Add font tag support and /rainbow command

ui/command-processor.go

@@ -78,6 +78,7 @@ func NewCommandProcessor(parent *MainView) *CommandProcessor {
 			"part":  {"leave"},
 			"send":  {"sendevent"},
 			"state": {"setstate"},
+			"rb":    {"rainbow"},
 		},
 		commands: map[string]CommandHandler{
 			"unknown-command": cmdUnknownCommand,
@@ -91,6 +92,7 @@ func NewCommandProcessor(parent *MainView) *CommandProcessor {
 			"logout":          cmdLogout,
 			"sendevent":       cmdSendEvent,
 			"setstate":        cmdSetState,
+			"rainbow":         cmdRainbow,
 		},
 	}
 }

ui/commands.go

@@ -20,6 +20,9 @@ import (
 	"encoding/json"
 	"maunium.net/go/gomuks/debug"
 	"strings"
+	"fmt"
+	"github.com/lucasb-eyer/go-colorful"
+	"unicode"
 )
 
 func cmdMe(cmd *Command) {
@@ -29,6 +32,56 @@ func cmdMe(cmd *Command) {
 	cmd.UI.Render()
 }
 
+// GradientTable from https://github.com/lucasb-eyer/go-colorful/blob/master/doc/gradientgen/gradientgen.go
+type GradientTable []struct {
+	Col colorful.Color
+	Pos float64
+}
+
+func (gt GradientTable) GetInterpolatedColorFor(t float64) colorful.Color {
+	for i := 0; i < len(gt)-1; i++ {
+		c1 := gt[i]
+		c2 := gt[i+1]
+		if c1.Pos <= t && t <= c2.Pos {
+			t := (t - c1.Pos) / (c2.Pos - c1.Pos)
+			return c1.Col.BlendHcl(c2.Col, t).Clamped()
+		}
+	}
+	return gt[len(gt)-1].Col
+}
+
+var rainbow = GradientTable{
+	{colorful.LinearRgb(1, 0, 0), 0.0},
+	{colorful.LinearRgb(1, 0.5, 0), 0.1},
+	{colorful.LinearRgb(1, 1, 0), 0.2},
+	{colorful.LinearRgb(0.5, 1, 0), 0.3},
+	{colorful.LinearRgb(0, 1, 0), 0.4},
+	{colorful.LinearRgb(0, 1, 0.5), 0.5},
+	{colorful.LinearRgb(0, 1, 1), 0.6},
+	{colorful.LinearRgb(0, 0.5, 1), 0.7},
+	{colorful.LinearRgb(0.5, 0, 1), 0.8},
+	{colorful.LinearRgb(1, 0, 1), 0.9},
+	{colorful.LinearRgb(1, 0, 0.5), 1},
+}
+
+// TODO this command definitely belongs in a plugin once we have a plugin system.
+func cmdRainbow(cmd *Command) {
+	text := strings.Join(cmd.Args, " ")
+	var html strings.Builder
+	fmt.Fprint(&html, "**🌈** ")
+	for i, char := range text {
+		if unicode.IsSpace(char) {
+			html.WriteRune(char)
+			continue
+		}
+		color := rainbow.GetInterpolatedColorFor(float64(i)/float64(len(text))).Hex()
+		fmt.Fprintf(&html, "<font color=\"%s\">%c</font>", color, char)
+	}
+	tempMessage := cmd.Room.NewTempMessage("m.text", html.String())
+	go cmd.MainView.sendTempMessage(cmd.Room, tempMessage, html.String())
+	cmd.UI.Render()
+}
+
 func cmdQuit(cmd *Command) {
 	cmd.Gomuks.Stop()
 }

ui/messages/parser/htmlparser.go

@@ -29,6 +29,7 @@ import (
 	"maunium.net/go/gomuks/ui/widget"
 	"maunium.net/go/tcell"
 	"strconv"
+	"github.com/lucasb-eyer/go-colorful"
 )
 
 var matrixToURL = regexp.MustCompile("^(?:https?://)?(?:www\\.)?matrix\\.to/#/([#@!].*)")
@@ -125,6 +126,26 @@ func (parser *htmlParser) basicFormatToTString(node *html.Node, stripLinebreak b
 	return str
 }
 
+func (parser *htmlParser) fontToTString(node *html.Node, stripLinebreak bool) tstring.TString {
+	str := parser.nodeToTagAwareTString(node.FirstChild, stripLinebreak)
+	hex := parser.getAttribute(node, "color")
+	if len(hex) == 0 {
+		return str
+	}
+
+	color, err := colorful.Hex(hex)
+	if err != nil {
+		return str
+	}
+
+	r, g, b := color.RGB255()
+	tcellColor := tcell.NewRGBColor(int32(r), int32(g), int32(b))
+	str.AdjustStyleFull(func(style tcell.Style) tcell.Style {
+		return style.Foreground(tcellColor)
+	})
+	return str
+}
+
 func (parser *htmlParser) headerToTString(node *html.Node, stripLinebreak bool) tstring.TString {
 	children := parser.nodeToTStrings(node.FirstChild, stripLinebreak)
 	length := int(node.Data[1] - '0')
@@ -172,6 +193,8 @@ func (parser *htmlParser) tagToTString(node *html.Node, stripLinebreak bool) tst
 		return tstring.NewTString("\n")
 	case "b", "strong", "i", "em", "s", "del", "u", "ins":
 		return parser.basicFormatToTString(node, stripLinebreak)
+	case "font":
+		return parser.fontToTString(node, stripLinebreak)
 	case "a":
 		return parser.linkToTString(node, stripLinebreak)
 	case "p":