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