Hi,
I would like to control the input of a QlineEdit in order to avoid the insertion of some characters.
I've written down the subsequent code that every time the user insert a new element in the QLineEdit, controls the input and erase the last character of the line if it is not valid!


Qt Code: 
  1. void ElaborationOffset::ElaborationOffset()
  2. {
  3.     [...]
  4.     par2 = new QLineEdit;
  5.     connect(par2,SIGNAL(textChanged(QString)),this,SLOT(updateGraph(QString)));
  6.     [...]
  7. }
  8.  
  9. void ElaborationOffset::updateGraph(QString dummy)
  10. {
  11.     bool ok;
  12.     int pos=0;
  13.     QString par2Str = par2->text();
  14.  
  15.     QRegExp expr("[-,+]{0,1}[0-9]+[.,,][0-9]+");
  16.     QRegExpValidator v(expr, 0);
  17.  
  18.     if(v.validate(par2Str,pos) == QValidator::Invalid)
  19.     {
  20.         par2->backspace();
  21.         return;
  22.     }
  23.  
  24.    [...]
  25. }
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It works... But the problem is that when I try to insert a non valid char, the updateGraph slot is called 2 times, because of the par2->backspace(); instruction that triggers another signal--->slot call !!!
I think there is no mask that I can use to avoid this problem, because I cannot know the number format (it depends on the particular value)...! For example I can insert -0.0002, but also 12900!!!
Any hints to solve this problem?

Thank you all.
Alex