gtk3: native focus rects are fine for flat buttons

Change-Id: I6a70696cd119e681b4850c624c9e4ff28312c152

vcl/inc/svdata.hxx

@@ -266,7 +266,8 @@ struct ImplSVNWFData
                                                             // toolbox dropdown buttons
     bool                    mbFlatMenu:1;                   // no popup 3D border
     bool                    mbOpenMenuOnF10:1;              // on gnome the first menu opens on F10
-    bool                    mbNoFocusRects:1;               // on Aqua focus rects are not used
+    bool                    mbNoFocusRects:1;               // on Aqua/Gtk3 use native focus rendering, except for flat butttons
+    bool                    mbNoFocusRectsForFlatButtons:1; // on Gtk3 native focusing is also preferred for flat buttons
     bool                    mbCenteredTabs:1;               // on Aqua, tabs are centered
     bool                    mbNoActiveTabTextRaise:1;       // on Aqua the text for the selected tab
                                                             // should not "jump up" a pixel

vcl/source/control/button.cxx

@@ -700,8 +700,11 @@ void PushButton::ImplInitSettings( bool bFont,
             EnableChildTransparentMode( true );
             SetParentClipMode( ParentClipMode::NoClip );
             SetPaintTransparent( true );
-            mpWindowImpl->mbUseNativeFocus = (GetStyle() & WB_FLATBUTTON) == 0
-                && ImplGetSVData()->maNWFData.mbNoFocusRects;
+
+            if ((GetStyle() & WB_FLATBUTTON) == 0)
+                mpWindowImpl->mbUseNativeFocus = ImplGetSVData()->maNWFData.mbNoFocusRects;
+            else
+                mpWindowImpl->mbUseNativeFocus = ImplGetSVData()->maNWFData.mbNoFocusRectsForFlatButtons;
         }
         else
         {

vcl/unx/gtk3/gdi/gtk3salnativewidgets-gtk.cxx

@@ -1935,6 +1935,7 @@ void GtkData::initNWF()
     pSVData->maNWFData.mbCanDrawWidgetAnySize = true;
     pSVData->maNWFData.mbDDListBoxNoTextArea = true;
     pSVData->maNWFData.mbNoFocusRects = true;
+    pSVData->maNWFData.mbNoFocusRectsForFlatButtons = true;
     pSVData->maNWFData.mbAutoAccel = true;
     pSVData->maNWFData.mbEnableAccel = true;
 }