API Reference Overview

Note

Under construction.

Lists all public Ruby APIs provided by Family mruby. Click each API name to jump to its detail page.

Quick Reference

Application

Class / Module	Role	Details
FmrbApp	Application base class. Lifecycle, window, messaging	FmrbApp
FmrbGfx	Shape and text drawing (@gfx)	FmrbGfx
SpriteImage / SpriteInstance / GfxBlock	Sprites	Sprite
TileSheet / TileMap	Tile map rendering + fmrb_map JSON loading	TileMap
P5	Processing/p5.js-style drawing DSL	P5
FmrbAudio	BGM, sound effects, tone synthesis (@audio)	FmrbAudio
Pub/Sub (subscribe / publish)	Inter-app messaging	Pub/Sub

Files and Data

Class / Module	Role	Details
IO / File / Dir	File and directory operations	File & I/O
Log	Logging	Log
JSON	JSON parsing and generation	Utilities
MessagePack	Binary serialization	Utilities
BMP332	RGB332 BMP image parsing	Utilities
RX8900	RTC (I2C-connected) driver	Utilities

Hardware and System

Class / Module	Role	Details
GPIO	Digital I/O	Peripherals
I2C	I2C communication	Peripherals
RMT	RMT (infrared, WS2812B, etc.)	Peripherals
FmrbConst	System constants (version, theme colors, PROC_ID, etc.)	Constants & System Info
FmrbHw	Pin usage queries	Constants & System Info
Task	Task control	Task / Machine
Machine	System control (clock, delay, reset, etc.)	Task / Machine

Cross-Method Index

FmrbApp (Lifecycle, Window, Messaging)

Method	Summary
initialize	Framework initialization (prepares @gfx, @user_area_*, etc.)
on_create	Called once when the app starts (initialization logic)
on_update	Called every frame (return value = wait time in ms until next call)
on_event(ev)	Called on keyboard / mouse / gamepad / HID input
on_suspend / on_resume	Called when switching to/from a fullscreen app
on_destroy	Called once when the app exits
start / stop / destroy	Execution control
subscribe(topic) / unsubscribe(topic) / publish(topic, data)	Pub/Sub
send_message(dest_pid, msg_type, data)	Direct message sending
set_window_position(x, y)	Window position
draw_window_frame / draw_scrollbar / scrollbar_hit	Window decorations
request_file_select(mode)	File selection dialog
request_reload	Reload the app
ev_ctrl?(ev) / ev_shift?(ev) / ev_alt?(ev)	Modifier key checks

FmrbGfx (Drawing)

Method	Summary
clear(color) / present	Clear / commit frame
set_pixel(x, y, color)	Draw a single pixel
draw_line(x1, y1, x2, y2, color)	Line
draw_rect / fill_rect(x, y, w, h, color)	Rectangle
draw_round_rect / fill_round_rect(x, y, w, h, r, color)	Rounded rectangle
draw_circle / fill_circle(x, y, r, color)	Circle
draw_ellipse / fill_ellipse(x, y, rx, ry, color)	Ellipse
draw_triangle / fill_triangle(x0,y0,x1,y1,x2,y2,color)	Triangle
draw_arc / fill_arc(x, y, r0, r1, ang0, ang1, color)	Arc
blend_rect(x, y, w, h, color, mode:)	Semi-transparent rectangle (mode: 0=ADD, 1=XOR)
set_text_size(size)	Text size (1 to 4)
draw_text(x, y, text, color [, bg_color])	Text drawing
FmrbGfx.hsv_to_rgb(h, s, v)	Color conversion
FmrbGfx.rgb_to_332(r, g, b)	24-bit to RGB332
set_output_level(0..255) / set_chroma_level(0..255)	NTSC output adjustment

Color constants: BLACK 0x00 / WHITE 0xFF / RED 0xE0 / GREEN 0x1C / BLUE 0x03 / YELLOW 0xFC / CYAN 0x1F / MAGENTA 0xE3 / GRAY 0x6D

SpriteImage / SpriteInstance / GfxBlock

Class	Key Methods
SpriteImage	new(gfx, w, h, trans_color, use_trans:) / load_bmp(path) / set_target / reset_target / destroy
SpriteInstance	new(gfx, frame_images, x, y, z_order) / move(x, y) / visible= / frame= / destroy
GfxBlock	new(gfx, kwargs) { |r, kwargs| ... } / draw(**kwargs) / destroy

FmrbAudio (@audio)

Method	Summary
play(path, track: 0)	Play a file
stop / pause / resume	Playback control
load_fmsq(slot_id, binary)	Load FMSQ into a slot
play_slot(slot_id)	Play a slot
note_on(channel, freq, volume=10, duty=2, sweep=0)	Tone synthesis
note_off(channel)	Stop tone

Pub/Sub

subscribe(topic) / unsubscribe(topic) / publish(topic, data=nil) / send_message(dest_pid, msg_type, data)

Messages are received via _handle_system_control(msg) through on_control(msg), not on_event. See Pub/Sub for details.

IO / File / Dir

File.open(path, mode, &block), File.exist? / file? / directory? / size / delete, Dir.open(path) / Dir.read / Dir.mkdir, etc.

Log

Log.error(msg) / Log.warn(msg) / Log.info(msg) / Log.debug(msg) (or shorthand e / w / i / d; two-argument form allows specifying a tag)

GPIO / I2C / RMT

API	Signature
GPIO.new(pin, flags)	flags = OR combination of GPIO::IN, GPIO::OUT, GPIO::PULL_UP, etc.
I2C.new(unit:, frequency: 100_000, sda_pin:, scl_pin:, timeout: 500)	unit: is e.g. "ESP32_I2C0"
RMT.new(pin, t0h_ns:, t0l_ns:, t1h_ns:, t1l_ns:, reset_ns:)	NRZ encoding timing

FmrbConst / FmrbHw

Key constants: PLATFORM, PROC_ID_KERNEL, etc., MSG_TYPE_*, OS_VERSION, MAC_ADDRESS, THEME_*. FmrbHw.pin_status(pin) / pin_available?(pin) / pin_status_all / pin_count.

Task / Machine

Task.pass, Machine.delay_ms(ms), Machine.uptime_us, Machine.set_hwclock(epoch), Machine._reboot.

Warning

sleep (Kernel) may stall when used outside _spin because tick does not advance. Use Machine.delay_ms for short waits (see Limitations).

Key Instance Variables (when inheriting FmrbApp)

Variable	Description
@gfx	FmrbGfx instance
@canvas	Canvas ID
@audio	FmrbAudio instance
@name	App display name (from .toml app_screen_name)
@platform	:esp32 / :linux
@fullscreen	Whether the app is in fullscreen mode
@window_width / @window_height	Overall window size
@user_area_x0 / @user_area_y0 / @user_area_x1 / @user_area_y1	Boundaries of the drawable area for the app (window coordinate system)
@user_area_width / @user_area_height	Size of the drawable area
@pos_x / @pos_y	Top-left coordinates of the window (screen coordinate system). Changes when the window is moved

In @fullscreen mode, (@pos_x, @pos_y) is (0, 0), pointing at the top-left of the screen.

Coordinate System and Color Format

• Coordinate system: origin at top-left (0, 0), X increases rightward, Y increases downward
• Color: RGB332 (8-bit, R:3 G:3 B:2). Use constants like FmrbGfx::WHITE or generate with FmrbGfx.rgb_to_332(r, g, b)

Drawing Flow

Drawing commands (fill_rect, etc.)
  | Accumulated in buffer
@gfx.present
  | Applied to screen

Nothing appears until present is called

Drawing methods are not displayed on screen until @gfx.present is called. Sprite operations such as SpriteInstance#move are also composited at the present timing.