output.py: harmonize variable names and group xterm title code

The global variables are inconsistently named and spread over the
module, similarly the title related code is not grouped together.
Harmonize this.

Also the double negative logic involving `_disable_xtermTitle` makes the
code harder to read. Invert the logic.

Signed-off-by: Matthias Gerstner <[email protected]>

lib/portage/output.py

@@ -268,20 +268,65 @@ def nc_len(mystr):
 _legal_terms_re = re.compile(
     r"^(xterm|xterm-color|Eterm|aterm|rxvt|screen|kterm|rxvt-unicode|gnome|interix|tmux|st-256color|alacritty|konsole|foot)"
 )
-_disable_xtermTitle = None
-_max_xtermTitle_len = 253
+_xterm_title_supported = None
+_max_xterm_title_len = 253
 _title_init_seq = None
 _title_finish_seq = None
+_default_xterm_title = None
+
+
+def init_xterm_titles():
+    global _xterm_title_supported
+    global _title_init_seq
+    global _title_finish_seq
+
+    if _xterm_title_supported is not None:
+        # already initialized
+        return
+
+    _xterm_title_supported = False
+
+    if not sys.__stderr__.isatty() or "TERM" not in os.environ:
+        return
+
+    try:
+        # by default check if we can dynamically query the proper title
+        # setting sequence via terminfo
+        curses = init_curses(sys.stderr)
+
+        if curses is not None:
+            tsl = curses.tigetstr("tsl").decode()
+            fsl = curses.tigetstr("fsl").decode()
+            if tsl and fsl:
+                _xterm_title_supported = True
+                _title_init_seq = tsl
+                _title_finish_seq = fsl
+            return
+    except curses.error:
+        pass
+
+    if _legal_terms_re.match(os.environ["TERM"]) is not None:
+        # as a fallback use the well known xterm escape sequences for the hard
+        # coded suppoted terminal list
+        _xterm_title_supported = True
+        _title_init_seq = "\x1b]0;"
+        _title_finish_seq = "\x07"
+
+
+def format_xterm_title(mystr):
+    if not _xterm_title_supported:
+        return mystr
+    return _title_init_seq + mystr + _title_finish_seq
 
 
 def xtermTitle(mystr, raw=False):
     init_xterm_titles()
 
-    if dotitles and not _disable_xtermTitle:
+    if dotitles and _xterm_title_supported:
         # If the title string is too big then the terminal can
         # misbehave. Therefore, truncate it if it's too big.
-        if len(mystr) > _max_xtermTitle_len:
-            mystr = mystr[:_max_xtermTitle_len]
+        if len(mystr) > _max_xterm_title_len:
+            mystr = mystr[:_max_xterm_title_len]
         if not raw:
             mystr = format_xterm_title(mystr)
 
@@ -294,18 +339,15 @@ def xtermTitle(mystr, raw=False):
         f.flush()
 
 
-default_xterm_title = None
-
-
 def xtermTitleReset():
     init_xterm_titles()
-    global default_xterm_title
-    if default_xterm_title is None:
+    global _default_xterm_title
+    if _default_xterm_title is None:
         prompt_command = os.environ.get("PROMPT_COMMAND")
         if prompt_command == "":
-            default_xterm_title = ""
+            _default_xterm_title = ""
         elif prompt_command is not None:
-            if dotitles and not _disable_xtermTitle:
+            if dotitles and _xterm_title_supported:
                 from portage.process import find_binary, spawn
 
                 shell = os.environ.get("SHELL")
@@ -329,14 +371,14 @@ def xtermTitleReset():
             home = os.environ.get("HOME", "")
             if home != "" and pwd.startswith(home):
                 pwd = "~" + pwd[len(home) :]
-            default_xterm_title = format_xterm_title("{}@{}:{}".format(
+            _default_xterm_title = format_xterm_title("{}@{}:{}".format(
                 os.environ.get("LOGNAME", ""),
                 os.environ.get("HOSTNAME", "").split(".", 1)[0],
                 pwd,
             ))
     # since PROMPT_COMMAND can already contain escape sequences, output the
     # title as a raw sequence without adding any additional sequences.
-    xtermTitle(default_xterm_title, raw=True)
+    xtermTitle(_default_xterm_title, raw=True)
 
 
 def notitles():
@@ -516,50 +558,6 @@ def init_curses(fd):
         return None
 
 
-def init_xterm_titles():
-    global _disable_xtermTitle
-    global _title_init_seq
-    global _title_finish_seq
-
-    if _disable_xtermTitle is not None:
-        # already initialized
-        return
-
-    _disable_xtermTitle = True
-
-    if not sys.__stderr__.isatty() or "TERM" not in os.environ:
-        return
-
-    try:
-        # by default check if we can dynamically query the proper title
-        # setting sequence via terminfo
-        curses = init_curses(sys.stderr)
-
-        if curses is not None:
-            tsl = curses.tigetstr("tsl").decode()
-            fsl = curses.tigetstr("fsl").decode()
-            if tsl and fsl:
-                _xtermTitle_supported = True
-                _title_init_seq = tsl
-                _title_finish_seq = fsl
-            return
-    except curses.error:
-        pass
-
-    if _legal_terms_re.match(os.environ["TERM"]) is not None:
-        # as a fallback use the well known xterm escape sequences for the hard
-        # coded suppoted terminal list
-        _disable_xtermTitle = False
-        _title_init_seq = "\x1b]0;"
-        _title_finish_seq = "\x07"
-
-
-def format_xterm_title(mystr):
-    if _disable_xtermTitle:
-        return mystr
-    return _title_init_seq + mystr + _title_finish_seq
-
-
 def get_term_size(fd=None):
     """
     Get the number of lines and columns of the tty that is connected to