Clear render caches before plotting.

Also fixes a bug where text variables in LIB_TEXT weren't getting
expanded when plotting.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/15765

eeschema/sch_screen.cpp

@@ -1168,12 +1168,14 @@ void SCH_SCREEN::Plot( PLOTTER* aPlotter ) const
         item->Plot( aPlotter, background );
     }
 
+    // Plot the background items
     for( const SCH_ITEM* item : other )
     {
         aPlotter->SetCurrentLineWidth( std::max( item->GetPenWidth(), defaultPenWidth ) );
         item->Plot( aPlotter, background );
     }
 
+    // Plot the foreground items
     for( const SCH_ITEM* item : other )
     {
         aPlotter->SetCurrentLineWidth( std::max( item->GetPenWidth(), defaultPenWidth ) );
@@ -1187,7 +1189,10 @@ void SCH_SCREEN::Plot( PLOTTER* aPlotter ) const
         aPlotter->SetCurrentLineWidth( std::max( sym->GetPenWidth(), defaultPenWidth ) );
 
         for( SCH_FIELD field : sym->GetFields() )
+        {
+            field.ClearRenderCache();
             field.Plot( aPlotter, false );
+        }
 
         sym->PlotPins( aPlotter );
 

eeschema/sch_symbol.cpp

@@ -2332,6 +2332,17 @@ void SCH_SYMBOL::Plot( PLOTTER* aPlotter, bool aBackground ) const
                 tempPin->SetFlags( IS_DANGLING );
         }
 
+        for( LIB_ITEM& item : tempSymbol.GetDrawItems() )
+        {
+            if( EDA_TEXT* text = dynamic_cast<EDA_TEXT*>( &item ) )
+            {
+                // Use SCH_FIELD's text resolver
+                SCH_FIELD dummy( (SCH_ITEM*) this, -1 );
+                dummy.SetText( text->GetText() );
+                text->SetText( dummy.GetShownText( false ) );
+            }
+        }
+
         TRANSFORM temp = GetTransform();
         aPlotter->StartBlock( nullptr );
 
@@ -2340,8 +2351,11 @@ void SCH_SYMBOL::Plot( PLOTTER* aPlotter, bool aBackground ) const
             tempSymbol.Plot( aPlotter, GetUnit(), GetConvert(), local_background, m_pos, temp,
                              GetDNP() );
 
-            for( const SCH_FIELD& field : m_fields )
+            for( SCH_FIELD field : m_fields )
+            {
+                field.ClearRenderCache();
                 field.Plot( aPlotter, local_background );
+            }
         }
 
         if( m_DNP )