Tchart crashes on MouseMouse event is scale/range is not set yet

[stephanweber]

Hi,

I use the mouse moving event to update a little text label to show the coordinates. But to get the coordinates x and y the ranges need to be setup already. This is not the case on program startup, so if the mouse cursor is (e.g. by chance) over the chart I get a runtime error.
To avoid this I created a boolean variable IsRun and use it in mouse-move event and initialize it in formcreate to False.
However, I still get the same crash. What to do?

Code:

Code: Pascal  [Select][+][-]

1. procedure TFormMain.Chart1MouseMove(Sender: TObject; Shift: TShiftState; X,
2.   Y: Integer);
3. Var xx, yy : Double;
4. begin
5.   If IsRun then Begin
6.   xx:=Chart1.XImageToGraph(X);
7.   yy:=Chart1.YImageToGraph(Y);
8.   LabelCursor.Caption:='Cursor: x=...';
9.   end
10. end;

If I use If False all is fine....


Bye Stephan

[TRon]

Hard to say without being able to see all the code/components/properties but as a general note: you can assign an event at runtime so would advise to try and set the event only after you have set the ranges correctly.

[stephanweber]

Hi, it looks I found a solution:

Using

If Chart1.ScalingValid then ...

works fine!!

However, I still do not know why using the boolean variable instead does not work.

Bye Stephan