ui: per-signal slide-over pages; the drop's assignment and the colour reset as shared functions

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

src/ui_app.hpp

@@ -44,6 +44,7 @@
 #include <array>
 #include <cmath>
 #include <cstdint>
+#include <map>
 #include <memory>
 #include <mutex>
 #include <string>
@@ -885,6 +886,8 @@ struct App {
   guint layout_save_source = 0;
   bool layout_loaded = false;
   unsigned signal_generation = ~0u;
+  /// Signal name -> the content box of its `signal:<name>` slide-over page (src/ui_signal_page.cpp).
+  std::map<std::string, GtkWidget*> signal_pages;
   bool updating_panels = false;  ///< guards signal handlers during a rebuild
   bool relayout_pending = false;
   /// True once the renderer's `Style` has been stated (see `tick()`): the renderer does not
@@ -1669,6 +1672,24 @@ std::string signal_chip_markup(App& app, const std::vector<SignalInfo>& signals,
 void on_signal_color_chosen(GObject* source, GAsyncResult* res, gpointer user);
 void open_signal_color(App& app, std::size_t signal);
 void rebuild_signal_list(App& app, const std::vector<SignalInfo>& signals);
+/// Every plottable signal once (the time base skipped, a group's layers folded to the first), in model order.
+/// The one rule the list and the badges share.
+std::vector<std::size_t> listed_signals(const std::vector<SignalInfo>& signals);
+/// Puts `signal` (an index into `signals()`) on plot `row` in the first free slot, switching it on first if
+/// need be. Says why not through `set_notice` and returns false when it cannot. The one path a drop and a
+/// signal page's "Plot on" button share.
+bool assign_signal_to_row(App& app, std::size_t signal, int row);
+/// Back to the palette colour for the signal's position.
+void reset_signal_color(App& app, std::size_t signal);
+/// Holds `widget` alive across the current emission: a handler that rebuilds the list or a page destroys the
+/// widget it was emitted from.
+void outlive_the_rebuild(GtkWidget* widget);
+/// Creates the page `signal:<name>` if it is missing, fills it, and returns whether it exists afterwards.
+bool signal_page_ensure(App& app, const std::string& name);
+/// Called at the end of `rebuild_signal_panels`: refills every existing signal page, drops the pages of
+/// signals the model no longer has (closing the slide-over first if one of them is open).
+void signal_pages_sync(App& app);
+gboolean signal_page_probe(gpointer user);  // UDPSCOPE_PROBE_SIGNAL_PAGES_MS
 /// The `MATH` divider row in the one channel list, and the `+` it carries.
 GtkWidget* make_math_divider(App& app, bool with_add);
 void on_math_add_clicked(GtkButton* button, gpointer user);
@@ -1915,6 +1936,8 @@ gboolean dock_session_probe(gpointer user);  // UDPSCOPE_PROBE_DOCK_SESSION_MS
 void build_slideover(App& app);  // once, after the plot_overlay exists
 bool slideover_add_page(App& app, const std::string& id, const std::string& title, GtkWidget* content);
 bool slideover_has_page(const App& app, const std::string& id);
+/// The inverse of `slideover_add_page`: false when the id is unknown or is the open page.
+bool slideover_remove_page(App& app, const std::string& id);
 bool slideover_open(App& app, const std::string& id);  // false when the id is unknown
 void slideover_close(App& app);
 bool slideover_toggle(App& app, const std::string& id);  // open if closed or on another page, else close