Allow a 0 pin-symbol-size.

This is particularly important when reading legacy projects as 0 is
what signals the painter to use the old algorithm (1/2 pin name/number
size).

Fixes https://gitlab.com/kicad/code/kicad/issues/10100

common/project/project_file.cpp

@@ -235,16 +235,22 @@ bool PROJECT_FILE::MigrateFromLegacy( wxConfigBase* aCfg )
     fromLegacy<int>(  aCfg, "SubpartIdSeparator",      "schematic.subpart_id_separator" );
     fromLegacy<int>(  aCfg, "SubpartFirstId",          "schematic.subpart_first_id" );
 
-    fromLegacy<int>( aCfg, "LineThickness",         "schematic.drawing.default_line_thickness" );
-    fromLegacy<int>( aCfg, "WireThickness",         "schematic.drawing.default_wire_thickness" );
-    fromLegacy<int>( aCfg, "BusThickness",          "schematic.drawing.default_bus_thickness" );
-    fromLegacy<int>( aCfg, "LabSize",               "schematic.drawing.default_text_size" );
-    fromLegacy<int>( aCfg, "PinSymbolSize",         "schematic.drawing.pin_symbol_size" );
-    fromLegacy<int>( aCfg, "JunctionSize",          "schematic.drawing.default_junction_size" );
+    fromLegacy<int>( aCfg, "LineThickness",            "schematic.drawing.default_line_thickness" );
+    fromLegacy<int>( aCfg, "WireThickness",            "schematic.drawing.default_wire_thickness" );
+    fromLegacy<int>( aCfg, "BusThickness",             "schematic.drawing.default_bus_thickness" );
+    fromLegacy<int>( aCfg, "LabSize",                  "schematic.drawing.default_text_size" );
 
-    fromLegacyString(   aCfg, "FieldNameTemplates", "schematic.drawing.field_names" );
+    if( !fromLegacy<int>( aCfg, "PinSymbolSize",       "schematic.drawing.pin_symbol_size" ) )
+    {
+        // Use the default symbol size algorithm of Eeschema V5 (based on pin name/number size)
+        Set( "schematic.drawing.pin_symbol_size", 0 );
+    }
+
+    fromLegacy<int>( aCfg, "JunctionSize",             "schematic.drawing.default_junction_size" );
+
+    fromLegacyString(   aCfg, "FieldNameTemplates",    "schematic.drawing.field_names" );
 
-    if( !fromLegacy<double>( aCfg, "TextOffsetRatio", "schematic.drawing.text_offset_ratio" ) )
+    if( !fromLegacy<double>( aCfg, "TextOffsetRatio",  "schematic.drawing.text_offset_ratio" ) )
     {
         // Use the spacing of Eeschema V5
         Set( "schematic.drawing.text_offset_ratio", 0.08 );

eeschema/schematic_settings.cpp

@@ -104,7 +104,7 @@ SCHEMATIC_SETTINGS::SCHEMATIC_SETTINGS( JSON_SETTINGS* aParent, const std::strin
             &m_LabelSizeRatio, DEFAULT_LABEL_SIZE_RATIO, 0.0, 2.0 ) );
 
     m_params.emplace_back( new PARAM_SCALED<int>( "drawing.pin_symbol_size",
-            &m_PinSymbolSize, Mils2iu( defaultPinSymbolSize ), Mils2iu( 5 ), Mils2iu( 1000 ),
+            &m_PinSymbolSize, Mils2iu( defaultPinSymbolSize ), Mils2iu( 0 ), Mils2iu( 1000 ),
             1 / IU_PER_MILS ) );
 
     // m_JunctionSize is only a run-time cache of the calculated size.  Do not save it.