split the selection panel into one card per kind of selection

src/ui/selection/BeltContent.cpp

@@ -0,0 +1,38 @@
+#include "BeltContent.h"
+
+#include <QVBoxLayout>
+
+#include "BuildingTarget.h"
+#include "ClearBeltControl.h"
+#include "SelectionNames.h"
+
+BeltContent::BeltContent(const SelectionContext& context,
+                         const SelectionRequest& request, QWidget* parent)
+    // Only an operational tile aggregates, so a card showing several is never a site;
+    // a single selected tile still can be one.
+    : SelectionContent(context,
+                       request.buildings.size() == 1
+                           ? asConstructionSite(context, request.buildings.front())
+                           : std::nullopt,
+                       parent)
+    , m_ids(request.buildings)
+{
+    getRuntimeLayout()->addWidget(new ClearBeltControl(context, m_ids, this));
+}
+
+void BeltContent::refreshConfiguration()
+{
+    const BuildingTarget target = resolveBuildingTarget(getContext(), m_ids.front());
+    if (!target.isValid())
+    {
+        return;
+    }
+
+    // An aggregated selection may mix belts with tunnel ends, so it is named after the
+    // first tile; the count says how many are held (REQ-UI-SELECTION-AGGREGATE).
+    setBuildingIdentity(target.type, getBuildingTypeName(target.type));
+    if (m_ids.size() > 1)
+    {
+        setCountSlot(static_cast<int>(m_ids.size()));
+    }
+}