klubalo / dd4seven

Desktop Duplication API implementation for Win7

Desktop Duplication for Windows 7

This project aims to implement parts of the Desktop Duplication API for Windows 7.

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Warning: DO NOT USE IN PRODUCTION! You have been warned.

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What works

• Acquiring desktop and mouse cursor images using the IDXGIOutputDuplication interface.
• It doesn't matter whether D3D10 or D3D11 is used, and no DXGI upgrade is required.

What's broken

• A running DWM (= Aero theme) is required.
• The reported timings are improvised and completely unusable for synchronization.
• Change and move regions are not supported.
• All other metadata or reported information is garbage, too.
• Mouse cursor and desktop updates are always delivered together.
• The 64bit Debug builds are mysteriously crashing (though I'm tempted to blame the compiler for this). The relese builds work fine.
• It will totally break everything but Win7. But that's OK, because Win8 and later contain the functionality natively. Just remember to uninstall before upgrading.

How to install

• There are no precompiled binaries. You can build it yourself using a recent MinGW-w64 toolchain. I personally only tried cross-compiling from my Fedora system, but you can probably adapt the Makefile to build on Cygwin or MinGW.
• For 32bit (x86) systems: Drop the x86 binaries (dd4seven-dwm.dll, dd4seven-api.dll) into %WINDIR%\System32.
• For 64bit (amd64) systems: Drop the amd64 binaries (dd4seven-dwm.dll, dd4seven-api.dll) into %WINDIR\System32. and the x86 api binary (dd4seven-api.dll) into %WINDIR%\SysWOW64.
• Add dd4seven-dwm.dll to the AppInitDLLs registry value.
• Restart the DWM (i.e. run tskill dwm.exe, restart the UxSms service, or just log off and on again)

How to use in applications

Use the DuplicateOutput function, exported by dd4seven-api.dll, as replacement for IDXGIOutput1::DuplicateOutput:

ID3D11Device *device; // D3D10 is also okay
IDXGIOutput *output;   // on Win7
IDXGIOutput1 *output1; // on Win8
IDXGIOutputDuplication *dupl = nullptr;

HMODULE ddApi = LoadLibraryA("dd4seven-api.dll");
if (ddApi) {
    // Win7
    HRESULT (__stdcall *duplicate)(IDXGIOutput *output, IUnknown *device, IDXGIOutputDuplication **dupl);
    duplicate = (decltype(duplicate))GetProcAddress(ddApi, "DuplicateOutput");

    duplicate(output, device, &dupl);
} else {
    // Win8
    output1->DuplicateOutput(device, &dupl);
}

Credits

This project uses the MinHook library by Tsuda Kageyu. See minhook/LICENSE.txt for details.