.. _luaengine: Scripting MAME via Lua ====================== .. contents:: :local: .. _luaengine-intro: Introduction ------------ It is now possible to externally drive MAME via Lua scripts. This feature initially appeared in version 0.148, when a minimal Lua engine was implemented. Today, the Lua interface is rich enough to let you inspect and manipulate devices’ state, access CPU registers, read and write memory, and draw a custom HUD on screen. Internally, MAME makes extensive use of `Sol3 `_ to implement this feature. The idea is to transparently expose as many of the useful internals as possible. Finally, a warning: the Lua API is not yet declared stable and may suddenly change without prior notice. However, we expose methods to let you know at runtime which API version you are running against, and most of the objects support runtime you can introspection. .. _luaengine-features: Features -------- The API is not yet complete, but this is a partial list of capabilities currently available to Lua scripts: - session information (app version, current emulated system, ROM details) - session control (starting, pausing, resetting, stopping) - event hooks (on frame painting and on user events) - device introspection (device tree listing, memory and register enumeration) - screen introspection (screens listing, screen details, frame counting) - screen overlay drawing (text, lines, boxes on multiple screens) - memory read/write (8/16/32/64 bits, signed and unsigned) - register and state control (state enumeration, get and set) Many of the classes are documented on the :ref:`Lua class reference ` page. .. _luaengine-usage: Usage ----- MAME supports external scripting via Lua (>= 5.3) scripts, either entered at the interactive console or loaded as a file. To reach the console, enable the console plugin (e.g. run MAME with ``-plugin console``) and you will be greeted with a ``[MAME]>`` prompt where you can enter Lua script interactively. To load a whole script at once, store it in a plain text file and pass it using ``-autoboot_script``. Please note that script loading may be delayed (a few seconds by default), but you can override the default with the ``-autoboot_delay`` option. To control the execution of your code, you can use a loop-based or event-based approach. The former is not encouraged as it is resource-intensive and makes control flow unnecessarily complex. Instead, we suggest to register custom hooks to be invoked on specific events (e.g. at each frame rendering). .. _luaengine-walkthrough: Walkthrough ----------- Let’s first run MAME in a terminal to reach the Lua console: :: $ mame -console YOUR_ROM /| /| /| /| /| _______ / | / | / | / | / | / / / |/ | / | / |/ | / ____/ / | / | / | / /_ / |/ | / |/ __/ / /| /| /| |/ /| /| /____ / / | / | / | / | / | / / _/ |/ / / |___/ |/ /_______/ / / / _/ mame 0.227 Copyright (C) Nicola Salmoria and the MAME team Lua 5.3 Copyright (C) Lua.org, PUC-Rio [MAME]> At this point, your game is probably running in demo mode, let’s pause it: :: [MAME]> emu.pause() [MAME]> Even without textual feedback on the console, you’ll notice the game is now paused. In general, commands are quiet and only print back error messages. You can check at runtime which version of MAME you are running, with: :: [MAME]> print(emu.app_name() .. " " .. emu.app_version()) mame 0.227 We now start exploring screen related methods. First, let's enumerate available screens: :: [MAME]> for tag, screen in pairs(manager.machine.screens) do print(tag) end :screen ``manager.machine`` is the :ref:`running machine ` object for your current emulation session. We will be using this frequently. ``screens`` is a :ref:`device enumerator ` that yields all emulated screens in the system; most arcade games only have one main screen. In our case, the main and only screen is tagged as ``:screen``, and we can further inspect it: :: [MAME]> -- keep a reference to the main screen in a variable [MAME]> s = manager.machine.screens[":screen"] [MAME]> print(s.width .. "x" .. s.height) 320x224 We have several methods to draw a HUD on the screen composed of lines, boxes and text: :: [MAME]> -- we define a HUD-drawing function, and then call it [MAME]> function draw_hud() [MAME]>> s:draw_text(40, 40, "foo") -- (x0, y0, msg) [MAME]>> s:draw_box(20, 20, 80, 80, 0xff00ffff, 0) -- (x0, y0, x1, y1, line-color, fill-color) [MAME]>> s:draw_line(20, 20, 80, 80, 0xff00ffff) -- (x0, y0, x1, y1, line-color) [MAME]>> end [MAME]> draw_hud() This will draw some useless art on the screen. However, when resuming the game, your HUD needs to be refreshed otherwise it will just disappear. In order to do this, you have to register your hook to be called on every frame repaint: :: [MAME]> emu.register_frame_done(draw_hud, "frame") All colors are specified in ARGB format (eight bits per channel), while screen origin (0,0) normally corresponds to the top-left corner. Similarly to screens, you can inspect all the devices attached to a machine: :: [MAME]> for tag, device in pairs(manager.machine.devices) do print(tag) end :audiocpu :maincpu :saveram :screen :palette [...] On some of them, you can also inspect and manipulate memory and state: :: [MAME]> cpu = manager.machine.devices[":maincpu"] [MAME]> -- enumerate, read and write state registers [MAME]> for k, v in pairs(cpu.state) do print(k) end D5 SP A4 A3 D0 PC [...] [MAME]> print(cpu.state["D0"].value) 303 [MAME]> cpu.state["D0"].value = 255 [MAME]> print(cpu.state["D0"].value) 255 :: [MAME]> -- inspect memory [MAME]> for name, space in pairs(cpu.spaces) do print(name) end program [MAME]> mem = cpu.spaces["program"] [MAME]> print(mem:read_i8(0xc000)) 41 33'>33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409