Define application-level exception handler of last resort.

src/AudacityApp.cpp

@@ -60,6 +60,7 @@ It handles initialization and termination by subclassing wxApp.
 #include <sys/stat.h>
 #endif
 
+#include "AudacityException.h"
 #include "AudacityLogger.h"
 #include "AboutDialog.h"
 #include "AColor.h"
@@ -1084,6 +1085,47 @@ void AudacityApp::OnFatalException()
    exit(-1);
 }
 
+bool AudacityApp::OnExceptionInMainLoop()
+{
+   // This function is invoked from catch blocks in the wxWidgets framework,
+   // and throw; without argument re-throws the exception being handled,
+   // letting us dispatch according to its type.
+
+   try { throw; }
+   catch ( AudacityException &e ) {
+      // Here is the catch-all for our own exceptions
+
+      // Use CallAfter to delay this to the next pass of the event loop,
+      // rather than risk doing it inside stack unwinding.
+      auto pProject = ::GetActiveProject();
+      std::shared_ptr< AudacityException > pException { e.Move().release() };
+      CallAfter( [=]      // Capture pException by value!
+      {
+
+         // Restore the state of the project to what it was before the
+         // failed operation
+         pProject->RollbackState();
+
+         pProject->RedrawProject();
+
+         // Give the user an alert
+         pException->DelayedHandlerAction();
+
+      } );
+
+      // Don't quit the program
+      return true;
+   }
+   catch ( ... ) {
+      // There was some other type of exception we don't know.
+      // Let the inherited function do throw; again and whatever else it does.
+      return wxApp::OnExceptionInMainLoop();
+   }
+
+   // Shouldn't ever reach this line
+   return false;
+}
+
 #if defined(EXPERIMENTAL_CRASH_REPORT)
 void AudacityApp::GenerateCrashReport(wxDebugReport::Context ctx)
 {

src/AudacityApp.h

@@ -63,6 +63,7 @@ class AudacityApp final : public wxApp {
    bool OnInit(void) override;
    int OnExit(void) override;
    void OnFatalException() override;
+   bool OnExceptionInMainLoop() override;
 
    int FilterEvent(wxEvent & event);