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;
 

src/libcamera/controls.cpp

@@ -907,13 +907,27 @@ ControlList::ControlList(const ControlInfoMap &infoMap,
  * \brief Removes all controls from the list
  */
 
+/**
+ * \enum ControlList::MergePolicy
+ * \brief The policy used by the merge function
+ *
+ * \var ControlList::MergePolicy::KeepExisting
+ * \brief Existing controls in the target list are kept
+ *
+ * \var ControlList::MergePolicy::OverwriteExisting
+ * \brief Existing controls in the target list are updated
+ */
+
 /**
  * \brief Merge the \a source into the ControlList
  * \param[in] source The ControlList to merge into this object
+ * \param[in] policy Controls if existing elements in *this shall be
+ * overwritten
  *
  * Merging two control lists copies elements from the \a source and inserts
  * them in *this. If the \a source contains elements whose key is already
- * present in *this, then those elements are not overwritten.
+ * present in *this, then those elements are only overwritten if
+ * \a policy is MergePolicy::OverwriteExisting.
  *
  * Only control lists created from the same ControlIdMap or ControlInfoMap may
  * be merged. Attempting to do otherwise results in undefined behaviour.
@@ -921,7 +935,7 @@ ControlList::ControlList(const ControlInfoMap &infoMap,
  * \todo Reimplement or implement an overloaded version which internally uses
  * std::unordered_map::merge() and accepts a non-const argument.
  */
-void ControlList::merge(const ControlList &source)
+void ControlList::merge(const ControlList &source, MergePolicy policy)
 {
 	/**
 	 * \todo ASSERT that the current and source ControlList are derived
@@ -936,7 +950,7 @@ void ControlList::merge(const ControlList &source)
 	 */
 
 	for (const auto &ctrl : source) {
-		if (contains(ctrl.first)) {
+		if (policy == MergePolicy::KeepExisting && contains(ctrl.first)) {
 			const ControlId *id = idmap_->at(ctrl.first);
 			LOG(Controls, Warning)
 				<< "Control " << id->name() << " not overwritten";

test/controls/control_list.cpp

@@ -196,6 +196,56 @@ protected:
 			return TestFail;
 		}
 
+		/*
+		 * Create two lists with overlapping controls. Merge them with
+		 * overwriteExisting = true, verifying that the existing control
+		 * values *get* overwritten.
+		 */
+		mergeList.clear();
+		mergeList.set(controls::Brightness, 0.7f);
+		mergeList.set(controls::Saturation, 0.4f);
+
+		list.clear();
+		list.set(controls::Brightness, 0.5f);
+		list.set(controls::Contrast, 1.1f);
+
+		mergeList.merge(list, ControlList::MergePolicy::OverwriteExisting);
+		if (mergeList.size() != 3) {
+			cout << "Merged list should contain three elements" << endl;
+			return TestFail;
+		}
+
+		if (list.size() != 2) {
+			cout << "The list to merge should contain two elements"
+			     << endl;
+			return TestFail;
+		}
+
+		if (!mergeList.get(controls::Brightness) ||
+		    !mergeList.get(controls::Contrast) ||
+		    !mergeList.get(controls::Saturation)) {
+			cout << "Merged list does not contain all controls" << endl;
+			return TestFail;
+		}
+
+		if (mergeList.get(controls::Brightness) != 0.5f) {
+			cout << "Brightness control value did not change after merging lists"
+			     << endl;
+			return TestFail;
+		}
+
+		if (mergeList.get(controls::Contrast) != 1.1f) {
+			cout << "Contrast control value changed after merging lists"
+			     << endl;
+			return TestFail;
+		}
+
+		if (mergeList.get(controls::Saturation) != 0.4f) {
+			cout << "Saturation control value changed after merging lists"
+			     << endl;
+			return TestFail;
+		}
+
 		return TestPass;
 	}
 };