Define an AudacityException subclass for file errors

src/FileException.cpp

@@ -0,0 +1,45 @@
+//
+//  FileException.cpp
+//  
+//
+//  Created by Paul Licameli on 11/22/16.
+//
+//
+
+#include "Audacity.h"
+#include "FileException.h"
+
+FileException::~FileException()
+{
+}
+
+std::unique_ptr< AudacityException > FileException::Move()
+{
+   return std::unique_ptr< AudacityException >
+      { safenew FileException{ std::move( *this ) } };
+}
+
+wxString FileException::ErrorMessage() const
+{
+   wxString format;
+   switch (cause) {
+      case Cause::Open:
+         format = _("Audacity failed to open a file at %s.\n");
+         break;
+      case Cause::Read:
+         format = _("Audacity failed to read from a file at %s.\n");
+         break;
+      case Cause::Write:
+         format = _(
+"Audacity failed to write to a file at %s.\nAttempt this operation again after removing unnecessary files.\nOne way to do that is with the Discard buttons in the History dialog.\nSee the View menu.");
+         break;
+      case Cause::Rename:
+         format = _(
+"Audacity successfully wrote the file %s but failed to rename it as %s.");
+      default:
+         break;
+   }
+   return wxString::Format(
+      format, fileName.GetFullPath(), renameTarget.GetFullPath() );
+}
+

src/FileException.h

@@ -0,0 +1,46 @@
+//
+//  FileException.h
+//  
+//
+//  Created by Paul Licameli on 11/22/16.
+//
+//
+
+#ifndef __AUDACITY_FILE_EXCEPTION__
+#define __AUDACITY_FILE_EXCEPTION__
+
+#include "AudacityException.h"
+#include <wx/filename.h>
+
+class FileException /* not final */ : public MessageBoxException
+{
+public:
+   enum class Cause { Open, Read, Write, Rename };
+
+   explicit FileException
+      ( Cause cause_, const wxFileName &fileName_,
+        const wxString &caption = wxString{},
+        const wxFileName &renameTarget_ = {})
+   : MessageBoxException{ caption }
+   , fileName{ fileName_ }, cause{ cause_ }, renameTarget{ renameTarget_ }
+   {}
+
+   FileException(FileException&& that)
+      : MessageBoxException(std::move(that))
+   {}
+
+   ~FileException() override;
+
+protected:
+   std::unique_ptr< AudacityException > Move() override;
+
+   // Format a default, internationalized error message for this exception.
+   wxString ErrorMessage() const override;
+
+public:
+   Cause cause;
+   wxFileName fileName;
+   wxFileName renameTarget;
+};
+
+#endif

src/Makefile.am

@@ -133,6 +133,8 @@ audacity_SOURCES = \
 	FFmpeg.h \
 	FFT.cpp \
 	FFT.h \
+	FileException.cpp \
+	FileException.h \
 	FileIO.cpp \
 	FileIO.h \
 	FileNames.cpp \