How to register a windows wise hot key for bringing tray application back?

[LeoBruno]

Hi:

I need to register an Operating System wide hot key to bring a hiddn application (minimized to tray) back in to focus.

I have been searching for a solution and found several that does't work animore.

The solution provided here does not work, and the link pointing to another solution is broken.
https://forum.lazarus.freepascal.org/index.php?topic=16733.0

Also, the method that should be called when the hotkey is detected, is declared at the main form class, because it messes with some of that class properties.

Any help?

Thanx...

[Thausand]

... and the link pointing to another solution is broken.

Forum have change location then have copy-paste (topic nr same): https://forum.lazarus.freepascal.org/index.php/topic,4964.0.html

[Thaddy]

Global hotkeys are a can of worms, but the older examples for windows ALL still work, provided you are testing, and this is important, OUTSIDE the Lazarus IDE since that already registers a lot of hotkeys.
Global hotkey? Test OUTSIDE of the IDE and the debugger.

One further caveat is that you can not easily change OS provided hotkeys like alt-tab, alt-f4 and all winkey + key.

You must also ensure the hotkeys are UNregistered when your program terminates, otherwise they will be in effect until system restart and can/WILL cause crashes.

Summary:
Your hotkey will likely work, but you run your program under control of the IDE or the debugger.
And that will fail..... Hotkeys on Windows rely internally on global atoms, independent of fpc/lazarus.

[LeoBruno]

no they don't.
The code does not compile, and I couldn't figure out whats wrong.

Code: Pascal  [Select][+][-]

1.  
2. uses
3.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, windows;
4.  
5. var
6.   PrevWndProc: WNDPROC;
7. const
8.   MY_ID=1;
9.  
10. type
11.  
12.   { TForm1 }
13.  
14.   TForm1 = class(TForm)
15.     procedure FormCreate(Sender: TObject);
16.   private
17.   public
18.     procedure test;
19.   end;
20.  
21. var
22.   Form1: TForm1;
23.  
24. implementation
25.  
26. function WndCallback(Ahwnd: HWND; uMsg: UINT; wParam: WParam; lParam: LParam):LRESULT; stdcall;
27. begin
28.   if (uMsg=WM_HOTKEY) and (WParam=MY_ID) then
29.     begin
30.       Form1.test;
31.     end;
32.   result := CallWindowProc(PrevWndProc, Ahwnd, uMsg, WParam, LParam);
33. end;
34.  
35. {$R *.lfm}
36.  
37. { TForm1 }
38.  
39. procedure TForm1.FormCreate(Sender: TObject);
40. begin
41.   PrevWndProc := Windows.WNDPROC(SetWindowLong(Self.Handle, GWL_WNDPROC, PtrInt(@WndCallback)));
42.   RegisterHotKey(Self.Handle, MY_ID, 0, vk_F9);
43. end;
44.  
45. procedure TForm1.test;
46. begin
47.   ShowMessage('test');
48. end;
49.  
50.  

```
Compile Project, Target: C:\Users\Leonardo.Bruno\Documents\project1.exe: Exit code 1, Errors: 1, Hints: 1
unit1.pas(47,74) Hint: Conversion between ordinals and pointers is not portable
unit1.pas(47,18) Error: Illegal type conversion: "LongInt" to "<procedure variable type of function(QWord;LongWord;Int64;Int64):Int64;StdCall>"
```

Global hotkeys are a can of worms, but the older examples for windows ALL still work, provided you are testing, and this is important, OUTSIDE the Lazarus IDE since that already registers a lot of hotkeys.
Global hotkey? Test OUTSIDE of the IDE and the debugger.

One further caveat is that you can not easily change OS provided hotkeys like alt-tab, alt-f4 and all winkey + key.

You must also ensure the hotkeys are UNregistered when your program terminates, otherwise they will be in effect until system restart and can/WILL cause crashes.

Summary:
Your hotkey will likely work, but you run your program under control of the IDE or the debugger.
And that will fail..... Hotkeys on Windows rely internally on global atoms, independent of fpc/lazarus.

[rca]

no they don't.
The code does not compile, and I couldn't figure out whats wrong.

```
Compile Project, Target: C:\Users\Leonardo.Bruno\Documents\project1.exe: Exit code 1, Errors: 1, Hints: 1
unit1.pas(47,74) Hint: Conversion between ordinals and pointers is not portable
unit1.pas(47,18) Error: Illegal type conversion: "LongInt" to "<procedure variable type of function(QWord;LongWord;Int64;Int64):Int64;StdCall>"
```

That error had already been resolved in the forum.

See @440bx's solution here:
https://forum.lazarus.freepascal.org/index.php/topic,67162.msg516256.html#msg516256

Change "SetWindowLong" to "SetWindowLongPtr".

Code: Pascal  [Select][+][-]

1. procedure TForm1.FormCreate(Sender: TObject);
2. begin
3.   PrevWndProc := Windows.WNDPROC(SetWindowLongPtr(Self.Handle,GWL_WNDPROC,PtrInt(@WndCallback)));
4.   RegisterHotKey(Self.Handle, MY_ID, 0, vk_F9);
5. end;
6.  

[Remy Lebeau]

Change "SetWindowLong" to "SetWindowLongPtr".

Instead of using SetWindowLongPtr(GWL_WNDPROC), a better/safer option is to use SetWindowSubclass().

See Safer subclassing

[Thaddy]

Same remark as Unregister: don't forget to unsubclass at program termination.
And probably test outside of the IDE/Debugger.