Cleaning up ( SelectObject )

[JohnOne]

Something I'm not certain about with regards this function, if anyone can help.

msdn says

The SelectObject function selects an object into the specified device context (DC). The new object replaces the previous object of the same type.

So does that mean I only need to clean up the original object?

Example:

HDC hdc = GetDC(NULL);
HDC hdcMEM = CreateCompatibleDC(hdc);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, iWidth, iHeight);
SelectObject(hdcMEM,hBitmap);

DeleteObject(hBitmap);
DeleteDC(hdcMEM);

Is that sufficient to clean that up, or do I need to assign are variable to SelectObject and clean that up too, or just the new object?

HDC hdc = GetDC(NULL);
HDC hdcMEM = CreateCompatibleDC(hdc);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, iWidth, iHeight);
HANDLE hObj = SelectObject(hdcMEM,hBitmap);

DeleteObject(hObj);
DeleteDC(hdcMEM);

[trancexx]

Usually if you don't have the use for replaced you do this:

::DeleteObject(::SelectObject(hdcMEM,hBitmap));

... And you should call ReleaseDC for hdc.

Edited February 28, 2013 by trancexx

[JohnOne]

Sounds sensible.

Thank you kindly ma'am.

[UEZ]

Something like that maybe in AutoIt notation:

$hDC = _WinAPI_GetDC(0)
$hdcMEM = _WinAPI_CreateCompatibleDC($hDC)
$hBitmap = _WinAPI_CreateCompatibleBitmap($hDC, $iWidth, $iHeight)
_WinAPI_SelectObject ($hdcMEM, $hBitmap)


_WinAPI_DeleteObject($hDC)
_WinAPI_ReleaseDC(0, $hDC)
_WinAPI_DeleteDC($hdcMEM)
_WinAPI_DeleteObject($hBitmap)
_WinAPI_DeleteDC($hDC)

Br,

UEZ

Edited February 28, 2013 by UEZ

[JohnOne]

Are those three operations on $hDC really necessary, or just being thorough?

[UEZ]

I think thorough but you can create a loop with 1000 calls and leave some off to see whether memory consumption is increasing constantly to check for memory leaks.

Br,

UEZ

[trancexx]

You must not call DeleteDC for hdc.

Edited February 28, 2013 by trancexx

[JohnOne]

Thanks UEZ.

Just finishing up on "SearchPixel" function I was talking about yesterday

[forever0donotknowme]

UEZ & JohnOne had beautiful picture in profile

[UEZ]

I'm really a big fan of them - one of the best comedians ever!

Br,

UEZ

[JohnOne]

One, which one?