From 3a344d86febd397be8d4087595640f4efe8e7944 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sat, 7 Oct 2017 09:01:31 +0530
Subject: [PATCH] Add graphics protocol detection to icat.py

---
 kitty/icat.py | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/kitty/icat.py b/kitty/icat.py
index bd85b80f6..6731389da 100755
--- a/kitty/icat.py
+++ b/kitty/icat.py
@@ -6,16 +6,21 @@ import argparse
 import fcntl
 import mimetypes
 import os
+import re
+import selectors
 import signal
 import struct
 import subprocess
 import sys
 import termios
+import tty
 import zlib
 from base64 import standard_b64encode
 from collections import namedtuple
 from gettext import gettext as _
 from math import ceil, floor
+from tempfile import NamedTemporaryFile
+from time import monotonic
 
 try:
     from kitty.constants import appname
@@ -173,9 +178,56 @@ def scan(d):
                 yield os.path.join(dirpath, f), mt
 
 
+def detect_support(wait_for=10):
+    fd = sys.stdin.fileno()
+    old = termios.tcgetattr(fd)
+    oldfl = fcntl.fcntl(fd, fcntl.F_GETFL)
+    fcntl.fcntl(fd, fcntl.F_SETFL, oldfl | os.O_NONBLOCK)
+    print('Checking for graphics ({}s max. wait)...'.format(wait_for), end='\r')
+    sys.stdout.flush()
+    tty.setraw(fd)
+    try:
+        received = b''
+        start_time = monotonic()
+        responses = {}
+
+        def parse_responses():
+            for m in re.finditer(b'\033_Gi=([1|2]);(.+?)\033\\\\', received):
+                iid = m.group(1)
+                if iid in (b'1', b'2'):
+                    iid = int(iid.decode('ascii'))
+                    if iid not in responses:
+                        responses[iid] = m.group(2) == b'OK'
+
+        def read():
+            nonlocal received
+            d = sys.stdin.buffer.read()
+            if not d:  # EOF
+                responses[1] = responses[2] = False
+                return
+            received += d
+            parse_responses()
+
+        with NamedTemporaryFile() as f:
+            f.write(b'abcd'), f.flush()
+            write_gr_cmd(dict(a='q', s=1, v=1, i=1), standard_b64encode(b'abcd'))
+            write_gr_cmd(dict(a='q', s=1, v=1, i=2, t='f'), standard_b64encode(f.name.encode(sys.getfilesystemencoding() or 'utf-8')))
+            sel = selectors.DefaultSelector()
+            sel.register(sys.stdin, selectors.EVENT_READ, read)
+            while monotonic() - start_time < wait_for and 1 not in responses and 2 not in responses:
+                for key, mask in sel.select(0.1):
+                    read()
+    finally:
+        sys.stdout.buffer.write(b'\033[J'), sys.stdout.flush()
+        termios.tcsetattr(fd, termios.TCSADRAIN, old)
+        fcntl.fcntl(fd, fcntl.F_SETFL, oldfl)
+    detect_support.has_files = bool(responses.get(2))
+    return responses.get(1, False)
+
+
 def main(args=sys.argv):
     signal.signal(signal.SIGWINCH, lambda: screen_size(refresh=True))
-    if not sys.stdout.isatty():
+    if not sys.stdout.isatty() or not sys.stdin.isatty():
         raise SystemExit(
             'Must be run in a terminal, stdout is currently not a terminal'
         )
@@ -186,6 +238,8 @@ def main(args=sys.argv):
     args = option_parser().parse_args(args[1:])
     if not args.items:
         raise SystemExit('You must specify at least one file to cat')
+    if not detect_support():
+        raise SystemExit('This terminal emulator does not support the graphics protocol, use a terminal emulator such as kitty that does support it')
     errors = []
     for item in args.items:
         try: