Desktop: Derive UserManual from QDialog

In commit d21d42b691 helpView was made
a child-object of MainWindow, which is Qt's idiomatic way of having
helpView deleted with MainWindow.

As an unintended consequence, the helpView didn't show. The reason
is that UserManual derives directly from QObject. In contrast, UserSurvey
derives from QDialog and is correctly shown. Therefore also derive
UserManual from QDialog.

Reported-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

desktop-widgets/mainwindow.cpp

@@ -100,7 +100,9 @@ extern "C" void showErrorFromC(char *buf)
 MainWindow::MainWindow() : QMainWindow(),
 	actionNextDive(0),
 	actionPreviousDive(0),
+#ifndef NO_USERMANUAL
 	helpView(0),
+#endif
 	state(VIEWALL),
 	survey(0)
 {

desktop-widgets/mainwindow.h

@@ -191,7 +191,9 @@ private:
 	Ui::MainWindow ui;
 	QAction *actionNextDive;
 	QAction *actionPreviousDive;
+#ifndef NO_USERMANUAL
 	UserManual *helpView;
+#endif
 	CurrentState state;
 	CurrentState stateBeforeEdit;
 	QString filter_open();

desktop-widgets/usermanual.cpp

@@ -56,7 +56,7 @@ MyQWebEngineView::MyQWebEngineView(QWidget* parent)
 }
 #endif
 
-UserManual::UserManual(QWidget *parent) : QWidget(parent)
+UserManual::UserManual(QWidget *parent) : QDialog(parent)
 {
 	QShortcut *closeKey = new QShortcut(QKeySequence(Qt::CTRL + Qt::Key_W), this);
 	connect(closeKey, SIGNAL(activated()), this, SLOT(close()));

desktop-widgets/usermanual.h

@@ -8,6 +8,7 @@
 #else
 #include <QWebView>
 #endif
+#include <QDialog>
 #include "ui_searchbar.h"
 
 class SearchBar : public QWidget{
@@ -47,7 +48,7 @@ public:
 #endif
 
 
-class UserManual : public QWidget {
+class UserManual : public QDialog {
 	Q_OBJECT
 
 public: