template_callbacks.c

Callback-based program structure using Banjo's automain feature.

Callback-based program structure using Banjo's automain feature.This demonstrates an alternative to writing main() yourself. Instead of managing the program loop manually, you define three callbacks that Banjo invokes at the right times. This pattern is required for Emscripten/web builds and provides cleaner separation of initialization, iteration, and cleanup phases.

 
// This macro tells Banjo to generate main() for you. Banjo will call your
// three callback functions (bj_app_begin, bj_app_iterate, bj_app_end) in
// the correct order and manage the program lifecycle.
#define BJ_AUTOMAIN_CALLBACKS
#include <banjo/log.h>
#include <banjo/main.h>
#include <banjo/system.h>
 
// Called once at program startup. Initialize your resources here.
//
// user_data: Pointer to store application state (allocated here, passed to
//            other callbacks). Use *user_data = bj_malloc(...) to allocate.
// Returns: bj_callback_continue to proceed to iterate phase
//          bj_callback_exit_error to abort with error code
int bj_app_begin(void** user_data, int argc, char* argv[]) {
    (void)user_data; (void)argc; (void)argv;
 
    // Initialize Banjo subsystems. Same as in template.c.
    if(!bj_begin(BJ_VIDEO_SYSTEM | BJ_AUDIO_SYSTEM, 0)) {
        return bj_callback_exit_error;
    }
 
    return bj_callback_continue;
}
 
// Called repeatedly in a loop (like while(1) { ... }). Your main logic goes here.
//
// user_data: Application state from bj_app_begin (or NULL if none allocated)
// Returns: bj_callback_continue to keep looping
//          bj_callback_exit_success to stop and cleanup normally
//          bj_callback_exit_error to stop and cleanup with error
int bj_app_iterate(void* user_data) {
    (void)user_data;
 
    bj_info("Hello Banjo!");
 
    // Exit after one iteration for this simple example. In a real program,
    // you'd return bj_callback_continue until the user closes the window or
    // some exit condition is met.
    return bj_callback_exit_success;
}
 
// Called once when iterate requests exit. Cleanup your resources here.
//
// user_data: Application state from bj_app_begin
// status: The return code from bj_app_iterate (success or error)
// Returns: Exit code for the program (typically just pass through status)
int bj_app_end(void* user_data, int status) {
    (void)user_data;
 
    // Shutdown Banjo and release resources. If you allocated user_data in
    // bj_app_begin, free it here with bj_free(user_data).
    bj_end();
 
    return status;
}