The correct way to DeletObject

Hi,

I've read a ton of different info. on how to clean up bitmap objects but alot of the information is different.   Can someone explain what the correct method is for cleaning up a GDI object such as a bitmap. I.E.

HDC pDC = ::GetWindowDC(hWnd);
hBitmapDC = ::CreateCompatibleDC(pDC);
HBITMAP       hBitmap = ::LoadBitmap(hInst,(LPCTSTR)nResID);

::SelectObject(hBitmapDC,hBitmap );
::BitBlt(pDC,0,0,10,10,hBitmapDC,0,0,SRCCOPY);
                        
...How do I clean up properly?
alsmorrisAsked:
Who is Participating?
 
_corey_Connect With a Mentor Commented:
You need to repeat your SelectObject call first to make sure.

Select all objects out of the DC, then destroy the DC and the objects.
0
 
MattAACommented:
You clean up any bitmap loaded with LoadBitmap by calling DeleteObject on its handle.  If this was a pen or a brush, you would have to unselect it from the device context before you could delete it, but there shouldn't be any problems with bitmaps.  So, to cleanup after that code, you would simply put:

::DeleteObject(hBitmap);

You should also delete your memory device context (hBitmapDC) with ::DeleteDC when you are done with it.
0
 
alsmorrisAuthor Commented:
MattAA,

I have tried this but I get resource errors... and finally the window goes black.  I am finding out that what works on 2000/XP does not work on 98.  For example what you said ::DeleteObject(hBitmap); will not give me a problem on 2000/xp but on 98 I get a black window and boundchecker tells me that the object is still selected in the DC.

Thanks :)
0
Cloud Class® Course: Microsoft Office 2010

This course will introduce you to the interfaces and features of Microsoft Office 2010 Word, Excel, PowerPoint, Outlook, and Access. You will learn about the features that are shared between all products in the Office suite, as well as the new features that are product specific.

 
alsmorrisAuthor Commented:
ok ... I think I figured it out...But I'm not sure this is the best way to do it...

HDC pDC = ::GetWindowDC(hWnd);
hBitmapDC = ::CreateCompatibleDC(pDC);
HBITMAP      hBitmap = ::LoadBitmap(hInst,(LPCTSTR)nResID);

HBITMAP hOld = ::SelectObject(hBitmapDC,hBitmap );

::BitBlt(pDC,0,0,10,10,hBitmapDC,0,0,SRCCOPY);

::SelectObject(hBitmapDC,hOld);
::DeleteObject(hBitmap);
::DeleteDC(hBitmapDC);




0
 
_corey_Commented:
That's about how DC/Object stuff goes.  You really need to keep it nicely cleared up for 98/etc because, if I'm not mistaken after this long, there are limited DC and GDI handles.
0
 
_corey_Commented:
Actually, just repeating the SelectObject(hBitmapDC, hBitmap) call should restore by itself.
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.