Lobby

All examples · Entry point

A complete room-selection interface: connect, create a public/private room, join by six-digit code, find a game, show player names and start a small moving-player demo. Built with Butano, with no audio.

Build and run

Set the shared example key, then from the SDK root:

make -C examples/lobby LIBBUTANO=/path/to/butano/butano -j2

Output: examples/lobby/lobby.gba. You need devkitARM, Python 3 and a Butano directory containing butano.mak; all graphics used by the example are bundled.

If rebuilding an older version that included audio, run make clean first with the same LIBBUTANO setting. Both audio backends are set to null.

Load the ROM on each console and press A on the title screen to connect. Loading and hardware requirements.

Try two players

Connect both consoles to open their sessions.
On the first, choose Create a room, a capacity and visibility.
On the second, choose Join with a code and enter the displayed digits.
Check that both names appear; the local player has (you), the master *.
The master presses A to start when at least two players are present.
Move with the D-pad and check that the other console receives movement.
Press START, then choose Leave the match to return to room selection.

Alternatively, choose Find a game on both consoles for public two-player matchmaking. Explicit room creation offers two to four seats. Room parameters are "demo".

Controls

Screen	Controls
Title	A connects
Menus	Up/down selects; A confirms; B returns
Code entry	Up/down changes digit; left/right moves; A joins; B cancels
Lobby	A starts for the master with at least two players; B leaves
Match	D-pad moves; START opens pause
Pause	Resume or leave; B resumes

Leaving the room preserves the online session. B from room selection closes the session and returns to the title.

Structure

title → session → room selection → lobby → match
                      ↑                    |
                      └──── leave ─────────┘

File	Responsibility
src/main.cpp	Title, connection, session loop and menu keepalive
src/scene_menu.cpp	Room options, code input and join errors
src/scene_lobby.cpp	Names, occupancy, master and start request
src/scene_match.cpp	Position transport and pause menu
src/ui.cpp	Text, navigation and frame handover
include/lobby_name.h	Font-safe display names

Keep the session alive

Menus call on_frame once per frame. In this example it polls without consuming game messages:

void keep_alive() {
    cf_poll(nullptr, 0);
    // The actual implementation also displays a reconnecting notice.
}

The match polls itself, because it needs received positions. During recovery, the UI keeps advancing and the SDK keeps attempting transport recovery. Do not copy a second menu poll into the same frame of a game that already polls.

This example sends no reliable events. If you add them, receive/process them while menus are open; NULL-output polls retain them and queues are bounded.

Presentation

The interface uses a white background, the CanoFlash multiboot logo, black 8x16 text and a black menu arrow. The font's white edge blends into the backdrop. Connection-error messages hide the logo.

The logo is bundled in graphics/logo.bmp; no external ROM checkout is needed. The white backdrop is set in code and does not require a background image. The selector sprite represents players in the moving demo.

Names refresh as room metadata arrives. Supported Spanish accents are retained; unsupported glyphs, malformed UTF-8 and control characters display as ?. Names are shortened to fit local/master/away markers. The SDK itself preserves UTF-8; this conversion is presentation code.

Data and limitations

Position messages contain x/y only. cf_last_sender() routes each received position to the relay-assigned seat. Use matching ROM builds on all consoles.

The demo is not a complete game protocol: it does not exchange ready/version messages, implement reliable actions or resynchronise an authoritative world after master migration. Follow Integration, Rooms and Reliable events when extending it.

Font attribution and licence: Third-party notices.