I get a flicker when first creating a calc window. This is because the Sdr idle handler:

>	vcllo.dll!OpenGLSalGraphicsImpl::flush() Line 2001	C++
 	vcllo.dll!OpenGLSalGraphicsImpl::PostDraw() Line 246	C++
 	vcllo.dll!OpenGLSalGraphicsImpl::DoCopyBits(const SalTwoRect & rPosAry, OpenGLSalGraphicsImpl & rImpl) Line 1664	C++
 	vcllo.dll!WinOpenGLSalGraphicsImpl::copyBits(const SalTwoRect & rPosAry, SalGraphics * pSrcGraphics) Line 27	C++
 	vcllo.dll!WinSalGraphics::copyBits(const SalTwoRect & rPosAry, SalGraphics * pSrcGraphics) Line 63	C++
 	vcllo.dll!SalGraphics::CopyBits(const SalTwoRect & rPosAry, SalGraphics * pSrcGraphics, const OutputDevice * pOutDev, const OutputDevice * pSrcOutDev) Line 590	C++
 	vcllo.dll!OutputDevice::drawOutDevDirect(const OutputDevice * pSrcDev, SalTwoRect & rPosAry) Line 720	C++
 	vcllo.dll!OutputDevice::DrawOutDev(const Point & rDestPt, const Size & rDestSize, const Point & rSrcPt, const Size & rSrcSize, const OutputDevice & rOutDev) Line 595	C++
 	svxcorelo.dll!sdr::overlay::OverlayManagerBuffered::ImpBufferTimerHandler(Idle * __formal) Line 326	C++
 	svxcorelo.dll!sdr::overlay::OverlayManagerBuffered::LinkStubImpBufferTimerHandler(void * instance, Idle * data) Line 209	C++
 	vcllo.dll!Link<Idle *,void>::Call(Idle * data) Line 84	C++
 	vcllo.dll!Idle::Invoke() Line 26	C++
 	vcllo.dll!ImplSchedulerData::Invoke() Line 41	C++
 	vcllo.dll!Scheduler::ProcessTaskScheduling(bool bTimerOnly) Line 171	C++
 	vcllo.dll!ImplYield(bool i_bWait, bool i_bAllEvents, const unsigned long nReleased) Line 519	C++
 	vcllo.dll!Application::Yield() Line 535	C++
 	vcllo.dll!Application::Execute() Line 471	C++
 	sofficeapp.dll!desktop::Desktop::DoExecute() Line 1292	C++
 	sofficeapp.dll!desktop::Desktop::Main() Line 1611	C++
 	vcllo.dll!ImplSVMain() Line 170	C++
 	vcllo.dll!SVMain() Line 208	C++
 	sofficeapp.dll!soffice_main() Line 96	C++
 	soffice_real.exe!sal_main() Line 48	C
 	soffice_real.exe!main(int argc, char * * argv) Line 47	C
 	soffice_real.exe!WinMain(void * _hinst, void * _dummy, char * _cmdline, int _nshow) Line 47	C
 	soffice_real.exe!__tmainCRTStartup() Line 618	C
 	soffice_real.exe!WinMainCRTStartup() Line 466	C
 	kernel32.dll!@BaseThreadInitThunk@12()	Unknown
 	ntdll.dll!___RtlUserThreadStart@8()	Unknown
 	ntdll.dll!__RtlUserThreadStart@8()	Unknown

Has a higher priority than the re-paint method; which is far from ideal.