12.1: feathered selections, Select Subject, Soft Light, the fixed-width font menu (Compositor 1.1.1–1.1.4)

src/Document/SubjectRemoval+Session.h

@@ -0,0 +1,8 @@
+// Swift's SubjectRemoval extension: Select → Subject.
+public:
+    bool canSelectSubject() const;
+    // The canvas's foreground, as Remove Background finds it, selected.
+    void selectSubject(SelectionMode mode, std::function<void()> done);
+
+private:
+    void finishSubject();