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gwin32: Add g_win32_clear_com()

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This is quite similar in concept to what g_clear_object() does, except
that is meant to deal with Windows COM objects. Note that there is a
separate C++ version available for this as there are COM interfaces that
are available in C++ only, such as DirectWrite that is shipped with the
Windows SDK (albeit a C interface is provided with the mingw-w64
toolchain.

This will call `->Release()` on the non-NULL COM object referenced by its
pointer  and sets the COM object to NULL; if the pointer refers to a
NULL COM object, this is a no-op.
This commit is contained in:
Chun-wei Fan 2024-11-11 17:42:53 +08:00
parent be72b8cc4a
commit aff6b930a1
1 changed files with 57 additions and 0 deletions
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57
glib/gwin32.h
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@ -43,6 +43,11 @@ G_BEGIN_DECLS
#ifdef G_OS_WIN32
/* needed include for C++ builds; including this in C mode will cause havoc of type conflicts */
#ifdef __cplusplus
#include <unknwn.h>
#endif
/*
* To get prototypes for the following POSIXish functions, you have to
* include the indicated non-POSIX headers. The functions are defined
@ -135,8 +140,60 @@ gboolean g_win32_check_windows_version (const gint major,
const gint spver,
const GWin32OSType os_type);
/**
* g_win32_clear_com:
* @com_obj: (not optional) (nullable): Pointer to COM object pointer to release and clear
*
* Releases the referenced COM object, and clears its pointer to `NULL`.
*
* The @com_obj pointer must not be `NULL`.
*
* If @com_obj references a `NULL` COM object, this function is a no-op.
*
* This is equivalent to `g_clear_object()` for dealing with
* Windows COM objects.
*
* Since: 2.84
*/
#ifndef __cplusplus
#define g_win32_clear_com(com_obj) \
G_STMT_START {\
IUnknown **unknown_com_obj = (IUnknown **)(com_obj); \
\
if (*unknown_com_obj) \
{ \
(*unknown_com_obj)->lpVtbl->Release (*unknown_com_obj); \
*unknown_com_obj = NULL; \
} \
} G_STMT_END \
GLIB_AVAILABLE_MACRO_IN_2_84
#endif
G_END_DECLS
#ifdef __cplusplus
/*
* There are COM objects that only have C++-style definitions, such as DirectWrite
* from the Windows SDK (albeit a C interface is provided for the mingw-w64 toolchain),
* so we need to have a C++ version for this
*/
template <typename com_interface>
inline void
g_win32_clear_com (com_interface **com_obj)
{
IUnknown **unknown_com_obj = reinterpret_cast<IUnknown **>(com_obj);
if (*unknown_com_obj != NULL)
{
(*unknown_com_obj)->Release ();
*unknown_com_obj = NULL;
}
}
#endif
#endif /* G_PLATFORM_WIN32 */
#endif /* __G_WIN32_H__ */