literature reference for
each point in the text parameter, e.g.
Code: [Select]    Chart1LineSeries1.AddXY(x,y,ReferenceText, clRed); 

- Add a ChartToolset to the form, and after doubleclicking on it, add
a DataPointToolHit

- Assign the ChartToolset to the corresponding Chart's property

- Write a handler for the DataPointToolHint.OnHint event:
Code: [Select]procedure
TForm1.ChartToolset1DataPointHintTool1Hint(ATool: TDataPointHintTool;
  const APoint: TPoint; var AHint: String);
begin
  AHint :=
TChartSeries(ATool.Series).Source.Item[ATool.PointIndex]^.Text;
end;
I did the above, except for AHint := TChartSeries..., I put AHint :=
TLineSeries...

However, I still do not get the x,y's text as a hint.

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wp · 2011-10-07 21:28

Try the attached project, it's working.

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dkjMusic · 2011-10-07 23:47

Thanks for the example. I found my mistake - a Private declaration of
the TLineSeries. I moved them Public and all worked just as you
recommended.

Thanks again very much.

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Ask · 2011-10-09 02:08

Minor note: in this particular case you can set
Code: [Select]Chart1LineSeries1.Marks.Style:=smsLabel;
Chart1LineSeries1.Marks.Visible:=false;
ChartToolset1DataPointHintTool1.UseDefaultHintText:=true;

...and the hint will work without the need to handle OnHint event.

See also http://wiki.lazarus.freepascal.org/TAChart_documentation#Data
_point_hint_tool

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dkjMusic · 2011-10-09 06:04

Quote from: Ask on October 09, 2011, 04:08:05 amMinor note: in this
particular case you can set
Code: [Select]Chart1LineSeries1.Marks.Style:=smsLabel;
Chart1LineSeries1.Marks.Visible:=false;
ChartToolset1DataPointHintTool1.UseDefaultHintText:=true;

...and the hint will work without the need to handle OnHint event.

See also http://wiki.lazarus.freepascal.org/TAChart_documentation#Data
_point_hint_tool
Yes, thanks Ask.