[Unicode placeholders] Detect tmux by default and ensure passthrough

kittens/icat/main.py

@@ -33,6 +33,7 @@
     render_as_single_image, render_image
 )
 from ..tui.operations import clear_images_on_screen, raw_mode
+from ..tui.utils import (running_in_tmux, make_sure_tmux_allows_passthrough)
 
 OPTIONS = '''\
 --align
@@ -147,9 +148,11 @@
 
 
 --tmux
-type=bool-set
-Surround graphics commands with tmux escape sequences and also enable
---unicode-placeholder.
+type=choices
+choices=detect,yes,no
+default=detect
+Whether to surround graphics commands with tmux escape sequences and also enable
+--unicode-placeholder. The default is to auto-detect tmux.
 '''
 
 
@@ -636,8 +639,11 @@ def main(args: List[str] = sys.argv) -> None:
         sys.stdin = open(os.ctermid())
 
     parsed_opts = ParsedOpts()
-    parsed_opts.unicode_placeholder = cli_opts.unicode_placeholder or cli_opts.tmux
-    inside_tmux = cli_opts.tmux
+    parsed_opts.unicode_placeholder = cli_opts.unicode_placeholder
+    if cli_opts.tmux == 'yes' or (cli_opts.tmux == 'detect' and running_in_tmux()):
+        make_sure_tmux_allows_passthrough()
+        parsed_opts.unicode_placeholder = True
+        inside_tmux = True
     if cli_opts.place:
         try:
             parsed_opts.place = parse_place(cli_opts.place)

kittens/ssh/main.py

@@ -43,7 +43,9 @@
     RESTORE_PRIVATE_MODE_VALUES, SAVE_PRIVATE_MODE_VALUES, Mode,
     restore_colors, save_colors, set_mode
 )
-from ..tui.utils import kitty_opts, running_in_tmux
+from ..tui.utils import (
+    kitty_opts, running_in_tmux, make_sure_tmux_allows_passthrough
+)
 from .config import init_config
 from .copy import CopyInstruction
 from .options.types import Options as SSHOptions
@@ -572,9 +574,7 @@ def dcs_to_kitty(payload: Union[bytes, str], type: str = 'ssh') -> bytes:
     ans = b'\033P@kitty-' + type.encode('ascii') + b'|' + payload
     tmux = running_in_tmux()
     if tmux:
-        cp = subprocess.run([tmux, 'set', '-p', 'allow-passthrough', 'on'])
-        if cp.returncode != 0:
-            raise SystemExit(cp.returncode)
+        make_sure_tmux_allows_passthrough()
         ans = b'\033Ptmux;\033' + ans + b'\033\033\\\033\\'
     else:
         ans += b'\033\\'

kittens/tui/utils.py

@@ -123,3 +123,33 @@ def running_in_tmux() -> str:
     if exe.lower() == 'tmux':
         return exe
     return ''
+
+def make_sure_tmux_allows_passthrough() -> None:
+    import subprocess
+    tmux = running_in_tmux()
+    if tmux:
+        # Check if the allow-passthrough option is set. `-p` means that it is a
+        # pane option, `-A` means that this option may be inherited from the parent.
+        # We use a timeout because `tmux show` may freeze when the version of the
+        # tmux executable is older than the version of the running tmux server.
+        try:
+            cp = subprocess.run([tmux, 'show', '-Ap', 'allow-passthrough'],
+                                capture_output=True, timeout=2)
+        except subprocess.TimeoutExpired:
+            print("Tmux command timed out. This often happens when the version "
+                  "of tmux on your PATH is older than the version of the running tmux server",
+                  file=sys.stderr)
+            raise SystemExit(1)
+        if cp.returncode != 0:
+            print("Could not check if tmux allows passthrough, you may need to update tmux",
+                  file=sys.stderr)
+            raise SystemExit(cp.returncode)
+        # Both `on` (allow passthrough if pane is visible) and `all` (allow
+        # passthrough even if it's invisible) are acceptable values.
+        if not (cp.stdout.endswith(b" on\n") or cp.stdout.endswith(b" all\n")):
+            # If the option is not set, set it to `on`.
+            cp = subprocess.run([tmux, 'set', '-p', 'allow-passthrough', 'on'])
+            if cp.returncode != 0:
+                print("Could not set the allow-passthrough option, you may need to update tmux",
+                      file=sys.stderr)
+                raise SystemExit(cp.returncode)