Introduce extended button handler

src/ButtonEventManager.h

@@ -0,0 +1,84 @@
+#pragma once
+
+#include <Arduino.h>
+
+#include "MappedInputManager.h"
+
+// Forward declaration for the global accessor used by Activity.h.
+// Defined in main.cpp alongside the ButtonEventManager instance.
+class ButtonEventManager;
+ButtonEventManager& globalButtonEvents();
+
+// Classifies raw button edges into Short, Double, and Long press events.
+//
+// Per-button state machines run each loop() tick. The key latency rule:
+//   - If no double-click action is configured for a button, Short fires immediately
+//     on release (zero extra wait).
+//   - If a double-click action IS configured, Short is delayed by DOUBLE_WINDOW_MS
+//     to allow disambiguation.
+//   - Long fires on release once hold time >= LONG_PRESS_MS (no extra wait).
+//   - Double fires on the second release within DOUBLE_WINDOW_MS.
+//
+// Activities query consumeEvent() each loop tick to receive pending events.
+// drain() resets all state machines — call it on activity transitions.
+
+class ButtonEventManager {
+ public:
+  using Button = MappedInputManager::Button;
+
+  static constexpr int NUM_BUTTONS = 9;  // matches MappedInputManager::Button count
+
+  enum class PressType { Short, Double, Long };
+
+  struct ButtonEvent {
+    Button button;
+    PressType type;
+  };
+
+  // Timing constants (milliseconds)
+  static constexpr unsigned long LONG_PRESS_MS = 600;
+  static constexpr unsigned long DOUBLE_WINDOW_MS = 300;
+
+  explicit ButtonEventManager(MappedInputManager& input) : input(input) {}
+
+  // Call once per main loop tick, after MappedInputManager::update().
+  void update();
+
+  // Returns the next pending event, or false if none. Call repeatedly until
+  // false to drain all events for this tick.
+  bool consumeEvent(ButtonEvent& out);
+
+  // Reset all per-button FSMs. Call on activity transitions to prevent bleed-through.
+  void drain();
+
+  // Returns true if a double-click action is configured for this button.
+  // ButtonEventManager queries CrossPointSettings internally.
+  static bool hasDoubleAction(Button button);
+
+ private:
+  static constexpr Button ALL_BUTTONS[NUM_BUTTONS] = {
+      Button::Back, Button::Confirm,  Button::Left,        Button::Right, Button::Up,
+      Button::Down, Button::PageBack, Button::PageForward, Button::Power,
+  };
+
+  enum class State { Idle, Pressed, ReleasedOnce, DoublePressed };
+
+  struct PerButton {
+    State state = State::Idle;
+    unsigned long pressDownTime = 0;  // when the current (or first) press started
+    unsigned long releaseTime = 0;    // when the first release happened (for double-click window)
+  };
+
+  PerButton buttons[NUM_BUTTONS];
+
+  // Pending events ring buffer (small — at most one event per button per tick)
+  static constexpr int EVENT_BUF = 16;
+  ButtonEvent eventBuf[EVENT_BUF] = {};
+  int eventHead = 0;
+  int eventTail = 0;
+
+  MappedInputManager& input;
+
+  void pushEvent(Button button, PressType type);
+  void processButton(int idx, Button btn);
+};