taskdialog: improved signalling

Ensures task errors are picked up and objects are deleted at the most
appropriate times.

app/dialog/task/task.cpp

@@ -13,25 +13,26 @@ TaskDialog::TaskDialog(Task* task, const QString& title, QWidget *parent) :
   // Connect the save manager progress signal to the progress bar update on the dialog
   connect(task_, &Task::ProgressChanged, this, &TaskDialog::SetProgress, Qt::QueuedConnection);
 
-  // Connect cancel signal (must be a direct connection or it'll be queued after the save is already finished)
-  connect(this, &TaskDialog::Cancelled, this, &TaskDialog::reject, Qt::DirectConnection);
+  // Connect error reporting
+  connect(task_, &Task::Failed, this, &TaskDialog::TaskFailed, Qt::QueuedConnection);
+
+  // Connect cancel signal (must be a direct connection or it'll be queued after the task has already finished)
+  connect(this, &TaskDialog::Cancelled, task_, &Task::Cancel, Qt::DirectConnection);
 
   // Connect cleanup functions (ensure everything new'd in this function is deleteLater'd)
-  connect(task_, &Task::Finished, this, &TaskDialog::accept, Qt::QueuedConnection);
-  connect(task_, &Task::Finished, this, &TaskDialog::deleteLater, Qt::QueuedConnection);
-  connect(task_, &Task::Finished, task_, &Task::deleteLater, Qt::QueuedConnection);
+  connect(task_, &Task::Finished, this, &TaskDialog::close, Qt::QueuedConnection);
+
+  // When task is finished, signal thread to quit
   connect(task_, &Task::Finished, thread_, &QThread::quit, Qt::QueuedConnection);
+
+  // When thread has quit, delete both task and thread
+  connect(thread_, &QThread::finished, task_, &Task::deleteLater, Qt::QueuedConnection);
   connect(thread_, &QThread::finished, thread_, &QThread::deleteLater, Qt::QueuedConnection);
 }
 
-void TaskDialog::open()
+void TaskDialog::showEvent(QShowEvent *e)
 {
-  ProgressDialog::open();
-
-  if (thread_->isRunning()) {
-    // Task has already started, no need to do anymore
-    return;
-  }
+  QDialog::showEvent(e);
 
   // Create a separate thread to run this task in
   thread_->start();
@@ -43,21 +44,24 @@ void TaskDialog::open()
   QMetaObject::invokeMethod(task_, "Start", Qt::QueuedConnection);
 }
 
-void TaskDialog::accept()
+void TaskDialog::closeEvent(QCloseEvent *e)
 {
-  if (task_failed_) {
+  // Show error if the task failed
+  if (!task_->IsCancelled() && task_failed_) {
     QMessageBox::critical(this,
-                          tr("Task Error"),
+                          tr("Error"),
                           task_error_,
                           QMessageBox::Ok);
   }
 
-  ProgressDialog::accept();
-}
-
-void TaskDialog::reject()
-{
+  // Cancel task if it is running
   task_->Cancel();
+
+  // Standard close function
+  QDialog::closeEvent(e);
+
+  // Clean up this dialog (FIXME: Is this necessary?)
+  deleteLater();
 }
 
 void TaskDialog::TaskFailed(const QString &s)

app/dialog/task/task.h

@@ -6,14 +6,14 @@
 
 class TaskDialog : public ProgressDialog
 {
+  Q_OBJECT
 public:
   TaskDialog(Task *task, const QString &title, QWidget* parent = nullptr);
 
-public slots:
-  virtual void open() override;
+protected:
+  virtual void showEvent(QShowEvent* e) override;
 
-  virtual void accept() override;
-  virtual void reject() override;
+  virtual void closeEvent(QCloseEvent* e) override;
 
 private:
   Task* task_;