GetKeyState(VK_SHIFT)

[balazsszekely]

What about this low level hook? It separately detects right/left shift. It's windows only, but since @pascal is under windows it should be ok.

Code: Pascal  [Select][+][-]

1. uses windows;
2.  
3. var
4.   llKeyboardHook: HHOOK = 0;
5.  
6. function LowLevelKeyboardHook(nCode: Integer; wParam: WPARAM; lParam: LPARAM): HRESULT; stdcall;
7. const
8.   LLKHF_UP = KF_UP shr 8;
9. type
10.   PKBDLLHOOKSTRUCT = ^TKBDLLHOOKSTRUCT;
11.   TKBDLLHOOKSTRUCT = packed record
12.     vkCode: DWORD;
13.     scanCode: DWORD;
14.     flags: DWORD;
15.     time: DWORD;
16.     dwExtraInfo: DWORD;
17.   end;
18. var
19.   pkbhs: PKBDLLHOOKSTRUCT;
20. begin
21.   pkbhs := PKBDLLHOOKSTRUCT(Pointer(lParam));
22.   if nCode = HC_ACTION then
23.   begin
24.     if (pkbhs^.vkCode = VK_LSHIFT) then
25.     begin
26.       if (pkbhs^.flags and LLKHF_UP) = LLKHF_UP then
27.         Form1.label1.Caption := 'Left shift up'
28.       else
29.         Form1.label1.Caption := 'Left shift down';
30.     end;
31.  
32.     if (pkbhs^.vkCode = VK_RSHIFT) then
33.     begin
34.       if (pkbhs^.flags and LLKHF_UP) = LLKHF_UP then
35.         Form1.label2.Caption := 'Right shift up'
36.       else
37.         Form1.label2.Caption := 'Right shift down';
38.     end;
39.   end;
40.   Result := CallNextHookEx(llKeyboardHook, nCode, wParam, lParam);
41. end;
42.  
43. function TForm1.Start: boolean;
44. const
45.   WH_KEYBOARD_LL = 13;
46. begin
47.   if llKeyboardHook = 0 then
48.     llKeyboardHook := SetWindowsHookEx(WH_KEYBOARD_LL, @LowLevelKeyboardHook, HInstance, 0);
49.   Result := (llKeyboardHook <> 0)
50. end;
51.  
52. function TForm1.Stop: Boolean;
53. begin
54.   Result := False;
55.   if (llKeyboardHook <> 0) and UnhookWindowsHookEx(llKeyboardHook) then
56.   begin
57.     llKeyboardHook := 0;
58.     Result := True;
59.   end;
60. end;
61.  
62. function TForm1.IsStarted: Boolean;
63. begin
64.   Result := (llKeyboardHook <> 0)
65. end;
66.  
67. procedure TForm1.FormDestroy(Sender: TObject);
68. begin
69.   if IsStarted then
70.     Stop;
71. end;
72.  
73. procedure TForm1.FormCreate(Sender: TObject);
74. begin
75.   if not Start then
76.     MessageDlg('Cannot start the hook!', mtError, [mbOk], 0)
77. end;

[Pascal]

Weird... You are on Windows? What Lazarus version do you have?
(O, I already see, latest trunk)

What do you get with the following?
A TTimer and TMemo on your form and this as TimerEvent:

Code: Pascal  [Select][+][-]

1. procedure TForm1.Timer1Timer(Sender: TObject);
2. begin
3.   Memo1.Lines.Add(IntToStr(GetKeyState(VK_SHIFT) and $8000));
4. end;

When holding shift I get 32768 and releasing it I get 0 in the Memo1.

Code: Pascal  [Select][+][-]

1. Memo1
2. 0
3. 0
4. 32768
5. 32768
6. 32768
7. 0
8. 0
9. 0
10. 32768
11. 0
12. 0
13. 0
14.  

[rvk]

So... GetKeyState(VK_SHIFT) and GetKeyShiftState just work fine for you.

I'd love to see your ORIGINAL code where you state it doesn't work in FormCreate. I think you might have made an error there.

[Fungus]

32768 = $8000 = 1000000000000000.
32768 and $8000 = 32768.

It works as intended. GetKeyState(...) and $8000 must be non-zero if the key is pressed. If it does not work during startup it may be related to a message loop not initialized yet.

[Pascal]

@Pascal
Try to start a new project, drop a TLabel and put this code below to see if it work or not.

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, StdCtrls, LCLIntf, LCLType;
9.  
10. type
11.  
12.   { TForm1 }
13.  
14.   TForm1 = class(TForm)
15.     Label1: TLabel;
16.     procedure FormActivate(Sender: TObject);
17.   private
18.     { private declarations }
19.   public
20.     { public declarations }
21.   end;
22.  
23. var
24.   Form1: TForm1;
25.  
26. implementation
27.  
28. {$R *.lfm}
29.  
30. { TForm1 }
31.  
32. procedure TForm1.FormActivate(Sender: TObject);
33. begin
34.   if (GetKeyState(VK_SHIFT) And $80) <> 0 then
35.     Label1.Caption := 'It works!';
36. end;
37.  
38. end.

Works with $8000 in OnCreate, OnShow, OnActivate 
But not in my complex prog.

[rvk]

Then you have something in your complex program that interferes.
Without being able to debug this (or code to look at), we can't tell what the problem exactly is.

[Pascal]

So... GetKeyState(VK_SHIFT) and GetKeyShiftState just work fine for you.

I'd love to see your ORIGINAL code where you state it doesn't work in FormCreate. I think you might have made an error there.

Here you are:

Code: Pascal  [Select][+][-]

1. procedure TprimeGlobalData.CheckIgnoreFileList;
2. begin
3.   if (GetKeyState(VK_SHIFT) and $8000 <> 0) then begin
4.     DebugLn('### SHIFT pressed');
5.     fIgnoreFileList := true;
6.   end;
7. end;

CheckIgnoreFileList is called several times during startup and initialization of my prog.
2 times in OnCreate
2 times in OnShow

[Fungus]

In you "complex prog" please make sure that you are using the instance of GetKeyState from LCL by using "LCLIntf.GetKeyState(LCLType.VK_SHIFT) and $8000 <> 0"

OT: Wondering what causes the difference in return values of GetKeyState between Linux / Windows. Anyone knows?

[Pascal]

OT: Wondering what causes the difference in return values of GetKeyState between Linux / Windows. Anyone knows?

It's a widgetset funktion which is used in GetKeyShiftState the correct way.

[rvk]

Code: Pascal  [Select][+][-]

1.   if (GetKeyState(VK_SHIFT) and $8000 <> 0) then begin

Wait... you do see you are missing () in the right spot !!

It should be

Code: Pascal  [Select][+][-]

1.   if (GetKeyState(VK_SHIFT) and $8000) <> 0 then begin

Edit: Never mind. Doesn't make a difference. And has priority.

[Pascal]

In you "complex prog" please make sure that you are using the instance of GetKeyState from LCL by using "LCLIntf.GetKeyState(LCLType.VK_SHIFT) and $8000 <> 0"

I did. But no difference. 

[Pascal]

Code: Pascal  [Select][+][-]

1.   if (GetKeyState(VK_SHIFT) and $8000 <> 0) then begin

Wait... you do see you are missing () in the right spot !!

It should be

Code: Pascal  [Select][+][-]

1.   if (GetKeyState(VK_SHIFT) and $8000) <> 0 then begin

Also, no difference.

Code: Pascal  [Select][+][-]

1. procedure TprimeGlobalData.CheckIgnoreFileList;
2. begin
3.   DebugLn('### GetKeyState(VK_SHIFT)=%d', [LCLIntf.GetKeyState(VK_SHIFT)]);
4.   if (LCLIntf.GetKeyState(VK_SHIFT) and $8000) <> 0 then begin
5.     DebugLn('### SHIFT pressed');
6.     fIgnoreFileList := true;
7.   end;
8. end;
9.  

This outputs 0 or 1

[rvk]

Do you have a FormKeyDown or any other key related event in your form/program?

(where you might mess up the state)

[Pascal]

This is driving me nuts

My program uses Anchordocking and a splash screen.
CheckIgnoreFileList is called during OnCreate and OnShow of the main dock site (while the splash screen is still visible).

Thanks everyone for time you have spend helping me. I do not have the leisure to investigate this any further.
Maybe on an other day 

[Fungus]

If one program correctly outputs 32768 or 0 and another wrongly outputs 1 or 0 for the same function call, then there must be some sort of issue in the second program.