Show variable usage count on variable tab

lib/variables/variable-usage.cpp

@@ -0,0 +1,35 @@
+#include "variable-usage.hpp"
+#include "macro-helpers.hpp"
+#include "macro.hpp"
+#include "sync-helpers.hpp"
+#include "variable-ref.hpp"
+
+#include <obs.hpp>
+
+namespace advss {
+
+static std::unordered_map<std::string, int> collectReferences(Macro *macro)
+{
+	VariableRefCollector collector;
+	OBSDataAutoRelease data = obs_data_create();
+	macro->Save(data);
+	return collector.Counts();
+}
+
+std::unordered_map<std::string, VariableUsage> GetVariableUsage()
+{
+	std::unordered_map<std::string, VariableUsage> result;
+	auto lock = LockContext();
+	// Nested macros are saved as part of their parent macro
+	for (const auto &macro : GetTopLevelMacros()) {
+		for (const auto &[name, count] :
+		     collectReferences(macro.get())) {
+			auto &usage = result[name];
+			usage.referenceCount += count;
+			usage.macroNames.emplace_back(macro->Name());
+		}
+	}
+	return result;
+}
+
+} // namespace advss