From ec4d377d15da4cc8a783c635cb8a3b06a699873e Mon Sep 17 00:00:00 2001
From: Jon Evans <jon@craftyjon.com>
Date: Fri, 27 Jan 2023 08:57:18 -0500
Subject: [PATCH] Stop removing islands for fully-isolated zones

It is hard for a user to tell what is going on when their zone
just doesn't fill at all.  We catch isolated areas in the DRC so
we can just leave them alone here until the zone has at least one
non-isolated filled area.

Also change default back to always remove islands to reduce confusion

Fixes https://gitlab.com/kicad/code/kicad/-/issues/13271
---
 pcbnew/zone_filler.cpp   | 21 +++++++++++++++++++++
 pcbnew/zone_settings.cpp |  2 +-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/pcbnew/zone_filler.cpp b/pcbnew/zone_filler.cpp
index 393a72e578..58350da91f 100644
--- a/pcbnew/zone_filler.cpp
+++ b/pcbnew/zone_filler.cpp
@@ -474,6 +474,27 @@ bool ZONE_FILLER::Fill( std::vector<ZONE*>& aZones, bool aCheck, wxWindow* aPare
     //
     for( CN_ZONE_ISOLATED_ISLAND_LIST& zone : islandsList )
     {
+        // If *all* the polygons are islands, do not remove any of them
+        bool allIslands = true;
+
+        for( PCB_LAYER_ID layer : zone.m_zone->GetLayerSet().Seq() )
+        {
+            if( !zone.m_islands.count( layer ) )
+                continue;
+
+            std::vector<int>& islands = zone.m_islands.at( layer );
+            std::shared_ptr<SHAPE_POLY_SET> poly = zone.m_zone->GetFilledPolysList( layer );
+
+            if( islands.size() != static_cast<size_t>( poly->OutlineCount() ) )
+            {
+                allIslands = false;
+                break;
+            }
+        }
+
+        if( allIslands )
+            continue;
+
         for( PCB_LAYER_ID layer : zone.m_zone->GetLayerSet().Seq() )
         {
             if( m_debugZoneFiller && LSET::InternalCuMask().Contains( layer ) )
diff --git a/pcbnew/zone_settings.cpp b/pcbnew/zone_settings.cpp
index bca1323f28..91de6549b5 100644
--- a/pcbnew/zone_settings.cpp
+++ b/pcbnew/zone_settings.cpp
@@ -71,7 +71,7 @@ ZONE_SETTINGS::ZONE_SETTINGS()
     m_cornerSmoothingType = SMOOTHING_NONE;
     m_cornerRadius = 0;
 
-    m_removeIslands = ISLAND_REMOVAL_MODE::AREA;
+    m_removeIslands = ISLAND_REMOVAL_MODE::ALWAYS;
     m_minIslandArea = 10 * pcbIUScale.IU_PER_MM * pcbIUScale.IU_PER_MM;
 
     SetIsRuleArea( false );