Log missing colors only once to make log output less spammy.

common/block.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
+	"sync"
 )
 
 // Error returned if a Producer has run to its end.
@@ -163,7 +164,7 @@ func NewDecodedBlock(data []byte, colors *Colors) (db *DecodedBlock, err error)
 						transparent = true
 					}
 				} else {
-					log.Printf("Missing color entry for %s.", name)
+					logMissing(name)
 				}
 			}
 		}
@@ -180,6 +181,20 @@ func NewDecodedBlock(data []byte, colors *Colors) (db *DecodedBlock, err error)
 	return
 }
 
+var missingColors = struct {
+	sync.Mutex
+	cols map[string]struct{}
+}{cols: map[string]struct{}{}}
+
+func logMissing(name string) {
+	missingColors.Lock()
+	defer missingColors.Unlock()
+	if _, found := missingColors.cols[name]; !found {
+		missingColors.cols[name] = struct{}{}
+		log.Printf("Missing color entry for %s.\n", name)
+	}
+}
+
 func (db *DecodedBlock) AirOnly() bool {
 	return db.AirId != -1 && len(db.IndexMap) == 0
 }