cross-platform and error-tolerant width check (#82)

beets/config_default.yaml

@@ -35,6 +35,7 @@ timeout: 5.0
 per_disc_numbering: no
 verbose: no
 terminal_encoding: utf8
+terminal_width: 80
 
 list_format_item: $artist - $album - $title
 list_format_album: $albumartist - $album

beets/ui/__init__.py

@@ -27,6 +27,7 @@ import logging
 import sqlite3
 import errno
 import re
+import struct
 
 from beets import library
 from beets import plugins
@@ -477,6 +478,28 @@ def print_obj(obj, lib, fmt=None):
     else:
         print_(obj.evaluate_template(template, lib=lib))
 
+def term_width():
+    """Get the width (columns) of the terminal."""
+    fallback = config['terminal_width'].get(int)
+
+    # The fcntl and termios modules are not available on non-Unix
+    # platforms, so we fall back to a constant.
+    try:
+        import fcntl
+        import termios
+    except ImportError:
+        return fallback
+
+    try:
+        buf = fcntl.ioctl(0, termios.TIOCGWINSZ, ' '*4)
+    except IOError:
+        return fallback
+    try:
+        height, width = struct.unpack('hh', buf)
+    except struct.error:
+        return fallback
+    return width
+
 
 # Subcommand parsing infrastructure.
 

beets/ui/commands.py

@@ -22,9 +22,6 @@ import os
 import time
 import itertools
 import re
-import fcntl
-import struct
-import termios
 
 import beets
 from beets import ui
@@ -185,10 +182,8 @@ def show_change(cur_artist, cur_album, match):
     pairs = match.mapping.items()
     pairs.sort(key=lambda (_, track_info): track_info.index)
 
-    # Calculate max column width.
-    buf = fcntl.ioctl(0, termios.TIOCGWINSZ, ' '*4)
-    height, width = struct.unpack('hh', buf)
-    col_width = (width - len(''.join([' * ', ' -> ']))) / 2
+    # The width of one column in track difference display.
+    col_width = (ui.term_width() - len(''.join([' * ', ' -> ']))) // 2
 
     # Get each change as a colorized LHS and RHS value, and the length of the
     # uncolored LHS value.