patch 7.4.949
Problem:    When using 'colorcolumn' and there is a sign with a fullwidth
            character the highlighting is wrong. (Andrew Stewart)
Solution:   Only increment vcol when in the right state. (Christian Brabandt)
diff --git a/src/screen.c b/src/screen.c
index d80ad6f..5816381 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -5422,7 +5422,12 @@
 		else
 		    /* DBCS: Put second byte in the second screen char. */
 		    ScreenLines[off] = mb_c & 0xff;
-		++vcol;
+		if (draw_state > WL_NR
+#ifdef FEAT_DIFF
+			&& filler_todo <= 0
+#endif
+			)
+		    ++vcol;
 		/* When "tocol" is halfway a character, set it to the end of
 		 * the character, otherwise highlighting won't stop. */
 		if (tocol == vcol)