[SOLVED] Windows only issue, invicible border

[Handoko]

Today I am writing a small Windows tool on a Windows 11 laptop.
Try this code on your Windows computer:

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button1Click(Sender: TObject);
2. begin
3.   Left := 0;
4.   Top := 0;
5. end;

I am a Linux user, I am not sure but I believe this behavior only happens on Windows 8 and above. After running the code above and clicking the button, the form won't move to the exact top left corner we expected. Here is an old discussion related with this issue:
https://forum.lazarus.freepascal.org/index.php/topic,65298.msg497415.html#msg497415

Does anybody know how to make the code above to work correctly on WinXP to Windows 11? Or how to detect the thickness of the invincible border?

[BrunoK]

Try this :

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls
9.   {$IFDEF WINDOWS}
10.   ,Windows
11.   {$ENDIF WINDOWS}
12.   ;
13.  
14. type
15.  
16.   { TForm1 }
17.  
18.   TForm1 = class(TForm)
19.     Button1: TButton;
20.     procedure Button1Click(Sender: TObject);
21.   private
22.     FFormXOffset: integer;
23.   public
24.  
25.   end;
26.  
27. var
28.   Form1: TForm1;
29.  
30. implementation
31.  
32. {$R *.lfm}
33.  
34. { TForm1 }
35.  
36. procedure TForm1.Button1Click(Sender: TObject);
37. var
38.   lPoint: TPoint;
39. begin
40.   {$IFDEF WINDOWS}
41.   lPoint.SetLocation(0, 0);         // Init lPoint to TopLeft of form
42.   lPoint:= ClientToScreen(lPoint);  // Retrieve screen coord of form
43.   FFormXOffset := Left - lPoint.X;  // Compute offset relative to declared left.
44.   {$ENDIF WINDOWS}
45.   Left := FFormXOffset + { Desired real left } 0; // Apply offset to desired position
46.   Top := 0;
47. end;
48.  
49. end.

[Handoko]

Yes, it work. Thank you very much. The code may look simple but very helpful. I learned something new today.