Overplot schematic symbol fields and pins

In the absence of z-ordering, we need to ensure that pin text and symbol
fields are always visible in plots as they are in the schematic window.
We do this by overplotting the fields/pins when symbols overlap each
other.

This can be removed if/when we implement https://gitlab.com/kicad/code/kicad/-/issues/2211

Fixes https://gitlab.com/kicad/code/kicad/issues/11969

eeschema/sch_rtree.h

@@ -225,6 +225,11 @@ public:
         {
             return type_tree->end( m_rect );
         }
+
+        bool empty()
+        {
+            return type_tree->Count() == 0;
+        }
     };
 
     EE_TYPE OfType( KICAD_T aType ) const

eeschema/sch_screen.cpp

@@ -1076,9 +1076,10 @@ void SCH_SCREEN::Print( const RENDER_SETTINGS* aSettings )
 void SCH_SCREEN::Plot( PLOTTER* aPlotter ) const
 {
     // Ensure links are up to date, even if a library was reloaded for some reason:
-    std::vector< SCH_ITEM* > junctions;
-    std::vector< SCH_ITEM* > bitmaps;
-    std::vector< SCH_ITEM* > other;
+    std::vector<SCH_ITEM*>   junctions;
+    std::vector<SCH_ITEM*>   bitmaps;
+    std::vector<SCH_SYMBOL*> symbols;
+    std::vector<SCH_ITEM*>   other;
 
     for( SCH_ITEM* item : Items() )
     {
@@ -1091,6 +1092,21 @@ void SCH_SCREEN::Plot( PLOTTER* aPlotter ) const
             bitmaps.push_back( item );
         else
             other.push_back( item );
+
+        // Where the symbols overlap each other, we need to plot the text items a second
+        // time to get them on top of the overlapping element.  This collection is in addition
+        // to the symbols already collected in `other`
+        if( item->Type() == SCH_SYMBOL_T )
+        {
+            for( SCH_ITEM* sym : m_rtree.Overlapping( SCH_SYMBOL_T, item->GetBoundingBox() ) )
+            {
+                if( sym != item )
+                {
+                    symbols.push_back( static_cast<SCH_SYMBOL*>( item ) );
+                    break;
+                }
+            }
+        }
     }
 
     /// Sort to ensure plot-order consistency with screen drawing
@@ -1127,6 +1143,18 @@ void SCH_SCREEN::Plot( PLOTTER* aPlotter ) const
         item->Plot( aPlotter, !background );
     }
 
+    // After plotting the symbols as a group above (in `other`), we need to overplot the pins
+    // and symbols to ensure that they are always visible
+    for( const SCH_SYMBOL* sym :symbols )
+    {
+        aPlotter->SetCurrentLineWidth( std::max( sym->GetPenWidth(), defaultPenWidth ) );
+
+        for( SCH_FIELD field : sym->GetFields() )
+            field.Plot( aPlotter, false );
+
+        sym->PlotPins( aPlotter );
+    }
+
     for( const SCH_ITEM* item : junctions )
     {
         aPlotter->SetCurrentLineWidth( std::max( item->GetPenWidth(), defaultPenWidth ) );

eeschema/sch_symbol.cpp

@@ -1946,6 +1946,35 @@ void SCH_SYMBOL::Plot( PLOTTER* aPlotter, bool aBackground ) const
 }
 
 
+void SCH_SYMBOL::PlotPins( PLOTTER* aPlotter ) const
+{
+    if( m_part )
+    {
+        LIB_PINS  libPins;
+        m_part->GetPins( libPins, GetUnit(), GetConvert() );
+
+        // Copy the source to stay const
+        LIB_SYMBOL tempSymbol( *m_part );
+        LIB_PINS tempPins;
+        tempSymbol.GetPins( tempPins, GetUnit(), GetConvert() );
+
+        TRANSFORM transform = GetTransform();
+
+        // Copy the pin info from the symbol to the temp pins
+        for( unsigned i = 0; i < tempPins.size(); ++ i )
+        {
+            SCH_PIN* symbolPin = GetPin( libPins[ i ] );
+            LIB_PIN* tempPin = tempPins[ i ];
+
+            tempPin->SetName( symbolPin->GetShownName() );
+            tempPin->SetType( symbolPin->GetType() );
+            tempPin->SetShape( symbolPin->GetShape() );
+            tempPin->Plot( aPlotter, false, m_pos, transform);
+        }
+    }
+}
+
+
 bool SCH_SYMBOL::HasBrightenedPins()
 {
     for( const auto& pin : m_pins )

eeschema/sch_symbol.h

@@ -662,6 +662,14 @@ public:
 
     void Plot( PLOTTER* aPlotter, bool aBackground ) const override;
 
+    /**
+     * Plot just the symbol pins.  This is separated to match the GAL display order.  The pins are
+     * ALSO plotted with the symbol group.  This replotting allows us to ensure that they are shown above
+     * other elements in the schematic
+     * @param aPlotter
+     */
+    void PlotPins( PLOTTER* aPlotter ) const;
+
     EDA_ITEM* Clone() const override;
 
 #if defined(DEBUG)