core: fix cut of chars in "cutscr" of evaluated strings

This fixes two problems:
- stop before max char displayed with wide chars
- preserve combining chars in the output

Before the fix (wrong):

>> ${cutscr:3,+,こんにちは世界}
== [こん+]
>> ${cutscr:1,+,a${\u0308}}
== [a+]

After the fix (OK):

>> ${cutscr:3,+,こんにちは世界}
== [こ+]
>> ${cutscr:1,+,a${\u0308}}
== [ä]

1 files changed, 3 insertions, 1 deletions

diff --git a/src/gui/gui-chat.c b/src/gui/gui-chat.c
index 02891ef06..5fc018dba 100644
--- a/src/gui/gui-chat.c
+++ b/src/gui/gui-chat.c
@@ -224,7 +224,7 @@ gui_chat_string_add_offset_screen (const char *string, int offset_screen)
 {
     int size_on_screen;
 
-    while (string && string[0] && (offset_screen > 0))
+    while (string && string[0] && (offset_screen >= 0))
     {
         string = gui_chat_string_next_char (NULL, NULL,
                                             (unsigned char *)string,
@@ -233,6 +233,8 @@ gui_chat_string_add_offset_screen (const char *string, int offset_screen)
         {
             size_on_screen = gui_chat_char_size_screen (string);
             offset_screen -= size_on_screen;
+            if (offset_screen < 0)
+                return string;
             string = utf8_next_char (string);
         }
     }