[RESOLVED] Is it possible to put AddressOf in a variable

[vb_lover]

I would like to create a Sub that can transfer an address of a subroutine, I've tried Long and Long_Ptr without success.

Function WndProc_Sounds
'working stuff is in here
End Function

Function SubClass_iDrive(hWnd as Long, lProc as Long, WndProc as Long) as Long
'of course the following line works if I use it outside the Function and insert the real variables
If lProc = False Then lProc = SetWindowLong (hWnd, GWL_WNDPROC, AddressOf WndProc)
End Function



My call:
Dim lProcSounds as Long
Dim hWndSounds as Long

hWndSounds = iDriveSound.hWnd

SubClass_iDrive hWndSounds, lProcSounds, AddressOf WndProc_Sounds


How can this be accomplished???

[LaVolpe]

You can do it via a helper function

Public Function GetAddressOf(inAddressOf As Long) As Long
    GetAddressOf = inAddressOf
End Function

Sample call: SubClass_iDrive hWndSounds, lProcSounds, GetAddressOf(AddressOf WndProc_Sounds)

The helper function doesn't need to be public if called from the same class object it exists in. If it will be in a module, then yes, make it a public function

[Bonnie West]

There is actually no need for a helper function. Just remove the AddressOf operator from the SetWindowLong call and the compilation error will be gone. Note that you cannot use the AddressOf operator with a procedure parameter (WndProc); as stated in the VB6 manual, the AddressOf operator only works with procedures that resides in a standard module (.BAS). Also, as stated again in the documentation, a helper function only becomes necessary when you want to cache a procedure's address in a variable.

Public Function WndProc_Sounds() As Variant
    'working stuff is in here
End Function

Public Function Subclass_iDrive(ByVal hWnd As Long, ByRef lProc As Long, ByVal WndProc As Long) As Long
    If lProc = 0& Then lProc = SetWindowLong(hWnd, GWL_WNDPROC, WndProc)
End Function

Dim lProcSounds As Long
Dim hWndSounds  As Long

hWndSounds = iDriveSound.hWnd

Subclass_iDrive hWndSounds, lProcSounds, AddressOf WndProc_Sounds

[vb_lover]

I haven't tried the helper yet. What I didn't mention is that the SubClass_iDriveSound routine should be in the .BAS because it will be called by 7 different forms.

I was just attempting to simplify things, the way it resides now is that I have a
If lProc = False Then lProc = SetWindowLong (hWnd, GWL_WNDPROC, AddressOf WndProc) in each form, changing the variables as required. All the different WndProc's reside in the .BAS

[LaVolpe]

A helper function, like the I provided, should do the trick since you are not using 1 window procedure. Having 7 different Window Procedures seems a bit inefficient, especially if they will basically being subclassing the same window or type of window.

[Bonnie West]

A helper function, like the I provided, should do the trick since you are not using 1 window procedure.

Isn't the helper function somewhat redundant?

SubClass_iDrive hWndSounds, lProcSounds, GetAddressOf(AddressOf WndProc_Sounds)

SubClass_iDrive hWndSounds, lProcSounds, AddressOf WndProc_Sounds '<-- Should work just fine

@ vb_lover

If possible, can you please show more of your code so we can get a clearer picture of what you're trying to do?

[LaVolpe]

@Bonnie. My original response was an answer to the title of the posting.

Now, it does appear that the OP has multiple subclass routines in the module. I'm assuming the request to store it in a variable will be for use within the form that is performing subclassing.

Above being said, not sure how the different subclassing procedures will know which lProc value to pass to CallWindowProc().

I agree that we probably need to see more code to help offer optional strategies.

[vb_lover]

The control I wish to subclass (combobox) resides on each form, the WndProc for each resides in the .BAS, more than one form could be open simultaneously, then wouldn't I need separate WndProcs? I was just trying to create a subcall that would contain the variables necessary to address each WndProc. Just a matter of having cleaner code I guess and I was curious if it could be done in this manner.

The goal was to have a common SubClass call "SubClass_iDrive" in the various Form_Loads with the variables required for that form's Control's subclassing to be handled properly.

I am actually subclassing the Edit box of the combobox so included in SubClass_iDrive is the sub which obtains the handle of the Edit box via enumeration of Child windows, this is why I thought about making one routine do it all. Its the Address Of that was my problem.

[Bonnie West]

Try the attached subclassing example and see if it meets your needs. It uses the newer subclassing APIs and is based on Karl E. Peterson's Subclassing the XP Way article.

[vb_lover]

I didn't need a helper Sub/Function after all.
This resolved it, it was that AddressOf that was confusing me.

in the .BAS
Public hwnd_frmSoundsEditbox as Long 'two global variables required for every form that uses SubClassing
Public lProcSoundsiDrive as Long

Function WndProc_Sounds
'working stuff is in here which disables the context popup
End Function

Function SubClass_iDrive(driveHwnd as Long, lProc as Long, WndProc as Long) as Long
Dim editboxHwnd as long

editboxHwnd = Get_ChildWindow (driveHwnd, "edit") 'this function enumerates the child windows for the textbox part of the combobox

If editboxHwnd > 0 then
If lProc = False Then lProc = SetWindowLong (editboxHwnd, GWL_WNDPROC, WndProc)
end if

SubClass_iDrive = editboxHwnd

End Function



My form load call:

hwnd_frmSoundsEditbox = SubClass_iDrive (iDriveSound.hWnd, lProcSoundsiDrive, AddressOf WndProc_Sounds)


and of course in the form Unload there is a call to stop subclassing using the two .BAS variables for each form that has subclassing turned on.