Hello,

I "updated" the A4 code from a book to the point where running
gcc tankwar.c -o tankwar -I/usr/include/allegro5 -L/usr/lib -lalleg

yielded
tankwar.c: In function ‘main’:
tankwar.c:503: warning: assignment makes pointer from integer without a cast
/usr/bin/ld: cannot find -lalleg
collect2: ld returned 1 exit status

on Lucid Lynx.

So I went to the Allegro wiki for how to compile programs in 5.x.x and pasted
gcc tankwar.c -o tankwar -I/usr/include/allegro5 -L/usr/lib

But then my console "blew up" with:

Package allegro-5.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `allegro-5.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'allegro-5.0' found
tankwar.c: In function ‘drawtank’:
tankwar.c:20: warning: implicit declaration of function ‘al_draw_filled_rectangle’
tankwar.c: In function ‘explode’:
tankwar.c:139: warning: implicit declaration of function ‘rest’
tankwar.c: In function ‘updatebullet’:
tankwar.c:159: warning: implicit declaration of function ‘rect’
tankwar.c:180: warning: implicit declaration of function ‘getpixel’
tankwar.c:187: warning: implicit declaration of function ‘textprintf_ex’
tankwar.c: In function ‘score’:
tankwar.c:417: warning: implicit declaration of function ‘makecol’
tankwar.c: In function ‘main’:
tankwar.c:498: warning: implicit declaration of function ‘install_keyboard’
tankwar.c:499: warning: implicit declaration of function ‘install_timer’
tankwar.c:502: warning: implicit declaration of function ‘al_init_ttf_addon’
tankwar.c:503: warning: implicit declaration of function ‘al_load_ttf_font’
tankwar.c:503: warning: assignment makes pointer from integer without a cast
tankwar.c:536: warning: implicit declaration of function ‘keypressed’
tankwar.c:544: warning: implicit declaration of function ‘allegro_exit’
tankwar.c:496: warning: unused variable ‘display’
/tmp/cc2mF6FH.o: In function `drawtank':
tankwar.c:(.text+0x85): undefined reference to `al_draw_filled_rectangle'
tankwar.c:(.text+0xb9): undefined reference to `al_draw_filled_rectangle'
tankwar.c:(.text+0xf9): undefined reference to `al_draw_filled_rectangle'
tankwar.c:(.text+0x12d): undefined reference to `al_draw_filled_rectangle'
tankwar.c:(.text+0x16f): undefined reference to `al_draw_filled_rectangle'
/tmp/cc2mF6FH.o:tankwar.c:(.text+0x1a3): more undefined references to `al_draw_filled_rectangle' follow
/tmp/cc2mF6FH.o: In function `explode':
tankwar.c:(.text+0x615): undefined reference to `rest'
tankwar.c:(.text+0x653): undefined reference to `al_draw_filled_rectangle'
/tmp/cc2mF6FH.o: In function `updatebullet':
tankwar.c:(.text+0x6dd): undefined reference to `rect'
tankwar.c:(.text+0x81b): undefined reference to `rect'
tankwar.c:(.text+0x84d): undefined reference to `getpixel'
tankwar.c:(.text+0x8de): undefined reference to `textprintf_ex'
/tmp/cc2mF6FH.o: In function `checkpath':
tankwar.c:(.text+0x8fd): undefined reference to `getpixel'
tankwar.c:(.text+0x913): undefined reference to `getpixel'
tankwar.c:(.text+0x929): undefined reference to `getpixel'
/tmp/cc2mF6FH.o: In function `getinput':
tankwar.c:(.text+0x1095): undefined reference to `al_wait_for_event'
tankwar.c:(.text+0x11aa): undefined reference to `rest'
/tmp/cc2mF6FH.o: In function `score':
tankwar.c:(.text+0x1210): undefined reference to `makecol'
tankwar.c:(.text+0x1257): undefined reference to `textprintf_ex'
/tmp/cc2mF6FH.o: In function `setupdebris':
tankwar.c:(.text+0x1422): undefined reference to `makecol'
tankwar.c:(.text+0x1464): undefined reference to `al_draw_filled_rectangle'
/tmp/cc2mF6FH.o: In function `setupscreen':
tankwar.c:(.text+0x149c): undefined reference to `makecol'
tankwar.c:(.text+0x14de): undefined reference to `textprintf_ex'
tankwar.c:(.text+0x14fa): undefined reference to `makecol'
tankwar.c:(.text+0x1522): undefined reference to `rect'
tankwar.c:(.text+0x153e): undefined reference to `makecol'
tankwar.c:(.text+0x1566): undefined reference to `rect'
/tmp/cc2mF6FH.o: In function `main':
tankwar.c:(.text+0x158d): undefined reference to `al_install_system'
tankwar.c:(.text+0x1592): undefined reference to `install_keyboard'
tankwar.c:(.text+0x1597): undefined reference to `install_timer'
tankwar.c:(.text+0x15b0): undefined reference to `al_init_font_addon'
tankwar.c:(.text+0x15b5): undefined reference to `al_init_ttf_addon'
tankwar.c:(.text+0x15d1): undefined reference to `al_load_ttf_font'
tankwar.c:(.text+0x1604): undefined reference to `keypressed'
tankwar.c:(.text+0x1619): undefined reference to `rest'
tankwar.c:(.text+0x1627): undefined reference to `allegro_exit'
collect2: ld returned 1 exit status

Why doesn't my code compile?

TIA,
xtheunknown0

Apparently, no help.

I can give you a screenshot of this:
foo@foo:~/Documents$ export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
foo@foo:~/Documents$ gcc tankwar.c -o tankwar $(pkg-config --libs allegro-5.0)
Package allegro-5.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `allegro-5.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'allegro-5.0' found
tankwar.c: In function ‘main’:
tankwar.c:503: warning: assignment makes pointer from integer without a cast
/tmp/ccZrCMPA.o: In function `drawtank':
tankwar.c:(.text+0x85): undefined reference to `al_draw_filled_rectangle'
tankwar.c:(.text+0xb9): undefined reference to `al_draw_filled_rectangle'
tankwar.c:(.text+0xf9): undefined reference to `al_draw_filled_rectangle'
tankwar.c:(.text+0x12d): undefined reference to `al_draw_filled_rectangle'
tankwar.c:(.text+0x16f): undefined reference to `al_draw_filled_rectangle'
/tmp/ccZrCMPA.o:tankwar.c:(.text+0x1a3): more undefined references to `al_draw_filled_rectangle' follow
/tmp/ccZrCMPA.o: In function `explode':
tankwar.c:(.text+0x615): undefined reference to `rest'
tankwar.c:(.text+0x653): undefined reference to `al_draw_filled_rectangle'
/tmp/ccZrCMPA.o: In function `updatebullet':
tankwar.c:(.text+0x6dd): undefined reference to `rect'
tankwar.c:(.text+0x81b): undefined reference to `rect'
tankwar.c:(.text+0x84d): undefined reference to `getpixel'
tankwar.c:(.text+0x8de): undefined reference to `textprintf_ex'
/tmp/ccZrCMPA.o: In function `checkpath':
tankwar.c:(.text+0x8fd): undefined reference to `getpixel'
tankwar.c:(.text+0x913): undefined reference to `getpixel'
tankwar.c:(.text+0x929): undefined reference to `getpixel'
/tmp/ccZrCMPA.o: In function `getinput':
tankwar.c:(.text+0x1095): undefined reference to `al_wait_for_event'
tankwar.c:(.text+0x11aa): undefined reference to `rest'
/tmp/ccZrCMPA.o: In function `score':
tankwar.c:(.text+0x1210): undefined reference to `makecol'
tankwar.c:(.text+0x1257): undefined reference to `textprintf_ex'
/tmp/ccZrCMPA.o: In function `setupdebris':
tankwar.c:(.text+0x1422): undefined reference to `makecol'
tankwar.c:(.text+0x1464): undefined reference to `al_draw_filled_rectangle'
/tmp/ccZrCMPA.o: In function `setupscreen':
tankwar.c:(.text+0x149c): undefined reference to `makecol'
tankwar.c:(.text+0x14de): undefined reference to `textprintf_ex'
tankwar.c:(.text+0x14fa): undefined reference to `makecol'
tankwar.c:(.text+0x1522): undefined reference to `rect'
tankwar.c:(.text+0x153e): undefined reference to `makecol'
tankwar.c:(.text+0x1566): undefined reference to `rect'
/tmp/ccZrCMPA.o: In function `main':
tankwar.c:(.text+0x158d): undefined reference to `al_install_system'
tankwar.c:(.text+0x1592): undefined reference to `install_keyboard'
tankwar.c:(.text+0x1597): undefined reference to `install_timer'
tankwar.c:(.text+0x15b0): undefined reference to `al_init_font_addon'
tankwar.c:(.text+0x15b5): undefined reference to `al_init_ttf_addon'
tankwar.c:(.text+0x15d1): undefined reference to `al_load_ttf_font'
tankwar.c:(.text+0x1604): undefined reference to `keypressed'
tankwar.c:(.text+0x1619): undefined reference to `rest'
tankwar.c:(.text+0x1627): undefined reference to `allegro_exit'
collect2: ld returned 1 exit status

Have you installed Allegro 5? Does the pc file exist in that location?

Note that many of the errors are references to Allegro 4 functions, so even when you get Allegro 5 working it still won't compile.

I think it's because I deleted the allegro-5.0 directory that svn created.

One thing that I can't apparently "fix" on my own is getpixel(). What is the "equivalent" in A5? I know that the answer to that may be pretty big, so I'll also ask: is it where for simple games (a main.c and a header) you declare a "screen" in the header and initialise it somewhere in main.c then start using it other functions? and how do I set up a screen?

BTW, so why was a "screen" argument removed from graphics primitives functions? I thought I could get away with using al_draw_[shape] functions but I need a "screen" for collision detection via getpixel...

The drawing target (which will also be used with al_get_pixel) in Allegro 5 is part of a stored state. You set it with al_set_target_bitmap and then just call drawing functions as necessary, and they will all draw to the most recent drawing target that you have set with that function.

There is no 'screen' in A5, but semantically, the backbuffer is similar. You draw everything you want to display to it, and then call al_flip_display.

Also, you will probably want to rework your collision detection, because reading from video memory is slow (if you read from the backbuffer, or another video bitmap). Depends on how many pixels you need to read though.

I've got the code to the point where it compiles but it aborts due to loading a font.
I tried the code in the wiki about fonts (http://wiki.allegro.cc/index.php?title=Allegro_5_Tutorial/Addons/Fonts) and it also

foo: /home/blah/allegro-5.0/addons/font/text.c:73: al_draw_ustr: Assertion `font' failed.

Why is this?

TIA,
xtheunknown0

Did you call al_init_font_addon and al_init_ttf_addon before loading your font?

Also, did you check to make sure the font returned by al_load_ttf_font returned a non-zero value? You may have a problem with the current working directory being different than the one your executable is expecting.

That is indeed the problem (returning zero). What do I do about it?

TIA,
xtheunknown0

See http://wiki.allegro.cc/index.php?title=Loading_Resources_%28Troubleshooting%29
and http://wiki.allegro.cc/index.php?title=Loading_Resources_(Troubleshooting)#Fix_the_Path for clues.

I think what wasn't clear from the start was the significance of having to load a font (, whereas my A4 book doesn't need to). Following from that is having an idea where A5 hunts for files.

So I read parts of the manual and I try
printf("%s\n", al_path_cstr(al_get_standard_path(ALLEGRO_RESOURCES_PATH), '/'));
font = al_load_ttf_font("DejaVuSans.ttf", 72, 0);

Now DejaVuSans.ttf is in my Documents/ where tankwar.c is (as well), so why is !font still "true"?

TIA,
xtheunknown0

It doesn't look anywhere for a font file, except for the exact spot you tell it to.

Your code does nothing but tries to load "DejaVuSans.ttf" from the current working directory. Your call to al_get_standard_path() is meaningless. Read Edgar's link and follow the instructions.

printf("%s\n", al_path_cstr(al_get_standard_path(ALLEGRO_RESOURCES_PATH), '/'));
font = al_load_ttf_font("DejaVuSans.ttf", 72, 0);

Allegro doesn't search from anywhere except from the current working directory. That might not be the same as what is returned by al_get_standard_path(ALLEGRO_RESOURCES_PATH). To be sure, you have to set the current working directory yourself like the wiki showed you :

ALLEGRO_PATH *path = al_get_standard_path(ALLEGRO_RESOURCES_PATH);
al_append_path_component(path, "resources");
al_change_directory(al_path_cstr(path, '/'));  // change the working directory
al_destroy_path(path);

ALLEGRO_PATH *path = al_get_standard_path(ALLEGRO_RESOURCES_PATH);
al_append_path_component(path, "resources");
al_change_directory(al_path_cstr(path, '/'));  // change the working directory
al_destroy_path(path);

I suppose that is the simplest way. I don't know why but the way I think of first is:

ALLEGRO_PATH *res_path = al_get_standard_path(ALLEGRO_RESOURCES_PATH);
al_append_path_component(res_path, "resources");

ALLEGRO_PATH *file_path = al_clone_path(res_path);
al_set_path_filename(file_path, 'filename.ext');

ALLEGRO_FONT *font = al_load_font(al_path_cstr(file_path, '/'));
al_destroy_path(file_path);

In the end its the same, and the first is easier.

Well, I think I've tried - please tell me if I haven't:

ALLEGRO_PATH *path = al_get_standard_path(ALLEGRO_RESOURCES_PATH);
al_append_path_component(path, "resources");
al_change_directory(al_path_cstr(path, '/')); // change the working directory
font = al_load_ttf_font("DejaVuSans.ttf", 72, 0);
if (!font) {
printf("Error loading DejaVuSans.ttf.\n");
return 1;
}
al_destroy_path(path);

I still have the same problem, and there is now a resources/ (storing the ttf) in Documents/

What is it that I do not get?
TIA,
xtheunknown0

Is your executable file in the Documents folder? If so, it should work. If it still does not work, link to the debugging version of allegro. Then your program will produce a file called allegro.log and you can look at it for clues as to why the font didn't load. You're sure you initialized both the font addon and the ttf addon before loading?

Code goes in <code>code goes here...</code> tags.

OH right, RESOURCES is actually the exe path on windows I think. You want ALLEGRO_USER_DOCUMENTS_PATH for your "My Documents" folder.

ALLEGRO_RESOURCES_PATH is actually the full path to the directory your executable is in. So if you use that, you put your data in the same dir as the exe.

How do I create an allegro.log?

Sorry for being a nuisance.

al_change_directory(al_path_cstr(path, '/')); // change the working directory
printf("The path: %s\n", al_path_cstr(path, '/'));

Is the TTF there in that path that is displayed in your console window?

You have to link with the Allegro debug library and define something like ALLEGRO_DEBUG. But that's really not necessary. Debugging is simple: start with the obvious or simple and continue on until you find the problem. There are only a few reasons why it would fail:

1. You didn't initialize the font and ttf addons, in that order.

2. The TTF file isn't in that path specified.

3. The file is corrupt.

4. Allegro or the TTF library has a bug.

9 out of 9 times you'll get the problem figured out after the first and second points are corrected.

I believe I've tried the first two - I'm not sure how to help myself now.

https://sites.google.com/site/xtheunknown0/allegro

The code in the link you just posted is clearly missing a call to al_init_ttf_addon before you load your font.