Some examples run at 100% CPU usage

[nh2]

E.g. libui-simple-counter-example, 100% CPU in htop

In strace it's busy-looping around poll (because poll() is given a 0-timeout):

[pid 31736] recvmsg(11, 0x7ffe9da1db20, 0) = -1 EAGAIN (Resource temporarily unavailable)
[pid 31736] poll([{fd=11, events=POLLIN}, {fd=12, events=POLLIN}, {fd=13, events=POLLIN}], 3, 0) = 0 (Timeout)
[pid 31736] recvmsg(11, 0x7ffe9da1db20, 0) = -1 EAGAIN (Resource temporarily unavailable)
[pid 31736] poll([{fd=11, events=POLLIN}, {fd=12, events=POLLIN}, {fd=13, events=POLLIN}], 3, 0) = 0 (Timeout)

Not sure if it's an issue with libui or haskell-libuil, or the example code calling the functions wrong.

[nh2]

I can confirm the upstream libui tester program as built by make tester doesn't have this problem, it has no CPU usage on idle and no strace output. It passes -1 to poll() for infinite timeout.

[nh2]

The fork you use also doesn't have this problem. So it seems to be somewhere in the Haskell code's usage of the library.

[nh2]

OK, I was wrong. Not all examples busy loop. READMEExample is fine. It's simply that loops written explicitly in Haskell like this one

haskell-libui/examples/SimpleCounter.hs

Lines 42 to 44 in 4d1fad2

	whileM_ getHasMain $ do
	h <- uiMainStep 0
	when (h == 0) $ threadDelay (1000 * 1000 * 16)

busy loop.