/* atoms.c from Pegasus Epsilon's Desktop Environment

** Goal: Less than a megabyte resident

** (C)opyright 2019-2020 "Pegasus Epsilon" <pegasus@pimpninjas.org>

** Distribute Unmodified - https://pegasus.pimpninjas.org/license

*/

#include <X11/Xlib.h> // XInternAtom()

#include <string.h> // strncmp(), strchr(), strncpy(), strncat()

#include <stdlib.h> // calloc(), exit(), free()

enum Atoms {

WM_Sn,

#define ATOM_EXPANDO(x) x,

#include "expandos.h"

ATOMS_LENGTH

};

Atom atom[ATOMS_LENGTH];

static char *atom_names[] = {

[WM_Sn] = NULL,

// Not needed, yet...

//#define ATOM_EXPANDO(x) [x] = #x,

//#include "expandos.h"

};

void shutdown_atom_cache (void) { free(atom_names[WM_Sn]); }

void initialize_atom_cache (Display *display, char **envp) {

// parse DISPLAY environment variable, and construct WM_S<screen number>

// atom name per ICCCM § Discriminated Names and § Manager Selections

for (unsigned i = 0; envp[i]; i++)

if (0 == strncmp(envp[i], "DISPLAY=:", 9)) {

char *end, *start = envp[i] + 9;

// This looks unsafe, but validity of the DISPLAY environment

// variable is already assured by XOpenDisplay before we ever

// get here. Maybe we won't understand the format of it, but

// we know it's *valid*, at least, so we can suck some sort of

// data out of it. Even if it's just a null string, which will

// result in WM_S. That's good enough, so long as we don't

// have to deal with another window manager. If the format of

// the DISPLAY environment variable ever changes, though, we

// *should* update this for the sake of continuing to operate

// according to the relevant standards, but we will at least

// continue to function (wrongly) without an update.

if (NULL == (end = strchr(start, '.'))) end = strchr(start, 0);

size_t len = (size_t)(end - start);

atom_names[WM_Sn] = calloc(1, len + 5);

// strcpy() returns a pointer to the beginning of the copied string

// strncpy() returns a pointer to the END of the copied string

// https://www.joelonsoftware.com/2001/12/11/back-to-basics/

strncat(strncpy(atom_names[WM_Sn], "WM_S", 5), start, len);

break;

}

atom[WM_Sn] = XInternAtom(display, atom_names[WM_Sn], False);

#define ATOM_EXPANDO(x) atom[x] = XInternAtom(display, #x, False);

#include "expandos.h"

}