New button interface

src/backinterface.h

@@ -0,0 +1,24 @@
+#pragma once
+
+namespace espgui {
+
+class BackInterface
+{
+public:
+    virtual void back() = 0;
+};
+
+template<typename T>
+class BackActionInterface : public virtual BackInterface
+{
+public:
+    void back() override { T{}.triggered(); }
+};
+
+class DummyBack : public virtual BackInterface
+{
+public:
+    void back() override {}
+};
+
+} // namespace espgui