-
I know the following code essentially does nothing, it is meant solely for example purposes. My question is when you use the DeleteDC function does it destroy whatever objects are currently selected into it as well. I have read somewhere that you should restore the previous object to the DC when you are done performing whatever operation you are attempting to it, but what if you want to, say for example, change the Pen and leave it as it is, is it OK to use the DeleteObject function to get rid of the original Pen that was created with the DC??
Code:
Private Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hdc As Long) As Long
Private Declare Function CreatePen Lib "gdi32" (ByVal nPenStyle As Long, ByVal nWidth As Long, ByVal crColor As Long) As Long
Private Declare Function SelectObject Lib "gdi32" (ByVal hdc As Long, ByVal hObject As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long
Private Sub Form_Load()
Dim lDC As Long
Dim lPenNew As Long, lPenOld As Long
Dim lRet As Long
' get handle to new dc
lDC = CreateCompatibleDC(Me.hdc)
' get handle to new pen
lPenNew = CreatePen(ps_solid, 1, vbRed)
' get handle to previous pen and select new pen into dc
lPenOld = SelectObject(lDC, lPenNew)
' destroy old pen
lRet = DeleteObject(lPenOld)
' destroy dc
lRet = DeleteDC(lDC)
End Sub
??
-
Just wanted to see if anybody that comes on later in the day might have an opinion on this, it was on the 3rd page in a few hours when I originally posted it. ;)
-
You need to put the original pen back into the DC before you delete the DC suing SelectObject. If you don't the handle to the pen is never released, and eventually you run out of handles to use and your application goes a little strange.
So the long and the short of it is (like your mother told you when you were growing up), if you use it, put it back wher you got it from. This holds true for and handle. Store all the old handles, then once you are down, put the old handles back into the DC, then delete the DC and delete the objects you created.
- gaffa
-
So even (as in my code above) you use the DeleteObject on the handle of the old pen (or any object for that matter) it is still using up memory. Just want to make sure I've got this right, the only way to remove the objects that are created along with the DC is to use the DeleteDC function??
