Ignore directional control chars in font::len()

They're invisible in font::print(), but they were still considered
characters with widths in the width function. This change made the
levels screen look better in RTL too - I was wondering why the level
options were too far left.

desktop_version/src/Font.cpp

@@ -1232,9 +1232,12 @@ int len(const uint32_t flags, const char* text)
     int text_len = 0;
     uint32_t codepoint;
     while ((codepoint = UTF8_next(&text)))
+    {
+        if (!is_directional_character(codepoint) && !is_joiner(codepoint))
         {
             text_len += get_advance(pf.font_sel, codepoint);
         }
+    }
     return text_len * pf.scale;
 }