calling GdiplusStartup() and GdiplusShutdown() on different dlls

[tfs]

Suppose I develop the following MFC-extended dlls: A.dll, B.dll, C.dll, and
each has exported its own dll-init and dll-release functions. Suppose that
there is an app linking to A.dll and B.dll, and in turn B.dll links to C.dll.

Question:

For A.dll, B.dll, C.dll and even the app, can they call for their own
GdiplusStartup() to obtain their own tokens, and call their own
GdiplusShutdown(), without interfering the gdi+ objs in other dlls?

Reason:

For some dlls I develop, they will be loaded (using AfxLoadLibrary) only
when they are demanded. Therefore if the case described in the question can
work, then I do not need to concern about whether some gdi+ objs will be
invalidated because GdiplusShutdown() is being called somewhere else when
that dll is unloaded.

[Dee Earley]

On 01/02/2010 15:45, tfs wrote:
> Suppose I develop the following MFC-extended dlls: A.dll, B.dll, C.dll, and
> each has exported its own dll-init and dll-release functions. Suppose that
> there is an app linking to A.dll and B.dll, and in turn B.dll links to C.dll.
>
> Question:
>
> For A.dll, B.dll, C.dll and even the app, can they call for their own
> GdiplusStartup() to obtain their own tokens, and call their own
> GdiplusShutdown(), without interfering the gdi+ objs in other dlls?

It doesn't say that they can be called multiple times, but seeing as it
returns a token that you have to explicitly shutdown, it implies that
you can.

Normally, Init/Cleanup functions that don't use a token explicitly say
they are reference counted and can be called multiple times.

GdiplusShutdown says "Each call to GdiplusStartup should be paired with
a call to GdiplusShutdown." again implying that you can have multiple
tokens.

--
Dee Earley (dee.e...@icode.co.uk)
i-Catcher Development Team

iCode Systems

[tfs]

"Dee Earley" wrote:

> .
>

I looked at the following article from MS:

http://support.microsoft.com/default.aspx/kb/322909

and there is a paragraph, as quoted:

This problem occurs because the CImage class initializes and then shuts down
GDI+ by using the static nested class CInitGDIPlus. This class initializes
GDI+ before any CImage function that requires GDI+ is called. GDI+ is shut
down by calling GdiplusShutdown when the CInitGDIPlus class is destructed.
CInitGDIPlus is a static class that is destructed in a DLL in the context of
DllMain. The documentation states that you cannot call GdiplusShutdown in
DllMain.

As far as I interpret it right, multiple callings of GdiplusStartup() is
allowed, but the corresponding calls of GdiplusShutdown() must be nested. If
that is true, this will be a big trouble for my scenario, because I cannot
control the order of dll-release, even explicitly calling an exported
dll-release function.

For some developers, they experienced app hanging after calling
GdiplusShutdown().

Is GDI+ that horrible?

[Christian Kaiser]

> As far as I interpret it right, multiple callings of
> GdiplusStartup() is
> allowed, but the corresponding calls of GdiplusShutdown() must be
> nested. If
> that is true, this will be a big trouble for my scenario, because I
> cannot
> control the order of dll-release, even explicitly calling an
> exported
> dll-release function.
>
> For some developers, they experienced app hanging after calling
> GdiplusShutdown().
>
> Is GDI+ that horrible?

Yes. We also sometimes experience these problems with our add-on
DLLs. You mght consider to ONCE load and initialize GDIPLUS and leave
shutdown to the process cleanup of the OS.

Christian