press_select
Activates the SELECT button on a GameBoy emulator for a specified duration in frames, enabling precise control within the MCP GameBoy Server environment.
Instructions
Press the SELECT button on the GameBoy
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| duration_frames | No | Number of frames to hold the button |
Implementation Reference
- src/tools.ts:20-37 (registration)Dynamic registration of the 'press_select' tool (and other press_* buttons) with inline input schema, description, and handler function. The handler presses the SELECT button via EmulatorService and returns the screen image.
// Register button press tools Object.values(GameBoyButton).forEach(button => { server.tool( `press_${button.toLowerCase()}`, `Press the ${button} button on the GameBoy`, { duration_frames: z.number().int().positive().optional().default(1).describe('Number of frames to hold the button').default(25) }, async ({ duration_frames }): Promise<CallToolResult> => { // Press the button using the service (advances one frame) emulatorService.pressButton(button, duration_frames); // Return the current screen using the service const screen = emulatorService.getScreen(); return { content: [screen] }; } ); }); - src/server/server.ts:24-26 (registration)Invokes registerGameBoyTools which registers the press_select tool among others.
// Register GameBoy tools registerGameBoyTools(server, emulatorService); // Pass emulatorService - src/types.ts:9-18 (helper)GameBoyButton enum defining SELECT button used in dynamic tool registration.
export enum GameBoyButton { UP = 'UP', DOWN = 'DOWN', LEFT = 'LEFT', RIGHT = 'RIGHT', A = 'A', B = 'B', START = 'START', SELECT = 'SELECT' } - src/emulatorService.ts:72-80 (helper)EmulatorService.pressButton method called by the press_select tool handler. Delegates to GameBoyEmulator and returns screen.
pressButton(button: GameBoyButton, durationFrames: number): ImageContent { log.debug(`Pressing button: ${button}`); if (!this.isRomLoaded()) { log.warn('Attempted to press button with no ROM loaded'); throw new Error('No ROM loaded'); } this.emulator.pressButton(button, durationFrames); // This advances one frame return this.getScreen(); } - src/gameboy.ts:43-67 (helper)Low-level GameBoyEmulator.pressButton implementation that maps SELECT to keycode, presses for duration_frames, and advances emulation frames.
public pressButton(button: GameBoyButton, durationFrames: number = 1): void { if (!this.romLoaded) { throw new Error('No ROM loaded'); } // Map our button enum to serverboy's keymap const buttonMap: Record<GameBoyButton, number> = { [GameBoyButton.UP]: Gameboy.KEYMAP.UP, [GameBoyButton.DOWN]: Gameboy.KEYMAP.DOWN, [GameBoyButton.LEFT]: Gameboy.KEYMAP.LEFT, [GameBoyButton.RIGHT]: Gameboy.KEYMAP.RIGHT, [GameBoyButton.A]: Gameboy.KEYMAP.A, [GameBoyButton.B]: Gameboy.KEYMAP.B, [GameBoyButton.START]: Gameboy.KEYMAP.START, [GameBoyButton.SELECT]: Gameboy.KEYMAP.SELECT }; for (let i=0; i < durationFrames; i++) { this.gameboy.pressKeys([buttonMap[button]]); this.gameboy.doFrame(); } // for now: advance one frame so we dont "hold" the button all the time. this.gameboy.doFrame(); }