If needed, perform resize in each update().
Client window may be too big, it must be resized to a certain reasonable size. Sometimes resizing in the constructor is not enough because it is too early and the client window is not fully initialized. Even if client window is resized, on first update it reverts back to original size (or just ignores the first request - some kind of a race condition).
In addition, I applied some rules from: https://community.kde.org/Policies/Kdelibs_Coding_Style