nano

commit f47ef539db50864bbd3b50a40987a30d834a68bd
parent 2148e857e586df78e85959bb660be52985ca42ee
Author: Benno Schulenberg <bensberg@telfort.nl>
Date:   Wed, 15 Jan 2020 17:28:14 +0100

display: skip zero-width characters on a Linux console, to avoid a mess

This is a workaround for the VT not being able to handle zero-width
characters properly, displaying them mistakenly as visible characters.

This avoids https://savannah.gnu.org/bugs/?52954.

The problem has existed since forever, but has become noticeable
since the capability for line numbers was added in version 2.7.1.

Diffstat:
M
src/winio.c
 | 
14
+++++++++++---

1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/src/winio.c b/src/winio.c
@@ -1939,13 +1939,21 @@ char *display_string(const char *buf, size_t column, size_t span,
 			continue;
 		}
 
+		/* Determine whether the character takes zero, one, or two columns. */
+		charwidth = wcwidth(wc);
+
+#ifdef __linux__
+		/* On a Linux console, skip zero-width characters, as it would show
+		 * them WITH a width, thus messing up the display.  See bug #52954. */
+		if (on_a_vt && charwidth == 0) {
+			buf += charlength;
+			continue;
+		}
+#endif
 		/* For any valid character, just copy its bytes. */
 		for (; charlength > 0; charlength--)
 			converted[index++] = *(buf++);
 
-		/* Determine whether the character occupies one or two columns. */
-		charwidth = wcwidth(wc);
-
 		/* If the codepoint is unassigned, assume a width of one. */
 		column += (charwidth < 0 ? 1 : charwidth);