== Introduction ==

This recipe offers a `wxComboBox` subclass that will display the first entire item from its
dropdown list whose initial characters match those that the user has typed, with untyped characters selected.

== What Objects are Involved ==

Only `wx.ComboBox` itself.

== Process Overview ==

When the user keys a 'c', for instance, we want the code to identify the first combobox
choice that begins with 'c', and to display it in the combobox with the characters following 'c' "selected".
One does this in response to the wx.EVT_TEXT event. When one changes the content of the combobox, however, 
this ellicits another wx.EVT_TEXT event and this leads to infinite recursion.

To prevent this we arrange to ignore the second wx.EVT_TEXT that is ellicited.

Similar code is used to make it possible for the control to respond properly to backspaces, and when
the user selects a choice from the dropdown list.

== Special Concerns ==

The code in the loop in the wx.EVT_TEXT handler might well be changed so that the combobox would accept 
plugins providing different suggestion options; for example, the most frequently selected option could be offered.

== Code Sample ==

{{{
#!python
import wx
 
class PromptingComboBox(wx.ComboBox) :
    def __init__(self, parent, value, choices=[], style=0, **par):
        wx.ComboBox.__init__(self, parent, wx.ID_ANY, value, style=style|wx.CB_DROPDOWN, choices=choices, **par)
        self.choices = choices
        self.Bind(wx.EVT_TEXT, self.EvtText)
        self.Bind(wx.EVT_CHAR, self.EvtChar)
        self.Bind(wx.EVT_COMBOBOX, self.EvtCombobox) 
        self.ignoreEvtText = False
        
    def EvtCombobox(self, event):
        self.ignoreEvtText = True
        event.Skip()
        
    def EvtChar(self, event):
        if event.GetKeyCode() == 8:
            self.ignoreEvtText = True
        event.Skip()
        
    def EvtText(self, event):
        if self.ignoreEvtText:
            self.ignoreEvtText = False
            return
        currentText = event.GetString()
        found = False
        for choice in self.choices :
            if choice.startswith(currentText):
                self.ignoreEvtText = True
                self.SetValue(choice)
                self.SetInsertionPoint(len(currentText))
                self.SetMark(len(currentText), len(choice))
                found = True
                break
        if not found:
            event.Skip()

class TrialPanel(wx.Panel):
    def __init__(self, parent):
        wx.Panel.__init__(self, parent, wx.ID_ANY)
        
        choices = ['grandmother', 'grandfather', 'cousin', 'aunt', 'uncle', 'grandson', 'granddaughter']
        for relative in ['mother', 'father', 'sister', 'brother', 'daughter', 'son']:
            choices.extend(self.derivedRelatives(relative))

        cb = PromptingComboBox(self, "default value", choices, style=wx.CB_SORT) 

    def derivedRelatives(self, relative):
        return [relative, 'step' + relative, relative + '-in-law']


if __name__ == '__main__':
    app = wx.App()
    frame = wx.Frame (None, -1, 'Demo PromptingComboBox Control', size=(400, 50))
    TrialPanel(frame)
    frame.Show()
    app.MainLoop()
}}}

=== Comments ===

Any comments or suggestions, to [[Bill Bell]], please.