Stuck in a loop...

[DarkJedi9]

I'm having a little trouble with a loop. When the user clicks the start button, it is supposed to draw a series of lines until the user clicks stop or it hits the far "wall".

It does stop when it hits the edge, but the outside input doesn't seem to be getting through. I threw in a DoEvents statement at the beginning of the loop, but still no luck.

I figure it's just something dumb, but any help would be greatly appreciated. Thanks.

[crptcblade]

how is the "stop" button telling the loop to break? Like this? :

Dim stopLoop As Boolean
 
  Do Until x=5 'whatever you use
    DoEvents
    If stopLoop = True Then
      Exit Do
    End If
    
    'do whatever
  Loop
 
Private Sub cmdStop_Click()
  stopLoop = True
End Sub

like that?

[DarkJedi9]

Here's what I've got:

Private Sub cmdStart_Click()
If cmdStart.Caption = "&Start" Then
Dim Drawing As Boolean
Drawing = True
cmdStart.Caption = "&Stop"
Do While Drawing = True And cmdStart.Caption = "&Stop"
DoEvents
DoEvents
LineY1 = 30 * Cos(LineX / 10)
LineY2 = 30 * Cos(LineX / 15)
If chkLine1.Value = 1 Then Dot StartX + LineX, StartY + LineY1, vbRed
If chkLine2.Value = 1 Then Dot StartX + LineX, StartY + LineY2, vbYellow
If chkResult.Value = 1 Then Dot StartX + LineX, StartY + LineY1 + LineY2, &H80FF&
LineX = LineX + 1
If LineX > picWave.ScaleWidth Then
Drawing = False
Exit Do
End If
If Not Drawing Then Exit Do
Loop
Else
Drawing = False
cmdStart.Caption = "&Start"
End If
End Sub

Hopefully you can make sense of that. I really need the loop to run but still allow my user input, so those check boxes actually do something.

[sunnyl]

I don't think theres any need to actually put in two checks in the loop. You'll just be increasing the chance of making a logic error

Private Sub cmdStart_Click()
    If cmdStart.Caption = "&Start" Then
        cmdStart.Caption = "&Stop"
        Do While cmdStart.Caption = "&Stop"
            DoEvents
            'drawing code
            If HitTheWall = True Then
                cmdStart.Caption = "&Start"
            End If
        Loop
    Else
        cmdStart.Caption = "&Start"
    End If
End Sub

[DarkJedi9]

Um, I think I was unclear. The loop does exit when line hits the wall; that part works fine. The problem is I want the loop to allow user input while it is executing, so that the user can cancel the loop whenever they want to.

Oh, and I knew I didn't need the double check, but I put it there because nothing else was working.

[DarkJedi9]

Somebody has to know!

[NotLKH]

Well,

I encountered a similar problem once, but what it was was there was a lag in the picture drawing commands and the actual picture
update. So, when I selected a button to trigger a control variable to stop the picture processing, it appeared that my picture processing kept going for a while, then it stopped. Now, my picture drawing procedure did not have a self stop check built in, so it did stop when the trigger changed, it just took a while.

So, in essence, I think your procedure kills itself, but the picture is still refreshing, so you think it still is active, and when you press the button to stop it, it's too late.


Just as a test, throw in a msgbox command where your button triggers the stop.

Change:

Drawing = False
cmdStart.Caption = "&Start"
End If

to:

Drawing = False
cmdStart.Caption = "&Start"
msgbox "Well, your Trigger activated, anyway"
End If

And let me know what happens.

-Lou

[DarkJedi9]

I did what you said, and the msgbox popped up, but not until the loop had ended 5 seconds later because it exited itself when the drawing hit the wall.

I decided to try it a few more times and sometimes the msgbox would pop up a second after I clicked the button and actually end the loop, sometimes it would wait 2 seconds then end the loop, sometimes not at all. I'm looking for pretty much instantaneous reaction, as would happen normally. (By normally, I mean if the loop weren't running).

I think I'm going to try putting the drawing in a sub and having to different buttons.

[DarkJedi9]

Maybe I've been asking the wrong question.

If you guys (and girls) wanted to have something looping in the backgroung and still allow user input, how would you do it? I've already tried a timer, which works but too slowly, so don't bother with that unless you know how to make them work faster.

[NotLKH]

I'd like to do some investigating, but...

I've recreated your code with form & controls, However, now I
need to know a couple of things:

DOT: Obviously a user defined function, maybe a variation of picWave.line?

StartX, StartY, LineX, LineY1, LineY2: Are they Public type
variables, and if so, what are their initial values?

-If I can get these, I'll play with it and see if I can help you out.

-Lou

[InvisibleDuncan]

I'd go with something similar to what Sunny gave you:

Dim blnStopLoop As Boolean
 
Private Sub SubTestLoop()
    blnStopLoop = False
    Do While blnStopLoop = False And x <= 5
        ' Run your code
        DoEvents
    Loop
End Sub
 
Private Sub cmdStop_Click()
    blnStopLoop = True
End Sub

If your loop takes too long to run, test for the boolean in a couple of places in the code with a DoEvents and an Exit Do

[DarkJedi9]

NotLKH-

Dot is a simple function that takes a point and then draws a three by three square of the given color around it. Basically a setpixel function that sets a bigger pixel.

StartX, StartY are public in the form module, with StartX being 0 and StartY being half of the pixels scaleheight. They basically set the origin of the waves (that's what I'm drawing).

LineX, LineY1, and LineY2 are also public in the form module. LineX is the current X position of the three waves I'm drawing. They all use the same X coordinate and it is incremented by 1 each time through the loop. LineY1 and LineY2 are the Y coordinates (in relation to my origin, not 0,0) of first two waves. They are found with a couple of slightly different sin(LineX) statements. The third wave gets its Y coordinate from the sum of LineY1 and LineY2.

That what you need?

[Helger]

Maybe it doesn't matter but IMO it could:

try it duncan-style: dont put all the code into your button event procedure but rather make the event procedure call the drawing one.
(If all else fails try making two buttons on top of each other for a test to make isolating the problem easier and make one button visible and active while the other is not - THAT shouldn't make a difference to the above approach but sometimes VB does things that it shouldn't )

hih

helger

[DarkJedi9]

Thanks for the input, but I tried that, and it doesn't help. The problem is in the method of looping, I think, not the buttons.

[NotLKH]

Is your program something like this?

Dim StartX As Long
Dim StartY As Long

Private Sub cmdStart_Click()
If cmdStart.Caption = "&Start" Then
Call picWave_Click
Dim Drawing As Boolean
Drawing = True
cmdStart.Caption = "&Stop"
Do While Drawing = True And cmdStart.Caption = "&Stop"
DoEvents
DoEvents
LineY1 = 30 * Cos(LineX / 10)
LineY2 = 30 * Cos(LineX / 15)
If chkLine1.Value = 1 Then Dot StartX + LineX, StartY + LineY1, vbRed
If chkLine2.Value = 1 Then Dot StartX + LineX, StartY + LineY2, vbYellow
If chkResult.Value = 1 Then Dot StartX + LineX, StartY + LineY1 + LineY2, &H80FF&
LineX = LineX + 1
If LineX > picWave.ScaleWidth Then
Drawing = False
Exit Do
End If
If Not Drawing Then Exit Do
Loop
Else
Drawing = False
cmdStart.Caption = "&Start"
End If
End Sub

Private Sub Form_Load()
StartX = 0
StartY = picWave.ScaleHeight \ 2
End Sub
Private Sub Dot(ByVal MY_X As Long, ByVal MY_Y As Long, ByVal MY_C As Long)
picWave.DrawWidth = 3
picWave.PSet (MY_X, MY_Y), MY_C
Form1.Caption = StartX & " " & picWave.ScaleWidth
DoEvents

End Sub

Private Sub picWave_Click()
picWave.Cls
StartX = 0
StartY = picWave.ScaleHeight \ 2
End Sub

[DarkJedi9]

I don't do anything with the picWave_Click, although from the looks of it, that shouldn't change much, and your picture came out fine, so I'd say you pretty much got it.

Oh, and my dot worked differently, it actually set nine pixels, but yours works better when I try it (less gaps) so I'll go with that!

[NotLKH]

Glad you like it.

Just wondering, the stop click works instantly on my machine.
Does it work for you?

-Lou

[DarkJedi9]

What are your stats?

[DarkJedi9]

Just found something that works: GetTickCount!

If I use GetTickCount like this:

Do Until NextFrame <= GetTickCount
    DoEvents
Loop
NextFrame = NextFrame + (1000 / 40)  '1000 / frames per second

Everything works. If I increase 40, it goes faster, but if I decrease it, user response is quicker. Woohoo!

Well, thanks guys, although I still don't know why notLKH's worked on his machine. Oh, well.

[NotLKH]

OOPS...

the stop click works instantly on my machine

heh,heh

It worked instantly, but not on the program we were talking
about. I was remembering it working on a development
version that led up to my code post.

It actually works, but not instantly. Its got some cumulative
stall time.

-Lou

[DarkJedi9]

Yeah, that's what mine does. The higher the frame rate, the faster the drawing, and the slower the response, but it works well at about 30 fps, which is good enough for me.