feat: the session file remembers which sidebar tab was showing

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

src/layout_store.cpp

@@ -496,6 +496,8 @@ bool load_layout(const std::string& path, LayoutState& out) {
         }
       } else if (key == "measure_stats") {
         st.measure_stats = value == "true";
+      } else if (key == "side_tab") {
+        st.side_tab = strip_quote(value);
       } else if (key == "multicast") {
         st.multicast = strip_quote(value);
       } else if (key == "interface") {
@@ -645,6 +647,7 @@ bool save_layout(const std::string& path, const LayoutState& state) {
     o << "]\n";
   }
   o << "measure_stats = " << (state.measure_stats ? "true" : "false") << "\n";
+  o << "side_tab = \"" << state.side_tab << "\"\n";
   if (!state.comment.empty()) o << "comment = " << toml_escape(state.comment) << "\n";
   if (state.buffer_mb > 0.0) o << "buffer_mb = " << state.buffer_mb << "\n";
   o << "relative_time = " << (state.relative_time ? "true" : "false") << "\n";

src/layout_store.hpp

@@ -66,6 +66,10 @@ struct LayoutState {
   /// stream and mean nothing restored against another one.
   bool measure_stats = false;
 
+  /// Which sidebar tab was showing: "measure" or "signals". The one thing the panel persists --
+  /// no revealer states remain, and the 320 px width is the `.ui`'s.
+  std::string side_tab = "signals";
+
   /// The measurements pane, by signal *name* and with the type and options a row was built with.
   std::vector<Measure> measures;
 

src/ui_layout.cpp

@@ -58,6 +58,7 @@ LayoutState collect_layout(App& app) {
   st.math = app.math;
   st.measures = app.measures;
   st.measure_stats = app.measure_stats_on;
+  st.side_tab = app.side_tab;
   // The connection is the session's too: the file's name carries only host and port.
   st.multicast = app.source_multicast;
   st.interface_addr = app.source_interface;
@@ -327,6 +328,7 @@ void apply_layout(App& app, const LayoutState& st) {
   app.measures = st.measures;
   app.measure_stats_on = st.measure_stats;
   app.updating_panels = true;
+  select_side_tab(app, st.side_tab.c_str());
   if (app.measures_stats_check != nullptr) {
     gtk_check_button_set_active(GTK_CHECK_BUTTON(app.measures_stats_check),
                                 app.measure_stats_on);