Prepare Plot Gerber file to include advanced aperture and net attributes.

This option is not yet activated because the net attributes are not yet fully fixed by Ucamco, in Gerber file format specifications.
(To activate it, see dialog_plot.cpp, line 43)

pcbnew/pcbplot.cpp

@@ -85,8 +85,7 @@ const wxString GetGerberProtelExtension( LAYER_NUM aLayer )
     }
 }
 
-
-wxString GetGerberFileFunctionAttribute( const BOARD *aBoard,
+const wxString GetGerberFileFunctionAttribute( const BOARD *aBoard,
                 LAYER_NUM aLayer, bool aUseX1CompatibilityMode )
 {
     wxString attrib;
@@ -94,81 +93,81 @@ wxString GetGerberFileFunctionAttribute( const BOARD *aBoard,
     switch( aLayer )
     {
     case F_Adhes:
-        attrib = wxString( wxT( "Glue,Top" ) );
+        attrib = "Glue,Top";
         break;
 
     case B_Adhes:
-        attrib = wxString( wxT( "Glue,Bot" ) );
+        attrib = "Glue,Bot";
         break;
 
     case F_SilkS:
-        attrib = wxString( wxT( "Legend,Top" ) );
+        attrib = "Legend,Top";
         break;
 
     case B_SilkS:
-        attrib = wxString( wxT( "Legend,Bot" ) );
+        attrib = "Legend,Bot";
         break;
 
     case F_Mask:
-        attrib = wxString( wxT( "Soldermask,Top" ) );
+        attrib = "Soldermask,Top";
         break;
 
     case B_Mask:
-        attrib = wxString( wxT( "Soldermask,Bot" ) );
+        attrib = "Soldermask,Bot";
         break;
 
     case F_Paste:
-        attrib = wxString( wxT( "Paste,Top" ) );
+        attrib = "Paste,Top";
         break;
 
     case B_Paste:
-        attrib = wxString( wxT( "Paste,Bot" ) );
+        attrib = "Paste,Bot";
         break;
 
     case Edge_Cuts:
         // Board outline.
         // Can be "Profile,NP" (Not Plated: usual) or "Profile,P"
         // This last is the exception (Plated)
-        attrib = wxString( wxT( "Profile,NP" ) );
+        attrib = "Profile,NP";
         break;
 
     case Dwgs_User:
-        attrib = wxString( wxT( "Drawing" ) );
+        attrib = "Drawing";
         break;
 
     case Cmts_User:
-        attrib = wxString( wxT( "Other,Comment" ) );
+        attrib = "Other,Comment";
         break;
 
     case Eco1_User:
-        attrib = wxString( wxT( "Other,ECO1" ) );
+        attrib = "Other,ECO1";
         break;
 
     case Eco2_User:
-        attrib = wxString( wxT( "Other,ECO2" ) );
+        attrib = "Other,ECO2";
         break;
 
     case B_Fab:
-        attrib = wxString( wxT( "Other,Fab,Bot" ) );
+        attrib = "Other,Fab,Bot";
         break;
 
     case F_Fab:
-        attrib = wxString( wxT( "Other,Fab,Top" ) );
+        attrib = "Other,Fab,Top";
         break;
 
     case B_Cu:
-        attrib = wxString::Format( wxT( "Copper,L%d,Bot" ), aBoard->GetCopperLayerCount() );
+        attrib.Printf( wxT( "Copper,L%d,Bot" ), aBoard->GetCopperLayerCount() );
         break;
 
     case F_Cu:
-        attrib = wxString::Format( wxT( "Copper,L1,Top" ) );
+        attrib = "Copper,L1,Top";
         break;
 
     default:
         if( IsCopperLayer( aLayer ) )
-            attrib = wxString::Format( wxT( "Copper,L%d,Inr" ), aLayer+1 );
+            attrib.Printf( wxT( "Copper,L%d,Inr" ), aLayer+1 );
         else
-            attrib = wxString::Format( wxT( "Other,User" ), aLayer+1 );
+            attrib.Printf( wxT( "Other,User" ), aLayer+1 );
         break;
     }
 
@@ -180,13 +179,13 @@ wxString GetGerberFileFunctionAttribute( const BOARD *aBoard,
         switch( type )
         {
         case LT_SIGNAL:
-            attrib += wxString( wxT( ",Signal" ) );
+            attrib += ",Signal";
             break;
         case LT_POWER:
-            attrib += wxString( wxT( ",Plane" ) );
+            attrib += ",Plane";
             break;
         case LT_MIXED:
-            attrib += wxString( wxT( ",Mixed" ) );
+            attrib += ",Mixed";
             break;
         default:
             break;   // do nothing (but avoid a warning for unhandled LAYER_T values from GCC)
@@ -203,16 +202,69 @@ wxString GetGerberFileFunctionAttribute( const BOARD *aBoard,
     return fileFct;
 }
 
+
+static const wxString GetGerberFilePolarityAttribute( LAYER_NUM aLayer )
+{
+    /* build the string %TF.FilePolarity,Positive*%
+     * or  %TF.FilePolarity,Negative*%
+     * an emply string for layers which do not use a polarity
+     *
+     * The value of the .FilePolarity specifies whether the image represents the
+     * presence or absence of material.
+     * This attribute can only be used when the file represents a pattern in a material layer,
+     * e.g. copper, solder mask, legend.
+     * Together with.FileFunction it defines the role of that image in
+     * the layer structure of the PCB.
+     * Note that the .FilePolarity attribute does not change the image -
+     * no attribute does.
+     * It changes the interpretation of the image.
+     * For example, in a copper layer in positive polarity a round flash generates a copper pad.
+     * In a copper layer in negative polarity it generates a clearance.
+     * Solder mask images usually represent solder mask openings and are then negative.
+     * This may be counter-intuitive.
+     */
+    int polarity = 0;
+
+    switch( aLayer )
+    {
+    case F_Adhes:
+    case B_Adhes:
+    case F_SilkS:
+    case B_SilkS:
+    case F_Paste:
+    case B_Paste:
+        polarity = 1;
+        break;
+
+    case F_Mask:
+    case B_Mask:
+        polarity = -1;
+        break;
+
+    default:
+        if( IsCopperLayer( aLayer ) )
+            polarity = 1;
+        break;
+    }
+
+    wxString filePolarity;
+
+    if( polarity == 1 )
+        filePolarity = "%TF.FilePolarity,Positive*%";
+    if( polarity == -1 )
+        filePolarity = "%TF.FilePolarity,Negative*%";
+
+    return filePolarity;
+}
+
 /* Add some X2 attributes to the file header, as defined in the
  * Gerber file format specification J4 and "Revision 2015.06"
  */
-#define USE_REVISION_2015_06_ATTR
 void AddGerberX2Attribute( PLOTTER * aPlotter,
             const BOARD *aBoard, LAYER_NUM aLayer )
 {
     wxString text;
 
-#ifdef USE_REVISION_2015_06_ATTR
     // Creates the TF,.GenerationSoftware. Format is:
     // %TF,.GenerationSoftware,<vendor>,<application name>[,<application version>]*%
     text.Printf( wxT( "%%TF.GenerationSoftware,KiCad,Pcbnew,%s*%%" ), GetBuildVersion() );
@@ -278,11 +330,16 @@ void AddGerberX2Attribute( PLOTTER * aPlotter,
 
     text.Printf( wxT( "%%TF.ProjectId,%s,%s,%s*%%" ), msg.ToAscii(), GetChars( guid ), rev.ToAscii() );
     aPlotter->AddLineToHeader( text );
-#endif
 
     // Add the TF.FileFunction
     text = GetGerberFileFunctionAttribute( aBoard, aLayer, false );
     aPlotter->AddLineToHeader( text );
+
+    // Add the TF.FilePolarity (for layers which support that)
+    text = GetGerberFilePolarityAttribute( aLayer );
+
+    if( !text.IsEmpty() )
+        aPlotter->AddLineToHeader( text );
 }