One instance on all OS & with Systray app - question for Madshi et al

   One instance :
   http://www.swissdelphicenter.ch/torry/showcode.php?id=42

   Systray :
   http://www.latiumsoftware.com/en/delphi/00035.php

http://delphi.about.com/library/weekly/aa110203a.htm

Controlling the number of application instances [page 1/4]
Controlling the number of application instances. In this article you'll learn how to 'run-once enable' a Delphi application that can check for its previous (running) instance. Along the process, several techniques of implementing such a check will be

http://delphi.about.com/library/weekly/aa100703a.htm


Controlling the number of application instances [page 2/4]
Controlling the number of application instances. In this article you'll learn how to 'run-once enable' a Delphi application that can check for its previous (running) instance. Along the process, several techniques of implementing such a check will be

http://delphi.about.com/library/weekly/aa100703b.htm

Controlling the number of application instances [page 3/4]
Controlling the number of application instances. In this article you'll learn how to 'run-once enable' a Delphi application that can check for its previous (running) instance. Along the process, several techniques of implementing such a check will be

http://delphi.about.com/library/weekly/aa100703c.htm


Hope this helps!

Shane

hello Pandora, from all I've read about it, the  CreateMutex method is the most sure fire (reliable, and tested) method to use.. . however the other methods also work. . . Here is a version that I use


program EETest;

uses
  Windows, Forms,    // Put Windows in your Uses clause
  EETest1 in 'EETest1.pas' {Form1};

{$R *.RES}

var
MutexHandle: Cardinal;

function MakeMutex(UniqueName: String) : THandle;
var
SecAtr: TSecurityAttributes;
SecDes: TSecurityDescriptor;

begin
secAtr.nLength := sizeOf(SecAtr);
secAtr.lpSecurityDescriptor := @SecDes;
secAtr.bInheritHandle := False;
InitializeSecurityDescriptor(@SecDes, SECURITY_DESCRIPTOR_REVISION);
SetSecurityDescriptorDacl(@secDes, True, nil, False);
Result := CreateMutex(@secAtr, False, PChar(UniqueName));
if getlasterror = ERROR_ALREADY_EXISTS then
  begin
  CloseHandle(Result);
  Result := 0;
  end;
end;

begin
  MutexHandle := MakeMutex('G6H8jfr4d2');
  if MutexHandle = 0 then Exit;

  Application.Initialize;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
  CloseHandle(MutexHandle);
end.

If you read the articles I posted above, you can choose the method of your choice.

The CreateMutex function requires the name of the mutex object (unique). What this means, is that for every application you want to be executed only once, you'll need to assign a different mutex name - and this could lead you into problems."

http://delphi.about.com/library/weekly/aa100703b.htm


Shane

The mutex solution has never let me down yet. But please don't give me the points for this one sentence. The others have earned it more...   :-)

>(but does this work with Systray?)

Yes. I can't see any reason for not using FindWindow and an unique WindowClassName (unless your app is windowless, of course). Both methods (mutex and ClassName) require an unique identifier but mutex solution requires/ocupies additional resourses.

Regards, Geo

Hi all, thanks ever so much for your help on this. I would of course like to give you all some points ;-) but actually I'm gonna give them to rlibby as he answered the question first by allaying my fears and doing a bit of hand-holding on the mutex front - and thats what I asked for - gotta be the easiest 350 points you've ever got rlibby, but still worth it for me so thanks! Shaneholmes & Slick thanks for your code/component (that's a great article v interesting - I've posted 2 questions for each of you for 100 points as your contributions were really helpful too).
Shaneholmes: https://www.experts-exchange.com/questions/20967560/Points-for-Shaneholmes.html
Slick: https://www.experts-exchange.com/questions/20967562/Points-for-Slick812.html
And of course thanks to Geo & Madshi for customary wisdom - no points for you but a nice smile instead! :-)
Hope you think is fair! Thx all
P