@# @# This is the source for the Allegro FAQ list, in a weird custom format. @# Read makedoc.c for a description of what is going on... @# @html_text_substitution=readme.txt|readme.txt @html_text_substitution=allegro.txt|allegro.txt @document_title=Allegro FAQ @html_spaced_list_bullet @!html @!rtf ___ _ _ _____ ___ ___ / _ \| | | ___ __ _ _ __ ___ | ___/ _ \ / _ \ | |_| | | |/ _ \/ _` | '__/ _ \ | |_ | |_| | | | | | _ | | | __/ (_| | | | (_) | | _|| _ | |_| | |_| |_|_|_|\___|\__, |_| \___/ |_| |_| |_|\__\_\ |___/ @html @external-css=allegro.css @rtf @!text
redir -eo make > logfile.txt
set_volume_per_voice()
,
described in the docs. This will enable you to adjust the overall
volume of Allegro's digital sound output.
@@ Why doesn't it work with my video card?
Try using a FreeBE/AF driver (http://www.talula.demon.co.uk/freebe/),
or the commercial SciTech Display Doctor (http://www.scitechsoft.com).
If it still doesn't work, post a description of your problem to the
Allegro mailing list, along with a copy of the output from running the
afinfo and vesainfo programs.
@@ Why not use some sort of dynamic linking system?
The VBE/AF interface already provides this for the video drivers: see
the FreeBE/AF project on http://www.talula.demon.co.uk/freebe/.
For more general things like the sound, VESA, and mode-X routines,
this would be very difficult to do because the drivers depend on a lot
of helper functions from the core lib. The djgpp DXE format is nowhere
near flexible enough to support this, and we don't want to make Allegro
dependent on any other dynamic linking packages.
@\ I get an "out of environment space" error when I run fix.bat or
@@ vcvars32.bat!
Well duh, you need to increase the size of your environment then :-)
You can do this by changing the settings for your DOS box (click the
system menu and select "properties"), or at startup in your config.sys
file (eg. shell=c:\command.com /e:8192 /p).
END_OF_MAIN()
just after your main()
function.
Allegro uses this, along with some preprocessor magic, to turn a normal
main()
function into a Windows-style WinMain()
entry point.
@@ I get an error about an "unresolved external symbol _main"!
Make sure you're building a Windows GUI Application, and not a Windows
Console Application. This is a setting when you create the project in
MSVC, Dev-C++ or Borland C++ Builder. Alternatively, this is specified
on the command line by the -subsystem:windows option for the MSVC
linker, by the -Wl,--subsystem,windows option for the MinGW compiler
or the -tW option for the Borland C++ compiler. Either that, or define
the preprocessor symbol ALLEGRO_USE_CONSOLE prior to including Allegro
headers if you really need the console for your program.
@@ I get lots of compile errors about conflicting types for "struct BITMAP"!
If your program directly includes Win32 API header files, see the
"Windows specifics" section of the documentation.
If your program only includes header files of the C++ standard library, you're very likely trying to compile it with gcc 3.x for MinGW; if so, define the symbol __GTHREAD_HIDE_WIN32API on the compiler command line:
g++ -D__GTHREAD_HIDE_WIN32API program.cpp -lalleg@\ In windowed mode artifacts are left on the desktop when the window @@ is moved or when another window is placed on top of it. Disable direct updating for the DirectX windowed driver by using the dedicated configuration variable. See the 'Configuration routines' section in the docs and the allegro.cfg template file for more detailed informations. @\ In windowed mode the screen stays black unless the window is placed @@ under another window on the desktop. Disable direct updating for the DirectX windowed driver by using the dedicated configuration variable. See the 'Configuration routines' section in the docs and the allegro.cfg template file for more detailed informations.
END_OF_MAIN()
just after your main()
function.
Allegro uses this, along with some preprocessor magic, to get a copy
of your argv[]
parameters (it needs those for various internal things).
@@ I get an error about a duplicate definition of the "_main" symbol!
You are probably on a Darwin/MacOS X system. If so, make sure the symbol
USE_CONSOLE
is not defined in your program: it is a deprecated symbol
that must be replaced by ALLEGRO_USE_CONSOLE
. Also note that the magic
main can't be disabled on such a system: you simply can't define the
symbol ALLEGRO_NO_MAGIC_MAIN
in a program linked against Allegro.
@@ Compile errors scroll off the screen way too quickly for me to read them!
You need to redirect stderr into a file, so you can view them later.
The method for doing this depends on your shell: if you are using a
Bourne-style shell like bash, try make 2> logfile.txt
@\ When I try to run Allegro programs, I get "error while loading shared libraries:
@@ liballeg.so.4.1: cannot open shared object file: No such file or directory".
You need to teach the dynamic linker where to find the Allegro shared library.
See docs/build/unix.txt, near the end of the 'Installing Allegro' section.
@\ When I try to use DGA2, I get "resolution not supported", but the
@@ X server does actually support that resolution !
There are two possible reasons:
1) DGA2 may support different resolutions/color depths than X,
run the gfxinfo program to know what combinations you can use,
2) You may have a buggy DGA2 implementation, see next question.
@\ When I try to use DGA2, the screen goes black and the PC completely
@@ halts!
You are probably using a XFree86 server with a very buggy DGA2
implementation, such as 4.0.3 (shipped with Red Hat 7.1 for example).
Upgrading to 4.1.0 will probably solve your problem. You can obtain
it from ftp://ftp.xfree86.org/pub/XFree86/4.1.0/binaries/ selecting
the directory suited to your platform and following the instructions
you find in the Install file.
datedit.c
. But you
shouldn't have to worry about doing this by hand: just run make
and
that will build everything for you.
@\ When I compile Allegro, make fails with something like `Error: operands
@\ given don't match any known 386 instruction' or `Error: no such
@@ instruction `maskmovq %mm3, %mm1''.
You need to update your version of GNU binutils. See readme.txt to
find out what the minimum required version you need is.
@@ Can I use Allegro with my <foobar> compiler?
Not unless <foobar> is mentioned in readme.txt as one of the
supported platforms. You could port it, but that is usually a lot of
work. If <foobar> is a 16 bit DOS compiler like Borland C, you
might as well just forget the idea :-)
@@ What is this "Allegro WIP" that I see people talking about?
WIP stands for "work in progress", and refers to any changes that are
more recent than the last official release. WIP versions of the
library can be obtained as patches from the Allegro website
(http://alleg.sourceforge.net/), and are usually
quite stable, although obviously not so well tested as a final release
version.
@@ I got the WIP patch, but I can't apply it.
Do you have a copy of patch.exe? If not, go and get it from the same
place that you downloaded the rest of djgpp: this tool is a standard
part of the compiler distribution. Similarly, you can get the Mingw
compiled version from http://sourceforge.net/projects/gnuwin32/.
If you do have the patch program but it isn't working properly, make
sure that you are installing the patch over the top of an unmodified
copy of whatever Allegro version it is intended to update (this will
usually be the most recent official release from before the WIP was
made, but check the text file that comes with the WIP to be sure).
@@ When I run the demo game, it says it can't find demo.dat.
That file is distributed separately in the WIP versions. It is here:
http://alleg.sourceforge.net/wip.html. (alldata.zip)
@\ How can I display several different images at the same time?
@@ When I show the second one it messes up the palette for the first.
This is just the way that the video hardware works: there can only be
one palette in use at any given moment. Either convert your images so
they all use the same palette, or switch to a truecolor graphics mode.
@@ How can I convert my graphics to all use the same 256 color palette?
See the Allegro.cc homepage (http://www.allegro.cc/)
for some utilities, for example FixPal and Smacker.
@\ My colors always come out wrong. And how can I make a greyscale palette
@@ with 256 different shades?
The VGA hardware only uses 6 bits for each color component, which
means the red, green, and blue values in the palette structure range
from 0 to 63, not all the way up to 255. That gives you a potential
2^18 = 262144 different colors, or 64 shades of grey. If you need more
than this you could try using VESA function 0x4F08 to select an 8 bit
wide DAC, but Allegro doesn't support this directly and I don't know
how reliable it will be across different hardware.
@@ Why do I have a funny color border at the edges of my monitor?
When you are in a 256 color mode, the VGA card displays color #0
around the border of the display area (in truecolor modes it displays
black). Your funny color will go away if you change the palette so
that color #0 is black.
@@ How can I fade the screen in a truecolor graphics mode?
With great difficulty :-) There is no such easy trick as just altering
the palette, so you will have to repeatedly redraw the image in a
lighter or darker form. You could draw black translucent rectangles
over the screen to darken it down, or use draw_lit_sprite()
to tint a
bitmap while copying it to the screen, but be warned that these
operations are expensive and will require a fast PC!
Also, have a look at http://www.allegro.cc/ for add-on packages
(notably FBlend v0.5) that attempt to make this operation as fast as
possible.
@\ I tried using fade_in() and fade_out() with truecolor modes but nothing
@@ happened. What am I doing wrong?
However, if you are interested in using OpenGL for graphics and Allegro
for everything else, you can try the various add-ons libraries linked
from http://www.allegro.cc/ such as AllegroGL.
@@ Why not add a MOD playing function?
Several very good ones already exist, for instance the JGMOD or DUMB
packages. See the audio library extensions section on the Allegro.cc
website (http://www.allegro.cc/). You are not allowed to suggest
that one of these libraries be merged into Allegro, because this topic
has already been done to death on the mailing list and we are tired of it.
@@ Why not add networking support?
There are several networking packages currently in development or
floating around on the net, though, and in our opinion this sort of
code is more useful as an external library than it would be as part of
Allegro.
@@ Why can't Allegro read GIF files?
Unisys has a patent on the LZW compression algorithm that is used by
the GIF format. We want everything in Allegro to be freely usable
without any restrictions whatsoever, which means we can't include any
code that is subject to licensing or the payment of royalties.
@@ My program crashes all the time. Could this be a bug in Allegro?
Perhaps. Try to isolate the smallest fragment of code that is able to
reproduce the problem, and we'll have a look at it. If you can send us
a 10 line program, we will fix it. 100 lines, and we can probably fix
it. 1000 lines, and we don't have a chance :-)
@@ Can I use Allegro in my <whatever> commercial application?
Sure. See the giftware terms in readme.txt. We don't mind what you do
with it, and there are no problems with commercial usage.
@@ When will <foobar> be finished? I can't wait...
Whenever it is done! A little encouragement is always welcome, but we
don't have any completion deadlines and we're not going to make one up
for you :-) As soon as it is finished, it will be released.
@@ Where can I get some fonts to use with Allegro?
The grabber can import directly from GRX or BIOS format .fnt files, or
you can draw them onto a .pcx image using any paint program. See
http://www.talula.demon.co.uk/ttf2pcx/ for a utility that
will convert Windows TrueType fonts into this .pcx format.
@@ Where can I find a set of instrument samples for the DIGMID driver?
See the Allegro homepage (http://alleg.sourceforge.net/)
for some links. You can use Gravis patches (.pat format), or SoundFont
2.0 (.sf2) files, but the latter must be converted into a patches.dat
file with the pat2dat utility.
@@ How can I convert the documentation into Windows Help format?
You need to download the makertf conversion utility
(ftp://ftp.coast.net/Coast/win3/winhelp/mkrtf104.zip), and the Windows
Help compiler (ftp://ftp.microsoft.com/Softlib/MSLFILES/HC505.EXE).
Make a temporary directory, copy the fade_in()
and fade_out()
only work in 8-bit paletted modes.
See the previous question for details.
@@ How can I generate FLI or FLC format animations?
See the Allegro.cc homepage (http://www.allegro.cc/)
for some utilities, for example DTA and Smacker. Also, you can use ASE
(Allegro Sprite Editor, http://ase.sourceforge.net/), which allows
drawing/editing each frame of the animation and save it as a FLI. Or
you can use The GIMP (http://www.gimp.org/) along with it's GFli
plugin, using layers as frames, and saving your work as file.fli.
The GIMP allows you to edit existent FLI files too.
@\ How can I make parts of my sprite transparent in truecolor modes?
@@ I don't understand what the docs mean by "bright pink"...
In your favourite paint program, get hold of the RGB sliders and drag
the red and blue ones up as far as they go (usually to 255, but this
will depend on what units your software uses), and the green one right
down to zero. The result is a special shade of Magic Pink, or as some
people prefer to call it, magenta.
@@ I can't get the 3D polygon functions to work!
Remember that the vertex positions are stored in fixed point format,
so you must use the itofix()
macro or shift your coordinates 16 bits
to the left.
@@ I can't get the rotate_sprite() function to work!
Remember that the angle of rotation is stored in fixed point format,
so you must use the itofix()
macro or shift your coordinates 16 bits
to the left. For example, rotate_sprite(bmp, spr, x, y, itofix(32))
will rotate the graphic by 45 degrees.
@@ I can't get the d_bitmap_proc() or d_icon_proc() GUI object to work!
You are probably trying to initialise the dialog structure with a
pointer to your bitmap, right? That won't work because the dialog is
created at compile time, but the bitmap is only loaded at runtime, so
the compiler doesn't yet know where it will be located. You need to
fill in the dialog structure with a NULL
pointer, and then copy the
real bitmap pointer into the dp
field as part of your program init
code, after you've loaded the bitmap into memory.
@@ Should I use regular bitmaps, RLE sprites, or compiled sprites?
It depends on exactly what you are doing. If your images are totally
opaque, there is no advantage to using an RLE sprite, and it will
probably be faster to use a regular bitmap with the blit()
function.
If your graphics contain masked areas, an RLE sprite may be both smaller
and faster than the draw_sprite()
function, depending on your CPU
and your bitmaps.
Compiled sprites are in general quite a bit faster than both the
others for masked images, and slightly faster for opaque graphics, but
this is far more variable. They are at their best with small sprites,
on older machines and in mode-X, and may actually be slower than
blit()
when using SVGA modes on a pentium (the large size of a
compiled sprite is very bad for the cache performance).
@@ How can I make my game run at the same speed on any computer?
You need to make sure the game logic gets updated at a regular rate,
but skip the screen refresh every now and then if the computer is too
slow to keep up. This can be done by installing a timer handler that
will increment a global variable at your game logic speed, eg:
save_bitmap()
somewhere in your code. See the
save_bitmap()
documentation for a discussion of one common pitfall
when doing this, and some example code.
@@ How can I generate a random number?
Call srand(time(NULL))
at the beginning of your program, and then use
rand()%limit
to obtain a pseudo-random number between 0
and limit-1
.
@\ Why not make a "lite" version of Allegro?
@@ I don't need any of the sound, maths, or GUI routines...
There is no need. The linker will only include the parts of the
library that you actually use, so if you don't call any of, say, the
texture mapping or FLIC playing functions, they will be left out of
your executable. This doesn't work perfectly because a lot of the
Allegro code uses tables of function pointers that cause some
unnecessary routines to be linked in, so the majority of the graphics
functions will be included in every executable, but I have tried to
keep this to a minimum. See allegro.txt for information about more
precise ways to remove some of the graphics and sound drivers.
@@ Will you ever add support for 3D accelerator hardware?
No. This sort of hardware support would be most useful as part of a
proper 3D API, which Allegro is not, and will never be. If you want
to do some work on this, the MESA library (a free implementation
of OpenGL) is IMHO the place to start.
allegro.txi
file from the
allegro/docs
dir, and run the commands makertf --no-warn allegro.txi
-o allegro.rtf -J allegro.hpj followed by hcp allegro.hpj. The
second command will give a lot of warnings, but they can safely be
ignored.
@@ How can I print out the documentation?
The allegro.rtf file can be read directly into Microsoft Word and
printed from there, but you should right-click and update the table of
contents and index fields to fill them with the correct data first.
Alternatively you can install the TeX package and use the tex and
dvips programs to convert allegro.txi into Postscript format.
@@ Where can I find example source code, add-on packages, and tutorials?
Check the Allegro.cc homepage, http://www.allegro.cc/.
If you have anything to add to this, please post the URL!
@\ Why is it considered good coding practice to define PI as a constant,
@@ rather than just using the value 3.141592 in my code?
It simplifies the maintenance of your program, in case the value of PI
ever needs to be changed. Also it will make your program more portable
to other compilers that use different values of PI.
@@ Why doesn't vsync() seem to work?
A number of graphics cards have buggy or incomplete VESA
implementations, and often the vsync()
function is not implemented. For
examples on flicker-free drawing, look at the code for the demo game,
which uses a variety of methods to draw itself.
@\ Why doesn't busy waiting on the key array work? For example,
@@ "while (!key[KEY_ENTER]);" doesn't work.
If the code works without optimisations, then it could be the
compiler's fault. You can try beating the compiler into submission,
for example:
readkey()
instead.
Or consider upgrading or downgrading your compiler.
@@ I get lots of errors when I try to compile my C++ Allegro program.
You are probably declaring the use of a namespace before including
Allegro headers. For example: