From b9fa29247a460ee5ed4d89d4877fab9f044e1ea1 Mon Sep 17 00:00:00 2001
From: nick black <dankamongmen@gmail.com>
Date: Mon, 11 Oct 2021 19:05:50 -0400
Subject: [PATCH] [automaton] detect GNU screen + version #2261

---
 src/lib/in.c       | 29 +++++++++++++++++++++++++++++
 src/lib/in.h       |  3 ++-
 src/lib/termdesc.c | 10 ++++++++--
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/src/lib/in.c b/src/lib/in.c
index 8942e07ba..6248d7002 100644
--- a/src/lib/in.c
+++ b/src/lib/in.c
@@ -981,6 +981,34 @@ da1_attrs_cb(inputctx* ictx){
   return 1;
 }
 
+// GNU screen primarily identifies itself via an "83" as the first parameter
+// of its DA2 reply. the version is the second parameter.
+static int
+da2_screen_cb(inputctx* ictx){
+  if(ictx->initdata == NULL){
+    return 2;
+  }
+  if(ictx->initdata->qterm != TERMINAL_UNKNOWN){
+    logwarn("already identified term (%d)\n", ictx->initdata->qterm);
+    return 2;
+  }
+  unsigned ver = amata_next_numeric(&ictx->amata, "\x1b[>83;", ';');
+  if(ver < 10000){
+    logwarn("version %u doesn't look like GNU screen\n", ver);
+    return 2;
+  }
+  char verstr[9]; // three two-digit components plus two delims
+  int s = snprintf(verstr, sizeof(verstr), "%u.%02u.%02u",
+                   ver / 10000, ver / 100 % 100, ver % 100);
+  if(s < 0 || (unsigned)s >= sizeof(verstr)){
+    logwarn("bad screen version %u\n", ver);
+    return 2;
+  }
+  ictx->initdata->version = strdup(verstr);
+  ictx->initdata->qterm = TERMINAL_GNUSCREEN;
+  return 2;
+}
+
 // we use secondary device attributes to recognize the alacritty crate
 // version, and to ascertain the version of old, pre-XTVERSION XTerm.
 static int
@@ -1268,6 +1296,7 @@ build_cflow_automaton(inputctx* ictx){
     { "[?\\N;\\Dc", da1_attrs_cb, },
     { "[?1;0;\\NS", xtsmgraphics_cregs_cb, },
     { "[?2;0;\\N;\\NS", xtsmgraphics_sixel_cb, },
+    { "[>83;\\N;0c", da2_screen_cb, },
     { "[>\\N;\\N;\\Nc", da2_cb, },
     { "[=\\Sc", da3_cb, }, // CSI da3 form as issued by WezTerm
     // DCS (\eP...ST)
diff --git a/src/lib/in.h b/src/lib/in.h
index 73cf82f5b..12fb4e5f0 100644
--- a/src/lib/in.h
+++ b/src/lib/in.h
@@ -41,8 +41,9 @@ typedef enum {
     TERMINAL_FOOT,          // TDA: "\EP!|464f4f54\E\\"
     TERMINAL_MLTERM,        // XTGETTCAP['TN'] == 'mlterm'
     TERMINAL_TMUX,          // XTVERSION == "tmux ver"
+    TERMINAL_GNUSCREEN,     // SDA: "83;ver;0c"
     TERMINAL_WEZTERM,       // XTVERSION == 'WezTerm *'
-    TERMINAL_ALACRITTY,     // can't be detected; match TERM+DA2
+    TERMINAL_ALACRITTY,     // can't be detected; match TERM+SDA
     TERMINAL_CONTOUR,       // XTVERSION == 'contour ver'
     TERMINAL_ITERM,         // XTVERSION == 'iTerm2 [ver]'
     TERMINAL_TERMINOLOGY,   // TDA: "~~TY"
diff --git a/src/lib/termdesc.c b/src/lib/termdesc.c
index 233877040..63deba55b 100644
--- a/src/lib/termdesc.c
+++ b/src/lib/termdesc.c
@@ -341,6 +341,9 @@ init_terminfo_esc(tinfo* ti, const char* name, escape_e idx,
                   SECDEVATTR
 
 // query background, replies in X color https://www.x.org/releases/X11R7.7/doc/man/man7/X.7.xhtml#heading11
+// GNU screen passes this on to the underlying terminal rather than answering
+// itself, unlike most other queries, so send this first since it will take
+// longer to be answered.
 #define CSI_BGQ "\x1b]11;?\e\\"
 
 // FIXME ought be using the u7 terminfo string here, if it exists. the great
@@ -367,8 +370,8 @@ init_terminfo_esc(tinfo* ti, const char* name, escape_e idx,
 // request the cell geometry of the textual area
 #define GEOMCELL "\x1b[18t"
 
-#define DIRECTIVES KBDQUERY \
-                   CSI_BGQ \
+#define DIRECTIVES CSI_BGQ \
+                   KBDQUERY \
                    SUMQUERY \
                    "\x1b[?1;3;256S" /* try to set 256 cregs */ \
                    KITTYQUERY \
@@ -604,6 +607,9 @@ apply_term_heuristics(tinfo* ti, const char* termname, queried_terminals_e qterm
   }else if(qterm == TERMINAL_TMUX){
     termname = "tmux";
     // FIXME what, oh what to do with tmux?
+  }else if(qterm == TERMINAL_GNUSCREEN){
+    termname = "GNU screen";
+    // FIXME disable rgb?
   }else if(qterm == TERMINAL_MLTERM){
     termname = "MLterm";
     ti->caps.quadrants = true; // good caps.quadrants, no caps.sextants as of 3.9.0