256 color support

Expose termbox OutputMode so users can override the default.
addColorMap to extend textbuilder with custom colors
ColorRGB24 to convert from web to terminal colors

helper.go

@@ -45,6 +45,18 @@ var (
 	dotw = rw.StringWidth(dot)
 )
 
+// termbox passthrough
+type OutputMode int
+
+// termbox passthrough
+const (
+	OutputCurrent OutputMode = iota
+	OutputNormal
+	Output256
+	Output216
+	OutputGrayscale
+)
+
 /* ----------------------- End ----------------------------- */
 
 func toTmAttr(x Attribute) tm.Attribute {
@@ -220,3 +232,19 @@ func CellsToStr(cs []Cell) string {
 	}
 	return str
 }
+
+// Passthrough to termbox using termbox constants above
+func SetOutputMode(mode OutputMode) {
+	switch mode {
+	case OutputCurrent:
+		tm.SetOutputMode(tm.OutputCurrent)
+	case OutputNormal:
+		tm.SetOutputMode(tm.OutputNormal)
+	case Output256:
+		tm.SetOutputMode(tm.Output256)
+	case Output216:
+		tm.SetOutputMode(tm.Output216)
+	case OutputGrayscale:
+		tm.SetOutputMode(tm.OutputGrayscale)
+	}
+}

textbuilder.go

@@ -52,6 +52,11 @@ var attrMap = map[string]Attribute{
 	"reverse":   AttrReverse,
 }
 
+// Allow users to add/override the string to attribute mapping
+func AddColorMap(str string, attr Attribute) {
+	colorMap[str] = attr
+}
+
 func rmSpc(s string) string {
 	reg := regexp.MustCompile(`\s+`)
 	return reg.ReplaceAllString(s, "")
@@ -85,10 +90,10 @@ func (mtb MarkdownTxBuilder) readAttr(s string) (Attribute, Attribute) {
 		if len(subs) > 1 {
 			if subs[0] == "fg" {
 				fgs = append(fgs, subs[1])
-			}
-			if subs[0] == "bg" {
+			} else if subs[0] == "bg" {
 				bgs = append(bgs, subs[1])
 			}
+			// else maybe error somehow?
 		}
 	}
 

theme.go

@@ -138,3 +138,8 @@ func ColorRGB(r, g, b int) Attribute {
 	r, b, g = within(r), within(b), within(g)
 	return Attribute(0x0f + 36*r + 6*g + b)
 }
+
+// Convert from familiar 24 bit colors into 6 bit terminal colors
+func ColorRGB24(r, g, b int) Attribute {
+	return ColorRGB(r/51, g/51, b/51)
+}