Scrolling mouse wheel will change font size

[colinxp]

Hello everyone,

Recently I have installed Gentoo on my new computer. I have installed plasma 5 as my desktop environment. It looks very nice.

I am now facing one problem. When I scrolled my mouse wheel in Konsole, Firefox, or Kate editor, the text size would automatically be increased or decreased, although I did not press the ctrl key at all. This phenomenon happened very often. It is very annoying, because the font size changed continuously, when I scrolled my mouse wheel.

Does anyone also have the same experiences? Thanks in advance for your suggestions.