handle window resize event and set width accordingly (#291)

This fixes #215 and gives proper aligned tab-completion.

pwndbg/__init__.py

@@ -5,6 +5,8 @@ from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
 
+import signal
+
 import gdb
 
 import pwndbg.android
@@ -67,6 +69,7 @@ import pwndbg.prompt
 import pwndbg.regs
 import pwndbg.stack
 import pwndbg.typeinfo
+import pwndbg.ui
 import pwndbg.version
 import pwndbg.vmmap
 import pwndbg.wrappers
@@ -131,13 +134,13 @@ set follow-fork-mode child
 set backtrace past-main on
 set step-mode on
 set print pretty on
-set width 0
+set width %i
 set print elements 15
 handle SIGALRM nostop print nopass
 handle SIGBUS  stop   print nopass
 handle SIGPIPE nostop print nopass
 handle SIGSEGV stop   print nopass
-""".strip() % prompt
+""".strip() % (prompt, pwndbg.ui.get_window_size()[1])
 
 for line in pre_commands.strip().splitlines():
     gdb.execute(line)
@@ -147,3 +150,7 @@ try:
     gdb.execute("set disassembly-flavor intel")
 except gdb.error:
     pass
+
+
+# handle resize event to align width and completion
+signal.signal(signal.SIGWINCH, lambda signum, frame: gdb.execute("set width %i" % pwndbg.ui.get_window_size()[1]))

pwndbg/ui.py

@@ -9,6 +9,7 @@ from __future__ import print_function
 from __future__ import unicode_literals
 
 import fcntl
+import os
 import struct
 import sys
 import termios
@@ -22,13 +23,21 @@ theme.Parameter('banner-separator', '─', 'repeated banner separator character'
 
 def banner(title):
     title = title.upper()
-    try:
-        _height, width = struct.unpack('hh', fcntl.ioctl(sys.stdin.fileno(), termios.TIOCGWINSZ, '1234'))
-    except:
-        width = 80
+    _height, width = get_window_size()
     width -= 2
     return C.banner(("[{:%s^%ss}]" % (config.banner_separator, width)).format(title))
 
 def addrsz(address):
     address = int(address) & pwndbg.arch.ptrmask
     return "%{}x".format(2*pwndbg.arch.ptrsize) % address
+
+def get_window_size():
+    fallback = (int(os.environ.get('LINES', 20)), int(os.environ.get('COLUMNS', 80)))
+    if not sys.stdin.isatty:
+        return fallback
+    try:
+        # get terminal size and force ret buffer len of 4 bytes for safe unpacking by passing equally long arg
+        rows, cols = struct.unpack('hh', fcntl.ioctl(sys.stdin.fileno(), termios.TIOCGWINSZ, '1234'))
+    except:
+        rows, cols = fallback
+    return rows, cols