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Index > Windows > [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
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?
Post 21 Jun 2021, 15:51
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bitRAKE



Joined: 21 Jul 2003
Posts: 3307
Location: vpcmipstrm
bitRAKE
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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Post 22 Jun 2021, 04:29
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fasm14



Joined: 23 Jan 2021
Posts: 14
Location: Russia
fasm14
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?
Post 22 Jun 2021, 08:44
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bitRAKE



Joined: 21 Jul 2003
Posts: 3307
Location: vpcmipstrm
bitRAKE
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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Post 22 Jun 2021, 18:40
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sinsi



Joined: 10 Aug 2007
Posts: 738
Location: Adelaide
sinsi
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
    
Post 22 Jun 2021, 20:53
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fasm14



Joined: 23 Jan 2021
Posts: 14
Location: Russia
fasm14
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!
Post 23 Jun 2021, 13:31
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fasm14



Joined: 23 Jan 2021
Posts: 14
Location: Russia
fasm14
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)
Post 24 Jun 2021, 08:43
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bitRAKE



Joined: 21 Jul 2003
Posts: 3307
Location: vpcmipstrm
bitRAKE
My comment was in error. Too much time in 64-bit. Embarassed

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Post 25 Jun 2021, 01:07
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