GUI: Save/restore last scroll position in the list save/load dialog.

This should give a better user experience, since the user will not have to
scroll back to where he was when he used the dialog last.

Thanks to wjp for suggesting this.

gui/saveload-dialog.cpp

@@ -422,7 +422,28 @@ void SaveLoadChooserSimple::updateSelection(bool redraw) {
 	}
 }
 
+void SaveLoadChooserSimple::open() {
+	SaveLoadChooserDialog::open();
+
+	// Scroll the list to the last used entry.
+	_list->scrollTo(ConfMan.getInt("gui_saveload_last_pos"));
+}
+
 void SaveLoadChooserSimple::close() {
+	// Save the current scroll position/used entry.
+	const int result = getResult();
+	if (result >= 0) {
+		ConfMan.setInt("gui_saveload_last_pos", result);
+	} else {
+		// Use the current scroll position here.
+		// TODO: This means we canceled the dialog (or switch to the grid). Do
+		// we want to save this position here? Does the user want that?
+		// TODO: Do we want to save the current scroll position or the
+		// currently selected item here? The scroll position is what the user
+		// currently sees and seems to make more sense.
+		ConfMan.setInt("gui_saveload_last_pos", _list->getCurrentScrollPos());
+	}
+
 	_metaEngine = 0;
 	_target.clear();
 	_saveList.clear();

gui/saveload-dialog.h

@@ -103,6 +103,7 @@ public:
 	virtual SaveLoadChooserType getType() const { return kSaveLoadDialogList; }
 #endif // !DISABLE_SAVELOADCHOOSER_GRID
 
+	virtual void open();
 	virtual void close();
 private:
 	virtual int runIntern();

gui/widgets/list.h

@@ -105,6 +105,7 @@ public:
 
 	void scrollTo(int item);
 	void scrollToEnd();
+	int getCurrentScrollPos() const { return _currentPos; }
 
 	void enableQuickSelect(bool enable) 		{ _quickSelect = enable; }
 	String getQuickSelectString() const 		{ return _quickSelectStr; }