Title: One instance w/ command line passing
Question: one of many methods to restrict the number of instances of an application, and pass the command line to the already running instance
Answer:
.dpr file
----------
uses
Forms, Windows, Messages, Clipbrd,
{List of forms and what not}
{$R *.RES}
var mHnd : THandle;
{procedure to send command line}
procedure Send;
var hnd : HWND; st : string; cl : TClipboard;
begin
hnd := FindWindow('TMnFrm',nil);
if hnd 0 then begin
if ParamCount = 1 then begin
st := ParamStr(1);
cl := Clipboard;
cl.SetTextBuf(PChar(st));
SendMessage(hnd, WM_USER+UM_PassParam, Length(st), 1);
end;
ShowWindow(hnd,SW_SHOWNORMAL);
end;
end;
begin
Application.Initialize;
Application.Title := 'MyApp';
mHnd := OpenMutex(MUTEX_ALL_ACCESS,false,'mymutt');
if mHnd 0 then begin
CloseHandle(mHnd); //Thanks Andreas
Send;
Exit;
end;
mHnd := CreateMutex(nil,TRUE,'mymutt');
Application.CreateForm(TMnFrm, MnFrm);
Application.Run;
CloseHandle(mHnd);
end.
----------------------------------------------------------------
{.pas file}
unit Main;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
Buttons, StdCtrls, MPlayer, Clipbrd, ExtCtrls, ComCtrls, IniFiles;
const UM_PassParam = 42;
type
TMnFrm = class(TForm)
procedure FormCreate(Sender: TObject);
procedure FormShow(Sender: TObject);
procedure FormDestroy(Sender: TObject);
private
procedure WMUserMsg(var Msg:TMessage); message WM_USER+UM_PassParam;
public
end;
var
MnFrm: TMnFrm;
implementation
{$R *.DFM}
{blah blah blah}
// Here's the part where we read the command line from other instance
procedure TMnFrm.WMUserMsg(var Msg:TMessage);
var cl : TClipBoard; FNam : PChar;
begin
cl := Clipboard;
Getmem(FNam,Msg.WParam+1);
cl.GetTextBuf(FNam,Msg.WParam+1);
ShowMessage:=Fnam;
FreeMem(FNam);
end;
---------------------------------------------
So basically we just check to see if an instance is already running, and if it is, we copy the command line args to the clipboard and send a message to the other instance, then shut ourselves down
I know, there are probably a couple of problems with using the clipboard that I haven't thought of yet, but I haven't yet run into any problems with it, and hey....it's a start.
CJK