How to use RegisterHotKey?
lazarus / 34-Windows

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Marion · 2012-04-23 20:42

Can someone explain or provide an example of using RegisterHotKey?
I just need to detect if the user hits F9 and I will unhide my window.

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Marion · 2012-04-24 10:33

I am afraid this is going to be the hardest requirement for Lazarus to
fulfill. I have been looking through this forum and it seems this is a
challenge. If it makes it easier, it only has to work on Windows.
Please, this is the last requirement that Lazarus has to meet.

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BigChimp · 2012-04-24 10:46

Marion,

Assuming there's no documentation in the wiki either: you can also ask
on the Lazarus mailing list... perhaps you'll have more luck with a
quick answer there..

Good luck,
BigChimp

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avra · 2012-04-24 11:26

In my Lazarus CodeTyphon installation I have RegisterHotKey API call
defined in this converted JEDI file:
c:\codetyphon\fpcsrc\packages\winunits-jedi\src\jwawinuser.pas
and it looks something like this:
Code: [Select]...

function RegisterHotKey(hWnd: HWND; id: Integer; fsModifiers, vk:
UINT): BOOL; stdcall;
{$EXTERNALSYM RegisterHotKey}
function UnregisterHotKey(hWnd: HWND; id: Integer): BOOL; stdcall;
{$EXTERNALSYM UnregisterHotKey}

...

var
  _RegisterHotKey: Pointer;

function RegisterHotKey;
begin
  GetProcedureAddress(_RegisterHotKey, user32, 'RegisterHotKey');
  asm
        MOV     ESP, EBP
        POP     EBP
        JMP     [_RegisterHotKey]
  end;
end;

var
  _UnregisterHotKey: Pointer;

function UnregisterHotKey;
begin
  GetProcedureAddress(_UnregisterHotKey, user32, 'UnregisterHotKey');
  asm
        MOV     ESP, EBP
        POP     EBP
        JMP     [_UnregisterHotKey]
  end;
end;

...

function RegisterHotKey; external user32 name 'RegisterHotKey';
function UnregisterHotKey; external user32 name 'UnregisterHotKey';

I guess it shouldn't be hard to use that API call like shown here:
http://www.delphigroups.info/2/77/488140.html

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ludob · 2012-04-24 11:47

The difficulty is that, contrary to Delphi, Lazarus doesn't allow to
easily handle no user messages such as WM_HOTKEY. The following code
does what you want (system wide F9 restores app):

Code: [Select]uses ...,windows;

var
  PrevWndProc: WNDPROC;
const
  MY_ID=1;

function WndCallback(Ahwnd: HWND; uMsg: UINT; wParam: WParam; lParam:
LParam):LRESULT; stdcall;
begin
  if (uMsg=WM_HOTKEY) and (WParam=MY_ID) then
    begin
      Application.Restore;
    end;
  result:=CallWindowProc(PrevWndProc,Ahwnd, uMsg, WParam, LParam);
end;


procedure TForm1.FormCreate(Sender: TObject);
begin
  PrevWndProc:=Windows.WNDPROC(SetWindowLong(Self.Handle,GWL_WNDPROC,P
trInt(@WndCallback)));
  RegisterHotKey(Self.Handle,MY_ID,0,vk_F9);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  UnRegisterHotkey(Self.Handle,MY_ID);
end;

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Marion · 2012-04-24 12:40

I also found a working example here:

http://www.lazarus.freepascal.org/index.php/topic,4964.msg23924.html#m
sg23924

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Marion · 2012-04-24 12:42

This example does look more straight forward. Thank you.

Quote from: ludob on April 24, 2012, 01:47:33 pmThe difficulty is
that, contrary to Delphi, Lazarus doesn't allow to easily handle no
user messages such as WM_HOTKEY. The following code does what you want
(system wide F9 restores app):

Code: [Select]uses ...,windows;

var
  PrevWndProc: WNDPROC;
const
  MY_ID=1;

function WndCallback(Ahwnd: HWND; uMsg: UINT; wParam: WParam; lParam:
LParam):LRESULT; stdcall;
begin
  if (uMsg=WM_HOTKEY) and (WParam=MY_ID) then
    begin
      Application.Restore;
    end;
  result:=CallWindowProc(PrevWndProc,Ahwnd, uMsg, WParam, LParam);
end;


procedure TForm1.FormCreate(Sender: TObject);
begin
  PrevWndProc:=Windows.WNDPROC(SetWindowLong(Self.Handle,GWL_WNDPROC,P
trInt(@WndCallback)));
  RegisterHotKey(Self.Handle,MY_ID,0,vk_F9);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  UnRegisterHotkey(Self.Handle,MY_ID);
end;