Better support for transposition and Nashville numbers.

- Non-diatonic pitches are supported using Nashville numbers (#5).
- When using Nashville numbers chord variants with non-diatonic roots
  are now recognized (e.g. b7)
- Pitch rendering is now aware of key centers. For example, F# is F#
  rendered as F# when in the key of G but Gb when in the key of Ab.

src/pco_chordspkg/html.nim

@@ -113,9 +113,9 @@ func scaleDegree(root: ChordChartPitch, p: ChordChartPitch): string =
   else: raise newException(Exception, "Impossible")
 
 func format(ctx: FormatContext, chord: ChordChartChord, useNumber = false): string =
-  if not useNumber and chord.original.isSome: return chord.original.get
+  ##if not useNumber and chord.original.isSome: return chord.original.get
 
-  elif useNumber:
+  if useNumber:
     result = "<span class=root>" &
       ctx.currentKey.scaleDegree(chord.rootPitch) & "</span>"
 
@@ -127,11 +127,15 @@ func format(ctx: FormatContext, chord: ChordChartChord, useNumber = false): stri
         ctx.currentKey.scaleDegree(chord.bassPitch.get) & "</span>"
 
   else:
-    result = $chord.rootPitch
-    if chord.flavor.isSome: result &= chord.flavor.get
-    if chord.bassPitch.isSome: result &= "/" & $chord.bassPitch.get
-    #debug "transposed " & $ctx.sourceKey & " -> " & $ctx.currentKey &
-    #  " (distance " & $distance & ")\p\tchord: " & $chord & " to " & result
+    result = "<span class=root>" &
+      renderPitchInKey(chord.rootPitch, ctx.currentKey) & "</span>"
+
+    if chord.flavor.isSome:
+      result &= "<span class=flavor>" & chord.flavor.get & "</span>"
+
+    if chord.bassPitch.isSome:
+      result &= "<span class=bass>/" &
+        renderPitchInKey(chord.bassPitch.get, ctx.currentKey) & "</span>"
 
 proc transpose(ctx: FormatContext, chord: ChordChartChord): ChordChartChord =
   result = chord