Root cause: LVGL9 canvas = lv_image backed by draw_buf with image cache.
Mutating raw uint16_t* buffer without lv_image_cache_drop + lv_draw_buf_invalidate_cache
leaves stale texture (gray/black). Only label (FPS) updated via lv_label_set_text_fmt,
so symptom = FPS counter works, game invisible.
Fix:
- fb_native typed uint16_t* raw RGB565, not lv_color16_t bitfield (endian bug)
- keep lv_draw_buf_t* from lv_canvas_get_draw_buf()
- each frame after gb_run_frame(): invalidate_cache + cache_drop + invalidate
- initial buffer fill check pattern removed, added lines_drawn debug in FPS label
- forward-decl lv_image_cache_drop (not in public SDK headers but firmware exports it)
- requires firmware feature/gameboy-canvas-full-api:
lv_draw_buf_invalidate_cache, lv_image_cache_drop, lv_canvas_get_draw_buf,
lv_image_set_scale/pivot, display resolution
SDK 0.8.0-dev built with IDF 5.5.2 - 0 undefined beyond firmware exports.
Builds to 50K GameBoy.app
Also preserves mDNS browse API from parent branch (Mdns.h/cpp, tt_mdns.h/cpp)
which sits on top of 60764979 'kidsOS-XXXX' mdns init.
Adolfo
653ad8902f