core: fix display bugs with some UTF-8 chars that truncates messages displayed

Example of char causing problems: U+26C4 (snowman without snow)

ChangeLog

@@ -1,7 +1,7 @@
 WeeChat ChangeLog
 =================
 Sébastien Helleu <flashcode@flashtux.org>
-v0.4.2-dev, 2013-06-28
+v0.4.2-dev, 2013-06-29
 
 
 This document lists all changes for each version.
@@ -14,6 +14,8 @@ http://weechat.org/files/releasenotes/ReleaseNotes-devel.html[release notes]
 Version 0.4.2 (under dev!)
 --------------------------
 
+* core: fix display bugs with some UTF-8 chars that truncates messages displayed
+  (for example U+26C4)
 * core: update man page and add translations (in french, german, italian, and
   japanese)
 * core: remove extra space after empty prefix (when prefix for action, error,

src/gui/gui-chat.c

@@ -150,11 +150,19 @@ gui_chat_utf_char_valid (const char *utf_char)
 int
 gui_chat_char_size_screen (const char *utf_char)
 {
+    int size_screen;
+
     /* if char is invalid, it will be displayed as one space on screen */
     if (!gui_chat_utf_char_valid (utf_char))
         return 1;
 
-    return utf8_char_size_screen (utf_char);
+    size_screen = utf8_char_size_screen (utf_char);
+
+    /*
+     * ensure the size is always >= 1, to prevent any display bug
+     * (for example UTF-8 char U+26C4 returns size < 1)
+     */
+    return (size_screen >= 1) ? size_screen : 1;
 }
 
 /*