OSX popup accent menu does not appear when holding letter 'e'.

Since OS 10.8, it is possible to enter accented characters by holding down the letter that should be accented for a brief period. E.g. to type é, hold down letter e for a second, then a popup showing e with various accents appears to choose from.

The feature is described here: https://support.apple.com/en-us/HT201586

From trying out other applications, it seems like this is available in the text input fields of nearly every application on OSX, but is not available in any Qt applications. I tried both a qtwidgets application (Examples/Qt-5.5/widgets/richtext) and a qtquick application (Examples/Qt-5.5/quick/controls/texteditor)

From what I have read, it should be available automatically for any application that implements the NSTextInputClient protocol. I confirmed that Qt does implement NSTextInputClient.

It can also be disabled by setting the ApplePressAndHoldEnabled value in [NSUserDefaults standardUserDefaults] to false. This value is intended to restore key repeat behaviour, which was present before OS10.8, for applications that prefer key repeat to accented characters. I confirmed that this value is not set when I was testing. (I also tried setting it to true, which produced no effect).

I'm not sure if this might be intentional, to get key repeat behaviour for all Qt applications, but I couldn't find anything in the code or documentation indicating that that was the case.