Marks AtDataOnly
lazarus / 55-TAChart

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fpcoder · 2017-01-28 01:54

If BottomAxis.Marks.AtDataOnly is True, then only the last one of the
3 added days gets a visible label. Isn't that a bit odd?
Style of Marks is set to smsLabel, and BottomAxis.Marks.Source is set
to Source of the actual series as you can see in code below.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.FormCreate(Sender: TObject);var  ylist: array[0..3] of
Double;begin  Chart1.BottomAxis.Marks.Source :=
Chart1OpenHighLowCloseSeries1.Source;  Chart1.BottomAxis.Marks.Style
:= smsLabel;  Chart1.BottomAxis.Marks.AtDataOnly:=True;  ylist[0]:=20;
 //Low  ylist[1]:=20;  //Open  ylist[2]:=25;  //Close  ylist[3]:=25;
 //High  lcsData.AddXYList(1, ylist, 'Day 1');  lcsData.AddXYList(2,
ylist, 'Day 2');  lcsData.AddXYList(3, ylist, 'Day 3');end;
Sample attached
(Latest Lazarus trunk)

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wp · 2017-01-28 12:56

Thanks for the example - this helps a lot!

Basically your problem is due to a "misuse" of the Marks.AtDataOnly:
This feature is intended for "paned" charts where several axes are
overlayed at the same side of the chart, and where an
AutoscaleAxisTransformation shifts the related axis ranges such that
the corresponding series do not overlap. Setting Marks.AtDataOnly to
true here makes sure that labels are drawn only within the range of
the related series. -- See attached demo for "correct" usage (it is
available in the folder demo/panes-3 of TAChart now as well).

In your particular case, setting Marks.AtDataOnly in the normal case
of a non-paned chart leads to the described issue because you did not
assign an AxisIndexY to the series. This way the axis cannot determine
the range of the data assigned to it.

Fortunately I found an easy fix, and this is in r54023 now. Since it
is more or less a bug it will be backported to Laz 1.6.4. Please test
and tell me if if fixes your issue.

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fpcoder · 2017-01-29 05:21

It works fine now, thanks wp!