[RESOLVED] Subclassing usercontrols (Previously: App closing sequence)

Hello!

I'm stuck on a problem i cant overcome. The problem is that my app is wont close up itself in the right order. Ive put a tons of debug out lines, to see what is the initialization, then termination and unload sequence of each usercontrol, class, forms and the main mdiform. (theres a lot of objects, i used a timestamped file output for my custom debugging)

At in every log, i see differences, sometimes the main mdi form will unload then terminates itself, in the middle of the closing sequence, but sometimes (just like i want it to) it closes itself at the end, but before terminating its content form. Sometimes, i also see 'rumbles' in the termination of class objects and usercontrols. They just change their order, found no reason why. (there are some usercontrols they contain timers, but not those im talking about)

The most painful thing is, that on rare case, it crashes the app also. unfortunately these crashes are just happen pretty much rare cases, so i cant track down what the reason of it. But im sure, that all timers are set to offline.

I use DoEvents in Terminate() and Unload() events, to fire the timers once again, before the form or object will close. Is that could happen, that the reason will be the timers or the DoEvents? What else can i do to stop everything before i execute the shutdown? Especially in case, when the mdi form will not unload/terminate itself, but after the half of its content?!

The project is huge enough, that i cant upload here.

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In the meantime i typing this i included some routine into my mdi form's queryunload, that will walk thru on each mdi child and execute a speicifed subroutine that will do some inner workings, to unset the timers in their contained usercontrols, classes and so on... I hope it will works, ill report here my experiments.

Any input is welcome.

What exactly would be your problem?

Thanks for reading the long version.

In short, i found out that each time when i close my mdiform (the app), the class modules and usercontrols that used on its mdichilds will not be closing in the same order. I also found that sometimes, my mdiform will receive the terminate/unload event, before the latest object will be unloaded completely , but objects still unloading in the 'background'...

Sometimes it leads to a crash, but i just cant track down that, at which object is happening. But i think the main reason of the crash is this 'deranged' sequence of closing.

The crash may appear also, because a usercontrol does some unwanted event, just like executes a resize (but as i see i already handled all of them), that there want the code to access any array/variable etc that is not exists anymore. Unfortunately, i dont get any error messages in IDE, but it also crashing the whole IDE. Just like the standalone application as well.

Upon unloading sequences do you do any references to other objects?

It is hard to say anything without any code; I guess at this point most important information you could provide is all the unload procedures.

Do you have any long lasting loops that use DoEvents to keep the application responsive?


One thing that could work as a bubblegum solution is using a boolean variable that'll tell whether the project is closing. Procedures should then check whether this variable is set to True and if it is simply not run any code that could cause trouble.

This is from the FAQ, perhaps you may want to brush up on the things listed there.

@dee-u Thanks, all passed.

@Merri: Yes, i included booleans for posting the shutdown. I also included the checks inside the timer events, they just kick out the execution, by checking the bTerminateMe is True, using exit sub in the front of the timers.

The problem is, not because of i cant shut down one form, but i cant shut down multiple forms.

So. I open up 8 clones of an mdi child for example, each mdi have a tons of usercontrols (13), plus a usercontrol (that is duplicated) instantiates 11 (*2) classes. Maybe i can avoid to use these classes, but im not sure i exceeded any limit by using this way.

I do some work on each mdi child, then i press mr X at the corner, now im getting the log output what is happening.

I can provide some output log, that i get, if you wish, but it doesnt help me either to track down what is the problem. The only thing you can see that the objects and classes just terminating in an arranged sequence, for a while, but then sh*t happens.

But! Not every app close lead to a crash, but just in a few case. For example i can execute the app 10 times or more without any crashes. But i cant find any timer that is still running..

:eek2:

I know this topic going to be meaningless, but what i need is ideas and tips what else would you go, if you get a same situation.

Perhaps you could put up a trimmed down version of your project that you could upload here so others would be able to have a peek at it? What I am doing in my applications it to put error handlers in every place and even take a screenshot of the screen when the error occured for easier debugging.

Are you using the Tag properties of your forms and controls?

If not, maybe you could store a flag value in them, cstr(g_lOrder).

Then in the main form unload, do a nested loop to close the forms.
Test the Tag to see if it's that form's or control's turn to close?

Oh, the first thing I'd do during closing is disable all the timers.

Umm that will take for a while, to remove components one by one, test thru the problem still presists or not. I also using usercontrols, that contains other usercontrols just like a customized scrollbar for example.

Lets see what i get, i start to cut down the project.

Aside from longwolf's suggestion you should try removing the DoEvents in your Terminate() and Unload() events.

Code:

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Are you using the Tag properties of your forms and controls?

If not, maybe you could store a flag value in them, cstr(g_lOrder).

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No im not, instead of that, i store an public available index variable for the forms, that i set right after i instaniate a new form. The controls on this form is share this index property, i can walk thru what components on what form does what.

Quote:

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'in form
Public lIndexMe As Long

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Quote:

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Originally Posted by Jim Davis

Umm that will take for a while, to remove components one by one, test thru the problem still presists or not. I also using usercontrols, that contains other usercontrols just like a customized scrollbar for example.

Lets see what i get, i start to cut down the project.

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I don't envy you :)

@dee-u Ok i will, i just used them, to let the code execute the last timer tick, that may occur, before the form unloads.

Quote:

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[22:11:36] - Unload: visual project form (8)
[22:11:36] - Terminate: (MagicCheck)
[22:11:36] - Terminate: (xTextBox)
[22:11:36] - Terminate: (MagicCheck)
;.......... trimmed down
[22:11:37] - Terminate: visual project form (8)
[22:11:37] - Terminate: frmDesigner (0).uChartBox
;.... more controls was terminated after this

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Dang, what a mess! the form just terminated, before the contained usercontrols. The referenced index for the usercontrols, just good for nothing after this line. I do some cleanups here also, to prevent accessing any variable on this form.

Can anybody tell me why the form terminated, before its contained usercontrols?

How are you determining that a usercontrol has terminated?

Sorry, but there were a mistake in my logging that lead me to this bad conclusion.

Quote:

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[22:41:25] - Terminate: visual project form (4)
[22:41:25] - Terminate: frmDesigner (4).uChartBox

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maybe you need something like this in each of your forms

Code:

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Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    Dim crtlX As Control
    Dim lX As Long

    'an outer loop to make sure they're deleted in the order you want       
    For lX = m_lOrder To 0 Step -1
        For Each crtlX In Controls
            If Val(crtlX.Tag) >= lX Then
                Set crtlX = Nothing
            End If
        Next
    Next
End Sub

---

Building on Longwolf...

.. maybe you could make a log of when anything is ADDED
in the first place. My guess is that you would want to
TERMINATE in reverse chronological order.

Spoo

Do any of your usercontrols or classes reference their parent objects? If so, you may have circular references and unloading them in "correct" order may be nearly impossible. What are circular references? Here is an example:
Form1: has a UserControl1
UserControl1 has a ref to Form1: Set myParentForm = Form1

What happens here is that form1 tries to unload UserControl1, but since Usercontrol1 has a reference to Form1, it can't unload until Form1 unloads. But that is not possible because Form1 can't unload. Generally, one tries to resolve this by placing Set x=Nothing in a terminate event. Depending on how deep the circular references go or how many you may have, unloading could surely be "mangled".

Read this from vbAccelerator, it can explain a bit better than I can. It does sound like your problems are symptoms of circular references. But those symptoms could be from other things too.
http://www.vbaccelerator.com/home/vb...es/article.asp

Quote:

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Originally Posted by Jim Davis

@dee-u Ok i will, i just used them, to let the code execute the last timer tick, that may occur, before the form unloads.

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There is absolutely no guarantee that DoEvents will allow a Timer to fire (even at the lowest interval). If you want the timer event to run, you should explicitly call it (preferably disabling it first, otherwise it could fire automatically too).

I find it odd that you want the timers to fire during an unload process, but of course it does depend on the app.

Quote:

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There is absolutely no guarantee that DoEvents will allow a Timer to fire (even at the lowest interval).

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Thats may be true. I used them in the following way:

Quote:

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tmrThing1.enabled = false
tmrThing2.enabled = false
DoEvents
WriteLog "Terminate: objectnameXY"
End Sub

---

But now.

What if i'm going to subclass all forms 'close' or 'temination' flag. In the subclassed event, there i can start a timer on each form, but wont forward the form unload/termination event, that is will be simply ignored. The timer will makes the first tick, that there i can stop all the timers on the form (i also can call a sub on each usercontrol, that will does the same: Call xyUserControl.StopTimers), and set a boolean bTerminateMe = true, that the timers will identify, and kick out their execution. And then, in the next tick, it just simply call the Unload Me on the form, but now, the subclasser will lets the form to forward the unload event.

Is this could be a solution?

@LaVolpe:

Code:

---

Private Sub UserControl_InitProperties()
    bMultiline = False
    bEnterTab = True
    bSelectFocus = True
    Set UserControl.Font = UserControl.Parent.Font

---

Is this could be a problem? .. But i cant see that the InitProperties is executed in the app, but only at when i create an object on a form (in design time)

Adding subclassing is a bad idea, as if you make any mistakes it will cause similar problems to the ones you are trying to fix (and may actually be the actual cause here, if you are using it for something else already).

What you intended to do wouldn't make much difference anyway - all it would do is add a delay to unloading, which is unlikely to have any effect (even if it did, it would be inconsistent).


Somehow you need to find out what the actual cause of the problem is, and correct it as apt - but in a large project that is hard to do.

Try running it with fewer forms, to see if the problem only occurs when certain forms are used. Also add code to Form_Load of each form to see if any forms are being re-loaded as part of the unload process (eg: Debug.Print CStr(Time) & " loading form: " & Me.Name , or a MsgBox).

@longwolf, @Spoo:

I only add a timer, and two picturebox controls in a usercontrol, that i just simply remove on the usercontrol termination. Can i unset controls that is i made in design time, not runtime??

@si_the_geek: I can properly start up, then X out a child form, without any issues. But the crash is occurs as long as i create more than one (around 5+ the problem is appears), but 2 or 3 is still seems to be ok.

Yeah i know that the subclassing may be very painful, thats why i want to use ssubtmr6.dll that is pretty much stable (afaik). Do you still feel like subclassing is a bad idea in this case?

Quote:

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Try running it with fewer forms, to see if the problem only occurs when certain forms are used. Also add code to Form_Load of each form to see if any forms are being re-loaded as part of the unload process (eg: Debug.Print CStr(Time) & " loading form: " & Me.Name , or a MsgBox).

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Yes i did, there were no reload never!

At best subclassing is pointless for this - it doesn't give you any advantage. At worst, it causes the problem.

Quote:

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Yes i did, there were no reload never!

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Did it still crash?

If so, that's one potential cause eliminated (or rather, it shows that there is another problem - this may still be an intermittent issue).

@si_the_geek: At first time, when i included the logging to my app, i built in each unload/termination and initialization/load events. There were i never got any reload, that means the timer can't reload the form (in case it still running), or just simply doesn't running (the better case). I also placed some logging in critical event, that is driven by timers. Maybe it will be better to place the logging in the timer that is executed, instead of the event that is executed by the timer's tick.

Code:

---

Private Sub tmrRedraw_Timer()
  WriteLog "tmrRedraw executed"
  If bTerminateME Then tmrRedraw.Enabled = False: Exit Sub 'this line is kicking out the execution
  tmrRedraw.Enabled = False
  LB_Redraw = True
  RedrawGui
End Sub

---

-post removed-

i misread the logging, the timer is just stoping as well. The forms i unload is reverse ordered, so the timers on first, second and third forms' usercontrols are still running, while im removing the forth form. Its all ok.

Just a stupid idea: Please check the form_resize event. I just hit a problem about 100% CPU usage when loading a form. Finally, i found out that it is because in form_resize event, i have added a code about setting the height of an object that never exist in the form!

All the objects i used are identified, and exists for sure. I also set the break on all errors on the ide settings, that will point out if anything is wrong, but it doesnt.
I'm going to double check all the timers, but i feel like that is not the reason of the misterious crashes im getting.

Do you know this one, use crtl+F5 to start your app from the IDE.
You might find some surprises.

Quote:

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Originally Posted by longwolf

Do you know this one, use crtl+F5 to start your app from the IDE.
You might find some surprises.

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"Start with compile", i never used before, i compile manually and start from explorer.

I saw no any issues. The program normal start and shutdown. But on 7-8 mdi childs the app still crashes at where i am going to shutdown the app.

Got absolutely no any suprise :)

Have you tried this,
Set breakpoints in the Form_QueryUnload events of the 7-8 mdi child forms.
Then F8 you way through the closing to see where the crash happens?

I can monitor most of the happenings/events. The app is crashes Exactly before the closing sequence reaches the Form_Terminate() event.
- That means, the code is still running (but i dont know where), or
- a subclassed object is fails (dunno why, because i can close 4 or 5 instances without any issues, but then the crash will occur in the next 2-3 forms), or
- the form is unable to unload an object, that is made by design time (not runtime, those i unloaded properly)
- or it is refencing to a value/array or usercontrol that is not exists because the closing/termination sequence.

Maybe i should have to completely walk thru the whole code line by line to see what the heck is happening, and where the problem occurs. (It is takes a pretty long time, but i will do this)

To make things clear, i load up 8 instances (for a crash test) of the same mdi child form, by this way.

Code:

---

Private CurrIdx As Long

Private Sub mnuShowProjekt_Click()
Dim NewDesigner As frmDesigner
  Set NewDesigner = New frmDesigner
  NewDesigner.Show
  NewDesigner.lIndexMe = CurrIdx
  CurrIdx = CurrIdx + 1
End Sub

---

I also initialize a form at the mdi form load event (at startup i mean)

Code:

---

Private Sub MDIForm_Load()
Dim NewDesigner As frmDesigner

'.....
  CurrIdx = 1
  Set NewDesigner = New frmDesigner
  NewDesigner.Show
  NewDesigner.lIndexMe = CurrIdx
  CurrIdx = CurrIdx + 1

---

Quote:

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Originally Posted by Jim Davis

I also initialize a form at the mdi form load event (at startup i mean)

Code:

---

Private Sub MDIForm_Load()
Dim NewDesigner As frmDesigner

'.....
  CurrIdx = 1
  Set NewDesigner = New frmDesigner
  NewDesigner.Show
  NewDesigner.lIndexMe = CurrIdx
  CurrIdx = CurrIdx + 1

---

---

it looks like all your mdi's would get an index of one.

Assuming CurrIdx is a global var...

Code:

---

Private Sub MDIForm_Load()
Dim NewDesigner As frmDesigner

'.....
  CurrIdx = CurrIdx + 1
  Set NewDesigner = New frmDesigner
  NewDesigner.Show
  NewDesigner.lIndexMe = CurrIdx

---

not that that will help the crashes :(

The Curridx is a private variable, also mnuShowProjekt_Click() is the menu event, both placed on the MDI parent form, that is the caller of the Mdi childs.

I can only think of one more thing to try.
There are several projects on PSC that can add error handling/logging to your code for you.

They really bloat the code so I've used them by backing up my code, then used their code on it.

Once the error location is found/fixed go fix it in your backed up project and delete the other one.

Ok i have found the reason my problem. First of all, a big thanks to all inputs here. You are all nice to trying to help me, you all gave me here, good tips how to find and resolve, what to avoid in coding.

The crash is occurs when i place a subclassed usercontrol. Theres no trackable reason for the crash, it just does. Simply, i have a usercontrol (name it as A), that contains some subclassed usercontrol (name them as Bs). The B's got their termination event, they unsubclass theirself, then all are done without any problem. But then, the A just receives the termination flag, and after leaving the Usercontrol_Terminate() a crash will occur immediately. I've done a walk-thru using the F8, started from the Usercontrol_Terminate(). At the end Sub, the crash will occur, the debugger doesnt show me a line that is executed after end sub, but crashes the whole ide as well. The most frustrating thing is, that i can unload 4-7 mdi childs (seems randomly) without issues, then the next will crash.

Any input (experiences) about subclassed usercontrols, would be interesting!

Here is an example project that will show you simplified the problem, im facing with. Theres dont need to put these controls to a usercontrol-container, its just enough to place them to an mdi child, to get the crash.

The code will create 10 clones of form1, each form will contain 10 instances of ccXpButton.

I had to modify the usercontrol, to avoid the Client Site not available error, i included the InDevelopment "hack". I think this is not the reason of the crash, because the compiled code is also crashing. But if you feel like, you can double check it of course. Its better to close the child forms one by one (even better to use the ctrl+f4 for mass closing them). The crash will occur immediately, but in rare cases it just doesnt. In case you didnt got any crash, just restart the app, do the mass-closing, then the crash will occur i am sure.


I know, that bugfixing someone else's code is stinks, i dont ask you to do. What i only to ask you, about experiences how did you avoid crashes, using subclassed usercontrols.

Quote:

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12/22/2004 11:23:03 PM: James...

Hi Chris i tried to email but got returned email form the email supplied. I think there is a problem when you run it in a MDI environment as a complied exe. Have not been able to pinpoint it but it will cause a random crash when the form is unloading. Only happens when the control and project are comlpied.

12/29/2004 4:14:14 PM: Chris Cochran

James,
The problem you mentioned above is related to the mouseleave trapping. I am working the issue.
Not sure why you are having problem with the e-mail link, it works for all others.
Chris

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Ok, it seems like the control have the issue, ive just missed this conversation :(

I've seen this problem before. The uc is subclassing the parent. When multiple uc's subclass the same parent, the crashes are common. What is happening is that the uc's are subclassing in order of loading: uc1, uc2, uc3, etc. But when unloading, they do not unload in reverse order to restore the subclassing stack, they unload in first loaded, first unloaded order. Let's look at it this way

Code:

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' When UCs are loaded
UC1 subclasses: oldWndProc is Original
UC2 subclasses: oldWndProc is that in UC1
UC3 subclasses: oldWndProc is that in UC2

' When UC's are unloaded
UC1 unloads & resets subclass procedure to Original procedure
UC2 unloads & resets subclass procedure to that in UC1
>> crash. The procedure in UC1 is no longer in memory, it was unloaded

---

You can verify this yourself with a simple test project:

Code:

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1. Add new form
2. Add new usercontrol (not yours, just a blank uc)
3. In UC, add this to Initialize event: Debug.Print "Loaded "; ObjPtr(Me)
4. In UC, add this to Terminate event: Debug.Print "Unloaded "; ObjPtr(Me)
5. Add 3 UCs to your form
6. Close your form in design view, Open Debug window (CTRL+G)
7. Clear any entries in it. Run test project. Close test project normally (X)
8. Open debug window & look at order loaded, unloaded.

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I have tweaked Paul Caton's subclassing to avoid this issue. Basically, I've added a delay timer in the ASM thunk. The thunks prevent unloading the window procedure until a short timer expires, then unloads it. This works really well for UCs. You can find the modified thunks on PSC (as of this reply, PSC appears down for maintenance, so the link was obtained from googling & hopefully it is the correct one).
http://www.planetsourcecode.com/vb/s...68737&lngWId=1

Edited: This becomes even more crash prone when you have other UCs (3rd party) that subclass the parent also. The order of subclassing/unsubclassing is not in your control. And if those others use similar subclassing techniques as does your uc, what a mess! Which is the reason I don't write UCs to subclass any container/outside object, unless subclassing starts in a sub/function and terminates subclassing before the sub/function terminates.

Oh thanks! I will look forward how to avoid and/or replace these methods to get the proper functionality.

Thanks for informing me!

Quite frankly, I had a similar, if not the same problem.

I created a SubClassed UserControl and realised if only 1 instance was placed on a form it worked fine, without any crashes. But if multiple instances of the control were placed, then there was always a crash.

After tracking down, I spotted the problem and seem to have fixed it.

I always start off with a template of Paul Caton, which has a ready made Subclassed template of a UserControl.

In the SubClassed UserControl, you should probably have a Subclass_StopAll function. Find it and change it to this:

vb Code:

'Stop all subclassing
Private Sub Subclass_StopAll()
  Dim i As Long
  Dim getControlNo As Single
  Dim wasHere      As Boolean
 
    
  i = UBound(sc_aSubData())                                                             'Get the upper bound of the subclass data array
  Do While i >= 0                                                                       'Iterate through each element
    With sc_aSubData(i)
      If .hWnd <> 0 Then                                                                'If not previously Subclass_Stop'd
           ' Debug.Print .hWnd, mParentHwnd
           'Prevents crash if there are multiple controls on the form, because the Form is subclassed for MouseDown events
            If .hWnd = mParentHwnd Then
                If wasHere = False Then
                  ' Call Subclass_Stop(.hWnd)
                End If
                wasHere = True
            Else
                Call Subclass_Stop(.hWnd)                                                       'Subclass_Stop
            End If
      End If
    End With
    
    i = i - 1                                                                           'Next element
  Loop
End Sub

Ssubtmr6.dll has a memory leak that will eventually crash Vb. It depends on how much memory you have, how many instances of the subclassed usercontrol are on the Form, and finally how many times the Form is Loaded/Unloaded. Also check to make sure that for every AttachMessage there is a corresponding DetachMessage when using Ssubtmr6.dll. You may want to try one of the subclassing Thunks on Planet Source Code.

Quote:

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Originally Posted by some1uk03

In the SubClassed UserControl, you should probably have a Subclass_StopAll function. Find it and change it to this:

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Its nice to you to show me your example, but its just not works. I am getting subscript out of range error codes, i also dont know where and how should i set the parent hwnd (mParentHwnd)!

Quote:

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Originally Posted by Jim Davis

Its nice to you to show me your example, but its just not works. I am getting subscript out of range error codes, i also dont know where and how should i set the parent hwnd (mParentHwnd)!

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Ohh yea I forgot about mParentHwnd : )

Decalre this in the General Declaration Section.

Code:

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Private mParentHwnd  As Long              'Remember parent Hwnd to stop crash

---

Then in your UserControl_ReadProperties add this.

Code:

---

mParentHwnd = UserControl.Parent.hWnd

---

--------------------
The Subscrit Out Of Range errors, are other coding errors you have, which can be tracked down through simple error coding in the subs.

Nevermind, its ok now. About the array issue, i found that the line i = UBound(sc_aSubData()) is raised the error, because in design time havent got dimensions of the array, therefore it have no upper bound. It is also fixed now.

I still got a crash once in IDE. But later there were no problems! By regarding LaVolpe's post, this wouldnt solve the problem. I will do some test to see it is stable or not.

You can usually avoid IDE crashes caused by subclassing by only using your programs controls to close the app.
In other words, don't use the vb6 Stop button.

Quote:

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Originally Posted by LaVolpe

Edited: This becomes even more crash prone when you have other UCs (3rd party) that subclass the parent also. The order of subclassing/unsubclassing is not in your control. And if those others use similar subclassing techniques as does your uc, what a mess! Which is the reason I don't write UCs to subclass any container/outside object, unless subclassing starts in a sub/function and terminates subclassing before the sub/function terminates.

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i'm facing issues with subclassing uc

i created a listview window on vb uc
then subclass the uc to get messages,

one of the issues for example is:
the uc doesn't get some messages if there is no other control
on the uc parent

if i place the uc on an empty form, some messages simply don't arrived
i put debug.print in the wndproc, to print all the messages


i downloaded stuff from vbaccelerator to learn.


but any idea on how to get messages without subclassing
the uc would be helpfull.