setup.sh: Use automic 256color check for GNU screen.

diff --git a/setup.sh b/setup.sh
index 8873bf601137bcd78511472159609b6198fbe9f1..c2a56d574475118bd5a32b8545609ca3c45e9c38 100755 (executable)
--- a/setup.sh
+++ b/setup.sh
@@ -20,6 +20,20 @@
 
 . ../lib.sh
 
+# Helper functions.
+terminal_info() {
+    infocmp "$@" 2>&1
+}
+terminal_available() {
+    terminal_info "$@" > /dev/null
+}
+# Check if `infocmp` is available.
+if ! infocmp > /dev/null 2>&1; then
+    echo 'Warning: `infocmp` not available! 256color checks will fail.'
+    echo
+fi
+
+
 hostname=`hostname`
 
 # Create private temporary directory used by many tools (including GNU screen
@@ -31,10 +45,38 @@ chmod 0700 ~/.tmp
 lesskey lesskey
 chmod 0600 ~/.less
 
-# As screen-256color is not widely supported use it only on machines known to
-# work.
 generate cat screenrc .in
-if [ $hostname != asp -a $hostname != systemofadown ]; then
+# As screen-256color is not widely supported use it only on machines where the
+# matching terminfo entry is available. This also requires a terminal emulator
+# which supports 256 colors. Also used for tmux.
+use_256colors=
+if terminal_available screen-256color; then
+    # Called through SSH connection, assume the local system supports 256
+    # colors.
+    if test -n "$SSH_CONNECTION"; then
+        use_256colors=1
+    # We have rxvt-unicode installed, check if it supports 256 colors.
+    elif installed urxvt; then
+        # Thanks to deryni in #rxvt-unicode on Freenode (2012-10-14 22:54
+        # CEST) for the strings/grep idea. The grep check is for "correct" 256
+        # rxvt-unicode binaries (e.g. Debian's rxvt-unicode-256color), the
+        # terminal_info check for manual installations which modify
+        # rxvt-unicode's terminfo entry.
+        urxvt_path=`which urxvt`
+        urxvt_grep=`strings "$urxvt_path" | grep '^TERM=rxvt-')`
+        if test x"$urxvt_grep" = 'xTERM=rxvt-unicode-256color' \
+                || terminal_info rxvt-unicode \
+                    | grep -F 'colors#256' >/dev/null; then
+            use_256colors=1
+        fi
+    # Check if XTerm supports 256 colors (not a perfect check, but most XTerm
+    # support 256 colors).
+    elif terminal_available xterm-256color; then
+        use_256colors=1
+    fi
+fi
+if test -z "$use_256colors"; then
+    echo screenrc: removing 256 colors
     sed 's/Enable 256 color/Disable 256 color/;
          s/screen-256color/screen/' screenrc > screenrc.tmp
     mv screenrc.tmp screenrc