In qlineedit_p.cpp -> QLineEditIconButton::paintEvent(), Qt sets the "clear" icon size to 32px when the line-edit height is greater than 34px. That's wrong because it ignores the fact that margins may not be the same in different style plugins – not all of them are like Fusion and, even with Fusion, it can result in a blurred icon when the font is big enough (see the attatched screenshot).

In Qt4, we could add a nice clear tool-button in the code without this problem.