OpenSNES Code Style Guide

Consistent code style makes the codebase easier to read and maintain.

C Code

General

• Indentation: 4 spaces (no tabs)
• Line length: 80 characters soft limit, 100 hard limit
• Braces: K&R style (opening brace on same line)

// Good
if (condition) {
    do_something();
} else {
    do_other();
}
 
// Bad
if (condition)
{
    do_something();
}

Naming Conventions

Element	Convention	Example
Functions	snake_case	sprite_init()
Variables	snake_case	player_x
Constants	UPPER_CASE	MAX_SPRITES
Types	PascalCase	SpriteData
Macros	UPPER_CASE	DMA_ENABLE
Enums	UPPER_CASE	SPRITE_SIZE_8X8

Types

Use fixed-width types from snes.h:

// Good
u8 byte_value;
u16 word_value;
s16 signed_value;
s32 long_value;
 
// Bad
unsigned char byte_value;
int value;

Function Documentation

Use Doxygen-style comments:

 
u8 sprite_init(u8 id, u16 x, u8 y);

Error Handling

// Return FALSE/NULL on error
u8 sprite_init(u8 id, u16 x, u8 y) {
    if (id >= MAX_SPRITES) {
        return FALSE;
    }
    // ...
    return TRUE;
}
 
// Check return values
if (!sprite_init(id, x, y)) {
    // Handle error
}

Memory

// Always check allocations
void* ptr = malloc(size);
if (ptr == NULL) {
    // Handle allocation failure
}
 
// Zero-initialize structures
SpriteData sprite;
memset(&sprite, 0, sizeof(sprite));

Assembly (65816 - WLA-DX)

General

• Indentation: Labels at column 0, instructions indented with tab
• Comments: Explain non-obvious operations
• Sections: Use .section for code organization

Format

;============================================================================
; Function: sprite_update
; Description: Update all active sprites
; Input: None
; Output: None
; Clobbers: A, X, Y
;============================================================================
.section ".text" superfree
 
sprite_update:
    php                     ; Save processor status
    rep #$20                ; 16-bit accumulator
 
    ldx #0                  ; Start at sprite 0
-   lda sprite_active,x     ; Check if active
    beq +                   ; Skip if inactive
 
    jsr _update_single      ; Update this sprite
 
+   inx
    inx                     ; Next sprite (16-bit index)
    cpx #MAX_SPRITES * 2
    bne -
 
    plp                     ; Restore processor status
    rtl
 
.ends

Register Documentation

; Document register state changes
    rep #$20                ; A = 16-bit
    sep #$10                ; X/Y = 8-bit
 
; Document expected register values
; Input: A = sprite ID (0-127)
; Output: X = OAM offset

Labels

; Public labels: _function_name
_sprite_init:
 
; Local labels: use anonymous (+ -)
    bne +           ; Forward reference
    bra -           ; Backward reference
 
; Named local: .local_name
.calculate_offset:

File Organization

Headers (.h)

 
#ifndef OPENSNES_SPRITE_H
#define OPENSNES_SPRITE_H
 
#include <snes.h>
 
/* Constants */
#define MAX_SPRITES 128
 
/* Types */
typedef struct {
    u16 x;
    u8 y;
    u16 tile;
} SpriteData;
 
/* Functions */
u8 sprite_init(u8 id, u16 x, u8 y);
void sprite_update(void);
 
#endif /* OPENSNES_SPRITE_H */

Source (.c)

 
#include "sprite.h"
 
/* Private data */
static SpriteData sprites[MAX_SPRITES];
 
/* Public functions */
u8 sprite_init(u8 id, u16 x, u8 y) {
    // Implementation
}

Formatting Tools

Consider using:

• clang-format for C code (config in .clang-format)
• Consistent editor settings (.editorconfig)