[SOLVED] Form scaling

[Pe3s]

Hello, I have a question: is it possible to implement proportional scaling of a form, e.g. 16:9, but without unnecessary flickering of the form so that it scales nicely and smoothly?

Code: Pascal  [Select][+][-]

1. private
2.      FIgnoreResize: Boolean;
3.  
4.   public
5.  
6.   end;
7.  
8. var
9.   Form1: TForm1;
10.  
11. implementation
12.  
13. {$R *.lfm}
14.  
15. { TForm1 }
16.  
17. procedure TForm1.FormCreate(Sender: TObject);
18. begin
19.   Width := 854;
20.    Height := 480;
21.    DoubleBuffered := True;
22.    FIgnoreResize := False;
23. end;
24.  
25. procedure TForm1.FormResize(Sender: TObject);
26. const
27. Ratio: Double = 16 / 9;
28. var
29. NewHeight: Integer;
30. begin
31. if FIgnoreResize then Exit;
32.  
33. FIgnoreResize := True;
34. try
35.  
36.   NewHeight := Round(Width / Ratio);
37.   if NewHeight <> Height then
38.     Height := NewHeight;
39. finally
40.   FIgnoreResize := False;
41. end;
42. end;                              
43.  

[Ally]

Hello Pe3s,

I have reduced the whole thing to the bare minimum.
The window changes size without flickering. (Win11, Lazarus 4.2)

[Pe3s]

The code works, but you just need to add it to OnResize Form
and change the size, then it's a disco.

[Ally]

That's not a problem for me on Windows either. Your code also runs without flickering.
However, the problem could be the following: FormResize is called when the size of Form changes.
If you change the size of Form within FormResize, FormResize is called again.
That doesn't normally make sense. That's why I put the size change of Form in a ButtonClick to prevent the recursive call.

[Ally]

I must apologize.
I have now understood the problem.
Enclosed is a solution that prevents flickering when changing the size.

[Pe3s]

Thank you