separate display to its own file

display.h

@@ -0,0 +1,73 @@
+
+/* display.h
+ * Generated from display.cpp — public declarations for the OLED helper
+ */
+
+#ifndef DISPLAY_H
+#define DISPLAY_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+
+// Display API is provided via the C++ `DisplayManager` singleton below.
+
+#ifdef __cplusplus
+// Expose the C++ DisplayManager so callers can use the class API directly.
+//
+// Note: The implementation constructs the `SSD1306` display object in-place
+// using static storage (no heap allocation). Construct a `DisplayManager` in
+// `main()` and pass it by reference to functions that need to update the
+// display. This avoids global singletons and makes ownership explicit.
+//
+// Example:
+//   int main() {
+//     stdio_init_all();
+//     DisplayManager display;
+//     // pass the display I2C address (common values: 0x3C or 0x3D)
+//     display.init(0x3C);
+//     while (true) {
+//       wait_for_usb_connection();
+//       run_echo_session(display);
+//     }
+//   }
+//
+//   void run_echo_session(DisplayManager &display) {
+//     display.refresh("> ", nullptr);
+//     // ...
+//   }
+//
+// Forward-declare the SSD1306 type to avoid pulling the full display header into
+// every translation unit that includes `display.h`.
+namespace pico_ssd1306 { class SSD1306; }
+
+class DisplayManager {
+public:
+	// Initialize the hardware and display.
+	DisplayManager();
+	~DisplayManager();
+	// Initialize the hardware and display. Pass the SSD1306 I2C address (default 0x3C).
+	void init(uint8_t i2c_addr = 0x3C);
+
+	// Refresh the display content. Either pointer may be nullptr.
+	void refresh(const char *current_input, const char *last_echo);
+
+	// Update stored last-echo text used when `last_echo` is not provided to `refresh()`.
+	void set_last_echo(const char *text);
+
+	// Non-copyable
+	DisplayManager(const DisplayManager &) = delete;
+	DisplayManager &operator=(const DisplayManager &) = delete;
+
+	// Implementation details kept small in the header: pointer to the concrete SSD1306
+	// type (defined in `pico-ssd1306/ssd1306.h`).
+	pico_ssd1306::SSD1306 *display_;
+	char last_echo_[64];
+	static const size_t LAST_ECHO_VISIBLE_CHARS = 10;
+};
+#endif
+
+
+
+#endif // DISPLAY_H
+