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API to delete GDI objects that are not in use

Posted on 2003-11-19
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Last Modified: 2008-02-01
Is there an API that I can call, that will free up the GDI objects that I have created, and finished using ?

We have a heavy application in terms of GDI objects count, and this might be a work around for the main problem.
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Question by:UriS
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by:NBrownoh
ID: 9783409
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
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by:Mike Tomlinson
ID: 9783515
You have to be careful when creating and deleting GDI objecst as you can suck the life (memory) out of a system really fast by creating too many GDI objects.

As NBrownoh pointed out, you use the DeleteObject() API to delete your objects.

Here is some wisdom I just learned earlier today.  When you use the SelectObject() API, it returns a handle to the previously selected object.  You should then put this object back as the selected object and before deleting the object you just created and used.

Dim hbrush As Long
Dim ret As Long
   
hbrush = GetStockObject(NULLBRUSH) ' create an object
ret = SelectObject(hDC, hbrush) ' store handle to previous object
Polygon hDC, points(0), Me.numVertices ' use the object
SelectObject hDC, ret ' put previous object back
DeleteObject hbrush ' delte the object we created

Regards,

Idle_Mind
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by:UriS
ID: 9784912
how can I delete the objects without first saving a pointer to them?
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by:Mike Tomlinson
ID: 9788277
You can't.

Idle_Mind
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Mike Tomlinson earned 125 total points
ID: 9828296
When you create objects and no longer have pointers to them, you create what is commonly known as a "memory leak".  The API calls you are making are not part of Visual Basic and as such, do not fall under its garbage collection scheme.  You have to manage your pointers and free the resources yourself.  Failure to do so will cause the system memory to be lost to all applications running until the system is rebooted.

Idle_Mind
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