Access Violation on clicking buttons and deleting text

[Paul-SFL]

Hi all ,

I finally wrote the calculator mode and now trying to connect it with GUI. But somewhy I get access violation errors on testing the calculator:

• when type a number and then delete it by pressing BackSpace (error when I delete the latest char);
• when clicking "+", "-" or "C" after typing the number
• when clicking "="

Unit references seems to be correct.. I have no idea on why  does it happen . The calculator "engine", gncalc, has been tested - works 100%-correctly, so I believe the problem is in unit2.

I'll appreciate very much if someone skims over the source and gives me some advice.

I'm using Lazarus 0.9.30 + FRC 2.4.2.

[Blaazen]

There are more bugs. It gives me SIGSEGV on closing the app.

Anyway, you should add there something like:

Code: [Select]

procedure Tcalculator_mode.fieldChange(Sender: TObject);
     var s:string;
begin
  field.Readonly:=false;
  if length(field.text)=0 then exit;  //ADD THIS LINE
  if ((field.text[1]='-') and (length(field.text)>254)) or (length(field.text)>253)       then         
because you are trying to read field.text[1] even if field.text is empty.

EDIT:
You shouldn't have Application.Terminate on closing of main form. When you close main form then app is terminated automaticly.

Code: [Select]

procedure Tcalculator_mode.FormClose(Sender: TObject;
  var CloseAction: TCloseAction);
begin
//application.Terminate;
end;   

EDIT2:
Bug: You delete something and then you assign it ! :-)

Code: [Select]

procedure Tcalculator_mode.plusClick(Sender: TObject);
begin
  gncalc.plus:=true;
  field.text:='';
  gncalc.Operand_0:=field.text;
end;     

must be :

Code: [Select]

procedure Tcalculator_mode.plusClick(Sender: TObject);
begin
  gncalc.plus:=true;
  gncalc.Operand_0:=field.text;
  field.text:='';
end;     

And TMemo loses focus after pressing "C".

[Paul-SFL]

Thank you a lot, Blaazen! It works!

Code: [Select]

  if length(field.text)=0 then exit;  //ADD THIS LINE   


Done.

You shouldn't have Application.Terminate on closing of main form. When you close main form then app is terminated automaticly.

Thanks for the advice. Actually, I set calculator form to be main temporarily .

EDIT2:
Bug: You delete something and then you assign it ! :-)

Code: [Select]

procedure Tcalculator_mode.plusClick(Sender: TObject);
begin
  gncalc.plus:=true;
  field.text:='';
  gncalc.Operand_0:=field.text;
end;     

must be :

Code: [Select]

procedure Tcalculator_mode.plusClick(Sender: TObject);
begin
  gncalc.plus:=true;
  gncalc.Operand_0:=field.text;
  field.text:='';
end;     


Fixed. I also added to every button click procedure a boolean which shows whether the first operand is entered, and if it's not - the procedures are exited without doing anything.

And TMemo loses focus after pressing "C".

Fixed too. BTW it's an interesting thing: TMemo loses focus on pressing "=" or "C" and stays focused on pressing "+" or "-" - why does it happen?

EDIT:
So, finally I've got it 100% working .
Blaazen, thank you once more - you saved a lot of my time, I think.

[Blaazen]

BTW it's an interesting thing: TMemo loses focus on pressing "=" or "C" and stays focused on pressing "+" or "-" - why does it happen?

Because "+" and "-" are TSpeedButton, which cannot be focused. "=" and "C" are TButton.

[Paul-SFL]

Thanks, got it .