libcamera: controls: Add policy parameter to ControlList::merge()

This is useful in many cases although not included in the stl.

Note: This is an ABI incompatible change.

Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>

include/libcamera/controls.h

@@ -352,6 +352,11 @@ private:
 	using ControlListMap = std::unordered_map<unsigned int, ControlValue>;
 
 public:
+	enum class MergePolicy {
+		KeepExisting = 0,
+		OverwriteExisting,
+	};
+
 	ControlList();
 	ControlList(const ControlIdMap &idmap, const ControlValidator *validator = nullptr);
 	ControlList(const ControlInfoMap &infoMap, const ControlValidator *validator = nullptr);
@@ -368,7 +373,7 @@ public:
 	std::size_t size() const { return controls_.size(); }
 
 	void clear() { controls_.clear(); }
-	void merge(const ControlList &source);
+	void merge(const ControlList &source, MergePolicy policy = MergePolicy::KeepExisting);
 
 	bool contains(unsigned int id) const;