Web_browser - WBDLL.DLL 1.1.5.6 - Fatal Error

[Fab]

Hi everyone, including you!

I have found a strange error that keeps happening each time I press the F1 key while any program with the web browser component is running, and in keyboard focus. (I click on the browser window then press F1)
Its happened on a few different computers I've tried, XP home and XP Prof

I found that the cause was the system calling IDocHostShowUI@ShowMessage handler with NULL lpstrCaption and lpstrText pointers.
I fixed the code by not showing a messagebox for empty strings, and not modifying the plResult if it happens (I believe thats what causes the error)

I dont see how the code is wrong at all, I've check the specs for this function, and the code seems to comply perfectly
I also dont know why its calling ShowMessage, when you think F1 would call showhelp atleast.

Code Select Expand


IDocHostShowUI@ShowMessage proc pif:DWORD,hwnd:DWORD,lpstrText:DWORD,lpstrCaption:DWORD,dwType:DWORD,lpstrHelpFile:DWORD,dwHelpContext:DWORD,plResult:DWORD

; This Proc is called by MSHTML when it needs to display a message box.
.IF plResult
invoke MessageBox,hwnd,lpstrText,addr szDisplayName,dwType
mov edx,plResult
mov [edx],eax <- seems to be why it crashes when the title and caption are blank
.ELSE
invoke MessageBox,hwnd,lpstrText,addr szDisplayName,dwType
.ENDIF
;S_OK Host displayed its UI. MSHTML will not display its message box.
;S_FALSE Host did not display its UI. MSHTML will display its message box.
return S_OK

IDocHostShowUI@ShowMessage endp



Hope someone can explain the strange crashes, because I cant figure out why

Thanks!
Fab  :eek

[akane]

I've noticed in custom implementation of IDropTarget (see api RegisterDragDrop)
in method DragEnter - the last argument is pdwEffect (pointer to dword)
NOPE! if you hange  dword pointed by this pointer you get crash.
But changing this 'pointer' (only on stack) works ok :green, so as the caller has pushed a dword, called your method and read the dword back from stack :/

Code Select Expand

push ...
push dwEffect
push this_droptarget
call  IDropTarget@DragEnter
mov dwEffect,[esp-8] ;<- something like this, hehe

[KetilO]

Thanks Fab

You can just remove that and the above line.

KetilO