QLineEdit lost focus

[codebehind]

I have an application with some QLineEdit elements. Their signal lostfocus is conected with the QDialog slot which i defined "SetKoraki()".

Then i have a button "btnGraf" which opens another window - a widget derivered from a QwtPlot. When the window opened the main dialog lost the focus and it is OK.
What i don't understand is why the QLineEdit set the signal lostfocus??
I've tried to workaround whit using the function isModified(), but it looks like the text in the QLineEdit has been changed. but it hasn't?

the project sourec files are attached.