I started programming in C.
I started programming with allegro.
Following Programm:
#include <allegro.h>

int main(){
allegro_init();
install_keyboard();
set_color_depth(16);
set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0);
ALLEGRO_BITMAP *screen;

putpixel(screen, 10, 30, makecol(255, 255, 255));//macht einen Punkt
vline(screen, 30, 80, 300, makecol(0, 255, 0));//senkrechte Linie
hline(screen, 40, 20, 400, makecol(0, 0, 255));//waagrechte Linie
line(screen, 0, 0, 640, 480, makecol(255, 0, 0)); //Linie
triangle(screen, 0, 400, 0, 450, 100, 450, makecol(255, 0, 255));//gefülltes Dreieck
rect(screen, 100, 200, 200, 250, makecol(255, 255, 0));//leeres Viereck
rectfill(screen, 125, 210, 175, 240, makecol(255, 255, 0));//gefülltes Viereck
circle(screen, 500, 400, 50, makecol(255, 0, 0)); //leerer Kreis
circlefill(screen, 500, 400, 25, makecol(255, 255, 255));//gefüllter Kreis

readkey();
return 0;
}

I got the error from Gcc compiler:
johannes@linux-myvz:~/programme-c> gcc zeichnen.c -o zeichnen -I /usr/local/include/allegro5
zeichnen.c: In function ‘main’:
zeichnen.c:7:17: error: ‘GFX_AUTODETECT’ undeclared (first use in this function)
set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0);
^
zeichnen.c:7:17: note: each undeclared identifier is reported only once for each function it appears in

What is wrong?
Sincerely Johannes Fangmeyer

The term:
set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0);
is allegro5, why the error message?

I changed the program in allegro5:
#include <allegro.h>
#include <allegro5.h>
#include <allegro_primitives.h>
#include <allegro5/allegro_color.h>
#include <base.h>

int main(){

int w=640;
int h=480;
const char *white="white";
const char *red="red";
al_init();
al_install_keyboard();
set_color_depth(16);
al_create_display(w,h);
al_color_name(*white);
al_color_name(*red);

al_draw_line(0, 0, 640, 480, white,1); //Linie
al_draw_triangle( 0, 400, 0, 450, 100, 450, white,1);//gefülltes Dreieck
al_draw_rectangle(100, 200, 200, 250,white,1);//leeres Viereck
al_draw_filled_rectangle( 125, 210, 175, 240, red);//gefülltes Viereck
al_draw_circle( 500, 400, 50,white,1); //leerer Kreis
al_draw_filled_circle(500, 400, 25,white);//gefüllter Kreis

readkey();
return 0;
}
I got error messages with gcc. What ist wrong?
Sincerely Johannes Fangmeyer

I got the error:
zeichnen.c: In function ‘main’:
zeichnen.c:31:10: error: ‘ev’ undeclared (first use in this function)
} while (ev.type != ALLEGRO_EVENT_KEY_DOWN);
^
zeichnen.c:31:10: note: each undeclared identifier is reported only once for each function it appears in

I don't know, what the programming means.
Sincerely Johannes Fangmeyer

I got following error messages:
/tmp/ccjg5tJd.o: In function `main':
zeichnen.c:(.text+0x22): undefined reference to `al_install_system'
zeichnen.c:(.text+0x27): undefined reference to `al_install_keyboard'
zeichnen.c:(.text+0x36): undefined reference to `al_create_display'
zeichnen.c:(.text+0x40): undefined reference to `al_color_name'
zeichnen.c:(.text+0x93): undefined reference to `al_draw_line'
zeichnen.c:(.text+0x9d): undefined reference to `al_color_name'
zeichnen.c:(.text+0xfe): undefined reference to `al_draw_triangle'
zeichnen.c:(.text+0x108): undefined reference to `al_color_name'
zeichnen.c:(.text+0x165): undefined reference to `al_draw_rectangle'
zeichnen.c:(.text+0x16f): undefined reference to `al_color_name'
zeichnen.c:(.text+0x1c4): undefined reference to `al_draw_filled_rectangle'
zeichnen.c:(.text+0x1ce): undefined reference to `al_color_name'
zeichnen.c:(.text+0x223): undefined reference to `al_draw_circle'
zeichnen.c:(.text+0x22d): undefined reference to `al_color_name'
zeichnen.c:(.text+0x27a): undefined reference to `al_draw_filled_circle'
zeichnen.c:(.text+0x27f): undefined reference to `al_create_event_queue'
zeichnen.c:(.text+0x288): undefined reference to `al_get_keyboard_event_source'
zeichnen.c:(.text+0x29a): undefined reference to `al_register_event_source'
zeichnen.c:(.text+0x2ad): undefined reference to `al_wait_for_event'
collect2: error: ld returned 1 exit status

What is wrong?
Sincerely Johannes fangmeyer

Haw have I to use pkg-config.
Allegro.h is in the directory /usr/local/include/allegro5.
Sincerely Johannes Fangmeyer

I got following error message:
johannes@linux-myvz:~/programme-c> gcc -Wall -g -o zeichnen -I usr/local/include zeichnen.c `pkg-config --libs allegro-5.0 allegro-primitives-5.0` -I /usr/local/include/allegro5
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
Package allegro-primitives-5.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `allegro-primitives-5.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'allegro-primitives-5.0' found
and then the former listed errors
MfG Johannes Fangmeyer

How can I set allegro-5.pc to the PKG_CONFIG_PATH? allegro-5.pc ist in the /bin/allegro-5.2.2.0/build/lib/pkgconfig directory.

That's a rather strange path... This looks more like the source tree than the installation path to me... Perhaps he didn't install... The usual incantation is something like:

git clone https://domain/path/to/repo ~/src/allegro5
cd ~/src/allegro5
mkdir build
cd build
cmake ..
make
sudo make install

Is that the directory you built allegro in? You need to 'make install' allegro and then pkg-config should be able to find its entries for allegro. To do that, you have to have pkg-config installed before you run cmake. You may need to rebuild allegro and rerun cmake after deleting CMakeCache.txt.

Allegro 5's output is buffered. You have to call al_flip_display to show what you've drawn since the last call to al_flip_display.

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