title: Qt custom form for QGIS and autocompleted data entering with “validation check”
body: <p>In Qt-Designer I created a custom form where I can choose several species names in two different combo boxes. This combo boxes are linked via "value relation" to the accordant non spatial tables (gattung and art) in my SpatiaLite database. The whole species name consists of "gattung" and "art". Because these tables ("gattung" and "art") contain a lot of species names (latin) which one can choose I think about an eased editing feature.</p>
  
  <p>1) I'd like to generate an autocompletion when entering the first 3 characters into a line edit (instead of a combo box) for "gattung" so that on can choose only these species that beginns for example with "Que" from a list.</p>
  
  <p>2) When I've chosen a name that matches with these 3 characters for example "Que" for "Quercus", in the second field "art" only valid names can be chosen. For example "petrea" ore "robur" as a subset of the whole "art-names" which one can choose. Valid names are "Quercus robur" or "Quercus petrea". This could be done via line edit when entering 4 characters or with a combo box.</p>
  
  <p>I thought about python and a lettercode (Quepetr for Quercus petrea) to solve this but doesn't know where to start and also where to enter the code for the widgets in QT-Designer.</p>
  
  <p>I'm grateful for any help or idea!</p>