display_gif_sd: load GIF from SD into PSRAM once, play from memory (9.8 -> 15.4 fps)

Also enable a 16 KB LVGL stdio read cache (no measurable effect for the GIF).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

10-OBD-Display-2024/display_gif_sd/src/main.cpp

@@ -22,14 +22,26 @@ void display_animation() {
   lv_mem_monitor(&mem_mon);
   printf("Free memory: %d bytes\n", mem_mon.free_size);
 
-  lv_fs_file_t file;
-  if (lv_fs_open(&file, "A:wallpaper.gif", LV_FS_MODE_RD) == LV_FS_RES_OK) {
-    lv_fs_close(&file);  // File exists, proceed with loading
-    lv_gif_set_src(img, "A:wallpaper.gif");
-    Serial.println("GIF Loaded Successfully");
+  // Load the whole GIF from the SD card into PSRAM once and play it from memory:
+  // no SD access while playing (faster, and kinder to flaky cards)
+  static lv_image_dsc_t gif_dsc;
+  File f = SD_MMC.open("/wallpaper.gif");
+  size_t size = f ? f.size() : 0;
+  uint8_t* data = size ? (uint8_t*)ps_malloc(size) : NULL;
+  if (data && f.read(data, size) == size) {
+    gif_dsc.header.magic = LV_IMAGE_HEADER_MAGIC;
+    gif_dsc.header.cf = LV_COLOR_FORMAT_RAW;
+    gif_dsc.header.w = data[6] | (data[7] << 8);  // GIF logical screen size
+    gif_dsc.header.h = data[8] | (data[9] << 8);
+    gif_dsc.data_size = size;
+    gif_dsc.data = data;
+    lv_gif_set_src(img, &gif_dsc);
+    Serial.printf("GIF loaded into PSRAM: %u bytes, %u x %u\n", size, gif_dsc.header.w, gif_dsc.header.h);
   } else {
-    Serial.println("Failed to Load GIF: File not found or inaccessible");
+    Serial.println("Failed to load /wallpaper.gif from the SD card");
+    free(data);
   }
+  if (f) f.close();
 
   Serial.print("Available Heap after: ");
   Serial.println(esp_get_free_heap_size());

shared/include/lv_conf.h

@@ -1967,7 +1967,7 @@
 #define LV_FS_STDIO_PATH "/sdcard/"
 
 /** Read cache size in bytes for stdio (0 = disabled) */
-#define LV_FS_STDIO_CACHE_SIZE 0
+#define LV_FS_STDIO_CACHE_SIZE 16384  /* JC3636W518: fewer small SD reads (GIF decoding) */
 
 #endif /*LV_USE_FS_STDIO*/