Lib Graphics -- Turbo C's graphics.h in Linux

What is it?

It is an implementation of TC graphics.h functions in Linux using SDL --

Simple DirectMedia Layer (www.libsdl.org for more).

The sole objective of this package is to enable people to run programs 

written using graphics.h functions directly in Linux. It does not aim to be a complete graphics solution. Effort has been made to suppress flexibility and genericity in order to provide an interface closer to the original. Basically this software is provided with the sincere hope that it will prevent you from booting into Windoze.

For more power and flexibility use libSDL directly. The website

(libsdl.org) contains a number of links to great useful, generic and powerful support libraries for SDL.

What do I need ?

You need to have the following installed : 
    SDL-x.x.x.rpm               -- the main SDL library
    SDL-devel-x.x.x.rpm         -- the developer package
    SDL_image-x.x.x.rpm         -- image library for fonts
    SDL_image-devel-x.x.x.rpm   -- image library developer 
                                    package

These libaries are a standard part of most current distributions 

(which is why we chose SDL over SVGAlib in the first place). The libaries will probably already be installed. You may have to install the developer packages.

SDL can render onto X or a framebuffered console(fbdev). The VGA mode console

can be used directly through SVGAlib but we haven't tried it (on the TODO list).

How to use ?

See INSTALL for instructions on how to compile.

 Just include graphics.h in your C file ( as you normally would do).

While compiling your applications you must link with libgraph as in :

$ gcc foo.c -lgraph -o foo

If your fingers give you too much trouble then we have provided a 

simple script "grc" to the same effect.

$grc foo

You can now run your executable.

IMPORTANT :

If your program goes into an infinite loop press CTRL-C. The program will 

quit in anywhere between 10 to 30 seconds(depending on CPU load).
If the program doesn't exit you may have to restart the X-server (just CTRL-BACKSPACE-ALT). We have not yet seen a complete lock-up requiring a reboot.

If this makes you uncomfortable (too slow or too sophisticated

for your taste), you can xkill libgraph in case of a lock-up and get nasty error messages for X.

There exists a loop-hole in scanf. If you enter invalid input,

specifically text where numbers are expected, the function goes into a loop (the program would have seg-faulted or mal-functioned anyway).Here you can easily use CTRL-C to exit --- this feature is guaranteed to work.

If you just want to use the library you have learnt all ye need to 

know. We have provided documentation of standard TC functions(see {prefix}/share/libgraph/index.html). For a closer look at the functions/constants provided, just glance through the header files.

Any problems/destructive criticism/flames may be sent on 
    <faraz_ms@rediffmail.com>   

/ User section END; developer section BEGINS /

If you are a developer wanting to contribute readon...  

Files :

In this package are : 

graphics.h : the default header that includes all the others required 
         so that you don't have to do anything differently.
libgraph.c : the code for functions in graphics.h. These are mainly
         the basic settings and initialization functions.

grtext.h : the functions for text manipulation -- This basic part 
       of this code has been borrowed from Karl Bartel's 
       <karlb@gmx.net> SFont library. We extended it to fit 
       our needs. 
text.c : code for functions in grtext.h

shapes.h : functions for drawing various shapes, filling and positioning. 
shapes.c : Code for the above definitions.

polygon.h : functions for drawing and filling polygons.
polygon.c :  Code for above functions. These two functions were made
        into a separate module because the code for fillpoly() is pretty
        healthy all by itself and requires quite a few book-keeping 
        trivial functions.

Makefile : We don't know how to write Makefiles. This one has been 
       hacked up from someone else software. If u know more than us
       on the subject please oblige by writing a custom Makefile
       for the package.

README : That's what you are reading.

grc : a no-brainer script to compile libgraph programs.

./Font : Directory containing font(.png) files. There are a number of different
        colors but of the same font. Default font is white. Font-color 
        selection is still to be implemented. You can change the color by
        changing the FONT definition in graphics.h to a different color file
        and recompiling the library.

 sample.c : small sample file to try out the library.
        Just compile with
            $ ./grc sample
        and execute with
            $ ./sample

What you need ?

I would suggest that you familiarize yourself with the basic SDL 

functions before scratching around. All the SDL functions are documented in man-pages. For a good intro, html documentation and samples refer the homepage at www.libsdl.org.

Regarding the text functions :

The basic code for text functions has been borrowed from 

Karl Bartel's karlb@gmx.net SFont library ( We can't seem to stress that point enough ). We actually don't understand much of the basic initialization. We just modified his output function to emulate terminal behaviour (eg. scrolling of text onto newline).

The input functions although written from scratch also borrow heavily 

from Karl's code. Our code is not neatly organized or efficiently written. There are parts which we think are unnecessary but are afraid to remove lest we break something. The main challenge in this code ( and one that has not yet been met with ) is to emulate terminal behaviour by redirecting standard I/O functions to use the graphical screen.

The reason for stressing this is that we often see/use code like

initgraph( , , );
....
printf("Hello",,);
...
closegraph();

Now this may seem normal in DOS but in SDL the drawing is done on a 

separate SDL_Surface structure while all I/O functions operate on stdin/stdout. Hence we check wether we are in graphics mode by setting and querying an environment variable --- "LIBGRAPHICS_ACTIVE=1". Correspondingly we use either our native functions or call variadic printf/scanf functions. You
might want to look up the variadic call conventions in "$info libc".

CAVEAT : scanf input buffer is limited to 256 characters. This means that it will stop accepting input after you enter 256 characters. This behaviour is unlike the normal scanf function that allows you to enter arbitrarily long strings and scans only the required amount of characters. You can increase the buffer size by changing the definition SCAN_BUF in grtext.h and recompiling.

Another thing is that scanf can only perform 10 input conversions in 

one call i.e. it can process an input string with maximum 10 %. Even this feature is a pure hack since "C does not provide any way of determining the number of arguments recieved" by a variadic function like scanf. Basically we just scan the format string over an arbitrary constant string of 10 integers to determine the number of arguments and scan the users input at every enter keypress to see if we've got all we expected.

Unfortunately this only fixes the number-of-arguments problem. There is

still no way of determining what rubbish the user has entered, which is why the function goes into a loop when characters are entered where numbers are expected. This was overcome by providing a special clause CTRL-C to quit the program altogether. Don't blame us, the info-page itself says that there is no way of recovering from a scanf error.

To try new functions :

If you have implemented a function which has not yet been included, 

I suggest that you write it in a separate header or program and test it before
adding it to the main library. This way you can tweak it without recompiling the library.

Libtool :

Libtool is used for cascaded linking of dynamic libraries. For more see
    $ info libtool