The transition from Qt 5.7 to 5.8 made scrolling and editing operations in the QtCreator text editor visibly sluggish, especially under load. The problem is most apparent when editing a C++-style comment: the entered text appears on screen with the delay as big as 100s of ms. Validated by building the same version of QtCreator (4.2.0) with Qt 5.7 and 5.8 (installed via Homebrew). The problem is present in official QtCreator releases (appeared after upgrading to version 4.2.1).