added tooltip to GameInfoDialog 'Save' button

src/gui/Dialog.cxx

@@ -971,10 +971,10 @@ void Dialog::addDefaultsExtraOKCancelBGroup(
                    buttonWidth, buttonHeight, defaultsText, GuiObject::kDefaultsCmd));
   wid.push_back(_defaultWidget);
 
-  wid.push_back(new ButtonWidget(this, font, HBORDER + buttonWidth + BUTTON_GAP,
-                      _h - buttonHeight - VBORDER, buttonWidth, buttonHeight,
-                      extraText, extraCmd)
-  );
+  addExtraWidget(new ButtonWidget(this, font, HBORDER + buttonWidth + BUTTON_GAP,
+                 _h - buttonHeight - VBORDER, buttonWidth, buttonHeight,
+                 extraText, extraCmd));
+  wid.push_back(_extraWidget);
 
   addOKCancelBGroup(wid, font, okText, cancelText, focusOKButton, buttonWidth);
 }

src/gui/Dialog.hxx

@@ -76,6 +76,7 @@ class Dialog : public GuiObject
     void addBGroupToFocusList(const WidgetArray& list) { _buttonGroup = list; }
     void addTabWidget(TabWidget* w);
     void addDefaultWidget(Widget* w) { _defaultWidget = w; }
+    void addExtraWidget(Widget* w) { _extraWidget = w; }
     void addOKWidget(Widget* w)     { _okWidget = w;     }
     void addCancelWidget(Widget* w) { _cancelWidget = w; }
     void setFocus(Widget* w);
@@ -196,6 +197,7 @@ class Dialog : public GuiObject
     Widget* _focusedWidget{nullptr};
     Widget* _dragWidget{nullptr};
     Widget* _defaultWidget{nullptr};
+    Widget* _extraWidget{nullptr};
     Widget* _okWidget{nullptr};
     Widget* _cancelWidget{nullptr};
 

src/gui/GameInfoDialog.cxx

@@ -93,6 +93,8 @@ GameInfoDialog::GameInfoDialog(
 
   // Add Defaults, OK and Cancel buttons
   addDefaultsExtraOKCancelBGroup(wid, font, "Save", kSavePressed);
+  _extraWidget->setToolTip("Save the current ROM's properties in a\n"
+                           "separate file in the default directory.");
   addBGroupToFocusList(wid);
 }