cleanup: un-singletonize ShiftTimesDialog

There is no reason that this dialog is a singleton. Since it is modal,
it can be created on demand. Apart from removing superfluous global state,
this simplifies code, because preparing the widget can now be done in
the constructor instead of overriding the showEvent() function.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

desktop-widgets/divelistview.cpp

@@ -860,7 +860,8 @@ void DiveListView::contextMenuEvent(QContextMenuEvent *event)
 
 void DiveListView::shiftTimes()
 {
-	ShiftTimesDialog::instance()->show();
+	ShiftTimesDialog dialog(MainWindow::instance());
+	dialog.exec();
 }
 
 void DiveListView::loadImages()

desktop-widgets/simplewidgets.cpp

@@ -179,12 +179,6 @@ SetpointDialog::SetpointDialog(struct dive *dIn, int dcNrIn, int seconds) : QDia
 	connect(quit, &QShortcut::activated, MainWindow::instance(), &QWidget::close);
 }
 
-ShiftTimesDialog *ShiftTimesDialog::instance()
-{
-	static ShiftTimesDialog *self = new ShiftTimesDialog(MainWindow::instance());
-	return self;
-}
-
 void ShiftTimesDialog::buttonClicked(QAbstractButton *button)
 {
 	int amount;
@@ -196,10 +190,7 @@ void ShiftTimesDialog::buttonClicked(QAbstractButton *button)
 		if (amount != 0)
 			Command::shiftTime(getDiveSelection(), amount);
 	}
-}
 
-void ShiftTimesDialog::showEvent(QShowEvent*)
-{
 	ui.timeEdit->setTime(QTime(0, 0, 0, 0));
 	when = get_times(); //get time of first selected dive
 	ui.currentTime->setText(get_dive_date_string(when));

desktop-widgets/simplewidgets.h

@@ -78,15 +78,13 @@ private:
 class ShiftTimesDialog : public QDialog {
 	Q_OBJECT
 public:
-	static ShiftTimesDialog *instance();
+	explicit ShiftTimesDialog(QWidget *parent);
-	void showEvent(QShowEvent *event);
 private
 slots:
 	void buttonClicked(QAbstractButton *button);
 	void changeTime();
 
 private:
-	explicit ShiftTimesDialog(QWidget *parent);
 	int64_t when;
 	Ui::ShiftTimesDialog ui;
 };