Prevent PUI menubar obscuring startup tips

Add an additional visibility flag to the menubar implementations, 
conditional on whether or not the menubar overlaps the window content.
(I.e for PUI but not Cocoa). This flag is linked to a new property
/sim/menubar/overlap-hide, which the renderer drives off the splash-
screen visibility.

src/GUI/FGCocoaMenuBar.hxx

@@ -56,6 +56,14 @@ public:
    */
   virtual bool isVisible () const;
     
+    /**
+     * This is a no-op on Cocoa - the menubar doesn't overlap the window
+     * when its drawn.
+     */
+    void setHideIfOverlapsWindow(bool hide) override;
+    
+    bool getHideIfOverlapsWindow() const override;
+  
   class CocoaMenuBarPrivate;
 private:
   std::unique_ptr<CocoaMenuBarPrivate> p;

src/GUI/FGCocoaMenuBar.mm

@@ -9,6 +9,7 @@
 #include <simgear/debug/logstream.hxx>
 #include <simgear/structure/SGBinding.hxx>
 #include <simgear/misc/strutils.hxx>
+#include <simgear/sg_inlines.h>
 
 #include <Main/fg_props.hxx>
 #include <GUI/CocoaHelpers_private.h>
@@ -325,3 +326,14 @@ void FGCocoaMenuBar::hide()
   // no-op
 }
 
+void FGCocoaMenuBar::setHideIfOverlapsWindow(bool hide)
+{
+    SG_UNUSED(hide);
+    // no-op
+}
+
+bool FGCocoaMenuBar::getHideIfOverlapsWindow() const
+{
+    return false;
+}
+

src/GUI/FGPUIMenuBar.cxx

@@ -111,17 +111,15 @@ FGPUIMenuBar::init ()
 void
 FGPUIMenuBar::show ()
 {
-    if (_menuBar != 0)
-        _menuBar->reveal();
     _visible = true;
+    recomputeVisibility();
 }
 
 void
 FGPUIMenuBar::hide ()
 {
-    if (_menuBar != 0)
-        _menuBar->hide();
     _visible = false;
+    recomputeVisibility();
 }
 
 bool
@@ -130,6 +128,32 @@ FGPUIMenuBar::isVisible () const
     return _visible;
 }
 
+void
+FGPUIMenuBar::setHideIfOverlapsWindow(bool hide)
+{
+    _hideOverlapping = hide;
+    recomputeVisibility();
+}
+
+bool
+FGPUIMenuBar::getHideIfOverlapsWindow() const
+{
+    return _hideOverlapping;
+}
+
+void
+FGPUIMenuBar::recomputeVisibility()
+{
+    if (_menuBar) {
+        const bool actualVis = _visible && (!_hideOverlapping);
+        if (actualVis) {
+            _menuBar->reveal();
+        } else {
+            _menuBar->hide();
+        }
+    }
+}
+
 void
 FGPUIMenuBar::fireItem (puObject * item)
 {

src/GUI/FGPUIMenuBar.hxx

@@ -69,6 +69,9 @@ public:
      */
     virtual bool isVisible () const;
 
+    void setHideIfOverlapsWindow(bool hide) override;
+
+    bool getHideIfOverlapsWindow() const override;
     
     /**
      * IGNORE THIS METHOD!!!
@@ -113,8 +116,11 @@ private:
     // Add <enabled> listener that enables/disables menu entries.
     void add_enabled_listener(SGPropertyNode * node);
 
+    void recomputeVisibility();
+    
     // Is the menu visible?
     bool _visible;
+    bool _hideOverlapping = false;
     
     // The top-level menubar itself.
     puMenuBar * _menuBar;

src/GUI/menubar.hxx

@@ -48,6 +48,19 @@ public:
      */
     virtual bool isVisible () const = 0;
 
+    /**
+     * Request the menubar to be hidden if its display overlays the main window content.
+     * (Which essentially means the PUI menubar at the moment). This is used to prevent
+     * the menubar overlapping the splash-screen during startup.
+     *
+     * The state of this flag is independant of the normal menubar visibility, i.e this
+     * flag and the normal visibility and AND-ed together inside the code.
+     */
+    virtual void setHideIfOverlapsWindow(bool hide) = 0;
+    
+    // corresponding getter to valye able.
+    virtual bool getHideIfOverlapsWindow() const = 0;
+    
     /**
      * Read a menu label from the menu's property tree.
      * Take care of mapping it to the appropriate translation, if available.

src/GUI/new_gui.cxx

@@ -71,6 +71,9 @@ NewGUI::init ()
     fgTie("/sim/menubar/visibility", this,
           &NewGUI::getMenuBarVisible, &NewGUI::setMenuBarVisible);
     
+    fgTie("/sim/menubar/overlap-hide", this,
+          &NewGUI::getMenuBarOverlapHide, &NewGUI::setMenuBarOverlapHide);
+
     setStyle();
     SGPath p(globals->get_fg_root(), "gui/dialogs");
     readDir(p);
@@ -305,6 +308,18 @@ NewGUI::setMenuBarVisible (bool visible)
         _menubar->hide();
 }
 
+bool
+NewGUI::getMenuBarOverlapHide() const
+{
+    return _menubar->getHideIfOverlapsWindow();
+}
+
+void
+NewGUI::setMenuBarOverlapHide(bool hide)
+{
+    _menubar->setHideIfOverlapsWindow(hide);
+}
+
 void
 NewGUI::newDialog (SGPropertyNode* props)
 {

src/GUI/new_gui.hxx

@@ -201,6 +201,8 @@ protected:
      */
     virtual void reset (bool reload);
 
+    bool getMenuBarOverlapHide() const;
+    void setMenuBarOverlapHide(bool hide);
 private:
     void createMenuBarImplementation();
     

src/Viewer/renderer.cxx

@@ -468,6 +468,11 @@ FGRenderer::preinit( void )
     _updateVisitor->setFrameStamp(_frameStamp.get());
     viewer->setUpdateVisitor(_updateVisitor.get());
     fgSetDouble("/sim/startup/splash-alpha", 1.0);
+    
+    // hide the menubar if it overlaps the window, so the splash screen
+    // is completely visible. We reset this value when the splash screen
+    // is fading out.
+    fgSetBool("/sim/menubar/overlap-hide", true);
 }
 
 class ShadowMapSizeListener : public SGPropertyChangeListener {
@@ -1594,6 +1599,7 @@ FGRenderer::update( ) {
         _splash_alpha->setDoubleValue((sAlpha < 0) ? 0.0 : sAlpha);
 
         syncPausePopupState();
+        fgSetBool("/sim/menubar/overlap-hide", false);
     }
 
     FGLight *l = static_cast<FGLight*>(globals->get_subsystem("lighting"));