replaced shaded UI redraws with shading surface

src/gui/Dialog.cxx

@@ -227,8 +227,6 @@ void Dialog::redraw()
   center();
   drawDialog();
   render();
-
-//  return true;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -242,6 +240,28 @@ void Dialog::render()
       surface->render();
     });
   }
+  if(parent().myDialogStack.top() != this)
+  {
+    if(_shadeSurface == nullptr)
+    {
+      uInt32 data = 0xff000000;
+
+      _shadeSurface = instance().frameBuffer().allocateSurface(
+        1, 1, ScalingInterpolation::sharp, &data);
+
+      FBSurface::Attributes& attr = _shadeSurface->attributes();
+
+      attr.blending = true;
+      attr.blendalpha = 25; // darken background dialogs by 25%
+      _shadeSurface->applyAttributes();
+    }
+
+    const Common::Rect& rect = _surface->dstRect();
+    _shadeSurface->setDstPos(rect.x(), rect.y());
+    _shadeSurface->setDstSize(rect.w(), rect.h());
+
+    _shadeSurface->render();
+  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -408,7 +428,7 @@ void Dialog::drawDialog()
     //cerr << "*** draw dialog " << typeid(*this).name() << " ***" << endl;
 
     // Dialog is still on top if e.g a ContextMenu is opened
-    _onTop = parent().myDialogStack.top() == this
+    _onTop = true/*parent().myDialogStack.top() == this*/
       || (parent().myDialogStack.get(parent().myDialogStack.size() - 2) == this
           && !parent().myDialogStack.top()->hasTitle());
 

src/gui/Dialog.hxx

@@ -230,6 +230,7 @@ class Dialog : public GuiObject
 
     WidgetArray _buttonGroup;
     shared_ptr<FBSurface> _surface;
+    shared_ptr<FBSurface> _shadeSurface;
 
     int _tabID{0};
     uInt32 _max_w{0}; // maximum wanted width

src/gui/DialogContainer.cxx

@@ -146,9 +146,10 @@ int DialogContainer::addDialog(Dialog* d)
       "Unable to show dialog box; FIX THE CODE", MessagePosition::BottomCenter, true);
   else
   {
-    // "darken" current top dialog
+    //// "shade" current top dialog
-    if(!myDialogStack.empty())
+    //if(!myDialogStack.empty())
-      myDialogStack.top()->setDirty();
+    //  myDialogStack.top()->setDirty();
+
     d->setDirty();
     myDialogStack.push(d);
   }
@@ -164,14 +165,16 @@ void DialogContainer::removeDialog()
 
     if(!myDialogStack.empty())
     {
-      // this "undarkens" the top dialog
+      //// this "unshades" the top dialog
-      myDialogStack.top()->setDirty();
+      //myDialogStack.top()->setDirty();
 
       // Rerender all dialogs (TODO: top dialog is rendered twice)
       myDialogStack.applyAll([&](Dialog*& d){
           //d->setDirty();
           d->render();
       });
+      // TODO: the screen is not updated until an event happens
+      // FrameBuffer::myBackend->renderToScreen() doesn't help
     }
   }
 }