Quote Originally Posted by Gizmo View Post
Nice function, very useful. Therefore I think there is a mistake on the indexes and for my part I would add a test if there is no number.
There's a slight error in the code I posted. If for example the number to compare is not at the end of the string, before ".jpg" but at the beginning followed by a underscore ("_"). The function will return a wrong and unstable value. Why? Because "." is before numbers and "_" after numbers in the ASCII table. As long as I am doing the native comparison for two numbers with a different length, a bug should pop up. Example with "1_..." & "12_..." sometimes it will return true sometimes false. But it should return the smallest which is always "1" (1 < 12).
Qt Code: 
  1. bool SailSlideShowWidget::compareNames(const QString& s1,const QString& s2)
  2. {
  3.     // ignore common prefix..
  4.     int i = 0;
  5.     while ((i < s1.length()) && (i < s2.length()) && (s1.at(i).toLower() == s2.at(i).toLower()))
  6.         ++i;
  7.     ++i;
  8.     // something left to compare?
  9.     if ((i < s1.length()) && (i < s2.length()))
  10.     {
  11.         // get number prefix from position i - doesnt matter from which string
  12.         int k = i-1;
  13.         //If not number return native comparator
  14.         if(!s1.at(k).isNumber() || !s2.at(k).isNumber())
  15.         {
  16.             //Two next lines
  17.             //E.g. 1_... < 12_...
  18.             if(s1.at(k).isNumber())
  19.                 return false;
  20.             if(s2.at(k).isNumber())
  21.                 return true;
  22.             return QString::compare(s1, s2, Qt::CaseSensitive) < 0;
  23.         }
  24.         QString n = "";
  25.         k--;
  26.         while ((k >= 0) && (s1.at(k).isNumber()))
  27.         {
  28.             n = s1.at(k)+n;
  29.             --k;
  30.         }
  31.         // get relevant/signficant number string for s1
  32.         k = i-1;
  33.         QString n1 = "";
  34.         while ((k < s1.length()) && (s1.at(k).isNumber()))
  35.         {
  36.             n1 += s1.at(k);
  37.             ++k;
  38.         }
  39.  
  40.         // get relevant/signficant number string for s2
  41.         //Decrease by
  42.         k = i-1;
  43.         QString n2 = "";
  44.         while ((k < s2.length()) && (s2.at(k).isNumber()))
  45.         {
  46.             n2 += s2.at(k);
  47.             ++k;
  48.         }
  49.  
  50.         // got two numbers to compare?
  51.         if (!n1.isEmpty() && !n2.isEmpty())
  52.             return (n+n1).toInt() < (n+n2).toInt();
  53.         else
  54.         {
  55.             // not a number has to win over a number.. number could have ended earlier... same prefix..
  56.             if (!n1.isEmpty())
  57.                 return false;
  58.             if (!n2.isEmpty())
  59.                 return true;
  60.             return s1.at(i) < s2.at(i);
  61.         }
  62.     }
  63.     else
  64.     {
  65.         // shortest string wins
  66.         return s1.length() < s2.length();
  67.     }
  68. }
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I hope this is correct and at least now I get a decent result with all strings.

Giz