2015 MacBook Pro Retina 13 running OSX Yosemite 10.10.5
This is just a little weird bug I found: While running DeSmuME, the battery percentage indicator doesn't update at all. Doesn't indicate whether plugged in or not, and doesn't show battery draining or gaining charge.
Easily fixed by toggling "show percentage" on and off, it updates.
Perhaps this is just an effect of the amount of memory in use, rather in DeSmuME itself, but it did act normally after I quit the app, and it's never happened during other times I've been using a lot of memory.