1) Add 32 Cu Layers.

2) Change from legacy Cu stack to counting down from top=(F_Cu or 0).
   The old Cu stack required knowing the count of Cu layers to make
   sense of the layer number when converting to many exported file types.
   The new Cu stack is more commonly used, although ours still gives
   B_Cu a fixed number.
3) Introduce class LSET and enum LAYER_ID.
4) Change *.kicad_pcb file format version to 4 from 3.
5) Change fixed names Inner1_Cu-Inner14_Cu to In1_Cu-In30_Cu and their
   meanings are typically flipped.
6) Moved the #define LAYER_N_* stuff into legacy_plugin.cpp where they
   can die a quiet death, and switch to enum LAYER_ID symbols throughout.
7) Removed the LEGACY_PLUGIN::Save() and FootprintSave() functions.
   You will need to convert to the format immediately, *.kicad_pcb and
   *.kicad_mod (=pretty) since legacy format was never going to know
   about 32 Cu layers and additional technical layers and the reversed Cu
   stack.

pcbnew/pcb_plot_params.cpp

@@ -74,10 +74,9 @@ static bool setInt( int* aInt, int aValue, int aMin, int aMax )
 
 // PCB_PLOT_PARAMS
 
-PCB_PLOT_PARAMS::PCB_PLOT_PARAMS()
+PCB_PLOT_PARAMS::PCB_PLOT_PARAMS() :
+    m_layerSelection( 4, B_Cu, F_Cu, F_SilkS, B_SilkS )
 {
-    m_layerSelection       = LAYER_BACK | LAYER_FRONT
-        | SILKSCREEN_LAYER_FRONT | SILKSCREEN_LAYER_BACK;
     m_useGerberExtensions  = true;
     m_excludeEdgeLayer     = true;
     m_lineWidth            = g_DrawDefaultLineThickness;
@@ -125,8 +124,10 @@ void PCB_PLOT_PARAMS::Format( OUTPUTFORMATTER* aFormatter,
     const char* trueStr = getTokenName( T_true );
 
     aFormatter->Print( aNestLevel, "(%s\n", getTokenName( T_pcbplotparams ) );
-    aFormatter->Print( aNestLevel+1, "(%s %ld)\n", getTokenName( T_layerselection ),
-                       long(m_layerSelection) );
+
+    aFormatter->Print( aNestLevel+1, "(%s 0x%s)\n", getTokenName( T_layerselection ),
+                       m_layerSelection.FmtHex().c_str() );
+
     aFormatter->Print( aNestLevel+1, "(%s %s)\n", getTokenName( T_usegerberextensions ),
                        m_useGerberExtensions ? trueStr : falseStr );
     aFormatter->Print( aNestLevel+1, "(%s %s)\n", getTokenName( T_excludeedgelayer ),
@@ -306,7 +307,8 @@ PCB_PLOT_PARAMS_PARSER::PCB_PLOT_PARAMS_PARSER( char* aLine, const wxString& aSo
 void PCB_PLOT_PARAMS_PARSER::Parse( PCB_PLOT_PARAMS* aPcbPlotParams )
                              throw( PARSE_ERROR, IO_ERROR )
 {
-    T token;
+    T   token;
+
     while( ( token = NextTok() ) != T_RIGHT )
     {
         if( token == T_EOF)
@@ -321,42 +323,75 @@ void PCB_PLOT_PARAMS_PARSER::Parse( PCB_PLOT_PARAMS* aPcbPlotParams )
         switch( token )
         {
         case T_layerselection:
-            token = NextTok();
-            if( token != T_NUMBER )
-                Expecting( T_NUMBER );
-            aPcbPlotParams->m_layerSelection = atol( CurText() );
+            {
+                token = NeedSYMBOLorNUMBER();
+
+                const std::string& cur = CurStr();
+
+                if( token == T_NUMBER ) // pretty 3 format had legacy Cu stack.
+                {
+                    // unsigned legacy_mask = atol( cur.c_str() );
+
+                    /*  It's not possible to convert a legacy Cu layer number to a new
+                        Cu layer number without knowing the number or total Cu layers
+                        in the legacy board.  We do not have that information here.
+                        So simply set all layers ON.  User can turn them off in the UI.
+                        This is one of the superiorities of the new Cu sequence.
+                    aPcbPlotParams->m_layerSelection = LEGACY_PLUGIN::leg_mask2new( cu_count, legacy_mask );
+                    */
+
+                    // sorry, use the UI once to fix:
+                    aPcbPlotParams->m_layerSelection = LSET( 4, B_Cu, F_Cu, F_SilkS, B_SilkS );
+                }
+                else if( cur.find_first_of( "0x" ) == 0 )   // pretty ver. 4.
+                {
+                    // skip the leading 2 0x bytes.
+                    aPcbPlotParams->m_layerSelection.ParseHex( cur.c_str()+2, cur.size()-2 );
+                }
+                else
+                    Expecting( "integer or hex layerSelection" );
+            }
             break;
+
         case T_usegerberextensions:
             aPcbPlotParams->m_useGerberExtensions = parseBool();
             break;
+
         case T_psa4output:
             aPcbPlotParams->m_A4Output = parseBool();
             break;
+
         case T_excludeedgelayer:
             aPcbPlotParams->m_excludeEdgeLayer = parseBool();
             break;
+
         case T_linewidth:
-        {
-            // Due to a bug, this (minor) parameter was saved in biu
-            // and now is saved in mm
-            // If the read value is outside bounds, force a default value
-            double tmp = parseDouble();
-            if( !aPcbPlotParams->SetLineWidth( KiROUND( tmp * IU_PER_MM ) ) )
-                aPcbPlotParams->SetLineWidth( PLOT_LINEWIDTH_DEFAULT );
-        }
+            {
+                // Due to a bug, this (minor) parameter was saved in biu
+                // and now is saved in mm
+                // If the read value is outside bounds, force a default value
+                double tmp = parseDouble();
+                if( !aPcbPlotParams->SetLineWidth( KiROUND( tmp * IU_PER_MM ) ) )
+                    aPcbPlotParams->SetLineWidth( PLOT_LINEWIDTH_DEFAULT );
+            }
             break;
+
         case T_plotframeref:
             aPcbPlotParams->m_plotFrameRef = parseBool();
             break;
+
         case T_viasonmask:
             aPcbPlotParams->m_plotViaOnMaskLayer = parseBool();
             break;
+
         case T_mode:
             aPcbPlotParams->m_mode = static_cast<EDA_DRAW_MODE_T>( parseInt( 0, 2 ) );
             break;
+
         case T_useauxorigin:
             aPcbPlotParams->m_useAuxOrigin = parseBool();
             break;
+
         case T_hpglpennumber:
             aPcbPlotParams->m_HPGLPenNum = parseInt( HPGL_PEN_NUMBER_MIN,
                                                      HPGL_PEN_NUMBER_MAX );
@@ -376,45 +411,58 @@ void PCB_PLOT_PARAMS_PARSER::Parse( PCB_PLOT_PARAMS* aPcbPlotParams )
         case T_pscolor:
             NeedSYMBOL(); // This actually was never used...
             break;
+
         case T_psnegative:
             aPcbPlotParams->m_negative = parseBool();
             break;
+
         case T_plotreference:
             aPcbPlotParams->m_plotReference = parseBool();
             break;
+
         case T_plotvalue:
             aPcbPlotParams->m_plotValue = parseBool();
             break;
+
         case T_plotothertext:   // no more in use: keep for compatibility
             parseBool();    // skip param value
             break;
+
         case T_plotinvisibletext:
             aPcbPlotParams->m_plotInvisibleText = parseBool();
             break;
+
         case T_padsonsilk:
             aPcbPlotParams->m_plotPadsOnSilkLayer= parseBool();
             break;
+
         case T_subtractmaskfromsilk:
             aPcbPlotParams->m_subtractMaskFromSilk = parseBool();
             break;
+
         case T_outputformat:
             aPcbPlotParams->m_format = static_cast<PlotFormat>(
                                     parseInt( PLOT_FIRST_FORMAT, PLOT_LAST_FORMAT ) );
             break;
+
         case T_mirror:
             aPcbPlotParams->m_mirror = parseBool();
             break;
+
         case T_drillshape:
             aPcbPlotParams->m_drillMarks = static_cast<PCB_PLOT_PARAMS::DrillMarksType>
                                             ( parseInt( 0, 2 ) );
             break;
+
         case T_scaleselection:
             aPcbPlotParams->m_scaleSelection = parseInt( 0, 4 );
             break;
+
         case T_outputdirectory:
             NeedSYMBOL();
             aPcbPlotParams->m_outputDirectory = FROM_UTF8( CurText() );
             break;
+
         default:
             Unexpected( CurText() );
             break;