Use type aliases FileExtension, FileExtensions...

... for wxString and wxArrayStringEx, holding file extensions (without dot);
to be replaced later with different types

(not yet using std::vector, becase of some uses of wxArrayString::Index with
two arguments)

And simplify some constructions of arrays

src/export/Export.cpp

@@ -128,9 +128,9 @@ void ExportPlugin::AddExtension(const wxString &extension,int index)
    mFormatInfos[index].mExtensions.push_back(extension);
 }
 
-void ExportPlugin::SetExtensions(const wxArrayString & extensions, int index)
+void ExportPlugin::SetExtensions(FileExtensions extensions, int index)
 {
-   mFormatInfos[index].mExtensions = extensions;
+   mFormatInfos[index].mExtensions = std::move(extensions);
 }
 
 void ExportPlugin::SetMask(const wxString & mask, int index)
@@ -158,12 +158,12 @@ wxString ExportPlugin::GetDescription(int index)
    return mFormatInfos[index].mDescription;
 }
 
-wxString ExportPlugin::GetExtension(int index)
+FileExtension ExportPlugin::GetExtension(int index)
 {
    return mFormatInfos[index].mExtensions[0];
 }
 
-wxArrayString ExportPlugin::GetExtensions(int index)
+FileExtensions ExportPlugin::GetExtensions(int index)
 {
    return mFormatInfos[index].mExtensions;
 }
@@ -177,8 +177,8 @@ wxString ExportPlugin::GetMask(int index)
    wxString mask = GetDescription(index) + wxT("|");
 
    // Build the mask
-   // wxString ext = GetExtension(index);
-   auto exts = GetExtensions(index);
+   // const auto &ext = GetExtension(index);
+   const auto &exts = GetExtensions(index);
    for (size_t i = 0; i < exts.size(); i++) {
       mask += wxT("*.") + exts[i] + wxT(";");
    }
@@ -201,8 +201,8 @@ bool ExportPlugin::IsExtension(const wxString & ext, int index)
    bool isext = false;
    for (int i = index; i < GetFormatCount(); i = GetFormatCount())
    {
-      wxString defext = GetExtension(i);
-      auto defexts = GetExtensions(i);
+      const auto &defext = GetExtension(i);
+      const auto &defexts = GetExtensions(i);
       int indofext = defexts.Index(ext, false);
       if (defext.empty() || (indofext != wxNOT_FOUND))
          isext = true;
@@ -616,7 +616,7 @@ bool Exporter::GetFilename()
          }
       }
 
-      wxString ext = mFilename.GetExt();
+      const auto &ext = mFilename.GetExt();
       defext = mPlugins[mFormat]->GetExtension(mSubFormat).Lower();
 
       //

src/export/Export.h

@@ -48,7 +48,7 @@ class AUDACITY_DLL_API FormatInfo
       wxString mFormat;
       wxString mDescription;
       // wxString mExtension;
-      wxArrayString mExtensions;
+      FileExtensions mExtensions;
       wxString mMask;
       unsigned mMaxChannels;
       bool mCanMetaData;
@@ -68,7 +68,7 @@ public:
    void SetFormat(const wxString & format, int index);
    void SetDescription(const wxString & description, int index);
    void AddExtension(const wxString &extension,int index);
-   void SetExtensions(const wxArrayString & extensions, int index);
+   void SetExtensions(FileExtensions extensions, int index);
    void SetMask(const wxString & mask, int index);
    void SetMaxChannels(unsigned maxchannels, unsigned index);
    void SetCanMetaData(bool canmetadata, int index);
@@ -78,10 +78,10 @@ public:
    virtual wxString GetDescription(int index);
    /** @brief Return the (first) file name extension for the sub-format.
     * @param index The sub-format for which the extension is wanted */
-   virtual wxString GetExtension(int index = 0);
+   virtual FileExtension GetExtension(int index = 0);
    /** @brief Return all the file name extensions used for the sub-format.
     * @param index the sub-format for which the extension is required */
-   virtual wxArrayString GetExtensions(int index = 0);
+   virtual FileExtensions GetExtensions(int index = 0);
    virtual wxString GetMask(int index);
    virtual unsigned GetMaxChannels(int index);
    virtual bool GetCanMetaData(int index);

src/export/ExportPCM.cpp

@@ -340,7 +340,7 @@ public:
                const Tags *metadata = NULL,
                int subformat = 0) override;
    // optional
-   wxString GetExtension(int index) override;
+   FileExtension GetExtension(int index) override;
    bool CheckFileName(wxFileName &filename, int format) override;
 
 private:
@@ -890,7 +890,7 @@ wxWindow *ExportPCM::OptionsCreate(wxWindow *parent, int format)
    return ExportPlugin::OptionsCreate(parent, format);
 }
 
-wxString ExportPCM::GetExtension(int index)
+FileExtension ExportPCM::GetExtension(int index)
 {
    if (index == WXSIZEOF(kFormats)) {
       // get extension libsndfile thinks is correct for currently selected format