Computer bogs down RESOLVED

[ac3100]

Newbie here,

From VB6 I open a project that has a single form.

I run the program that has a timer that has a 100 interval.

Within the timer code I use a getpixel API call and displays the color number on the form.

It seems to bog the computer down.

For example, I autohide my toolbar at the bottom of my screen.
Normally it smoothly popsup when I place my mouse cursor down to it.

When the program has run for awhile, the toolbar posup, but not very smoothly. It's kind of jerky.

After a while it gets real bad. I move the form and it leaves an image of where its been. Numbers appear in the top righthand corners of open windows.

Its really strange.

Any ideas?

Andy

[madjon]

Put a DoEvents in your timer and increase the interval.

[ac3100]

Thanks for the response.

I made the changes and it definitely helped.

Is this a type of program that will eventually deteriorate over time regardless of the timer setting?

Even though I wouldn't want to do this, I guess I could close VB and reopen it when it starts to get bad. I wish there was a way I could "reset" the program so that it starts fresh

Does having VB6 open cause this problem?
If I somehow can run this form without having VB6 open might be better?


Just curious

[Maldrid]

Can you post your code?

[ac3100]

Option Explicit
Private Declare Function GetDC Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As Long
Private Declare Function GetCursorPos Lib "user32" (lpPoint As POINTAPI) As Long

Private Type POINTAPI
x As Long
y As Long
End Type
Dim iPoint As POINTAPI

Private Sub Form_Load()
Show
Timer1.Interval = 350
End Sub

Private Sub Timer1_Timer()
Dim pt As POINTAPI
Dim hdc As Long
DoEvents
Call GetCursorPos(pt)
hdc = GetDC(0)
Text1.Text = GetPixel(GetDC(0), pt.x, pt.y)
Text2.Text = pt.x
Text3.Text = pt.y

'test for change in color (Black)
If GetPixel(hdc, 636, 186) = 0 Then
Text4.Text = "Hello!"
Else: Text4.Text = ""
End If
End Sub


You need 4 textboxes and a timer control on form1

[Maldrid]

The code runs smoothly on my computer. I am running a pentium 4 1.3 ghz. Also maybe you do not have enough virtual memory to handle everything.

If you want to try to run the application outside VB you need to first make it an executable. You can do that by having the project open and then go to File->Make Project.exe. Then it will ask you where you want to build the file, the default is the same directory as the project. After that close VB and go to your project folder and run the exe file.

Quick question though why are you checking to see if the pixel at 636,186 is black? I am not sure but I hope you know that regardless of where you mouse cursor is, if that pixel is black it will always come out true, maybe that is what you want.

[ac3100]

I will try it on another computer.


Try setting the interval length to 100.

Let it run for a while and see if it deteriorates.

How do I check for virtual memory?

If virtual memory is a problem how would you fix it?

Andy

[Maldrid]

You know what you are right. The program does start to really mess up after a while. So let me do some more testing.

For virtual memory you could either buy more, which is ram memory. Or you can use some of your harddrive space. The settings are different depending on the OS you are running, but you can try right click on my computer and looking through the properties to see if you can find it in there. Or looking through your settings in control panel, but regardless of how much memory you have it will eventually run out with this app that you have. So it might last longer but it will still go bad after a while.

I am trying to see if you declare your point type and your handle variable as private to the form instead of in the timer function if it fixes the memory problem.

[Maldrid]

Ok that did not work. I will keep trying to think of something.

Hopefully someone else can solve this problem for you.

[longwolf]

I believe you've created a memory leak.

Try adding:

Public Declare Function ReleaseDC Lib "user32" (ByVal hwnd As Long, ByVal hdc As Long) As Long

And then use ReleaseDC before you exit the sub

[BuggyProgrammer]

Would it be better if you bitblt the pixel, then use getdibits to get what the colour of the pixel is?

[longwolf]

Just noticed something.
You're calling GetDC twice when you only need it once

Change"

hdc = GetDC(0)
Text1.Text = GetPixel(GetDC(0), pt.x, pt.y)

to

hdc = GetDC(0)
Text1.Text = GetPixel(hdc, pt.x, pt.y)

Those DC's will getcha if you don't watch out

[ac3100]

Thanks for catching the GetDC twice Longwolf

I am not too familiar with using the ReleaseDC in my code.

I put the ReleaseDC API call in a module

I put ReleaseDC (hdc) in the timer1_timer sub but It wouldn't work.

I think I need another argument in there, but I don't know what it would be?

The bltbit looks like c+ programming in which I no experience whatsoever. Thanks though.

I really appreciate the help so far. It is helping me learn this stuff.

Andy

[Maldrid]

RelaseDC is delcare like this.

Public Declare Function ReleaseDC Lib "user32" (ByVal hwnd As Long, ByVal hdc As Long) As Long

As you can see you need a handle to the window that the device context is to be released. I guess since you use 0 as your handle to get the device context you can use that as your first parameter. I am not positive because anytime I got a device context I always had a window handle, but in your case you don't.

'So you can write you code like this.
 
ReleaseDC 0, hdc

[ac3100]

Thats it!!

I even set the timer interval to 1 and no leaks!

Thank you very much for your insight.

I've learned a lot more about API programming through VB.

It is very powerful because it looks like you can program outside the normal VB environment.

I still need to get a HANDLE on the hwnd stuff.

Thanks again to all.

Andy

[Maldrid]

Just to make things a little more clear for you on what a handle is.

A handle is just a long integer value given to a object such as a window, command button, textbox, etc. by the operating system to keep track of all the objects that are currently in memory. You use that handle to reference the object through API calls. So when you make an API call to get/set a property to an object in your application or some other application you need the handle (long integer value) so that the OS knows which object your talking about.

The handle will change each time you run your application since the OS gives the value to each object at runtime.

Also here is a website where you can d/l an API guide with a lot of examples on how to use them in code for VB.



http://www.mentalis.org/

[MartinLiss]

Originally posted by ac3100
Thats it!!

I even set the timer interval to 1 and no leaks!

Thank you very much for your insight.

I've learned a lot more about API programming through VB.

It is very powerful because it looks like you can program outside the normal VB environment.

I still need to get a HANDLE on the hwnd stuff.

Thanks again to all.

Andy

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