WM_COPYDATA problem

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10 total messages Started by anon5 Mon, 03 Sep 2007 01:37

#1353

Author: anon5
Date: Mon, 03 Sep 2007 01:37

93 lines
3775 bytes

Hey guys

I am trying to create a 'once-only' app (only one instance can run). 
When the user tries to run a second instance, it should pass its command 
line to the first instance. I have been following the code at 
http://bcbjournal.org/articles/vol3/9911/Single-instance_applications.htm 
(and also 
http://www.bcbjournal.org/articles/vol3/9911/Using_file_associations.htm) 
but I can't get it to work. I'm using C++Builder 6.

Here is the workings my code (slightly different from Kent's):


//---------------------------------------------------------------------------
// TFORMMAIN.CPP
//---------------------------------------------------------------------------
__fastcall TFormMain::TFormMain(TComponent* Owner)
     : TForm(Owner)
{
     WindowProc = MyWndProc;
}
//---------------------------------------------------------------------------
void __fastcall TFormMain::MyWndProc(Messages::TMessage &Message)

{
     if (Message.Msg == WM_COPYDATA) {
         Caption = "WM_COPYDATA";
     }
     else {
         WndProc(Message);
     }
}
//---------------------------------------------------------------------------


//---------------------------------------------------------------------------
// MUTEXTEST.CPP
//---------------------------------------------------------------------------
WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR cmdLine, int)
{
     try
     {
         CreateMutex(NULL, NULL, "the mutex of doom");

         if (GetLastError())
         {
             Application->Title = "Something Else";
             HWND hWnd = FindWindow("TApplication", "MutexTest");

             if (IsIconic(hWnd)) {
                 ShowWindow(hWnd, SW_SHOWDEFAULT);
             }
             SetForegroundWindow(hWnd);

             if (strlen(cmdLine) != 0)
             {
                 COPYDATASTRUCT cds;
                 cds.cbData = strlen(cmdLine) + 1;
                 cds.lpData = cmdLine;
                 SendMessage(hWnd, WM_COPYDATA, 0, (LPARAM)&cds);
             }
         }
         else
         {
             Application->Initialize();
             Application->Title = "MutexTest";
             Application->CreateForm(__classid(TFormMain), &FormMain);
             Application->Run();
         }
     }
     catch (Exception &exception)
     {
         Application->ShowException(&exception);
     }
     catch (...)
     {
         try
         {
             throw Exception("");
         }
         catch (Exception &exception)
         {
             Application->ShowException(&exception);
         }
     }
     return 0;
}
//---------------------------------------------------------------------------


Now, the once-only aspect of the app works great. But my WM_COPYDATA 
message isn't being picked up at all. If anyone can help at all it would 
be fantastic. Thanks!

Re: WM_COPYDATA problem

#1355

Author: Damon Chandler (TeamB)
Date: Mon, 03 Sep 2007 06:44

30 lines
1927 bytes

Hi,

You're catching the WM_COPYDATA in your TFormMain class, but you're 
sending the message to the window whose handle is returned via the 
following call...

HWND hWnd = FindWindow("TApplication", "MutexTest");

I don't believe the above call is returning the correct handle.  You 
should replace "TApplication" with "TFormMain" and adjust the second 
parameter to the form's caption.

As a side note, there's no need to use the WindowProc property since you 
can override the WndProc() method directly.

Cheers,
--
Damon Chandler (TeamB)
C++Builder Developer's Journal
http://bcbjournal.com
http://bcbjournal.org

anon5 wrote:
> Hey guys
> 
> I am trying to create a 'once-only' app (only one instance can run). 
[snip 8<----]
> Now, the once-only aspect of the app works great. But my WM_COPYDATA 
> message isn't being picked up at all. If anyone can help at all it would 
> be fantastic. Thanks!

Re: WM_COPYDATA problem

#1356

Author: anon5
Date: Mon, 03 Sep 2007 07:32

40 lines
2239 bytes

Lol... I don't believe it...  in a moment of tremendous stupidity I had 
combined code with one tutorial with code from another, making a 
complete pigs ear of it in the process!

We can all lol now.. at my expense.. hehe

Seriously though, thanks a lot!


Damon Chandler (TeamB) wrote:
> Hi,
> 
> You're catching the WM_COPYDATA in your TFormMain class, but you're 
> sending the message to the window whose handle is returned via the 
> following call...
> 
> HWND hWnd = FindWindow("TApplication", "MutexTest");
> 
> I don't believe the above call is returning the correct handle.  You 
> should replace "TApplication" with "TFormMain" and adjust the second 
> parameter to the form's caption.
> 
> As a side note, there's no need to use the WindowProc property since you 
> can override the WndProc() method directly.
> 
> Cheers,
> -- 
> Damon Chandler (TeamB)
> C++Builder Developer's Journal
> http://bcbjournal.com
> http://bcbjournal.org
> 
> anon5 wrote:
>> Hey guys
>>
>> I am trying to create a 'once-only' app (only one instance can run). 
> [snip 8<----]
>> Now, the once-only aspect of the app works great. But my WM_COPYDATA 
>> message isn't being picked up at all. If anyone can help at all it 
>> would be fantastic. Thanks!

Re: WM_COPYDATA problem

#1358

Author: anon5
Date: Mon, 03 Sep 2007 08:46

40 lines
2258 bytes

Ok my app is now working correctly, many thanks.

I now have another problem however. The call to FindWindow() to get the 
form's handle relies on the form's caption being a predefined value. 
What if I want to change the caption at runtime? Is there any way around 
this?



Damon Chandler (TeamB) wrote:
> Hi,
> 
> You're catching the WM_COPYDATA in your TFormMain class, but you're 
> sending the message to the window whose handle is returned via the 
> following call...
> 
> HWND hWnd = FindWindow("TApplication", "MutexTest");
> 
> I don't believe the above call is returning the correct handle.  You 
> should replace "TApplication" with "TFormMain" and adjust the second 
> parameter to the form's caption.
> 
> As a side note, there's no need to use the WindowProc property since you 
> can override the WndProc() method directly.
> 
> Cheers,
> -- 
> Damon Chandler (TeamB)
> C++Builder Developer's Journal
> http://bcbjournal.com
> http://bcbjournal.org
> 
> anon5 wrote:
>> Hey guys
>>
>> I am trying to create a 'once-only' app (only one instance can run). 
> [snip 8<----]
>> Now, the once-only aspect of the app works great. But my WM_COPYDATA 
>> message isn't being picked up at all. If anyone can help at all it 
>> would be fantastic. Thanks!

Re: WM_COPYDATA problem

#1357

Author: JD
Date: Mon, 03 Sep 2007 09:05

12 lines
1119 bytes

anon5 <bogus@mail.com> wrote:
>

Please trim your posts.

> Lol... I don't believe it...  in a moment of tremendous
> stupidity [...]

Join the club! New members are welcome!

~ JD

Re: WM_COPYDATA problem

#1359

Author: anon5
Date: Mon, 03 Sep 2007 09:13

6 lines
1154 bytes

JD wrote:
> anon5 <bogus@mail.com> wrote:
> 
> Please trim your posts.

Ok I will thanks

Re: WM_COPYDATA problem

#1360

Author: JD
Date: Mon, 03 Sep 2007 09:18

21 lines
1517 bytes

anon5 <bogus@mail.com> wrote:
>

Please trim your posts.

> [...] I now have another problem however. The call to
> FindWindow() to get the form's handle relies on the form's
> caption being a predefined value.

I would suggest that you give the MainForm a unique
name instead ... something like instead of TForm1,
TCompanyNameAppName. This will enable you to find the
HWND using it's class name instead of it's Caption.

For more, see my reply in the VCL.using group under
'SingleInst problem' or click here:

    http://tinyurl.com/2b2n35

~ JD

Re: WM_COPYDATA problem

#1361

Author: anon5
Date: Mon, 03 Sep 2007 09:23

7 lines
1328 bytes

JD wrote:
> I would suggest that you give the MainForm a unique
> name instead ... something like instead of TForm1,
> TCompanyNameAppName. This will enable you to find the
> HWND using it's class name instead of it's Caption.

Thankyou!

Re: WM_COPYDATA problem

#1362

Author: JD
Date: Mon, 03 Sep 2007 11:09

14 lines
1287 bytes

anon5 <bogus@mail.com> wrote:
>

LOL!

That was you in the vcl.using group!

I don't usually look at who's asking but I just happened to
notice.

Glad I could help ... in both cases.

~ JD

Re: WM_COPYDATA problem

#1363

Author: anon5
Date: Mon, 03 Sep 2007 13:56

10 lines
1157 bytes

JD wrote:
> anon5 <bogus@mail.com> wrote:
> 
> LOL!
> 
> That was you in the vcl.using group!

Lol

It was indeed :)

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