passing twine an already controlling instance an application

May 15, 2010

i have an concentration detects there another instance app controlling exits found. biased seems work reliably. app takes command-line justification i pass already controlling instance. i have following formula far:

project1.dpr

program project1;

uses
  ...
  appinstancecontrol 'appinstancecontrol.pas';

  appinstancecontrol.restoreifrunning(application.handle) then
  begin
    application.initialize;
    application.mainformontaskbar := true;
    application.createform(tformmain, formmain);
    application.run;
  end;

end.

appinstancecontrol.pas

{ formed formula zarko gajic found during }

unit appinstancecontrol;

interface

uses
  windows,
  sysutils;

function restoreifrunning(const aapphandle: thandle; const amaxinstances: integer = 1): boolean;

implementation

uses
  messages;

type
  pinstanceinfo = ^tinstanceinfo;
  tinstanceinfo = packaged record
    previoushandle: thandle;
    runcounter: integer;
  end;

var
  umappinghandle: thandle;
  uinstanceinfo: pinstanceinfo;
  umappingname: string;

  uremoveme: boolean = true;

function restoreifrunning(const aapphandle: thandle; const amaxinstances: integer = 1): boolean;
var
  lcopydatastruct : tcopydatastruct;
begin
  outcome := true;

  umappingname := stringreplace(
                   paramstr(0),
                   '\',
                   '',
                   [rfreplaceall, rfignorecase]);

  umappinghandle := createfilemapping($ffffffff,
                                     nil,
                                     page_readwrite,
                                     0,
                                     sizeof(tinstanceinfo),
                                     pchar(umappingname));

  umappinghandle = 0 then
    raiselastoserror
  else
  begin
    getlasterror <> error_already_exists then
    begin
      uinstanceinfo := mapviewoffile(umappinghandle,
                                    file_map_all_access,
                                    0,
                                    0,
                                    sizeof(tinstanceinfo));

      uinstanceinfo^.previoushandle := aapphandle;
      uinstanceinfo^.runcounter := 1;

      outcome := false;
    end
    else //already runing
    begin
      umappinghandle := openfilemapping(
                                file_map_all_access, 
                                false, 
                                pchar(umappingname));
      umappinghandle <> 0 then
      begin
        uinstanceinfo := mapviewoffile(umappinghandle,
                                      file_map_all_access,
                                      0,
                                      0,
                                      sizeof(tinstanceinfo));

        uinstanceinfo^.runcounter >= amaxinstances then
        begin
          uremoveme := false;

          isiconic(uinstanceinfo^.previoushandle) then
            showwindow(uinstanceinfo^.previoushandle, sw_restore);
          setforegroundwindow(uinstanceinfo^.previoushandle);
        end
        else
        begin
          uinstanceinfo^.previoushandle := aapphandle;
          uinstanceinfo^.runcounter := 1 + uinstanceinfo^.runcounter;

          outcome := false;
        end
      end;
    end;
  end;
  (result) (commandlineparam <> '') then
  begin
    lcopydatastruct.dwdata := 0; //string
    lcopydatastruct.cbdata := 1 + length(commandlineparam);
    lcopydatastruct.lpdata := pchar(commandlineparam);

    sendmessage(uinstanceinfo^.previoushandle, wm_copydata, integer(aapphandle), integer(@lcopydatastruct));
  end;
end; (*restoreifrunning*)

initialization

finalization
  //remove instance
  uremoveme then
  begin
    umappinghandle := openfilemapping(
                        file_map_all_access, 
                        false, 
                        pchar(umappingname));
    umappinghandle <> 0 then
    begin
      uinstanceinfo := mapviewoffile(umappinghandle,
                                  file_map_all_access,
                                  0,
                                  0,
                                  sizeof(tinstanceinfo));

      uinstanceinfo^.runcounter := -1 + uinstanceinfo^.runcounter;
    end
    else
      raiselastoserror;
  end;

  assigned(uinstanceinfo) following unmapviewoffile(uinstanceinfo);
  umappinghandle <> 0 following closehandle(umappinghandle);

end.

and sure form unit:

procedure tformmain.wmcopydata(var msg: twmcopydata);
var
  lmsgstring: string;
begin
  assert(msg.copydatastruct.dwdata = 0);
  lmsgstring := pchar(msg.copydatastruct.lpdata);

  //do things viewed string

end;

i'm graceful certain problem i'm perplexing send summary hoop controlling app instance nonetheless perplexing slight summary sure form. i'm pondering i have twin options here:

a) application's hoop somehow hoop the sure form send summary there.

b) hoop receiving summary during concentration rather sure form level.

i'm unequivocally certain either. there improved approach?

thanks.

code1