Use themed file dialogs everywhere. (#4298)

Previously lmms used themed dialogs for project saving/opening, but not
when editing settings (edit -> settings).

With this change, the settings editor also uses themed dialogs.

include/FileDialog.h

@@ -38,6 +38,16 @@ public:
 						const QString &directory = QString(),
 						const QString &filter = QString() );
 
+	static QString getExistingDirectory(QWidget *parent,
+										const QString &caption,
+										const QString &directory,
+										QFileDialog::Options options = QFileDialog::ShowDirsOnly);
+    static QString getOpenFileName(QWidget *parent = 0,
+									const QString &caption = QString(),
+									const QString &directory = QString(),
+									const QString &filter = QString(),
+									QString *selectedFilter = 0,
+									QFileDialog::Options options = 0);
 	void clearSelection();
 };
 

src/gui/dialogs/FileDialog.cpp

@@ -78,6 +78,39 @@ FileDialog::FileDialog( QWidget *parent, const QString &caption,
 }
 
 
+QString FileDialog::getExistingDirectory(QWidget *parent,
+										const QString &caption,
+										const QString &directory,
+										QFileDialog::Options options)
+{
+	FileDialog dialog(parent, caption, directory, QString());
+	dialog.setFileMode(QFileDialog::Directory);
+	dialog.setOptions(dialog.options() | options);
+	if (dialog.exec() == QDialog::Accepted) {
+		return dialog.selectedFiles().value(0);
+	}
+	return QString();
+}
+
+QString FileDialog::getOpenFileName(QWidget *parent,
+									const QString &caption,
+									const QString &directory,
+									const QString &filter,
+									QString *selectedFilter,
+									QFileDialog::Options options)
+{
+	FileDialog dialog(parent, caption, directory, filter);
+	dialog.setOptions(dialog.options() | options);
+	if (selectedFilter && !selectedFilter->isEmpty())
+		dialog.selectNameFilter(*selectedFilter);
+	if (dialog.exec() == QDialog::Accepted) {
+		if (selectedFilter)
+			*selectedFilter = dialog.selectedNameFilter();
+		return dialog.selectedFiles().value(0);
+	}
+	return QString();
+}
+
 
 void FileDialog::clearSelection()
 {
@@ -86,5 +119,3 @@ void FileDialog::clearSelection()
 	view->clearSelection();
 }
 
-
-