Added functionality to align display refreshes

TRMNL.h

@@ -18,6 +18,7 @@ private:
 	std::string m_api_key;
 	std::string m_friendly_id;
 	int m_refresh_rate;
+	bool m_is_refresh_aligned;
 
 	std::function<void (const TRMNL& trmnl)> m_update_handler;
 
@@ -26,7 +27,8 @@ public:
 	TRMNL(const std::string& id = "",
 		const std::string& api_key = "",
 		const std::string& friendly_id = "",
-		int refresh_rate = DEFAULT_REFRESH_RATE);
+		int refresh_rate = DEFAULT_REFRESH_RATE,
+		bool is_refresh_aligned = true);
 
 	TRMNL(const nlohmann::json& j);
 
@@ -35,12 +37,24 @@ public:
 	const std::string& api_key() const;
 	const std::string& friendly_id() const;
 	int refresh_rate() const;
+	bool is_refresh_aligned() const;
+
+	// Uses the current time to return when next this device should refresh
+	// min_time
+	// - if calculated time is lower than this - increase by refresh rate until higher
+	// - Capped to the refresh rate
+	// offset
+	// - offset to apply to the refresh rate
+	// - Capped to the refresh rate
+	// - useful when generating images via cron and you want the refresh to happen a few seconds later
+	int get_next_refresh(int min_time = 0, int offset = 0) const;
 
 	// Setters
 	void id(const std::string& id);
 	void api_key(const std::string& api_key);
 	void friendly_id(const std::string& friendly_id);
 	void refresh_rate(int refresh_rate);
+	void is_refresh_aligned(bool to_align);
 
 	void set_update_handler(std::function<void (const TRMNL& trmnl)> handler);