How do I fix strange cursor behavior in QLineEdit using inputMask containing spaces?

HowardHarkness

I noticed some strange behavior in QLineEdit after adding an inputMask. What I wanted was a binary display of a value, in groups of 4 for readability, and a hex display, also grouped by 4 hex chars. Then I added code to keep them in synch.

I added inputMasks as follows:

const QString hexDisplayMask("HHHH HHHH");
const QString binDisplayMask("BBBB BBBB BBBB BBBB BBBB BBBB BBBB BBBB");
...
ui->scratchPadRegisterLineEdit->setInputMask(binDisplayMask);
ui->scratchPadRegisterHexLineEdit->setInputMask(hexDisplayMask);

The input mask with spaces had the desired effect on the display:

However, the cursor position is one position off to the right of the character to edit in the binary display (shown), and also in the hex display when selected.

I have not used Qt for a while (last time was over 10 years ago), so I may have missed something important in the evolution of how the QLineEdit is handled. I think I can come up with a workaround, but I have not thought of any that I would consider elegant.

I can just leave the spaces out of the inputMask, and the cursor behaves -- but the output is much harder to read.

I hope I can find a solution to this that will not confuse my client/customer.

I am using Qt 5.14 (I am stuck with that due to client contraints).

Pl45m4

@HowardHarkness

Hi there was a similar topic / question few years ago.
@SGaist explained why there is one additional space after every mask -> to allow text selection by keyboard.
Of course Ctrl + A kinda "hacks" it (to select all, at least) and if you dont need it, you could implement a workaround, but unfortunately there is no "Qt-way" to switch it off.

https://forum.qt.io/topic/60633/qlineedit-using-input-mask-with-blank-space-replacement-cursor-select-replacement-char