core: check for newline characters in string_is_whitespace_char

This fixes a bug where if you had multiple lines in the input and
pressed ctrl-w when the cursor was after the first word of any line but
the first, it would delete both the word before the cursor and the last
word on the preceding line.

ChangeLog.adoc

@@ -23,6 +23,7 @@ Bug fixes::
 
   * core: force key "return" to command "/input return" when migrating legacy keys
   * core: display actual key name and command with key kbd:[Alt+k], remove key kbd:[Alt+K] (grab raw key) and associated commands `/input grab_raw_key` and `/input grab_raw_key_command`
+  * core: check for newline characters in string_is_whitespace_char (issue #1968)
   * api: do not convert option name to lower case in API functions config_set_plugin and config_set_desc_plugin
   * irc: reply to a CTCP request sent to self nick (issue #1966)
   * irc: sent "QUIT" message to servers connected with TLS on `/upgrade`

src/core/wee-string.c

@@ -1312,7 +1312,7 @@ string_convert_escaped_chars (const char *string)
 }
 
 /*
- * Checks if first char of string is a whitespace (space or tab).
+ * Checks if first char of string is a whitespace (space, tab, newline or carriage return).
  *
  * Returns:
  *   1: first char is whitespace
@@ -1322,7 +1322,11 @@ string_convert_escaped_chars (const char *string)
 int
 string_is_whitespace_char (const char *string)
 {
-    return (string && ((string[0] == ' ') || string[0] == '\t')) ? 1 : 0;
+    return (string && (
+            (string[0] == ' ')
+            || (string[0] == '\t')
+            || (string[0] == '\n')
+            || (string[0] == '\r'))) ? 1 : 0;
 }
 
 /*

tests/unit/core/test-core-string.cpp

@@ -1090,6 +1090,8 @@ TEST(CoreString, IsWhitespaceChar)
 
     LONGS_EQUAL(1, string_is_whitespace_char (" abc def"));
     LONGS_EQUAL(1, string_is_whitespace_char ("\tabc def"));
+    LONGS_EQUAL(1, string_is_whitespace_char ("\nabc def"));
+    LONGS_EQUAL(1, string_is_whitespace_char ("\rabc def"));
 }
 
 /*