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Fix CPU usage when using vsync #90

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Fix CPU usage when using vsync #90

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19 changes: 11 additions & 8 deletions nico/backends/sdl2.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -1876,15 +1876,18 @@ proc run*() =
if configInitialised:
step()

if not vsyncEnabled:
# calculate how long we should sleep for to reduce cpu usage, if we have vsync this will do it for us
let frameEndTime = getPerformanceCounter()
let frameTime = ((frameEndTime - frameStartTime)*1000).float / getPerformanceFrequency().float
let targetFrameTime = 1000.0 / frameRate.float
let sleepTime = targetFrameTime - frameTime
#echo "frame time: ", frameTime, " target: ", targetFrameTime, " sleep time: ", sleepTime
if sleepTime > 0f:
# calculate how long we should sleep for to reduce cpu usage
let frameEndTime = getPerformanceCounter()
let frameTime = ((frameEndTime - frameStartTime)*1000).float / getPerformanceFrequency().float
let targetFrameTime = 1000.0 / frameRate.float
let sleepTime = targetFrameTime - frameTime
# echo "frame time: ", frameTime, " target: ", targetFrameTime, " sleep time: ", sleepTime
if sleepTime >= 1.0:
if vsyncEnabled:
delay(1) # if we have vsync this will wait for us, but delay(1) is necessary to keep CPU usage down
else:
delay(sleepTime.uint32)

sdl.quit()

when defined(emscripten):
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