how to vsync winapi drawings

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how to vsync winapi drawings



I want to draw a frame number on my monitor screen sequentially



0 1 2 3 4 5 6 7 ...



One number per one physical frame (100 times per second
on 100 Hz refresh rate monitor) Is it possible under
winapi/gdi? How to do it?





100 times per second - this will be impossible to see. Anyway, vsync solution exists only in DirectX and OpenGL. Maybe also in Direct2D - I am not sure.
– Alex F
Sep 13 '12 at 16:20




2 Answers
2



Neither GDI nor GDI+ give you access to the vsync signal.



The deprecated DirectDraw APIs had a way to wait for the vsync. Newer DirectX APIs basically do it for you when you call the appropriate Present method (though I believe there are options to not wait for the vsync).





Could you explain "the appriopriate Present method" - I do not understand it. How to do a thing, I asked for: "1" on first monitor frame "2" on the secont and so on...? Under GDI I use blitting call but my prog generates 1000 fps sometimes and 900 of it are wasted :/
– grunge fightr
Sep 13 '12 at 19:00






Anything more than ~50fps is wasted anyway as Humans can't see it.
– Deanna
Sep 14 '12 at 12:38





@Deanna: It's not that clear cut. See 100fps.com/how_many_frames_can_humans_see.htm . And they point may not be for human consumption. Perhaps it's for making some timing display that will be captured by a high-speed camera.
– Adrian McCarthy
Sep 14 '12 at 19:37



Modern versions of have the Desktop Window Manager (a compositor. See https://en.wikipedia.org/wiki/Desktop_Window_Manager). You can ask it to block until "some event" occurs that is sync'd to the video frame rate. Just call DwmFlush(). I won't link to the docs because the link will go stale.



On my machine, my app is descheduled while waiting for DwmFlush(). In other words it doesn't waste CPU cycles busy-waiting, which is nice.



I believe Windows Vista and 7 had the DWM, but it could be disabled. On Windows 8 and above it is always present.






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