ui: reword the docs that still spoke of the list drag; keep disabled signals' badge order; stamp the signal generation before the snapshot

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -2931,11 +2931,10 @@ now — they are listed so they are not mistaken for anything else:
   controls** are pages of the slide-over, reached from the badge bar. Both panes also have a **locked** mode, which is what a returning user gets: the
   trigger pane shows one line saying what it is set to, the signal list shows only the signals that are
   on, and neither offers a control that changes the configuration -- each heading has an `[edit]` button
-  to switch to the full pane, and back. Dragging a signal onto a plot still works while locked -- filling
+  to switch to the full pane, and back. Dragging a signal's badge onto a plot still works while locked --
-  plots is what the list is for, not configuration -- and a locked row can be dragged from anywhere on it,
+  filling plots is not configuration. A signal's badge is dragged onto a plot, or onto another badge to
-  the colour chip included. In a window too narrow to show both, where the dock is *overlaid on* the
+  reorder the badges (the order is kept for the session only); the slide-over closes for the length of the
-  plot, the dock steps aside for the length of the drag so there is something under the pointer to drop
+  drag so there is something under the pointer to drop onto. A **first run** (no session file for that source) comes up
-  onto. A **first run** (no session file for that source) comes up
   unlocked, because configuring the host is what a first run is for. Each pane's heading also carries its **own switch**, the same control as the
   header bar's button -- clicking either moves both -- because a pane that is *disabled* while its
   feature is off is a pane whose controls you would otherwise have to leave to turn it back on. With the math

help/C/org.udpscope.app/layout.page

@@ -24,7 +24,7 @@
     <title>How to reach it</title>
     <steps>
       <item>
-        <p>Drag a signal's chip out of the side panel (<key>s</key>) and drop it on a row to
+        <p>Drag a signal's badge from the badge bar onto a row to
         add a trace.</p>
       </item>
       <item>

help/C/org.udpscope.app/overview.page

@@ -92,7 +92,7 @@
         derived from it; <gui>Signals</gui> holds the trigger and the channel list, where a
         math channel is a row of that one list under a <gui>MATH</gui> heading whose
         <gui>+</gui> creates one. One row per channel: its colour, an enable switch, its name
-        and its unit. Channels are dragged from here onto a plot row.</p>
+        and its unit. A channel's badge in the badge bar is dragged onto a plot row.</p>
       </item>
       <item>
         <title>The plot</title>

src/ui/signals-panel.ui

@@ -53,7 +53,7 @@
         <property name="spacing">6</property>
         <child>
           <object class="GtkLabel" id="signals_hint">
-            <property name="label" translatable="yes">drag a signal onto a plot</property>
+            <property name="label" translatable="yes">click a signal for its page; drag its badge onto a plot</property>
             <property name="halign">start</property>
             <property name="hexpand">1</property>
             <property name="css-classes">dim-label</property>

src/ui_badges.cpp

@@ -102,14 +102,23 @@ gboolean on_badge_drop(GtkDropTarget*, const GValue* value, double, double, gpoi
   if (prev != moved->button) {  // already directly in front: nothing to move
     gtk_box_reorder_child_after(GTK_BOX(app->badges.signals_row), moved->button, prev);
   }
-  // The order, as the widgets now stand.
+  // The order, as the widgets now stand; the names that are not shown (signals switched off) keep their old
-  app->badge_order.clear();
+  // relative order after the visible ones, so switching one back on finds it where it was remembered.
+  std::vector<std::string> order;
   for (GtkWidget* c = gtk_widget_get_first_child(app->badges.signals_row); c != nullptr;
        c = gtk_widget_get_next_sibling(c)) {
     for (auto& b : app->badges.signal_badges) {
-      if (b->button == c) app->badge_order.push_back(b->signal_name);
+      if (b->button == c) order.push_back(b->signal_name);
     }
   }
+  const std::size_t shown_count = order.size();
+  for (const std::string& n : app->badge_order) {
+    if (std::find(order.begin(), order.begin() + static_cast<std::ptrdiff_t>(shown_count), n) ==
+        order.begin() + static_cast<std::ptrdiff_t>(shown_count)) {
+      order.push_back(n);
+    }
+  }
+  app->badge_order = std::move(order);
   return TRUE;
 }
 

src/ui_signals.cpp

@@ -569,6 +569,9 @@ void rebuild_signal_panels(App& app) {
   // GTK calls (a use-after-free of the name strings otherwise).
   std::vector<SignalInfo> signals;
   bool have_signals = false;
+  // The generation this build answers to is read *before* the snapshot: a CONFIG landing between the two
+  // would otherwise be stamped as seen without having been, and the tick would never rebuild for it.
+  const unsigned generation = app.model->generation();
   {
     std::lock_guard<std::mutex> lock(app.model->mutex());
     signals = app.model->signals();
@@ -585,7 +588,7 @@ void rebuild_signal_panels(App& app) {
   }
   signal_pages_sync(app);
   sync_signal_badges(app);
-  app.signal_generation = app.model->generation();
+  app.signal_generation = generation;
 }
 
 GtkWidget* build_signal_panel(App& app) {