[perl-win32-gui-users] Having trouble Packing a string for SendMessage

[Mike C. <mc...@ro...>]

Hi all,

Trying to use Win32::GUI  Perl module to programmatically control a window in Windows from Perl. The window is a program called WinLirc which is used to control and iR Blaster for controlling equipment.

There’s already a command line program that interfaces with this window called transmit.exe, but I am trying to write a Perl version to make a web based interface.  So far, I can get the handle on the window and even issue a CloseWindow, so I know I’m hooked into it, but I am having trouble with sending the commands over WM_COPYDATA. Not sure if I’m building and packing my command line the same way transmitdoes it. Can anyone understand what they are doing by looking at the VC++ transmit.cpp code below?

Basically, you invoke transmit to send commands to the WINLirc window like this:

C:/transmit.exe Cable CHNUP 1

So, I assume in transmit.cpp, the lpCmdLine value receives the value “Cable CHNUP 1” which is what I hardcoded into my corresponding $command variable in Perl, for testing purposes.

Here’s the VC++ code from the transmit.cpp:

int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
                LRESULT copyDataResult;
                HWND pOtherWnd = FindWindow(NULL, "WinLirc");
                if (pOtherWnd)
                {
                                COPYDATASTRUCT cpd;
                                cpd.dwData = 0;
                                cpd.cbData = strlen(lpCmdLine);
                                cpd.lpData = (void*)lpCmdLine;
                                copyDataResult = SendMessage(pOtherWnd,WM_COPYDATA,(WPARAM)hInstance,(LPARAM)&cpd);
        // copyDataResult has value returned by other app
                }
                else
                {
                                return 1;
                }
                return 0;
}


Anyhow here’s my best attempt at translation into Perl:

#!/usr/bin/perl
# WinLiRC Perl interface

chdir ("cgi-bin");

use Win32::GUI;

$windowtitle='WinLIRC';
$command='Cable CHNUP 1';

$handle=Win32::GUI::FindWindow('', $windowtitle);

if ($handle eq "") {print "WinLIRC window not open."; exit(0);}

$copy_data_struct=pack('L2P',0,length($command),$command);

$result=Win32::GUI::SendMessage($handle,WM_COPYDATA,0,$copy_data_struct);

print "$result"

I keep getting a result code of "0" which tells me the command is failing. More than likely it's encoded wrong...

Any help would be greatly appreciated!

Thanks,

Mike