main.c File Reference

VBlank frame counter display, written against the gameloop framework. More...

#include <snes.h>
#include <snes/text.h>
#include <snes/gameloop.h>

Functions
int	main (void)
	Entry point — hand off to gameLoopRun().
static void	on_init (void)
	One-time hardware setup. Runs before the first VBlank sync.
static void	on_update (void)
	Per-frame work. Called once per VBlank by the gameloop.

Detailed Description

VBlank frame counter display, written against the gameloop framework.

Displays a live frame counter that increments every VBlank (60 fps NTSC, 50 fps PAL). The simplest possible real-time display: read a hardware counter, render it as text, repeat. Doubles as the canonical demo of the opt-in gameloop framework — init() runs the standard SNES boot sequence, update() runs once per VBlank, and main() never sees a while(1) itself.

Equivalent hand-rolled main loop:

while (1) {
    WaitForVBlank();
    update();
}

Both ship the same observable behaviour; the framework exists so the loop boilerplate isn't repeated 53 times across the SDK and so future scene/state machinery has one place to plug into.

SNES Concepts

• VBlank frame counter (frame_count from crt0.asm, incremented by NMI)
• Text module for real-time number display (textPrintU16; NMI auto-flushes)
• gameloop framework — init/update callbacks, hidden VBlank sync
• Mode 0 with 2bpp font for text output

What to Observe

• The counter increments by 1 every frame (60 per second on NTSC)
• At 65535 it wraps to 0 (~18 minutes of runtime)
• The display never stutters because each frame does minimal work

Modules Used

console, sprite, dma, background, text, input, gameloop

See also

gameloop.h, console.h (getFrameCount), text.h

Function Documentation

main()

int main

(

void

)

Entry point — hand off to gameLoopRun().

gameLoopRun never returns; the return 0 exists only to satisfy int main(void)'s control-flow contract.

on_init()

static void on_init ( void  )

static

One-time hardware setup. Runs before the first VBlank sync.

Standard text-mode boot: textModeInit() sets BG mode + text engine, the PrintAt writes our static label into the off-screen tilemap buffer, the explicit WaitForVBlank ensures the very first NMI has fired (so the buffer has been DMA'd to VRAM) before we turn the screen on.

on_update()

static void on_update ( void  )

static

Per-frame work. Called once per VBlank by the gameloop.

The framework has already done WaitForVBlank() before calling us, so we are inside the VBlank window — VRAM/CGRAM/OAM writes are safe at this point. Nothing here exceeds the budget so we never drop a frame.