Use wxString() instead of "" for empty strings

This will allow this code to work even when implicit conversion from
"const char*" is disabled in wxString and is already marginally more
efficient even now.

See https://github.com/wxWidgets/wxWidgets/pull/782

include/wx/bmpbuttn.h

@@ -59,7 +59,7 @@ public:
         // And we also use wxBU_EXACTFIT to avoid being resized up to the
         // standard button size as this doesn't make sense for bitmap buttons
         // which are not standard anyhow and should fit their bitmap size.
-        return wxButton::Create(parent, winid, "",
+        return wxButton::Create(parent, winid, wxString(),
                                 pos, size,
                                 style | wxBU_NOTEXT | wxBU_EXACTFIT,
                                 validator, name);

include/wx/stc/stc.h

@@ -5239,7 +5239,7 @@ public:
 
     virtual void Remove(long from, long to) wxOVERRIDE
     {
-        Replace(from, to, "");
+        Replace(from, to, wxString());
     }
     virtual void Replace(long from, long to, const wxString& text) wxOVERRIDE
     {

include/wx/string.h

@@ -1617,7 +1617,7 @@ public:
     static wxString FromUTF8(const char *utf8)
     {
         if ( !utf8 || !wxStringOperations::IsValidUtf8String(utf8) )
-            return "";
+            return wxString();
 
         return FromImpl(wxStringImpl(utf8));
     }
@@ -1627,7 +1627,7 @@ public:
             return FromUTF8(utf8);
 
         if ( !utf8 || !wxStringOperations::IsValidUtf8String(utf8, len) )
-            return "";
+            return wxString();
 
         return FromImpl(wxStringImpl(utf8, len));
     }

src/common/docview.cpp

@@ -1124,7 +1124,7 @@ void wxDocManager::OnFileNew(wxCommandEvent& WXUNUSED(event))
 
 void wxDocManager::OnFileOpen(wxCommandEvent& WXUNUSED(event))
 {
-    if ( !CreateDocument("") )
+    if ( !CreateDocument(wxString()) )
     {
         OnOpenFileFailure();
     }

src/common/filename.cpp

@@ -2464,7 +2464,7 @@ void wxFileName::SplitPath(const wxString& fullpath,
 wxString wxFileName::StripExtension(const wxString& fullpath)
 {
     wxFileName fn(fullpath);
-    fn.SetExt("");
+    fn.SetExt(wxString());
     return fn.GetFullPath();
 }
 

src/common/fldlgcmn.cpp

@@ -190,7 +190,7 @@ wxSize wxFileDialogBase::GetExtraControlSize()
     // create the extra control in an empty dialog just to find its size: this
     // is not terribly efficient but we do need to know the size before
     // creating the native dialog and this seems to be the only way
-    wxDialog dlg(NULL, wxID_ANY, "");
+    wxDialog dlg(NULL, wxID_ANY, wxString());
     return (*m_extraControlCreator)(&dlg)->GetSize();
 }
 

src/common/imagtiff.cpp

@@ -895,7 +895,7 @@ bool wxTIFFHandler::DoCanRead( wxInputStream& stream )
 
     wxString copyright;
     const wxString desc = ver.BeforeFirst('\n', &copyright);
-    copyright.Replace("\n", "");
+    copyright.Replace("\n", wxString());
 
     return wxVersionInfo("libtiff", major, minor, micro, desc, copyright);
 }

src/common/translation.cpp

@@ -1456,7 +1456,7 @@ void wxTranslations::SetLoader(wxTranslationsLoader *loader)
 void wxTranslations::SetLanguage(wxLanguage lang)
 {
     if ( lang == wxLANGUAGE_DEFAULT )
-        SetLanguage("");
+        SetLanguage(wxString());
     else
         SetLanguage(wxLocale::GetLanguageCanonicalName(lang));
 }
@@ -1926,7 +1926,7 @@ wxArrayString wxFileTranslationsLoader::GetAvailableTranslations(const wxString&
             continue;
 
         wxString lang;
-        for ( bool ok = dir.GetFirst(&lang, "", wxDIR_DIRS);
+        for ( bool ok = dir.GetFirst(&lang, wxString(), wxDIR_DIRS);
               ok;
               ok = dir.GetNext(&lang) )
         {

src/common/uri.cpp

@@ -177,7 +177,7 @@ wxString wxURI::GetPassword() const
       size_t posColon = m_userinfo.find(':');
 
       if ( posColon == wxString::npos )
-          return "";
+          return wxString();
 
       return m_userinfo(posColon + 1, wxString::npos);
 }
@@ -742,7 +742,7 @@ void wxURI::Resolve(const wxURI& base, int flags)
             // if we have an empty path it means we were constructed from a "."
             // string or something similar (e.g. "././././"), it should count
             // as (empty) segment
-            our.push_back("");
+            our.push_back(wxString());
         }
 
         const wxArrayString::const_iterator end = our.end();
@@ -753,7 +753,7 @@ void wxURI::Resolve(const wxURI& base, int flags)
                 // as in ParsePath(), while normally we ignore the empty
                 // segments, we need to take account of them at the end
                 if ( i == end - 1 )
-                    result.push_back("");
+                    result.push_back(wxString());
                 continue;
             }
 
@@ -764,7 +764,7 @@ void wxURI::Resolve(const wxURI& base, int flags)
                     result.pop_back();
 
                     if ( i == end - 1 )
-                        result.push_back("");
+                        result.push_back(wxString());
                 }
                 //else: just ignore, extra ".." don't accumulate
             }
@@ -773,7 +773,7 @@ void wxURI::Resolve(const wxURI& base, int flags)
                 if ( result.empty() )
                 {
                     // ensure that the resulting path will always be absolute
-                    result.push_back("");
+                    result.push_back(wxString());
                 }
 
                 result.push_back(*i);

src/generic/infobar.cpp

@@ -77,7 +77,7 @@ bool wxInfoBarGeneric::Create(wxWindow *parent, wxWindowID winid)
     // the icon is not shown unless it's assigned a valid bitmap
     m_icon = new wxStaticBitmap(this, wxID_ANY, wxNullBitmap);
 
-    m_text = new wxStaticText(this, wxID_ANY, "");
+    m_text = new wxStaticText(this, wxID_ANY, wxString());
     m_text->SetForegroundColour(wxSystemSettings::GetColour(wxSYS_COLOUR_INFOTEXT));
 
     m_button = wxBitmapButton::NewCloseButton(this, wxID_ANY);

src/generic/richtooltipg.cpp

@@ -77,7 +77,7 @@ public:
         }
         //else: Simply don't show any icon.
 
-        wxStaticText* const labelTitle = new wxStaticText(this, wxID_ANY, "");
+        wxStaticText* const labelTitle = new wxStaticText(this, wxID_ANY, wxString());
         labelTitle->SetLabelText(title);
 
         wxFont titleFont(titleFont_);

src/gtk/nativewin.cpp

@@ -110,7 +110,7 @@ bool wxNativeContainerWindow::Create(wxNativeContainerWindowHandle win)
 {
     wxCHECK( win, false );
 
-    if ( !wxTopLevelWindow::Create(NULL, wxID_ANY, "") )
+    if ( !wxTopLevelWindow::Create(NULL, wxID_ANY, wxString()) )
         return false;
 
     // we need to realize the window first before reparenting it

src/xrc/xmlres.cpp

@@ -2584,7 +2584,7 @@ void wxXmlResource::ReportError(const wxXmlNode *context, const wxString& messag
 {
     if ( !context )
     {
-        DoReportError("", NULL, message);
+        DoReportError(wxString(), NULL, message);
         return;
     }