A backend is part of the engine that handles some low-level task like displaying graphics and can be swapped out for a replacement which achieves the same thing in a different way, usually by using a different library. The OHRRPGCE uses several different backends for graphics and music. Different builds of the engine are available with differing backends or other "compile-time" options. Actually you can only get non-standard nightly builds; if you want a non-standard stable release you either need to compile it yourself, or use a nightly build from a nearby date.
The easiest way to see which backends you are using is to run Custom and go to Load Existing Game. At the bottom of the screen you'll see a line like "OHRRPGCE wip 20160610 directx/sdl" meaning gfx_directx and music_sdl. You can also examine c/g_debug.txt for lines starting with gfx_### or music_### (don't be fooled by the version info line, which lists all backends compiled in).
gfx backends provide the graphics and user-input (keyboard, mouse, joystick/gamepads) and often more (gfx_sdl contains nearly everything to do with Mac OSX or Android). The OHRRPGCE can be compiled with any combination of graphics backends, and the one to use selected with a commandline switch. Run with commandline option "/?" (or "--help") for usage information. The default graphics backend is always the first named, for example in the file ohrrpgce-wip-gfx-music.zip. By default the OHRRPGCE is compiled with support for any of gfx_sdl, gfx_directx, and gfx_fb which are available for the current platform.
|name||status||description||fullscreen||smoothing||platforms||resolutions other than 320x200|
|gfx_sdl||stable||Simple DirectMedia Layer (SDL) 1.2 graphics. This is the default backend on GNU/Linux, Macintosh, and Android, and for Custom.exe on Windows||Yes||Yes||GNU/Linux, BSD, Mac, Windows, Android||Yes|
|gfx_directx||stable||This backend exists as gfx_directx.dll - all Windows builds normally include support for it even if the .dll isn't included. This is the default backend on Windows for Game.exe. It has better joystick and fullscreen support than gfx_sdl||Yes||Yes (texture scaling)||Windows||No|
|gfx_fb||stable||Based on Freebasic's standard graphics library. This backend is fairly well-tested and used to be the default, but has a few minor unsolvable problems|| Windows:Yes
|Yes||GNU/Linux, BSD, Windows||No|
|gfx_alleg|| working?, but very little testing
Linux: keyboard input broken
|Allegro backend. Not currently compiled for nightly builds (due to a problem with the build machine)||Yes||No||(Mac?, Linux?), Windows||No|
|gfx_console||diagnostic||Curses-based backend (displays text only, no graphics). For testing only; no builds available.||NA||NA||All||No|
music backends provide the music and sound effects. The music backend is always the second named, for example, ohrrpgce-wip-gfx-music.zip. Unlike graphics backends, each build of the engine only supports a single music backend; they can't be selected with a command-line option.
|name||status||description||advanced MIDI looping|
|music_native|| Windows:only plays MIDI (MIDI playback very buggy)
Linux:No MIDI support
|Audiere and Native windows MIDI. MIDI playback is very buggy. Usually does not work on Linux because Audiere uses OSS. Since some years ago, Audiere has also mysteriously stopped playing anything on Windows.|| Windows:Yes|
|music_sdl||stable (crashy on Windows)||SDL 1.2+SDL_mixer backend. This is the default everywhere. MIDI playback on Windows sometimes crashes. Variable-bitrates and unusual sample rates are broken. Some MP3 files (variable bitrate?) cause crashes. Converting .mp3s to .oggs avoids some of these problems.||No|
|music_allegro||obsolete||Allegro backend. Unmaintained; no longer works or even compiles. Only worked together with gfx_alleg||No|
|music_native2||only plays MIDI (MIDI playback buggy)||(Windows-only) music_native variant with alternative, "better" (but still pretty buggy) MIDI implementation. Identical Audiere sound effects implementation. Since some years ago, Audiere has also mysteriously stopped playing anything on Windows.||Controller 111 loop points only|
|music_silence||diagnostic||Does not play any music or sound at all. Useful for checking whether or not a bug is related to music.||No|
These aren't backends but rather are other compile-time options.
|-debug||diagnostic||Any nightly build with -debug in the filename has been compiled with -g which adds debugging symbols for use with the GNU Debugger, and with -exx which adds extra error checking (asserts) for out-of-bounds array access and null pointer dereferencing. Failed asserts cause the program to instantly exit. These builds are many times slower, something which might be noticeable on very old computers.|