core: add key alt+backspace, change behavior of key ctrl+w (closes #559)

The key ctrl+w now deletes one word until whitespace.

The new key alt+backspace deletes one word (same behavior as ctrl+w in previous
releases).

src/core/wee-command.c

@@ -3294,6 +3294,8 @@ COMMAND_CALLBACK(input)
         gui_input_delete_next_char (buffer);
     else if (string_strcasecmp (argv[1], "delete_previous_word") == 0)
         gui_input_delete_previous_word (buffer);
+    else if (string_strcasecmp (argv[1], "delete_previous_word_whitespace") == 0)
+        gui_input_delete_previous_word_whitespace (buffer);
     else if (string_strcasecmp (argv[1], "delete_next_word") == 0)
         gui_input_delete_next_word (buffer);
     else if (string_strcasecmp (argv[1], "delete_beginning_of_line") == 0)
@@ -7985,6 +7987,8 @@ command_init ()
            "  delete_previous_char: delete previous char\n"
            "  delete_next_char: delete next char\n"
            "  delete_previous_word: delete previous word\n"
+           "  delete_previous_word_whitespace: delete previous word "
+           "(until whitespace)\n"
            "  delete_next_word: delete next word\n"
            "  delete_beginning_of_line: delete from beginning of line until "
            "cursor\n"
@@ -8041,7 +8045,8 @@ command_init ()
         "search_text || search_switch_case || search_switch_regex || "
         "search_switch_where || search_previous || search_next || "
         "search_stop_here || search_stop || delete_previous_char || "
-        "delete_next_char || delete_previous_word || delete_next_word || "
+        "delete_next_char || delete_previous_word || "
+        "delete_previous_word_whitespace || delete_next_word || "
         "delete_beginning_of_line || delete_end_of_line || delete_line || "
         "clipboard_paste || transpose_chars || undo || redo || "
         "move_beginning_of_line || move_end_of_line || move_previous_char || "

src/core/wee-string.c

@@ -1109,6 +1109,20 @@ string_convert_escaped_chars (const char *string)
     return output;
 }
 
+/*
+ * Checks if first char of string is a whitespace (space or tab).
+ *
+ * Returns:
+ *   1: first char is whitespace
+ *   0: first char is not whitespace
+ */
+
+int
+string_is_whitespace_char (const char *string)
+{
+    return (string && ((string[0] == ' ') || string[0] == '\t')) ? 1 : 0;
+}
+
 /*
  * Checks if first char of string is a "word char".
  *

src/core/wee-string.h

@@ -71,6 +71,7 @@ extern char *string_remove_quotes (const char *string, const char *quotes);
 extern char *string_strip (const char *string, int left, int right,
                            const char *chars);
 extern char *string_convert_escaped_chars (const char *string);
+extern int string_is_whitespace_char (const char *string);
 extern int string_is_word_char_highlight (const char *string);
 extern int string_is_word_char_input (const char *string);
 extern char *string_mask_to_regex (const char *mask);