Give Time to Other Events in My Application

[Pradeep1210]

I've observed with c++/non VB apps that when they are doing some CPU intensive work they run quite fast and still respond to user events like mouse-click, keypress etc.
Obviously they are not using any thing like the DoEvents of VB which processes the system message queue. Instead they seem to be giving time to only their own events.

In VB, the only way I know to let your app respond to events is to put a DoEvents in your procedure/loop.

Let's take a very simple example:

Option Explicit
Dim bCancel As Boolean
 
Private Sub cmdCancel_Click()
    If vbYes = MsgBox("Cancel Processing?", vbYesNo + vbQuestion) Then
        bCancel = True
    End If
End Sub
 
Private Sub cmdOK_Click()
    bCancel = False
    Do
        If bCancel Then Exit Do
        DoSomething
        DoEvents
    Loop
    MsgBox "OK", vbInformation
End Sub
 
Private Sub DoSomething()
    'Add code to do something here
End Sub

This code would work fine, but it is very slow. But if you comment out the Doevents, it would go very fast as it won't process the system message queue. But then it won't respond to cmdCancel_Click and you would ultimately have to End task teh application.
I was looking for some replacement for the DoEvents which won't process the entire system message queue, instead give time to my application only.


Pradeep

[Hack]

Don't you think if there were alternatives to DoEvents you would have heard all of us speak about it, and recommend it, by now?

[Pradeep1210]

I was wondering if we could make a dll in another language and implement it in VB applications instead of the DoEvents. I'm not sure how to do this though?

Pradeep

[Hack]

I was wondering if we could make a dll in another language and implement it in VB applications instead of the DoEvents. I'm not sure how to do this though?

Pradeep

Now that could be quite possible (although I wouldn't know how to do it either).

I suspect something in C++ might be done.

Check your PMs.

[Hack]

Moved to C/C++ at member's request. As the prior posts have indicated, he is looking for a possible C++ alternative to VB's DoEvents.

[sunburnt]

Moved back to General VB as requested.
There's still a soft link to this thread in the C/C++ forum.

[Pradeep1210]

I found some hints

This one is faster than the regular DoEvents.
Though it still processes the entire message queue.

Can someone guide me how to identify the messages related to my application only in the message queue?

Option Explicit
Private Type POINTAPI
    x As Long
    y As Long
End Type
 
Private Type MSG
    hwnd As Long
    message As Long
    wParam As Long
    lParam As Long
    time As Long
    pt As POINTAPI
End Type
 
Private Declare Function PeekMessage Lib "user32" Alias "PeekMessageA" (lpMsg As MSG, ByVal hwnd As Long, ByVal wMsgFilterMin As Long, ByVal wMsgFilterMax As Long, ByVal wRemoveMsg As Long) As Long
Private Declare Function TranslateMessage Lib "user32" (lpMsg As MSG) As Long
Private Declare Function DispatchMessage Lib "user32" Alias "DispatchMessageA" (lpMsg As MSG) As Long
 
Private Const PM_REMOVE = &H1
 
Dim bCancel As Boolean
 
'The alternative function for DoEvents:
Private Sub MyDoEvents()
    Dim CurrMsg As MSG
    'The following loop extract all messages from the queue and dispatch them
    'to the appropriate window.
    Do While PeekMessage(CurrMsg, 0, 0, 0, PM_REMOVE) <> 0
        TranslateMessage CurrMsg
        DispatchMessage CurrMsg
    Loop
End Sub
 
 
'uses regular DoEvents
Private Sub Command1_Click()
    Dim lCounter As Long, nStart As Double
    nStart = Timer
    bCancel = False
    For lCounter = 1 To 50000
        If bCancel Then Debug.Print "Hey! it got Cancelled": Exit Sub
        lblCounter.Caption = CStr(lCounter)
        DoEvents
    Next
    Debug.Print "Old Doevents : "; Timer - nStart
End Sub
 
'uses new MyDoEvents (using API)
Private Sub Command2_Click()
    Dim lCounter As Long, nStart As Double
    nStart = Timer
    bCancel = False
    For lCounter = 1 To 50000
        If bCancel Then Debug.Print "Hey! it got Cancelled": Exit Sub
        lblCounter.Caption = CStr(lCounter)
        MyDoEvents
    Next
    Debug.Print "New Doevents : "; Timer - nStart
End Sub
 
'Signals a cancel
Private Sub Command3_Click()
    Debug.Print "I clicked Cancel"
    bCancel = True
End Sub

[Pradeep1210]

Here' the form.

Pradeep

[anotherVBnewbie]

I havn't tried this, although it looks interesting, however I believe you should be able to simply specify your hwnd. i.e, change

Do While PeekMessage(CurrMsg, 0, 0, 0, PM_REMOVE) <> 0

to

Do While PeekMessage(CurrMsg, Me.hwnd, 0, 0, PM_REMOVE) <> 0

[Pradeep1210]

I havn't tried this, although it looks interesting, however I believe you should be able to simply specify your hwnd. i.e, change

Do While PeekMessage(CurrMsg, 0, 0, 0, PM_REMOVE) <> 0

to

Do While PeekMessage(CurrMsg, Me.hwnd, 0, 0, PM_REMOVE) <> 0

That increases the time taken

Pradeep