[solved] How do I enable the Help button in file dialogs?

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fasm14

Joined: 23 Jan 2021
Posts: 14
Location: Russia

fasm14 21 Jun 2021, 15:51

Hello! I was trying to enable the help button in an OpenFile dialog;

Code:

...
mov [_OpenFile.Flags], OFN_FILEMUSTEXIST+OFN_SHOWHELP
...
invoke GetOpenFileNameW, _OpenFile

According to the documentation, I needed to register the help message, so I did this:

Code:

themessage du 'HELPMSGSTRING', 0
...
invoke RegisterWindowMessageW, themessage
mov [msgid], eax
...
proc DProc hwnddlg, msg, wparam, lparam 
mov eax, [msgid]
cmp [msg], eax
je ExitProgram

but nothing happened when I clicked the help button! I tried this with RegisterWindowMessageA and an ASCII string but nothing changed... Can someone please share an example of how to use this button?

21 Jun 2021, 15:51

bitRAKE

Joined: 21 Jul 2003
Posts: 3623
Location: vpcmipstrm

bitRAKE 22 Jun 2021, 04:29

Maybe it's an explorer style and the hook proc is getting CDN_HELP notifications?

These things have changed so much through windows versions. If I created an example it's going to be the new notification mechanism.

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22 Jun 2021, 04:29

fasm14

Joined: 23 Jan 2021
Posts: 14
Location: Russia

fasm14 22 Jun 2021, 08:44

The hook flag wasn't set before, but when I added it and a pointer to a procedure, it started receiving WM_NOTIFY messages; according to this, lparam has a pointer to an OFNOTIFY structure, with the notification message being the third dword in it, but when I do this

Code:

mov ebx, [lparam]
mov eax, [ebx]

the app crashes (access violation, I assume?); running it with admin permissions doesn't change anything... Am I misunderstanding something?

22 Jun 2021, 08:44

bitRAKE

Joined: 21 Jul 2003
Posts: 3623
Location: vpcmipstrm

bitRAKE 22 Jun 2021, 18:40

lParam is a pointer - NOT has a pointer.

(Do you use a debugger? Just throwing an INT3 in there and running would allow you to see what is happening.)

The wording is rather brief in the English version - wonder if the Russian is any better?

https://docs.microsoft.com/ru-ru/windows/win32/dlgbox/cdn-help

Funny, enough google translation of the Russian is more exact than the English, lol!

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22 Jun 2021, 18:40

sinsi

Joined: 10 Aug 2007
Posts: 774
Location: Adelaide

sinsi 22 Jun 2021, 20:53

HELPMSGSTRING is defined in the C++ headers as

Code:

#define HELPMSGSTRING TEXT("commdlg_help")

Shouldn't your code use this?

Code:

themessage du "commdlg_help",0

22 Jun 2021, 20:53

fasm14

Joined: 23 Jan 2021
Posts: 14
Location: Russia

fasm14 23 Jun 2021, 13:31

bitRAKE wrote:

lParam is a pointer - NOT has a pointer.

Thanks, I managed to get the -605 (CDN_HELP) code from lparam in the hook procedure with

Code:

mov ebx, [lparam]
mov ebx, [ebx+8]

Replacing "HELPMSGSTRING" with

sinsi wrote:

Code:

themessage du "commdlg_help",0

also works, making it send messages to the main dialog procedure! Thanks a lot!

23 Jun 2021, 13:31

fasm14

Joined: 23 Jan 2021
Posts: 14
Location: Russia

fasm14 24 Jun 2021, 08:43

I now realized that this

Code:

mov ebx, [lparam]
mov eax, [ebx]

wasn't the problem, and the reason this

Code:

mov ebx, [lparam]
mov ebx, [ebx+8]

worked is because I added

Code:

cmp [msg], WM_NOTIFY
je continue1
ret
continue1:

right before it in the hook procedure; it was crashing because other WM messages set lparam to 0 and it tried to read memory there (I think)

24 Jun 2021, 08:43

bitRAKE

Joined: 21 Jul 2003
Posts: 3623
Location: vpcmipstrm

bitRAKE 25 Jun 2021, 01:07

My comment was in error. Too much time in 64-bit. Embarassed

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25 Jun 2021, 01:07

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