Quitting the TUI now asks whether to shut down or detach

include/fgc/ui/UiSnapshot.h

@@ -315,6 +315,14 @@ std::string formatDegrees(double deg);
 // Returns "—" when then_ms is 0 (never).
 std::string formatTimeAgo(long long now_ms, long long then_ms);
 
+// Whether the dashboard can be sent to the background, i.e. whether it is
+// running inside a tmux pane that a client can be detached from. Pass getenv
+//("TMUX"): tmux sets it to the server socket path, so a set, non-empty value is
+// both the test and what lets `tmux detach-client` find the right client.
+// Takes the value as an argument rather than reading the environment itself so
+// the rule is testable.
+bool backgroundAvailable(const char* tmux_env);
+
 // Last path segment of an MQTT topic ("GGS/FWT/Tower/CamEvent" -> "CamEvent").
 // Every row in the connectivity view shares the same prefix, which only eats
 // width. Returns the input unchanged when there is no '/'.

scripts/fgc

@@ -14,8 +14,8 @@
 #   scripts/fgc peek              print what the pane shows right now
 #   scripts/fgc restart [args...] stop, then start
 #
-# Detaching is Ctrl-b d. NOTE: the dashboard's own `q` key *exits the program*,
+# Detaching is Ctrl-b d. The dashboard's own `q` asks first, offering both:
-# it does not detach — that is the one thing to get right when attached.
+# quit the program, or background it (which detaches, same as Ctrl-b d).
 #
 # Only one instance may run. The binary enforces that itself with a lockfile
 # (see src/core/SingleInstance.cpp), so a bare ./build/fire_gimbal_control is
@@ -159,7 +159,7 @@ cmd_start() {
     tmux set-option -t "$pane" status-left-length 30 >/dev/null
     tmux set-option -t "$pane" status-right-length 80 >/dev/null
     tmux set-option -t "$pane" status-right \
-        ' Ctrl-b d = detach, keeps running   |   q = quit the program ' >/dev/null
+        ' Ctrl-b d = detach, keeps running   |   q = quit or background ' >/dev/null
 
     tmux respawn-pane -k -t "$win" -c "$repo" "$launch" >/dev/null
 
@@ -182,7 +182,7 @@ cmd_start() {
     fi
 
     echo "fgc: started detached as PID $(pane_pid) (session '$session')"
-    echo "     attach: scripts/fgc attach     (Ctrl-b d to detach; 'q' quits the program)"
+    echo "     attach: scripts/fgc attach     (Ctrl-b d to detach; 'q' asks quit/background)"
 }
 
 # Hidden: the command tmux runs inside the pane. Not for direct use.
@@ -228,7 +228,7 @@ cmd_attach() {
     if [[ -n "${TMUX:-}" ]]; then
         die "already inside tmux; use 'tmux switch-client -t $session'"
     fi
-    echo "fgc: attaching — Ctrl-b d detaches and leaves it running ('q' would quit it)" >&2
+    echo "fgc: attaching — Ctrl-b d detaches and leaves it running ('q' asks first)" >&2
     exec tmux attach-session -t "$target"
 }
 

src/core/HelpText.cpp

@@ -132,6 +132,11 @@ const std::vector<HelpSection>& helpCatalog() {
                 "still, and the LOG title shows 'scrollback'."}},
             {"Home/End",
              "Jump to the top/bottom; on the log, End resumes following the tail.", {}},
+            {"q",
+             "Ask whether to quit or leave the dashboard running in the background.", {
+                "Quitting stops capture and closes the camera; backgrounding detaches the",
+                "tmux client (same as Ctrl-b d) and leaves everything running. Ctrl-C still",
+                "shuts down immediately."}},
             {"p",
              "Freeze the 10 Hz repaint so terminal text selection survives.", {
                 "Any keypress repaints, so scrolling while paused drops the selection -",

src/ui/TuiUi.cpp

@@ -10,6 +10,7 @@
 #include <algorithm>
 #include <array>
 #include <chrono>
+#include <cstdlib>
 #include <cstdio>
 #include <map>
 #include <sstream>
@@ -209,6 +210,27 @@ Element keyBar(Overlay overlay) {
     return flexbox(std::move(e));
 }
 
+// The "are you sure?" block that replaces the key bar when q is pressed.
+//
+// q and Ctrl-b d are one keystroke apart and mean opposite things when the tower
+// is operated over ssh, and nothing on screen said so at the moment of choosing
+// (scripts/fgc resorts to warning about it in its tmux status line). This asks.
+Element exitPrompt(bool can_background) {
+    Element bg = can_background
+                     ? hbox({text("  b    ") | bold,
+                             text("Background \xE2\x80\x94 detach, leave it running "
+                                  "(same as Ctrl-b d)")})
+                     : hbox({text("  b    ") | dim,
+                             text("Background \xE2\x80\x94 unavailable, needs scripts/fgc") | dim});
+    return vbox({
+        text(" Exit the dashboard? ") | bold | color(Color::Black) | bgcolor(Color::Yellow),
+        hbox({text("  q    ") | bold,
+              text("Quit \xE2\x80\x94 stops capture, closes the camera, ends the program")}),
+        bg,
+        hbox({text("  Esc  ") | bold, text("Cancel") | dim}),
+    }) | border | color(Color::Yellow);
+}
+
 Element badge(const std::string& s, bool on, Color on_color) {
     auto e = text(" " + s + " ");
     return on ? (e | color(on_color) | bold) : (e | dim);
@@ -1044,6 +1066,7 @@ void TuiUi::uiLoop() {
     int         help_sel     = 0;
     bool        gimbal_dump_requested = false;  // auto-pull a dump the first time
     bool        calib_prompt = false;           // a yes/no calib-save question is showing
+    bool        exit_prompt  = false;           // 'q' asked; awaiting quit/background/cancel
 
     // Per-pane scroll positions. UI-thread-only view state (the renderer lambda
     // and CatchEvent below both run on this thread), so unlike screen_/paused_
@@ -1101,7 +1124,8 @@ void TuiUi::uiLoop() {
 
         Element bottom = command_mode
                              ? hbox({text(" : ") | inverted, input->Render() | flex}) | border
-                             : keyBar(overlay);
+                         : exit_prompt ? exitPrompt(backgroundAvailable(std::getenv("TMUX")))
+                                       : keyBar(overlay);
 
         // An open overlay takes over the whole body (the dashboard panels are
         // hidden) so it has the full height — otherwise tall content like the
@@ -1167,6 +1191,31 @@ void TuiUi::uiLoop() {
             }
             return false;  // let the Input edit the buffer
         }
+
+        // The exit question owns the keyboard while it is up: every key is
+        // consumed, so a stray press cannot reach the dashboard behind it.
+        if (exit_prompt) {
+            if (e == Event::Escape) { exit_prompt = false; return true; }
+            if (e == Event::Return) { exit_prompt = false; if (sink_) sink_("exit"); return true; }
+            if (e.is_character()) {
+                const std::string& k = e.character();
+                if (k == "q" || k == "Q") {
+                    exit_prompt = false;
+                    if (sink_) sink_("exit");
+                } else if ((k == "b" || k == "B") && backgroundAvailable(std::getenv("TMUX"))) {
+                    exit_prompt = false;
+                    // Detach the client viewing this pane; the program keeps
+                    // running and drawing into the pty, exactly as Ctrl-b d does.
+                    // A failure must never read as "quit", so on error we say so
+                    // and stay put.
+                    if (std::system("tmux detach-client") != 0)
+                        LOG_WARN << "could not detach from tmux; still running "
+                                    "(detach with Ctrl-b d, or press q to quit)";
+                }
+            }
+            return true;  // swallow everything else
+        }
+
         const int n = static_cast<int>(helpCatalog().size());
         if (overlay == Overlay::Help) {  // help pane navigation
             // Selecting a different section replaces the body wholesale, so the
@@ -1287,7 +1336,7 @@ void TuiUi::uiLoop() {
             if (c == "j") { help_sel = (help_sel + 1) % n; help_scroll = {}; return true; }
             if (c == "k") { help_sel = (help_sel - 1 + n) % n; help_scroll = {}; return true; }
         }
-        if (c == "q") { if (sink_) sink_("exit"); return true; }
+        if (c == "q") { exit_prompt = true; return true; }
         if (c == "s") { if (sink_) sink_("start"); return true; }
         if (c == "x") { if (sink_) sink_("stop"); return true; }
         if (c == "h") { if (sink_) sink_("gimbal home"); return true; }

src/ui/UiSnapshot.cpp

@@ -48,6 +48,12 @@ std::string formatTimeAgo(long long now_ms, long long then_ms) {
     return buf;
 }
 
+bool backgroundAvailable(const char* tmux_env) {
+    // An empty TMUX is not "in tmux": the variable exists but names no server,
+    // so detach-client would have nothing to talk to.
+    return tmux_env != nullptr && *tmux_env != '\0';
+}
+
 std::string topicLeaf(const std::string& topic) {
     const auto slash = topic.rfind('/');
     if (slash == std::string::npos) return topic;

tests/test_uisnapshot.cpp

@@ -118,3 +118,9 @@ TEST_CASE("formatClockMs renders wall-clock time, and never for 0") {
     CHECK(t[8] == '.');
     CHECK(t.substr(9) == "678");      // the ms field comes straight off the input
 }
+
+TEST_CASE("backgroundAvailable only accepts a set, non-empty TMUX") {
+    CHECK(backgroundAvailable("/tmp/tmux-1000/default,12345,0"));
+    CHECK_FALSE(backgroundAvailable(nullptr));   // not under tmux at all
+    CHECK_FALSE(backgroundAvailable(""));        // set but names no server
+}