improve comments in specctra stuff

pcbnew/specctra_export.cpp

@@ -170,7 +170,7 @@ static inline double scale( int kicadDist )
 {
 #if defined(USE_PCBNEW_NANOMETRES)
 
-// nanometers to um
+    // nanometers to um
     return kicadDist / 1000.0;
 
     // nanometers to mils
@@ -1037,12 +1037,14 @@ void SPECCTRA_DB::FromBOARD( BOARD* aBoard ) throw( IO_ERROR )
     {
 
 #if defined(USE_PCBNEW_NANOMETRES)
-        // tell freerouter about centi-mil
+        // tell freerouter to use "tenths of micrometers",
+        // which is 100 nm resolution.  Possibly more resolution is possible
+        // in freerouter, but it would need testing.
 
         pcb->unit->units = T_um;
         pcb->resolution->units = T_um;
-
-        pcb->resolution->value = 10;
+        pcb->resolution->value = 10;        // tenths of a um
+        // pcb->resolution->value = 1000;   // "thousandths of a um" (i.e. "nm")
 
 #else
         pcb->unit->units = T_mil;

pcbnew/specctra_import.cpp

@@ -145,11 +145,10 @@ namespace DSN {
 static int scale( double distance, UNIT_RES* aResolution )
 {
     double  resValue = aResolution->GetValue();
+    double  factor;
 
 #if defined(USE_PCBNEW_NANOMETRES)
 
-    double  factor;
-
     switch( aResolution->GetEngUnits() )
     {
     default:
@@ -173,7 +172,6 @@ static int scale( double distance, UNIT_RES* aResolution )
     int ret = wxRound( factor * distance / resValue );
 
 #else
-    double  factor;     // multiply this times session value to get mils for KiCad.
 
     switch( aResolution->GetEngUnits() )
     {