From: timsuth@... (Tim Sutherland)
Date: 2004-12-01T06:17:47+09:00
Subject: Re: Windows SendMessage

In article <1101833542.8224.33.camel@comp.rapiddsl.net>, Guillaume Marcais
wrote:
>Has anyone ever tried to send messages between applications using the
>Windows messaging system (SendMessage call).

Yes, I have done this. http://www.windows-spy.com/ is a useful tool for
seeing what messages are passed under the covers when the user does the
"usual thing".

>Given my little knowledge
>of Windows, I started with Ruby and Win32API (hopefully it is achievable
>that way).

DL is nicer. (See below!)

>I am trying to discuss with the pageant program from PuTTy to get the
>keys. I recompiled pageant with debugging enable so I can see the
>request coming in. It works with PuTTy. But with my Ruby app mimicking
>what PuTTy does to get the keys, it seems that pageant doesn't even get
>the message.
>
>The code is given in the attachement.The stuff about the file mapping
>can be ignored. The SendMessage call returns 0 and pageant doesn't
>display any debugging information, as if no message whatsoever was ever
>received.
>
>Is there any initialization to be done for Windows to agree to dispatch
>my message? 

No initialisation is needed that is not already done by Ruby.

[...]
>require 'Win32API'
[...]
>      cds = [AGENT_COPYDATA_ID, mapname.size, mapname].pack("NNp")

'N' means network byte order. Use 'L' for native byte order. Since you are
using Windows, you are probably using x86 (little-endian) while network byte
order is big-endian.

If you use the 'dl' library you don't need to worry about this sort of thing.

e.g. can just do (untested)


  require 'dl/import'
  require 'dl/struct'

  module Win32
    extend DL::Importable

    dlload 'user32'
    
    CopyData = struct [
      'ULONG *dwData',
      'DWORD cbData',
      'PVOID lpData'
    ]

    WM_COPYDATA = 1234 # whatever it is

    extern 'BOOL SendMessage(HWND, UINT, WPARAM, LPARAM)'
  end

  cds = CopyData.malloc
  cds.dwData = Win32::AGENT_COPYDATA_ID
  cds.cbData = mapname.size
  cds.lpData = mapname

  Win32::sendMessage(@win, Win32::WM_COPYDATA, nil, cds.to_i)

  puts("Now isn't that easy :-)")