%HWND_DESKTOP with FF 3.60

[Jean-pierre Leroy]

In one of my biggest FF project that was working well with FF 3.51 the application now GPF with FF3.60.

I found the exact line where the problem is:

Code Select Expand


FORMNAME_SHOW(%HWND_DESKTOP, %FALSE)

works with FF 3.51 but GPF with FF 3.60 in my project.

If I replace %HWND_DESKTOP by HWND_MAIN (the handle of the main FORM) it works in both FF 3.51 and FF 3.60.

I made a simple project to see if I was able to reproduce this issue; but I had no success; with a simple project with 2 or 3 forms it works perfectly with FF 3.51 and FF 3.60; so that should be something else ...

Any ideas ?

Thanks,
Jean-Pierre

[Carl Oligny]

I had the same problem and made this change:

Local hWnd as Dword

hWnd = FORMNAME_SHOW(%HWND_DESKTOP, %FALSE)

GPF's stopped occurring.

[Jean-pierre Leroy]

Hello Carl,

Thank you for your post.

I tried your workaround but it doesn't work for my project.

Regards,
Jean-Pierre

[José Roca]

And why are you using %HWND_DESKTOP? Only the main form can be child of the desktop. The secondary ones must be children of the main form.

[Jean-pierre Leroy]

And why are you using %HWND_DESKTOP? Only the main form can be child of the desktop. The secondary ones must be children of the main form.

For a very simple and practical reason: to be able to switch between forms with Alt+Tab keys !

[Jean-pierre Leroy]

I'm still trying to track down this weird issue.

For the moment I can say that I have the same behavior (GPF) on my both PCs :

    - Win XP Pro 32 bits SP3
    - Win 7 Pro 64 bits SP1

Jean-Pierre

[Paul Squires]

Hi Jean-Pierre, I am running some tests on this now to see if there is anything I can do.

[Paul Squires]

I get random GPF's if the main form is destroyed prior to the secondary windows being closed.

Maybe the following will help:

' load the second form as non-modal as a child of the main form
Form2_Show hWndForm, %FALSE     

Set the WindowStyles for the second form, WS_EX_APPWINDOW

[Jean-pierre Leroy]

Hi Paul,

Thank you for your help on this one.

To be more precise I got the GPF only when I try to open a form with %HWND_DESKTOP handle as the parent windows; this kind of code was working perfectly until FF 3.51.

If I replace %HWND_DESKTOP by HWND_MAIN (the handle of the main FORM in my project) it works in both FF 3.51 and FF 3.61.

But I would like to be able to use the %HWND_DESKTOP handle to be able to switch between forms with Alt+Tab keys.

PS: I made a test with an empty form (without any control) and I got the same issue.

[Jean-pierre Leroy]

Paul,

I added a dummy FORM (called Toto) in my project and compile it with both FF3.51 and FF3.60.

There is no control on this form. Then i compared the generated codes.

At the beginning of TOTO_FORMPROCEDURE we have now these lines of codes :

Code Select Expand


    FLY_pWindow = CWindow_GetObjectFromWindowHandle(hWndForm)
    If IsObject(FLY_pWindow) Then
       FLY_ScaleX = FLY_pWindow.rxRatio
       FLY_ScaleY = FLY_pWindow.ryRatio
    Else
       FLY_ScaleX = 1
       FLY_ScaleY = 1
    End If


I'm not able to explain but if I comment these lines of codes everything works fine with %HWND_DESKTOP as the parent handle when I open the FORM; if these lines are not commented I got a GPF.

I hope that could help.

Thanks.
Jean-Pierre

[Jean-pierre Leroy]

Paul,

I made more tests and I can tell you that the line that is causing the GPF is the first one :

Code Select Expand


FLY_pWindow = CWindow_GetObjectFromWindowHandle(hWndForm)


I'm happy to have been able to find the code that is causing this GPF in my project; I hope that you can understand why and that you could find a fix for that.

Thanks a lot for your support.
Jean-Pierre

[Paul Squires]

It seems strange that it would be that function call that would cause a GPF. I use that code to determine the scaling. I will replace that code with the better choices of AfxScaleX and AfxScaleY.

I will post a test exe for you shortly.

[Paul Squires]

Hi Jean-Pierre,

Try the attached exe to see if the GPF is gone. If not, then the problem probably exists elsewhere but was only triggered by that function call.


[attachment deleted by admin]

[Jean-pierre Leroy]

Hi Paul,

Thank you for the quick fix; I didn't get anymore GPF; the behavior of the application is now exactly the same as with FF3.51.

Thanks a lot
Jean-Pierre

[Paul Squires]

Awesome! Very happy that it is okay now.