Skeleton C framebuffer engine with a demo cartridge and PC SDL2 host.

This project is intended to run on ESP32 hardware in the future. The current PC
host exists as a native development target for testing the framebuffer engine and
demo cartridge before embedded integration.

rosakasa_core is also linked to the
Lys Entertainment System
project, which lives in a separate repository.

Layout

include/rosakasa/display/   Public framebuffer/display API
demo/                       Demo cartridge setup/update entrypoint
demo/src/                   Demo cartridge rendering helpers and sources
host/pc/                    PC executable that wires engine to demo cartridge
src/engine/                 Engine lifecycle, HTTP/WebSocket packages, and SDL display backend

Demo cartridge sources under demo/src/ are picked up automatically by CMake.

Native PC

make build
make run

If SDL2 is not installed locally, CMake downloads SDL2 with FetchContent by default.

Engine Configuration

rosakasa_engine owns package configuration through RosakasaEngineConfig.
The HTTP and WebSocket packages are present but disabled by default until an
embedded or PC backend is attached:

RosakasaEngineConfig config = rosakasa_engine_default_config();

config.websocket.enabled = true;
config.websocket.host = "192.168.1.10";
config.websocket.path = "/socket";
config.websocket.port = 80;
config.websocket.use_tls = false;
config.websocket.send = platform_websocket_send;
config.websocket.user_data = platform_websocket;

rosakasa_engine_create_with_config(&config, &engine);

The engine-facing send API is backend-neutral:

RosakasaWebSocket *websocket = rosakasa_engine_websocket(engine);

rosakasa_websocket_send_text(websocket, "{\"type\":\"ping\"}");

The configured send callback is responsible for the actual platform transport
and WebSocket frame write. On PC that can be backed by a native WebSocket
library; on ESP32 it can be backed by the ESP-IDF WebSocket client.

The PC host includes a basic ws:// backend. Enable it with environment
variables before running:

ROSAKASA_WS_HOST=127.0.0.1 ROSAKASA_WS_PORT=4000 ROSAKASA_WS_PATH=/socket make run

ROSAKASA_WS_TLS=1 is reserved for wss://, but the PC backend does not support
TLS yet.

Demo Drawing

The demo owns a local framebuffer abstraction:

typedef struct {
    uint8_t *pixels;
    int width;
    int height;
    int pitch_bytes;
} Framebuffer;

Drawing helpers take a Framebuffer *, so call sites do not need to repeat screen dimensions:

draw_line(&demo_framebuffer, (Point){20, 20}, (Point){220, 220}, 220);
draw_square(&demo_framebuffer, center, length, 255);

Screen coordinates start at the top-left:

(0, 0)              x increases ->
  |
  v
y increases

For the default 240x240 framebuffer, the screen center is:

Point screen_center = {
    demo_framebuffer.width / 2,
    demo_framebuffer.height / 2,
};

draw_square treats its Point argument as the square's center.