As described here, it's standard on macOS for the user to be able to hold down a key on the keyboard, or long-press it, and a popover with accented characters appears, allowing the user to select the desired accented version, either with the arrow keys or by typing the appropriate number shown in the popover.
Versions of Qt prior to Qt 5.11 did not show this popover at all on macOS, but Qt 5.11 does. Unfortunately, it continues inputting the repeated character while the popover is shown.
- Start a new Qt Widgets form in the Designer in Qt Creator.
- Add a QLineEdit control.
- Choose Tools > Form Editor > Preview to preview the form.
- Put the keyboard focus in the QLineEdit control.
- Press and hold the e key.
EXPECTED: The accented character popover should appear, allowing you to choose the accented character you want to input.
ACTUAL: A stream of e characters is input into the line edit, and the popover appears. If you type e.g. 3 to select the third accented character, "3" is also entered into the line edit, along with the actual accented character chosen.
There doesn't appear to be any workaround for this, e.g. to prevent the alternate characters popover from appearing.