The KDE display scales up and cannot get back

I’m using opensuse Leap 42.1, KDE.
Today I was using chrome and I use Ctrl + + to scale up the content in browser, and somehow the window switched to desktop and everything in my monitor scaled up, when I switched back to browser, the content in browser was even larger, and my monitor can not display all of the system and only displayed a rectangle area eighth of the size or even less which moves along with the mouse, and everything was blur because it displayed something 400300 pixels or so in a 19201080 monitor.
I thought it was just one time thing and will be okay after I logout login or restart, but I was wrong, I logged out and logged in, the bug was still there, I restarted and it was still there. I have no idea how to fix it, please help!
Many thanks, Li

could this be desktop zoom? look in system-settings:desktop-behaviour:desktop-effects:<zoom>. meta 0 (zero) i believe is shortcut to default.