In Tiny Core Linux 64-bit flwm_topside, it appears that if you click on a window, then move the cursor to a different window and click on one of that window's controls, the focus stays on the original window and it's the one that responds to the control click.
Sorry, kind of a long-winded description but can't think of how else to describe it!
Thane
I'm not able to duplicate this on Tiny Core 16.0, x86_84.
I killed off jwm and started flwm_topside (no reboot) then opened to terminal windows from the wbar icon. Made one of them active then licked the close button on the other one. The one on which I clicked the close button did close and the other did not.
FWIW, I have been fooling around with MikeLockmoore's fluff_testing extension so maybe it has loaded something relevant. Equally possible that I just didn't understand the issue completely because... y'know... me.
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Edit as of twenty minutes later:
The regular flwm seems to behave the same as flwm_topside - which is good.
As an aside, I just realized that a bunch of my personal tweaks and customizsations (an icon for this, a display for that, things not directly relevant to the window manager itself but sometimes relevant to the overall system) are attached to the jwm "tray"... and they don't appear in the flwm tray at all! (Or should I say they don't appear in the flwm "no tray".) So there's a whole nother project to play with.