Strange behavior of TChart
lazarus / 55-TAChart

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was.ok · 2020-06-01 20:44

Hi!

I was trying to create a Chart with multiple panes (something like
this one https://wiki.freepascal.org/TAChart_Tutorial:_Multiple_Panes_
in_one_Chart) and discovered some strange behavior of TChart:

- when axis X is aligned at the bottom and Y-axis (3 items) on the
left - all works fine (img_1.png);
- when axis X is aligned on the left and Y-axis at the bottom - the
first line on the Chart is not drawing at the point [x = 1, y = 1]
(img_2.png, img_3.png).

Is this a bug or just my mistake?

The code is simple:

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  for i := 1 to 1000 do
    begin
      Chart1LineSeries1.AddXY(i, i);
      Chart1LineSeries2.AddXY(i, i);
      Chart1LineSeries3.AddXY(i, i);
    end;
end;

FPC: 3.0.4
Lazarus: 2.0.8

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wp · 2020-06-01 21:56

Please don't double-post.

It seems to be a bug. I found this:
Open file TACustomSeries.pas in folder components/tachart of your
Lazarus installation (make a backup copy of this file before changing
anything)Find the implementation of procedure
TBasicPointSeries.FindExtentIntervalIn the center of this procedure
there is an "if IsRotated then"In the next line ("axisExtent :=
DoubleInterval(GraphToAxisY(a.Y), GraphToAxisY(b.Y))" replace the
GraphToAxisY by GraphToAxisX, i.e. the entire "if" block must beCode:
Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i       if
IsRotated then        axisExtent := DoubleInterval(GraphToAxisX(a.Y),
GraphToAxisX(b.Y))   // Replace GraphToAxisY by GraphToAxisX     
else        axisExtent := DoubleInterval(GraphToAxisX(a.X),
GraphToAxisX(b.X));Recompile the TAChart package: Go to "Package" >
"Open package file .lpk" > Select and load "tachartlazaruspkg.lpk" (in
components/tachart). In the package editor, click "Compile".Please
test and report back.

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was.ok · 2020-06-02 05:48

Quote from: wp on June 01, 2020, 11:56:16 pmPlease don't double-post.
Sorry about that. How to delete the first one?
(https://forum.lazarus.freepascal.org/index.php/topic,50047.0.html)
(It says "You cannot delete your own topics in this board.")

Quote
It seems to be a bug. I found this:
Open file TACustomSeries.pas in folder components/tachart of your
Lazarus installation (make a backup copy of this file before changing
anything)Find the implementation of procedure
TBasicPointSeries.FindExtentIntervalIn the center of this procedure
there is an "if IsRotated then"In the next line ("axisExtent :=
DoubleInterval(GraphToAxisY(a.Y), GraphToAxisY(b.Y))" replace the
GraphToAxisY by GraphToAxisX, i.e. the entire "if" block must beCode:
Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i       if
IsRotated then        axisExtent := DoubleInterval(GraphToAxisX(a.Y),
GraphToAxisX(b.Y))   // Replace GraphToAxisY by GraphToAxisX     
else        axisExtent := DoubleInterval(GraphToAxisX(a.X),
GraphToAxisX(b.X));Recompile the TAChart package: Go to "Package" >
"Open package file .lpk" > Select and load "tachartlazaruspkg.lpk" (in
components/tachart). In the package editor, click "Compile".Please
test and report back.

It works!!!

Thank you, wp!

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wp · 2020-06-02 07:25

Quote from: was.ok on June 02, 2020, 07:48:25 amQuote from: wp on June
01, 2020, 11:56:16 pmPlease don't double-post.
Sorry about that. How to delete the first one?
Maybe click on the "Report to moderator" button at the bottom of the
first post. There will be a single-line edit box in which you can drop
a note why you want it to be deleted.

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was.ok · 2020-06-02 07:43

Quote from: wp on June 02, 2020, 09:25:27 amMay click on the "Report
to moderator" button at the bottom of the first post. There will be a
single-line edit box in which you can drop a note why you want it to
be deleted.

Thanks!

Done.

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wp · 2020-06-03 09:19

The bug fix has been applied the Lazarus trunk and will be backported
to Lazarus fixes.