How to disable app labels in KDE taskbar

I've had this exact problem on all my newer KDE installations. It seems to be a bug in KDE though I've not seen anything specific on it. A quick fix that I've used is to change the height of the toolbar. It seems that if you change the height to something smaller, the problem disappears forever. It's just that the default height is buggy.

Depending on how your display/xsession manager is set up, ~/.bashrc may not be sourced before startkde is called, so if that's where you're setting up $JAVA_HOME, nothing on your KDE desktop may see it.

Helpfully, startkde is set up to source *.sh from every directory in kde4-config --path lib | tr : '\n' | sed -n -e 's,/lib[^/]*/,/env/,p'. This likely contains ~/.kde4/env or similar, so if you want a variable to be present KDE-sessionwide, just drop a shell script with an export in there.