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Bug 666

Summary:	TChart does not work properly, when Zooming with ZoomPercent
Product:	FireMonkey TeeChart	Reporter:	Mustafa Celik <celik>
Component:	Chart	Assignee:	Steema Issue Manager <issuemanager>
Status:	RESOLVED NOTABUG
Severity:	major	CC:	david, sandra
Priority:	Normal
Version:	140220
Target Milestone:	---
Hardware:	All
OS:	All
Chart Series:	---	Delphi / C++ Builder RAD IDE Version:

Description Mustafa Celik 2014-03-25 08:19:26 EDT

- I am using the TDBChart Component

- the user can change the zoom percentage over an TComboBox (1,15,25,50,100)%

- But after firing the ComboBox OnChange-Event the Chart gets zoomed out everytime, regardless of the double-value given to the procedure ZoomPercent(..)

The code i tried is:

-> fScale: double;
-> cbxScale has fix values (1,15,25,50,100)


procedure TForm1.cbxScaleChange(Sender: TObject);
begin
   fScale := (100/fScale) * StrToFloat(cbxScale.Selected.Text);
   TDBChart1.ZoomPercent(fScale);
end;

Comment 1 Mustafa Celik 2014-03-25 08:20:25 EDT

PS: The issues comes up on Win32 and on Android

Comment 2 david berneda 2014-03-27 13:11:51 EDT

I think this is not a bug. Its by design.
ZoomPercent applies a percentage zoom relative to the existing "zoom" (axis scales).

If you wish an absolute zoom, first reset the axes and then apply the zoom, like:

procedure TForm1.cbxScaleChange(Sender: TObject);
begin
   fScale := (100/fScale) * StrToFloat(cbxScale.Selected.Text);

   TDBChart1.Axes.Reset; // <-- Reset to 100%

   TDBChart1.ZoomPercent(fScale);
end;

Comment 3 Mustafa Celik 2014-03-28 03:33:24 EDT

(Bezüglich comment 2 von david berneda)
> I think this is not a bug. Its by design.
> ZoomPercent applies a percentage zoom relative to the existing "zoom" (axis
> scales).
> 
> If you wish an absolute zoom, first reset the axes and then apply the zoom,
> like:
> 
> procedure TForm1.cbxScaleChange(Sender: TObject);
> begin
>    fScale := (100/fScale) * StrToFloat(cbxScale.Selected.Text);
> 
>    TDBChart1.Axes.Reset; // <-- Reset to 100%
> 
>    TDBChart1.ZoomPercent(fScale);
> end;

Hello Mr. Berneda,
thank you for the fast response!
i tried to do it with TDBChart1.UndoZoom() before doing a ZoomPercent. But UndoZoom() has not been fired properly or is it not the correct procedure at this point?

I will try your solution. and give response. Thank you again!

Comment 4 Mustafa Celik 2014-03-28 03:56:49 EDT

Mr.Berneda,
the effect is the same as before. The existing zoom gets a percentage zoom again and again but not changing the axes back to 100%.

Code:

procedure TForm1.cbxScaleChange(Sender: TObject);
begin
   fScale := StrToFloat(cbxScale.Selected.Text);

   TDBChart1.Axes.Reset; // <-- Reset to 100%

   TDBChart1.ZoomPercent(fScale);
end;