MRView: changes to allow use of progress bar from different threads

Should get around issues #295 & #298. Also this seems to magically fix
the issue with the background being cleared to grey when the ProgressBar
is displayed (see previous commit), which is a nice bonus...

src/gui/dialog/progress.cpp

@@ -34,11 +34,6 @@ namespace MR
 
         namespace {
           QWidget* main_window = nullptr;
-          struct Data {
-            Data () : dialog (nullptr) { }
-            QProgressDialog* dialog;
-            Timer timer;
-          };
         }
 
         void set_main_window (QWidget* window) {
@@ -49,61 +44,21 @@ namespace MR
         {
           if (!p.data) {
             INFO (App::NAME + ": " + p.text);
-            main_window->setUpdatesEnabled (false);
-            p.data = new Data;
+            QMetaObject::invokeMethod (main_window, "startProgressBar");
+            p.data = new Timer;
           }
           else {
-#if QT_VERSION >= 0x050400
-            QOpenGLContext* context = QOpenGLContext::currentContext();
-            QSurface* surface = context ? context->surface() : nullptr;
-#endif
-            Data* data = reinterpret_cast<Data*> (p.data);
-            if (!data->dialog) {
-              if (data->timer.elapsed() > 1.0) {
-                data->dialog = new QProgressDialog (p.text.c_str(), "Cancel", 0, p.multiplier ? 100 : 0);
-                data->dialog->setWindowModality (Qt::ApplicationModal);
-                data->dialog->show();
-                qApp->processEvents();
-              }
-            }
-            else {
-              data->dialog->setValue (p.value);
-              qApp->processEvents();
-            }
-
-#if QT_VERSION >= 0x050400
-            if (context) {
-              assert (surface);
-              context->makeCurrent (surface);
-            }
-#endif
+            if (reinterpret_cast<Timer*>(p.data)->elapsed() > 1.0) 
+              QMetaObject::invokeMethod (main_window, "displayProgressBar", Q_ARG (ProgressInfo&, p));
           }
         }
 
 
         void done (ProgressInfo& p)
         {
           INFO (App::NAME + ": " + p.text + " [done]");
-          if (p.data) {
-            Data* data = reinterpret_cast<Data*> (p.data);
-            if (data->dialog) {
-#if QT_VERSION >= 0x050400
-              QOpenGLContext* context = QOpenGLContext::currentContext();
-              QSurface* surface = context ? context->surface() : nullptr;
-#endif
-              delete data->dialog;
-
-#if QT_VERSION >= 0x050400
-              if (context) {
-                assert (surface);
-                context->makeCurrent (surface);
-              }
-#endif
-            }
-            delete data;
-          }
+          QMetaObject::invokeMethod (main_window, "doneProgressBar");
           p.data = nullptr;
-          main_window->setUpdatesEnabled (true);
         }
 
       }