basic of display management. Backend to register and give image for the device. front end to manage displays etc.

Provider/main/api/devices/screen_image.cpp

@@ -0,0 +1,156 @@
+// GET /api/devices/screen.png?mac=XX — Render and return a PNG for the device's current screen
+// Uses LVGL to render the device's XML layout (or a fallback label) then encodes to PNG via lodepng.
+
+#include "lv_setup.hpp"
+#include "lodepng/lodepng.h"
+#include "esp_http_server.h"
+#include "esp_log.h"
+#include "esp_heap_caps.h"
+#include "lvgl.h"
+#include <string.h>
+#include "lodepng_alloc.hpp"
+
+#include "types.hpp"
+#include "device.hpp"
+
+internal const char *kTagDeviceScreenImage = "API_DEV_SCREEN_IMG";
+
+internal esp_err_t api_devices_screen_image_handler(httpd_req_t *req)
+{
+  httpd_resp_set_hdr(req, "Access-Control-Allow-Origin", "*");
+  httpd_resp_set_hdr(req, "Cache-Control", "no-cache, no-store, must-revalidate");
+  httpd_resp_set_type(req, "image/png");
+
+  // Extract mac query parameter
+  char mac[18] = {};
+  size_t buf_len = httpd_req_get_url_query_len(req) + 1;
+  if (buf_len > 1)
+  {
+    char query[64] = {};
+    if (httpd_req_get_url_query_str(req, query, sizeof(query)) == ESP_OK)
+    {
+      httpd_query_key_value(query, "mac", mac, sizeof(mac));
+    }
+  }
+
+  if (mac[0] == '\0')
+  {
+    httpd_resp_send_err(req, HTTPD_400_BAD_REQUEST, "Missing 'mac' query param");
+    return ESP_FAIL;
+  }
+
+  device_t *dev = find_device(mac);
+  if (!dev)
+  {
+    httpd_resp_send_err(req, HTTPD_404_NOT_FOUND, "Device not registered");
+    return ESP_FAIL;
+  }
+
+  // --- LVGL rendering (mutex-protected) ---
+  if (xSemaphoreTake(g_LvglMutex, pdMS_TO_TICKS(5000)) != pdTRUE)
+  {
+    ESP_LOGE(kTagDeviceScreenImage, "Failed to get LVGL mutex");
+    httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "LVGL busy");
+    return ESP_FAIL;
+  }
+
+  lv_obj_t *scr = lv_screen_active();
+
+  // Clear all children from the active screen
+  lv_obj_clean(scr);
+
+  // White background for grayscale
+  lv_obj_set_style_bg_color(scr, lv_color_white(), LV_PART_MAIN);
+
+  if (dev->xml_layout[0] != '\0')
+  {
+    // TODO: Use lv_xml_create() when LVGL XML runtime is verified working.
+    // For now, show the XML as text to prove the pipeline works end to end.
+    // Once we confirm LV_USE_XML compiles, we'll swap this for the real XML parser.
+    lv_obj_t *label = lv_label_create(scr);
+    lv_label_set_text(label, dev->xml_layout);
+    lv_obj_set_style_text_color(label, lv_color_black(), LV_PART_MAIN);
+    lv_obj_align(label, LV_ALIGN_TOP_LEFT, 10, 10);
+  }
+  else
+  {
+    // Fallback: render "Hello <mac>"
+    lv_obj_t *label = lv_label_create(scr);
+    char text[48];
+    snprintf(text, sizeof(text), "Hello %s", mac);
+    lv_label_set_text(label, text);
+    lv_obj_set_style_text_color(label, lv_color_black(), LV_PART_MAIN);
+    lv_obj_align(label, LV_ALIGN_CENTER, 0, 0);
+  }
+
+  // Force LVGL to fully render the screen
+  lv_refr_now(g_LvglDisplay);
+
+  lv_draw_buf_t *draw_buf = lv_display_get_buf_active(g_LvglDisplay);
+  if (!draw_buf)
+  {
+    xSemaphoreGive(g_LvglMutex);
+    ESP_LOGE(kTagDeviceScreenImage, "No active draw buffer");
+    httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "Display uninitialized");
+    return ESP_FAIL;
+  }
+
+  uint32_t width = CONFIG_CALENDINK_DISPLAY_WIDTH;
+  uint32_t height = CONFIG_CALENDINK_DISPLAY_HEIGHT;
+
+  // Handle stride != width
+  uint8_t *packed_data = (uint8_t *)draw_buf->data;
+  bool needs_free = false;
+
+  if (draw_buf->header.stride != width)
+  {
+    packed_data = (uint8_t *)heap_caps_malloc(width * height, MALLOC_CAP_SPIRAM);
+    if (!packed_data)
+    {
+      xSemaphoreGive(g_LvglMutex);
+      ESP_LOGE(kTagDeviceScreenImage, "Failed to allocate packed buffer");
+      httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "Out of memory");
+      return ESP_FAIL;
+    }
+    needs_free = true;
+    for (uint32_t y = 0; y < height; ++y)
+    {
+      memcpy(packed_data + (y * width),
+             (uint8_t *)draw_buf->data + (y * draw_buf->header.stride), width);
+    }
+  }
+
+  // Encode to PNG
+  unsigned char *png = nullptr;
+  size_t pngsize = 0;
+
+  lodepng_allocator_reset();
+
+  ESP_LOGI(kTagDeviceScreenImage, "Encoding %lux%lu PNG for device %s", width, height, mac);
+  unsigned error = lodepng_encode_memory(&png, &pngsize, packed_data, width, height, LCT_GREY, 8);
+
+  if (needs_free)
+  {
+    free(packed_data);
+  }
+
+  xSemaphoreGive(g_LvglMutex);
+
+  if (error)
+  {
+    ESP_LOGE(kTagDeviceScreenImage, "PNG encoding error %u: %s", error, lodepng_error_text(error));
+    httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "PNG generation failed");
+    return ESP_FAIL;
+  }
+
+  ESP_LOGI(kTagDeviceScreenImage, "PNG ready: %zu bytes. Sending...", pngsize);
+  esp_err_t res = httpd_resp_send(req, (const char *)png, pngsize);
+
+  return res;
+}
+
+internal const httpd_uri_t api_devices_screen_image_uri = {
+    .uri = "/api/devices/screen.png",
+    .method = HTTP_GET,
+    .handler = api_devices_screen_image_handler,
+    .user_ctx = NULL};