main.cpp

#include <Arduino.h>
#include <M5Unified.h>

#define LV_CONF_INCLUDE_SIMPLE
#include <lvgl.h>
#include <esp_timer.h>

constexpr int32_t HOR_RES=320;
constexpr int32_t VER_RES=240;

lv_display_t *display;
lv_indev_t *indev;

void my_display_flush(lv_display_t *disp, const lv_area_t *area, uint8_t *px_map) {
  uint32_t w = (area->x2 - area->x1 + 1);
  uint32_t h = (area->y2 - area->y1 + 1);

  lv_draw_sw_rgb565_swap(px_map, w*h);
  M5.Display.pushImageDMA<uint16_t>(area->x1, area->y1, w, h, (uint16_t *)px_map);
  lv_disp_flush_ready(disp);
}

uint32_t my_tick_function() {
  return (esp_timer_get_time() / 1000LL);
}

void my_touchpad_read(lv_indev_t * drv, lv_indev_data_t * data) {
  M5.update();
  auto count = M5.Touch.getCount();

  if ( count == 0 ) {
    data->state = LV_INDEV_STATE_RELEASED;
  } else {
    auto touch = M5.Touch.getDetail(0);
    data->state = LV_INDEV_STATE_PRESSED; 
    data->point.x = touch.x;
    data->point.y = touch.y;
  }
}

// LVGL code - Handle multiple events demo

static void event_cb(lv_event_t *e)
{
  lv_event_code_t code = lv_event_get_code(e);
  lv_obj_t *label = reinterpret_cast<lv_obj_t *>(lv_event_get_user_data(e));

  switch (code)
  {
  case LV_EVENT_PRESSED:
    lv_label_set_text(label, "The last button event:\nLV_EVENT_PRESSED");
    break;
  case LV_EVENT_CLICKED:
    lv_label_set_text(label, "The last button event:\nLV_EVENT_CLICKED");
    break;
  case LV_EVENT_LONG_PRESSED:
    lv_label_set_text(label, "The last button event:\nLV_EVENT_LONG_PRESSED");
    break;
  case LV_EVENT_LONG_PRESSED_REPEAT:
    lv_label_set_text(label, "The last button event:\nLV_EVENT_LONG_PRESSED_REPEAT");
    break;
  default:
    break;
  }
}

/**
 * Handle multiple events
 */
void lv_example_event_2(void)
{
  lv_obj_t *btn = lv_button_create(lv_screen_active());
  lv_obj_set_size(btn, 100, 50);
  lv_obj_center(btn);

  lv_obj_t *btn_label = lv_label_create(btn);
  lv_label_set_text(btn_label, "Click me!");
  lv_obj_center(btn_label);

  lv_obj_t *info_label = lv_label_create(lv_screen_active());
  lv_label_set_text(info_label, "The last button event:\nNone");

  lv_obj_add_event_cb(btn, event_cb, LV_EVENT_ALL, info_label);
}

// continue setup code
void setup() {
  M5.begin();
  lv_init();

  lv_tick_set_cb(my_tick_function);

  display = lv_display_create(HOR_RES, VER_RES);
  lv_display_set_flush_cb(display, my_display_flush);

  static lv_color_t buf1[HOR_RES * 15]; 
  lv_display_set_buffers(display, buf1, nullptr, sizeof(buf1), LV_DISPLAY_RENDER_MODE_PARTIAL);

  indev = lv_indev_create();
  lv_indev_set_type(indev, LV_INDEV_TYPE_POINTER);

  lv_indev_set_read_cb(indev, my_touchpad_read);

  lv_example_event_2();
}

void loop() {
  lv_task_handler();
  vTaskDelay(1);
}