Add basic HTML rendering (ref #16)

ui/messages/tstring/string.go

@@ -19,8 +19,8 @@ package tstring
 import (
 	"strings"
 
-	"maunium.net/go/tcell"
 	"github.com/mattn/go-runewidth"
+	"maunium.net/go/tcell"
 )
 
 type TString []Cell
@@ -49,6 +49,37 @@ func NewStyleTString(str string, style tcell.Style) TString {
 	return newStr
 }
 
+func (str TString) AppendTString(data TString) TString {
+	return append(str, data...)
+}
+
+func (str TString) Append(data string) TString {
+	newStr := make(TString, len(str)+len(data))
+	copy(newStr, str)
+	for i, char := range data {
+		newStr[i+len(str)] = NewCell(char)
+	}
+	return newStr
+}
+
+func (str TString) AppendColor(data string, color tcell.Color) TString {
+	newStr := make(TString, len(str)+len(data))
+	copy(newStr, str)
+	for i, char := range data {
+		newStr[i+len(str)] = NewColorCell(char, color)
+	}
+	return newStr
+}
+
+func (str TString) AppendStyle(data string, style tcell.Style) TString {
+	newStr := make(TString, len(str)+len(data))
+	copy(newStr, str)
+	for i, char := range data {
+		newStr[i+len(str)] = NewStyleCell(char, style)
+	}
+	return newStr
+}
+
 func (str TString) Colorize(from, length int, color tcell.Color) {
 	for i := from; i < from+length; i++ {
 		str[i].Style = str[i].Style.Foreground(color)