implement word wrap in text node

src/font.h

@@ -44,6 +44,13 @@ public:
 
 class TextMesh
 {
+    struct Token
+    {
+        std::string s;
+        float w;
+        Token(const std::string& str, float width) : s(str), w(width) {}
+    };
+    std::vector<Token> tokenize(const std::string& s, const Font& f) const noexcept;
 public:
     GLuint font_array = 0;
     int font_array_count = 0;