[wx-dev] #9560: improve compatibility of wxDateTime::ParseFormat() with old Unicode build

[wxTrac]

Ticket URL: <http://trac.wxwidgets.org/ticket/9560>

#9560: improve compatibility of wxDateTime::ParseFormat() with old Unicode build
----------------------------------------------------------+-----------------
 Reporter:  vadz                                          |       Owner:  vadz   
     Type:  defect                                        |      Status:  new    
 Priority:  normal                                        |   Milestone:  2.9.0  
Component:  base                                          |     Version:  2.9-svn
 Keywords:  unicode compatibility wxDateTime ParseFormat  |   Blockedby:         
    Patch:  0                                             |    Blocking:         
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 Currently code like
 {{{
 const wxChar *p = dt.ParseFormat(wxT("..."));
 }}}
 compiles. And so does
 {{{
 const char *p = dt.ParseFormat("...");
 const char *q = dt.ParseFormat(wxString());
 const char *s = dt.ParseFormat(wxString().c_str());
 }}}
 so compatibility with the old ANSI build is good.

 But the last 2 lines don't compile if `wxChar` is used for the variables
 to which return value is assigned. To fix this we need to return an object
 convertible to either narrow or wide string from `ParseFormat()` but it
 can't be `wxCStrData` because it can't be `NULL` (but return value of this
 function can).

 So the idea would be to add some `wxAnyStr` (name by Vaclav, thanks) which
 would just store any kind of string passed to it (without copying it), a
 la `wxFormatString`, but also be convertible to either kind of string.
 This should improve compatibility and also allow us to have only one
 overload of the method above instead of the 4 we have currently.


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Ticket URL: <http://trac.wxwidgets.org/ticket/9560>