conditional os in UI xml, add system dialog file open on osx, check api format or error message when opening a document, per-char text wrap on NodeText, additional info on create doc dialog like working path

src/font.cpp

@@ -75,9 +75,14 @@ void TextMesh::update(kFont id, const char* text)
             if (text[i] == '\n')
             {
                 x = 0;
-                y += f.size *2;
+                y += f.size * 2;
                 continue;
             }
+            if (max_width > 0 && x > max_width * 2 /*font scale factor*/)
+            {
+                x = 0;
+                y += f.size * 2;
+            }
             int c = text[i] - f.start_char;
             stbtt_aligned_quad q;
             stbtt_GetBakedQuad((stbtt_bakedchar*)f.chars.data(), f.w, f.h, c, &x, &y, &q, true);