Make extending the schematic by clicking pins discoverable and reliable

CLAUDE.md

@@ -287,6 +287,20 @@ to Driver"; both clear the view first, like "Show Equipotential") and from the
 schematic (right-click a pin -> "Trace to Driver"; this one *adds* to the view
 instead of clearing it).
 
+Extending the schematic by hand works pin by pin. A box drawn with a dashed
+border shows only the pins on nets already in view; double-clicking its body
+sends `expand_instance_terms` and reveals the rest. Pins whose net isn't in
+the view yet are "open" (`Port::open`, drawn with a hollow-circle stub), and a
+**single click** on one sends `load_equipotential` for its net (the stub fills
+while it loads; `SchematicInteraction::PendingRequests` stops repeat sends).
+A single click on a merged bus pin shows its bits instead. Hovering a pin
+highlights it and shows a tooltip naming its click action. When the requested
+net arrives the view pans so the clicked box stays put on screen, even if the
+hierarchy frames re-lay everything out. Pins are hit-tested nearest-first by
+`SchematicInteraction::pickPin`. `GUIData::addEquipotential()` rejects a net
+whose endpoints are all already shown (`equipotentialCovers()`), so neither a
+re-click nor a trace re-listing a shown net draws its wires twice.
+
 Occurrence `path` entries (in `equipotential_response` and each
 `trace_driver_response` net) are `[name, child_id, model_name]`; the third
 element is optional on parse (`InstTermOccurrence::pathModels`, `""` when
@@ -406,6 +420,17 @@ appear as boxes/pins there).
   instance placement and column de-overlap) and `layoutHierarchyGroups()`
   (module frames). Changes to how the schematic is laid out belong here,
   with a test; `EquipotentialView` only turns the result into drawn shapes.
+- **`SchematicInteraction`** — the pure side of the schematic's pin
+  interactions: `pickPin()` (nearest-pin hit test, radius capped in world
+  units so a pin doesn't swallow box-body clicks at low zoom) and
+  `PendingRequests` (in-flight pin requests, which expire after 5 s).
+  `tests/SchematicInteractionTest.cpp` tests them. The click flow itself is
+  covered end to end by `tests/EquipotentialViewTest.cpp`. That test drives
+  the real `EquipotentialView::renderSchematic()` in a headless ImGui context
+  with no render backend: it moves the mouse and clicks through the ImGui IO
+  API, then asserts on what `FakeNetlistProvider` received and on the
+  geometry, read through `EquipotentialView::schematicForTesting()`. Use the
+  same pattern for new canvas interactions.
 
 ### Diagnosis overlay
 

CMakeLists.txt

@@ -75,6 +75,7 @@ set(CORE_SOURCES
   src/NetlistTree.cpp
   src/EquipotentialView.cpp
   src/SchematicLayout.cpp
+  src/SchematicInteraction.cpp
   src/SchematicView.cpp
   src/DiagnosisStore.cpp
   src/DiagnosisView.cpp
@@ -209,8 +210,9 @@ endif()
 # Native only: exercises the logic layer (JSON parsing, DiagnosisStore,
 # SourceStore, NetlistTree structure, SchematicLayout geometry) without SDL/OpenGL/naja. Links only
 # ImGui's core (imgui.cpp/imgui_draw.cpp/imgui_tables.cpp/imgui_widgets.cpp),
-# not the SDL2/OpenGL3 backends, since none of the tested code needs a real
-# render backend -- render()/draw calls are never invoked from tests.
+# not the SDL2/OpenGL3 backends: tests that do run UI code (e.g.
+# EquipotentialViewTest) drive a headless ImGui context with simulated input
+# and never need anything actually drawn to a screen.
 if(NOT EMSCRIPTEN_BUILD)
   option(NAJA_SCHEMATIC_BUILD_TESTS "Build naja-schematic-tests" ON)
   if(NAJA_SCHEMATIC_BUILD_TESTS)
@@ -235,6 +237,9 @@ if(NOT EMSCRIPTEN_BUILD)
       src/SourceStore.cpp
       src/PropertiesStore.cpp
       src/SchematicLayout.cpp
+      src/SchematicInteraction.cpp
+      src/EquipotentialView.cpp
+      src/SchematicView.cpp
       ${IMGUI_DIR}/imgui.cpp
       ${IMGUI_DIR}/imgui_draw.cpp
       ${IMGUI_DIR}/imgui_tables.cpp

REUSE.toml

@@ -67,6 +67,8 @@ path = [
   "src/PropertiesView.cpp",
   "src/PropertiesView.h",
   "src/RenderTypes.h",
+  "src/SchematicInteraction.cpp",
+  "src/SchematicInteraction.h",
   "src/SchematicLayout.cpp",
   "src/SchematicLayout.h",
   "src/SchematicView.cpp",
@@ -85,8 +87,11 @@ path = [
   "src/main_native.cpp",
   "src/main_wasm.cpp",
   "tests/DiagnosisStoreTest.cpp",
+  "tests/EquipotentialViewTest.cpp",
   "tests/FakeNetlistProvider.h",
+  "tests/GUIDataTest.cpp",
   "tests/NetlistTreeTest.cpp",
+  "tests/SchematicInteractionTest.cpp",
   "tests/SchematicLayoutTest.cpp",
   "tests/SourceStoreTest.cpp",
   "tests/TypesJsonTest.cpp",

src/AppLogic.cpp

@@ -189,22 +189,28 @@ void setupProvider(AppState& state) {
         parent->createNetNode(net.name, net.msb, net.lsb);
       }
     } else if (resp == "equipotential_response") {
-      Console::Log("Equipotential data received");
-      state.guiData->addEquipotential(new Equipotential(j.get<Equipotential>()));
-      state.tableEquipotentialCount = 1;
+      if (state.guiData->addEquipotential(new Equipotential(j.get<Equipotential>()))) {
+        Console::Log("Equipotential data received");
+        state.tableEquipotentialCount = 1;
+      } else {
+        Console::Log("Equipotential already shown");
+      }
     } else if (resp == "trace_driver_response") {
       // Nets arrive breadth-first from the traced net toward the drivers, so
       // adding them in order lets the layout chain each one off an instance
       // that's already placed.
-      size_t n = 0;
+      // Nets already on screen (e.g. the one the trace started from, when
+      // it's launched from a schematic pin) are skipped rather than drawn twice.
+      size_t n = 0, added = 0;
       if (j.contains("equipotentials") && j["equipotentials"].is_array()) {
         for (const auto& e : j["equipotentials"]) {
-          state.guiData->addEquipotential(new Equipotential(e.get<Equipotential>()));
           ++n;
+          if (state.guiData->addEquipotential(new Equipotential(e.get<Equipotential>()))) ++added;
         }
       }
-      state.tableEquipotentialCount = std::max<size_t>(n, 1);
-      Console::Log("Driver trace received: " + std::to_string(n) + " net(s)" +
+      state.tableEquipotentialCount = std::max<size_t>(added, 1);
+      Console::Log("Driver trace received: " + std::to_string(n) + " net(s), " +
+                   std::to_string(added) + " new" +
                    (j.value("truncated", false) ? " (truncated)" : ""));
     } else if (resp == "expanded_instance_terms") {
       std::string pathKey = j.value("path_key", std::string(""));