Web (Emscripten) Build & Persistence

Overview

The Web build compiles Planet Blupi to WebAssembly using Emscripten. Save games are persisted in the browser's IndexedDB via Emscripten's IDBFS (IndexedDB File System) virtual filesystem.

Implementation: src/web_persistence.cpp

Save Game Persistence

Two C functions are exported to JavaScript for IndexedDB synchronisation:

// Flush in-memory save files to IndexedDB:
EMSCRIPTEN_KEEPALIVE void PlanetBlupi_ExportPersistentData();

// Load save files from IndexedDB into the virtual filesystem:
EMSCRIPTEN_KEEPALIVE void PlanetBlupi_ImportPersistentData();

From JavaScript:

// Export (flush saves to IndexedDB):
Module.ccall('PlanetBlupi_ExportPersistentData', null, [], []);

// Import (restore saves from IndexedDB):
Module.ccall('PlanetBlupi_ImportPersistentData', null, [], []);

How It Works

Game write (CDecor::Write)
    → writes to IDBFS virtual filesystem (in-memory)
    → PlanetBlupi_ExportPersistentData() called
        → FS.syncfs(false, callback)  ← flushes to IndexedDB

Game read (CDecor::Read)
    → PlanetBlupi_ImportPersistentData() called first
        → FS.syncfs(true, callback)   ← loads from IndexedDB
    → reads from IDBFS virtual filesystem

Limitations in Web Build

Data Reset

Clearing browser site data (cookies, storage) deletes all save games. There is no built-in export/import of saves from the browser.

Build Commands

# Configure:
emcmake cmake -S . -B build-web

# Build:
cmake --build build-web

The output is a .html + .js + .wasm bundle that can be served from any static web server.