Add icon: Lucide 1.58.0 SVG set, lazy parse, Must, Names

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

icon/icon.go

@@ -0,0 +1,57 @@
+// Package icon embeds the Lucide icons, parsed on first use.
+package icon
+
+import (
+	"embed"
+	"slices"
+	"strings"
+	"sync"
+
+	"github.com/egoist/mygo/ui"
+)
+
+//go:embed svg/*.svg
+var files embed.FS
+
+var (
+	names = list()
+	mu    sync.Mutex
+	cache = map[string]*ui.SVG{}
+)
+
+func list() []string {
+	entries, err := files.ReadDir("svg")
+	if err != nil {
+		panic(err)
+	}
+	out := make([]string, len(entries))
+	for i, e := range entries {
+		out[i] = strings.TrimSuffix(e.Name(), ".svg")
+	}
+	slices.Sort(out)
+	return out
+}
+
+// Must returns the icon named name; it panics when missing.
+func Must(name string) *ui.SVG {
+	mu.Lock()
+	defer mu.Unlock()
+	if s, ok := cache[name]; ok {
+		return s
+	}
+	if _, ok := slices.BinarySearch(names, name); !ok {
+		panic("icon: no icon " + name)
+	}
+	data, err := files.ReadFile("svg/" + name + ".svg")
+	if err != nil {
+		panic(err)
+	}
+	s := ui.MustParseSVG(data)
+	cache[name] = s
+	return s
+}
+
+// Names lists every icon name in order.
+func Names() []string {
+	return slices.Clone(names)
+}