[TUTORIAL] How to create a command - DarkPlaces engine C programming

Hello, all!
It's the first time I've touched engine code to test something simple.
IMPORTANT NOTE: only modifies engine part.

1. Open a file called console.c in xonotic/darkplaces folder

2. Write the following in the line 842 (NOTE: This line is specific, if you see something not empty, don't do. The code may change in some time due to the development, so don't write inside the functions, write it outside the functions)

Code:

//LegendGuard first time using engine code 27-03-2021
/*
================
Con_Hello_f
================
*/
static void Con_Hello_f (void)
{
   Con_Printf("HELLO XONOTIC! I'm LegendGuard, touching console code in the engine! :D\n");
   return;
}

3. Write the following line to call the command function in the line 917 more or less where says "// register our commands":

Code:

Cmd_AddCommand ("hello", Con_Hello_f, "output a hello message");

4. Save console.c file and go to console MSYS2 (as I use Windows)



5. In the console, while you're in xonotic/darkplaces directory, write and execute  make sdl-release 
(optionally, you can use  ./all compile -r   when you're in xonotic directory but IT'S NOT RECOMMENDED, since it compiles all contents and is slow to check the results of your code in the engine)

NOTE: about  make
sdl-release = xonotic-sdl
sv-release = xonotic-dedicated
You can compile graphical with glx or sdl interface or non graphical dedicated good for servers without a windowing system.

There are differences:
make sdl-release    uses sdl2-config (in my system is version 2.0.12)  (uses -ljpeg)   - USE THIS COMMAND IN xonotic/darkplaces DIRECTORY -
./all compile sdl   uses xonotic/misc/builddeps/win64/sdl/bin/sdl2-config (version 2.0.10)  (doesn't use -ljpeg)   - USE THIS COMMAND IN xonotic DIRECTORY -

You can see more info in the makefile

6. After compiled successfully, go to xonotic directory and run the game with ./all run


7. Press Shift + Esc, type  hello  and ENJOY!!!   

In this section, it will show you how to develop a Basic Calculator command:

There are things to keep in mind: 

• It's convenient to understand C programming problems. Functions like strcmp() has been used in this part.
  
• Some operations won't have the same result like the other tutorial, the code isn't the same.
  
• Takes effort improving the structure where we want to develop.
  With a little help, you can write those lines and look what happens to the parameters/variables:
  
  Code:

  Con_Printf("^1DEBUG: ^5Cmd_Argc() is: ^6%d\n", Cmd_Argc()); //number of parameters inserted, if there is no parameters, will be zero

Con_Printf("^1DEBUG: ^5Cmd_Argv(0) is: ^6%s\n", Cmd_Argv(0)); //command where execute or main parameter

Con_Printf("^1DEBUG: ^5Cmd_Argv(1) is: ^6%s\n", Cmd_Argv(1)); //first parameter

Con_Printf("^1DEBUG: ^5Cmd_Argv(2) is: ^6%s\n", Cmd_Argv(2)); //second parameter

Con_Printf("^1DEBUG: ^5Cmd_Argv(3) is: ^6%s\n", Cmd_Argv(3)); //third parameter

Requires having learned something from it, anyway, let's get started!


1. Open a file called console.c in xonotic/darkplaces folder

2. Write the following in the line 843 (NOTE: This line is specific, if you see something not empty, don't do. The code may change in some time due to the development, so don't write inside the functions, write it outside the functions)

Code:

/*
================
Con_Calc_f
================
*/
void InfoCalcParameters (void);
void InfoCalcParameters (void)
{
  char modulussign[] = "%";
  Con_Printf("Usage:^3 calc\n");
  Con_Printf("  Where '+', '-', '*', '/', '^' and '%s' are the operators to calculate.\n", modulussign);
  Con_Printf("  Examples:\n^3 calc 4 + 5\n^3 calc 3 ^ 2\n^3 calc 8 %s 2\n ^3calc pi * 0.5\n^3 calc 32.46 / π\n^3 calc τ * 0.112\n^3 calc 4.1 / tau\n", modulussign);
}

static void Con_Calc_f (void)
{
  int pipar1, pisignpar1, pipar3, pisignpar3, taupar1, tausignpar1, taupar3, tausignpar3,
  op_add, op_sub, op_mult, op_div, op_exp, op_mod;
  float result, numf1, numf2;

  numf1 = atof(Cmd_Argv(1));
  numf2 = atof(Cmd_Argv(3));

  pipar1 = strcmp(Cmd_Argv(1), "pi");
  pisignpar1 = strcmp(Cmd_Argv(1), "π");

  pipar3 = strcmp(Cmd_Argv(3), "pi");
  pisignpar3 = strcmp(Cmd_Argv(3), "π");

  taupar1 = strcmp(Cmd_Argv(1), "tau");
  tausignpar1 = strcmp(Cmd_Argv(1), "τ");

  taupar3 = strcmp(Cmd_Argv(3), "tau");
  tausignpar3 = strcmp(Cmd_Argv(3), "τ");

  op_add = strcmp(Cmd_Argv(2), "+");
  op_sub = strcmp(Cmd_Argv(2), "-");
  op_mult = strcmp(Cmd_Argv(2), "*");
  op_div = strcmp(Cmd_Argv(2), "/");
  op_exp = strcmp(Cmd_Argv(2), "^");
  op_mod = strcmp(Cmd_Argv(2), "%");

  if ((Cmd_Argv(1) != NULL && Cmd_Argv(2) != NULL && Cmd_Argv(3) != NULL) ||
  numf1 != atof("") || numf2 != atof(""))// || numf1 == atof(Cmd_Argv(1) || numf2 == atof(Cmd_Argv(3))
  {
     //if the parameter is pi number
     if (pipar1 == 0 || pisignpar1 == 0) //if user writes pi in the first parameter to calculate using pi number
         numf1 = 3.14159265358979323;
     if (pipar3 == 0 || pisignpar3 == 0) //if user writes pi in the third parameter to calculate using pi number
         numf2 = 3.14159265358979323;

     //if the parameter is tau number
     if (taupar1 == 0 || tausignpar1 == 0) //if user writes tau in the first parameter to calculate using tau number
         numf1 = 2 * 3.14159265358979323;
     if (taupar3 == 0 || tausignpar3 == 0) //if user writes tau in the third parameter to calculate using tau number
         numf2 = 2 * 3.14159265358979323;

     if (op_add == 0)
     {
         result = numf1 + numf2;
         Con_Printf("^5The sum result is: ^6%f\n", result);
         return;
     }
     else if (op_sub == 0)
     {
         result = numf1 - numf2;
         Con_Printf("^5The substraction result is: ^6%f\n", result);
         return;
     }
     else if (op_mult == 0)
     {
         result = numf1 * numf2;
         Con_Printf("^5The multiplication result is: ^6%f\n", result);
         return;
     }
     else if (op_div == 0)
     {
         result = numf1 / numf2;
         Con_Printf("^5The division result is: ^6%f\n", result);
         return;
     }
     else if (op_exp == 0)
     {
         result = pow(numf1, numf2);
         Con_Printf("^5The exponent result is: ^6%f\n", result);
         return;
     }
     else if (op_mod == 0)
     {
         result = fmod(numf1, numf2);
         Con_Printf("^5The modulus result is: ^6%f\n", result);
         return;
     }
     else
     {
         InfoCalcParameters();
         return;
     }
  }
  else
  {
     InfoCalcParameters();
     return;
  }
}

3. Write the following line to call the command function in the line 1019 more or less where says "// register our commands" inside "Con_Init" function:

Code:

Cmd_AddCommand ("calc", Con_Calc_f, "basic calculator, input parameters to get a result: [num1] [operator] [num2]");

4. Save console.c file and go to console MSYS2 (as I use Windows)


5. In the console, while you're in xonotic/darkplaces directory, write and execute  make sdl-release 
(optionally, you can use  ./all compile -r   when you're in xonotic directory but IT'S NOT RECOMMENDED, since it compiles all contents and is slow to check the results of your code in the engine)

NOTE: about  make
sdl-release = xonotic-sdl
sv-release = xonotic-dedicated
You can compile graphical with glx or sdl interface or non graphical dedicated good for servers without a windowing system.

There are differences:
make sdl-release    uses sdl2-config (in my system is version 2.0.12)  (uses -ljpeg)   - USE THIS COMMAND IN xonotic/darkplaces DIRECTORY -
./all compile sdl   uses xonotic/misc/builddeps/win64/sdl/bin/sdl2-config (version 2.0.10)  (doesn't use -ljpeg)   - USE THIS COMMAND IN xonotic DIRECTORY -

You can see more info in the makefile

6. After compiled successfully, go to xonotic directory and run the game with ./all run

7. Press Shift + Esc, use calc  command and ENJOY!!