Allegro DJGPP-specific information

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                    DJGPP-specific information.

             See readme.txt for a more general overview.

# djgpp notes

Status: complete. This is the original Allegro version, and has had plenty of time to become nice and stable. However, under Windows NT, 2000, or XP you will very likely experience problems and should consider using the native Windows version of Allegro instead, less likely to give you problems under such environments.

# Required software

- DJGPP 2.01 or later (`djdev*.zip`).
- GCC compiler 2.91.x or later (`gcc*b.zip`). Note: gcc 3.0.x (0 <;= x <;= 1) doesn't properly compile Allegro.
- Binutils 2.9.x or later (`bnu*b.zip`).
- GNU make (`mak*b.zip`).
- Texinfo (`txi*b.zip`).
- Optional: sed (`sed*b.zip`). Used by "`make depend`".

All of the above can be downloaded from your nearest SimTel mirror site, in the `/pub/simtelnet/gnu/djgpp/` directory, or you can use the zip picker on http://www.delorie.com/djgpp/. Please make sure that you have installed djgpp according to the instructions in `readme.1st`, and that you aren't mixing it with any files from different compilers (eg. the Borland version of make).

# Allegro SVN Notes

If you are using a SVN version of Allegro, then you will need to do some extra things to ensure that your copy of Allegro will compile correctly. These are covered in detail below, but briefly:

> 1. You must run the ```fix`'` script (either the batch file, under command.com, or the .sh file under bash). You must supply the argument ```djgpp`'`.

> 2. You must regenerate the dependency files: a simple ``make depend`' will do this. However, please note that you must have sed installed to do this.

# Installing Allegro

This is a source-only distribution, so you will have to compile Allegro before you can use it. To do this you should:

Go to wherever you want to put your copy of Allegro (your main djgpp directory would be fine, but you can put it somewhere else if you prefer), and unzip everything. Allegro contains several subdirectories, so you must specify the `-d` flag if you are using pkunzip.

If you are running under Linux, and want to cross-compile the djgpp version of Allegro, set the environment variable "`CROSSCOMPILE=1`", set `DJDIR` to the directory where your djgpp cross-compiler is installed, set `PATH` to access to the cross-compiler, and set `NATIVEPATH` to a path that will use your native version of gcc instead (_not_ the djgpp cross-compiler!) so that this can be invoked when converting the documentation. You might like to edit and use ```xmake.sh`'`; there are further instructions in comments in the file. You must also run '`fix.sh djgpp`' as detailed above - it is required to properly configure Allegro for building with djgpp.

Type "`cd allegro`", followed by "`make`". Then go do something interesting while everything compiles. When it finishes compiling, type "`make install`" to set the library up ready for use. If you have any trouble with the build, look at `docs/txt/faq.txt` for the solutions to some of the more common problems.

If you also want to install a debugging version of the library (highly recommended), now type "`make install DEBUGMODE=1`". Case is important, so it must be `DEBUGMODE`, not `debugmode`!

If you also want to install a profiling version of the library, now type "`make install PROFILEMODE=1`".

If you want to read the Allegro documentation with the Rhide online help system, go to the "`Help / Syntax help / Files to search`" menu, and add "`allegro`" after the existing "`libc`" entry (separated by a space).

If you want to create the HTML documentation as one large allegro.html file rather than splitting it into sections, edit `docs/allegro._tx`, remove the @multiplefiles statement from line 8, and run make again.

Once the build is finished you can recover some disk space by running "`make compress`" (which uses the DJP or UPX programs to compress the executable files), and/or "`make clean`" (to get rid of all the temporary files and HTML format documentation).

If your copy of Allegro is set up for use with some different compiler (if you downloaded a tar.gz archive or a SVN version), you will have to run '`fix.bat djgpp`' before compiling it. If you are using bash you can run '`fix.sh djgpp`' instead.

If your copy of Allegro doesn't include the makefile.dep dependency files (if you have run "`make veryclean`" or you have the SVN version), you can regenerate them by running "`make depend`".

If ```make`'` tells you that you need to download a new package, or if you need the ```sed`'` package to generate dependencies, you can find these at ftp://ftp.demon.co.uk/pub/mirrors/simtelnet/gnu/djgpp/.

A list of all the available options:

> `CROSSCOMPILE`
>   Set this if you are crosscompiling; it implies `UNIX_TOOLS`.

> `WARNMODE`
>   Set this if you want Allegro to display and stop on nearly all warnings issued by the compiler. Allegro should compile fine with this set.

> `TARGET_ARCH_COMPAT` or `TARGET_ARCH_EXCL`
>   These affect the level of processor dependant optimisation that Allegro uses. You can set either of these to the processor type you want to optimize for. The difference between these two is that `TARGET_ARCH_COMPAT` optimise for the given processor so that the code will still run on older processors, while `TARGET_ARCH_EXCL` will generate code that will run exclusively on the given processor and of course newer ones. Example: set `TARGET_ARCH_COMPAT=i686`

> `TARGET_OPTS`
>   Affects the general optimisations that Allegro uses.

> `UNIX_TOOLS`
>   If your system does not have the usual DOS tools available (```md`'`, ```rd`'`, ```copy`'`, etc., and commands which understand the `\` character), then set this to 1 to use the Unix equivalents. This is set implicitly when you set `CROSSCOMPILE`, and is also set automatically when you are running under bash.

To activate any of these, type (for example) "`make WARNMODE=1`".

# Using Allegro

All the Allegro functions, variables, and data structures are defined in `allegro.h`. You should include this in your programs, and link with either the optimised library `liballeg.a`, the debugging library `liballd.a`, or the profiling library `liballp.a`. To do this you should:

Put the following line at the beginning of all C or C++ files that use Allegro:

>           #include <allegro.h>

If you compile from the command line or with a makefile, add either '`-lalleg`' (for the optimised version), '`-lalld`' (debugging version), or '`-lallp`' (profiling version) to the end of the gcc command, eg:

>           gcc foo.c -o foo.exe -lalleg

If you are using Rhide, go to the Options/Libraries menu, type either '`alleg`' (for the optimised version), '`alld`' (debugging version), or '`allp`' (profiling version) into the first empty space, and make sure the box next to it is checked.

# Supported hardware

The bare minimum you need to use Allegro is a 386 with a VGA graphics card, but a 486 is strongly recommended. To get into SVGA modes you will need a compatible SVGA card, which means something that has a working VESA or VBE/AF driver.

Ideally you should use VBE/AF, because it allows Allegro to use hardware acceleration functions to speed up the drawing. The FreeBE/AF project (http://www.talula.demon.co.uk/freebe/) provides a number of free VBE/AF drivers (volunteers to write more are always welcome!), and accelerated drivers for a large number of cards are available commercially as part of the SciTech Display Doctor package (http://www.scitechsoft.com/).

If you have a VBE 2.0 or VBE 3.0 driver you are probably fine just using that, although unlike VBE/AF it won't provide any hardware acceleration. If you have an older VESA BIOS implementation (eg. VESA 1.2), beware. For one thing, everything will be much slower if Allegro can't use the sexy VBE 2.0 features. For another, I could go on all day telling horror stories about the buggy and generally just pathetic VESA implementations that I've come across. If you are having trouble with the SVGA modes, try getting a copy of the SciTech Display Doctor and see if that clears things up (it probably will: SciTech usually get these things right).

Note that the native SVGA chipset drivers from Allegro 3.0 and earlier have been removed. These are still available as an optional add-on package from the same sites as Allegro, but are not needed any more because you can get the same code in a more flexible format as part of the FreeBE/AF project.

On the sound front, Allegro supports sample playback on the SB (mono), the SB Pro (stereo), the SB16, the ESS AudioDrive, the Ensoniq Soundscape, and the Windows Sound System. It has MIDI drivers for the OPL2 FM synth (Adlib and SB cards), the OPL3 (Adlib Gold, SB Pro-II and above), the pair of OPL2 chips found in the SB Pro-I, the AWE32 EMU8000 chip, the raw SB MIDI output, and the MPU-401 interface, plus it can emulate a wavetable MIDI synth in software, running on top of any of the supported digital soundcards. The Creative Labs SB PCI-64 and PCI-128 cards are actually based on the Ensoniq chipset, so they can be used with the Soundscape and MPU-401 drivers. You'll have to manually select the MPU, though, because it won't be autodetected. Actually, quite a lot of wavetable boards emulate the MPU, so give this a try and see if it works on your card. If you feel like coming up with drivers for any other hardware, they would be much appreciated.

Audio recording is supported for all SB cards, but only in unidirectional mode, ie. you cannot simultaneously record and playback samples. MIDI input is provided by the MPU-401 and SB MIDI drivers, but there are some restrictions on this. The SB MIDI interface cannot be used at the same time as the digital sound system, and the MPU will only work when there is an IRQ free for it to use (this will be true if you have an SB16 or greater, or if no SB-type digital driver is installed, or if your MIDI interface uses a different IRQ to the SB).

# Notes for the musician

The OPL2 synth chip can provide either nine voice polyphony or six voices plus five drum channels. How to make music sound good on the OPL2 is left as an exercise for the reader :-) On an SB Pro or above you will have eighteen voices, or fifteen plus drums. Allegro decides whether to use drum mode individually for each MIDI file you play, based on whether it contains any drum sounds or not. If you have an orchestral piece with just the odd cymbal crash, you might be better removing the drums altogether as that will let Allegro use the non-drum mode and give you an extra three notes polyphony.

When Allegro is playing a MIDI file in looped mode, it jumps back to the start of the file when it reaches the end of the piece. To control the exact loop point, you may need to insert a dummy marker event such as a controller message on an unused channel.

All the OPL chips have very limited stereo capabilities. On an OPL2, everything is of course played in mono. On the SB Pro-I, sounds can only be panned hard left or right. With the OPL3 chip in the SB Pro-II and above, they can be panned left, right, or centre. I could use two voices per note to provide more flexible panning, but that would reduce the available polyphony and I don't want to do that. So don't try to move sounds around the stereo image with streams of pan controller messages, because they will jerk horribly. It is also worth thinking out the panning of each channel so that the music will sound ok on both SB Pro-I and OPL3 cards. If you want a sound panned left or right, use a pan value less than 48 or greater than 80. If you want it centred, use a pan value between 48 and 80, but put it slightly to one side of the exactly central 64 to control which speaker will be used if the central panning isn't possible.