EnumWindows not working

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asmMe

Joined: 14 Jun 2011
Posts: 18

asmMe

hello

I am using EnumWindows to try and get the titles of all top level windows like this:

Code:

        invoke  EnumWindows, EnumWindowsProc, 0
.
.
.
.
proc EnumWindowsProc, hWnd, lParam
        invoke  GetWindowText, [hWnd], windowTitle, 128
        or      eax, eax
        jnz     @f
        stdcall showLastError
    @@:
        mov     eax, TRUE
        ret
endp

windowTitle    db 128 dup ?

the EnumWindows goes through this proc, [hWnd] is always non-zero, eax is always 0 and GetLastError says the operation completed successfully¿

What am I missing?

thx for any help

Question

14 Jun 2011, 22:09

bitshifter

Joined: 04 Dec 2007
Posts: 786
Location: Massachusetts, USA

bitshifter

Q: Are you using unicode?

Non-Unicode:

Code:


format PE GUI 4.0
entry start

include 'win32a.inc'

section '.text' code readable executable

  start:

        invoke  EnumWindows,EnumWindowsProc,0
        invoke  MessageBox,HWND_DESKTOP,_sb,_ct,MB_ICONINFORMATION or MB_OK
        invoke  ExitProcess,0

proc EnumWindowsProc, hWnd, lParam
        invoke  GetWindowText,[hWnd],_wt,128
        test    eax,eax
        jz     @f
        invoke  lstrcat,_sb,_wt
        invoke  lstrcat,_sb,_nl
    @@: mov     eax,TRUE
        ret 
endp

section '.data' data readable writeable

  _ct db "xxx",0
  _nl db 13,10,0
  _sb rb 4096 ;careful!!!
  _wt rb 128

section '.idata' import data readable writeable

  library kernel32,'KERNEL32.DLL',\
          user32,'USER32.DLL'

  include 'api\kernel32.inc'
  include 'api\user32.inc'

14 Jun 2011, 22:57

asmMe

Joined: 14 Jun 2011
Posts: 18

asmMe

thx for the reply.
don't know if I'm using unicode or not? Embarassed

Anyway, it appears I misunderstood exactly what EnumWindows returns.

Quote:

The EnumWindows function enumerates all top-level windows on the screen by passing the handle of each window, in turn, to an application-defined callback function.

I assumed this meant that if I had 8 items on the taskbar, it would return 8 handles. I wrote a little extra code to write all the handles and window titles to a file. With 8 apps on taskbar, I got 99 handles ¿¿¿
A lot of them had no titles (this is why I thought I was doing something wrong). I also got these (amongst others)

Quote:

00010058 Start
0004008C Start Menu
00010396 Graphics, Windowing and Events (GWES)
00020038 CiceroUIWndFrame
00530584 D3D9Window
001C0750 D3D9Window
00040424 D3D9Window
001702AA D3D9Window
002E051A D3D9Window

strange but, at least the real open windows were there with titles so I can continue with what I was doing Very Happy

thx again

14 Jun 2011, 23:56

bitshifter

Joined: 04 Dec 2007
Posts: 786
Location: Massachusetts, USA

bitshifter

Unicode uses multibyte characters for languages with many chars.
In english we use ASCII characters, in other countries, sometimes not.
To make a program unicode compatible we can include "win32w.inc"
and use TCHAR data types instead of regular bytes with db
See FASM example EXAMPLES/TEMPLATE/TEMPLATE.ASM for
a basic Windows app which is unicode compatible.
Have Fun Smile

15 Jun 2011, 00:17

AsmGuru62

Joined: 28 Jan 2004
Posts: 1426
Location: Toronto, Canada

AsmGuru62

You got all tasks and services enumerated, probably. When you get an HWND into your callback - check if it has an extended style of WS_EX_APPWINDOW - that will be the taskbar item most likely.

15 Jun 2011, 00:38

asmMe

Joined: 14 Jun 2011
Posts: 18

asmMe

thx bitshifter, no, I'm not using unicode then Smile

AsmGuru62: Thought your idea sounded promising but, unfortunately, it doesn't hold true. Very few apps set the WS_EX_APPWINDOW style, just search the boards for createwindowex to see how many have the ext style as 0.
It appears the only way is to cycle through the titles to find what I'm looking for.

thx again

15 Jun 2011, 08:38

cod3b453

Joined: 25 Aug 2004
Posts: 618

cod3b453

If oyu looking for all "normal" windows, I think the WS_VISIBLE style flag should be ok for this (and possibly WS_MINIMISED ?).

If you're looking for a specific window, it might be better to use FindWindow(Ex).

15 Jun 2011, 17:11

asmMe

Joined: 14 Jun 2011
Posts: 18

asmMe

thx cod, I'll check out those flags. FindWindow would be no use for my purpose as I would only know part of the windows name (title).

Just as a note for anyone using the EnumWindows function, make sure your EnumWindowsProc returns with edi unchanged or thou shalt crash 'n' burn.

update
preserve all registers except eax or EnumWindows skips some of the open windows.

15 Jun 2011, 19:37

bitshifter

Joined: 04 Dec 2007
Posts: 786
Location: Massachusetts, USA

bitshifter

You only need to preserve ESI, EDI, EBX like any other Win32 proc should.

15 Jun 2011, 22:08

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid

Quote:

You only need to preserve ESI, EDI, EBX like any other Win32 proc should.

Also EBP (and ESP of course)

15 Jun 2011, 22:23

asmMe

Joined: 14 Jun 2011
Posts: 18

asmMe

Sounds fair enough bitshifter Very Happy

I assumed that EnumWindowsProc, being my own procedure could do as the info on it says

Quote:

Remarks

The callback function can perform any desired task.

and that windows would look after itself.
Apparently not so for a callback proc Sad

Oh well, I suppose a couple of extra lines of code to look after Bill will do no harm Laughing

15 Jun 2011, 22:26

AsmGuru62

Joined: 28 Jan 2004
Posts: 1426
Location: Toronto, Canada

AsmGuru62

Any callback function must preserve ESI,EDI,EBX,EBP and DF must be 0. If your code uses STD - DF must be restored with CLD. Callback is any procedure address passed to Windows to be called back (like a structure member or as any function parameter).

16 Jun 2011, 10:57

asmMe

Joined: 14 Jun 2011
Posts: 18

asmMe

thx guru, vid & bit for the clarification Very Happy

So if I use this template for all my procs I shouldn't go far wrong Smile

Code:

proc whateverProc
            locals

            endl

        push    ebx edi esi
        .
        .
        ; whatever code
        .
        .
    .finished:
        pop     esi edi ebx
        cld
        ret
endp

16 Jun 2011, 18:18

bitshifter

Joined: 04 Dec 2007
Posts: 786
Location: Massachusetts, USA

bitshifter

Keep the template in your head and only use the parts
that are needed for each implementation thereof.
No sense in useless instructions laying around, right.

16 Jun 2011, 18:50

asmMe

Joined: 14 Jun 2011
Posts: 18

asmMe

thx bit

16 Jun 2011, 19:58

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