Added a flag to decoded block to check if it contains any transparent colors. Useful to establish a fast path in transparent rendering if it does not.

common/block.go

@@ -43,12 +43,13 @@ type (
 	}
 
 	DecodedBlock struct {
-		Version    byte
-		MapContent []byte
-		AirId      int32
-		IgnoreId   int32
-		AirOnly    bool
-		IndexMap   map[int32]int32
+		Version     byte
+		MapContent  []byte
+		AirId       int32
+		IgnoreId    int32
+		AirOnly     bool
+		Transparent bool
+		IndexMap    map[int32]int32
 	}
 )
 
@@ -138,6 +139,7 @@ func NewDecodedBlock(data []byte, colors *Colors) (db *DecodedBlock, err error)
 	airId, ignoreId := int32(-1), int32(-1)
 	indexMap := make(map[int32]int32)
 	var airOnly bool
+	var transparent bool
 	if version >= 22 {
 		offset++
 		numMappings := int(binary.BigEndian.Uint16(data[offset:]))
@@ -157,6 +159,9 @@ func NewDecodedBlock(data []byte, colors *Colors) (db *DecodedBlock, err error)
 			default:
 				if index, found := colors.NameIndex[name]; found {
 					indexMap[nodeId] = index
+					if colors.IsTransparent(index) {
+						transparent = true
+					}
 				} else {
 					log.Printf("Missing color entry for %s.", name)
 				}
@@ -166,12 +171,13 @@ func NewDecodedBlock(data []byte, colors *Colors) (db *DecodedBlock, err error)
 	}
 
 	db = &DecodedBlock{
-		Version:    version,
-		MapContent: mapContent,
-		AirId:      airId,
-		IgnoreId:   ignoreId,
-		AirOnly:    airOnly,
-		IndexMap:   indexMap}
+		Version:     version,
+		MapContent:  mapContent,
+		AirId:       airId,
+		IgnoreId:    ignoreId,
+		AirOnly:     airOnly,
+		Transparent: transparent,
+		IndexMap:    indexMap}
 
 	return
 }

common/colors.go

@@ -14,9 +14,9 @@ import (
 )
 
 type Colors struct {
-	Colors      []color.RGBA
-	NameIndex   map[string]int32
-	Transparent int
+	Colors         []color.RGBA
+	NameIndex      map[string]int32
+	NumTransparent int32
 }
 
 type namedColor struct {
@@ -24,6 +24,10 @@ type namedColor struct {
 	color color.RGBA
 }
 
+func (colors *Colors) IsTransparent(index int32) bool {
+	return index < colors.NumTransparent
+}
+
 type sortByAlpha []namedColor
 
 func (colors sortByAlpha) Less(i, j int) bool {
@@ -70,14 +74,17 @@ func ParseColors(filename string) (colors *Colors, err error) {
 	cs := make([]color.RGBA, len(cols))
 	nameIndex := make(map[string]int32, len(cols))
 
-	transparent := 0
+	numTransparent := int32(0)
 	for i, nc := range cols {
 		if nc.color.A < 0xff {
-			transparent++
+			numTransparent++
 		}
 		cs[i] = nc.color
 		nameIndex[nc.name] = int32(i)
 	}
-	colors = &Colors{Colors: cs, NameIndex: nameIndex, Transparent: transparent}
+	colors = &Colors{
+		Colors:         cs,
+		NameIndex:      nameIndex,
+		NumTransparent: numTransparent}
 	return
 }