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/*
* This file is part of mpv.
*
* mpv is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* mpv is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#include <windows.h>
#include <winternl.h>
#include <pthread.h>
#include "exclusive_hack.h"
// Missing NT API definitions
typedef enum _MP_MUTANT_INFORMATION_CLASS {
MpMutantBasicInformation
} MP_MUTANT_INFORMATION_CLASS;
#define MUTANT_INFORMATION_CLASS MP_MUTANT_INFORMATION_CLASS
#define MutantBasicInformation MpMutantBasicInformation
typedef struct _MP_MUTANT_BASIC_INFORMATION {
LONG CurrentCount;
BOOLEAN OwnedByCaller;
BOOLEAN AbandonedState;
} MP_MUTANT_BASIC_INFORMATION;
#define MUTANT_BASIC_INFORMATION MP_MUTANT_BASIC_INFORMATION
static pthread_once_t internal_api_load_ran = PTHREAD_ONCE_INIT;
static bool internal_api_loaded = false;
static HANDLE excl_mode_mutex;
static NTSTATUS (NTAPI *pNtQueryMutant)(HANDLE MutantHandle,
MUTANT_INFORMATION_CLASS MutantInformationClass, PVOID MutantInformation,
ULONG MutantInformationLength, PULONG ReturnLength);
static void internal_api_load(void)
{
HMODULE ntdll = GetModuleHandleW(L"ntdll.dll");
if (!ntdll)
return;
pNtQueryMutant = (void*)GetProcAddress(ntdll, "NtQueryMutant");
if (!pNtQueryMutant)
return;
excl_mode_mutex = OpenMutexW(MUTANT_QUERY_STATE, FALSE,
L"Local\\__DDrawExclMode__");
if (!excl_mode_mutex)
return;
internal_api_loaded = true;
}
bool mp_w32_is_in_exclusive_mode(void)
{
pthread_once(&internal_api_load_ran, internal_api_load);
if (!internal_api_loaded)
return false;
// As far as we can tell, there is no way to know if a specific OpenGL
// program is being redirected by the DWM. It is possible, however, to
// know if some program on the computer is unredirected by the DWM, that
// is, whether some program is in exclusive fullscreen mode. Exclusive
// fullscreen programs acquire an undocumented mutex: __DDrawExclMode__. If
// this is acquired, it's probably by mpv. Even if it isn't, the penalty
// for incorrectly guessing true (dropped frames) is better than the
// penalty for incorrectly guessing false (tearing.)
// Testing this mutex is another problem. There is no public function for
// testing a mutex without attempting to acquire it, but that method won't
// work because if mpv is in fullscreen, the mutex will already be acquired
// by this thread (in ddraw.dll) and Windows will happily let it be
// acquired again. Instead, use the undocumented NtQueryMutant function to
// test the mutex.
// Note: SHQueryUserNotificationState uses this mutex internally, but it is
// probably not suitable because it sends a message to the shell instead of
// testing the mutex directly. mpv will check for exclusive mode once per
// frame, so if the shell is not running or not responding, it may cause
// performance issues.
MUTANT_BASIC_INFORMATION mbi;
NTSTATUS s = pNtQueryMutant(excl_mode_mutex, MutantBasicInformation, &mbi,
sizeof mbi, NULL);
if (!NT_SUCCESS(s))
return false;
return !mbi.CurrentCount;
}
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