image_view causes 100% CPU usage

[rursprung]

when i run image_view (using ros2 run image_view image_view --ros-args -r image:=/my/image) for 1-2 topics then the CPU usage goes up to 100%. i've tested this on several devices, all with the same result.

this is with ROS jazzy, image-view version 5.0.5 from apt (5.0.6 hasn't been synced to apt yet, but based on the commits it doesn't include anything relevant for this)

[rursprung]

see this screenshot of htop - this is running in a WSL2 Ubuntu 24.04 VM and you can see that i'm running image_view 4x (to see 4 different topics) and each one uses 100% of a CPU core:

this is at a time where there aren't even any new messages to be processed (i was playing a ROS bag but already stopped ros2 bag play but hadn't stopped the image_view nodes yet)

this is with latest & greatest image_view from the jazzy branch compiled locally.

[mikeferguson]

I think this is because if there is no new image, the window thread never sleeps - I created a possible fix in #1082