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_slideover.cpp

@@ -8,6 +8,7 @@
 
 #include <adwaita.h>
 
+#include <algorithm>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
@@ -122,6 +123,24 @@ bool slideover_has_page(const App& app, const std::string& id) {
          gtk_stack_get_child_by_name(GTK_STACK(app.slideover.stack), id.c_str()) != nullptr;
 }
 
+bool slideover_remove_page(App& app, const std::string& id) {
+  SlideOver& s = app.slideover;
+  if (!slideover_has_page(app, id) || s.page == id) return false;
+  GtkWidget* child = gtk_stack_get_child_by_name(GTK_STACK(s.stack), id.c_str());
+  if (is_source_page(id)) {
+    s.source_pages.erase(std::remove(s.source_pages.begin(), s.source_pages.end(), id),
+                         s.source_pages.end());
+    AdwToggle* t = adw_toggle_group_get_toggle_by_name(ADW_TOGGLE_GROUP(s.source_switch), id.c_str());
+    if (t != nullptr) {
+      s.syncing = true;
+      adw_toggle_group_remove(ADW_TOGGLE_GROUP(s.source_switch), t);
+      s.syncing = false;
+    }
+  }
+  gtk_stack_remove(GTK_STACK(s.stack), child);
+  return true;
+}
+
 bool slideover_open(App& app, const std::string& id) {
   SlideOver& s = app.slideover;
   if (!slideover_has_page(app, id)) return false;