[screensavers] / hacks / WolframAutomata / WolframAutomata.c

/* (c) 2021 Aaron Taylor <ataylor at subgeniuskitty dot com>   */
/* See LICENSE.txt file for copyright and license details.     */

#include "screenhack.h"

/* -------------------------------------------------------------------------- */
/* Data Structures                                                            */
/* -------------------------------------------------------------------------- */

struct state {
    /* Various X resources                                                    */
    Display * dpy;
    Window    win;
    GC        gc;

    /* These hold the pixel value of the foreground and background colors in  */
    /* the same format as an XColor struct's "pixel" member.                  */
    unsigned long fg, bg;

    /* This Pixmap will eventually hold the entire evolution of the CA. The   */
    /* displayed portion of the CA's evolution is merely a viewport into this */
    /* Pixmap.                                                                */
    Pixmap    evolution_history;

    /* Together, these three values define the display viewport into the      */
    /* 'evolution_history' Pixmap. The pair 'dpy_width' and 'dpy_height' are  */
    /* simply the width and height of the display window. They remain         */
    /* unchanged during normal operation. However, 'ypos' tracks the location */
    /* of the viewport in the 'evolution_history'. It must always keep the    */
    /* newest generation onscreen and display as much history as possible.    */
    int dpy_width, dpy_height, ypos;

    /* In the 'current_generation' array, the value True means a cell is      */
    /* alive. We only need to track the current generation since our rulesets */
    /* never consider older generations. Anything older can be rendered to    */
    /* the 'evolution_history' Pixmap and subsequently ignored.               */
    Bool * current_generation;

    /* When randomizing the seed generation, we can specify a population      */
    /* density, or we can restrict to a single living cell.                   */
    int population_density;
    Bool population_single;

    /* For more information on the encoding used for rule_number and on the   */
    /* method used to apply it: https://en.wikipedia.org/wiki/Wolfram_code    */
    uint8_t rule_number;

    /* At the end of the simulation, the user is given time to admire the     */
    /* output. Delay is available to user as CLI option '-admiration-delay'.  */
    Bool admiration_in_progress;
    size_t admiration_delay; /* ...in seconds.                                */

    /* The following values correspond directly to independent CLI options.   */
    Bool    rule_random;
    uint8_t rule_requested;  /* Note: Repurposing Rule 0 as null value.       */
    int     cell_size; /* If cell_size=N then draw NxN pixels per cell.       */
    int     delay_microsec; /* ...between calls to WolframAutomata_draw().    */
    int     num_generations; /* Reset simulation after this many generations. */

    /* Not strictly necessary, but makes some code easier to read.            */
    size_t number_of_cells;
};

enum seed_population {
    random_cell,
    middle_cell,
    edge_cell
};

struct curated_ruleset {
    uint8_t              rule;
    enum seed_population seed;
};

static const struct curated_ruleset curated_ruleset_list[] = {
    { 18, middle_cell},
    { 30, middle_cell},
    { 45, middle_cell},
    { 54, middle_cell},
    { 57, middle_cell},
    { 73, middle_cell},
    {105, middle_cell},
    {109, middle_cell},
    {129, middle_cell},
    {133, middle_cell},
    {135, middle_cell},
    {150, middle_cell},
    { 30, edge_cell},
    { 45, edge_cell},
    { 57, edge_cell},
    { 60, edge_cell},
    { 75, edge_cell},
    {107, edge_cell},
    {110, edge_cell},
    {133, edge_cell},
    {137, edge_cell},
    {169, edge_cell},
    {225, edge_cell},
    { 22, random_cell},
    { 30, random_cell},
    { 54, random_cell},
    { 62, random_cell},
    { 90, random_cell},
    {105, random_cell},
    {108, random_cell},
    {110, random_cell},
    {126, random_cell},
    {146, random_cell},
    {150, random_cell},
    {182, random_cell},
    {184, random_cell},
    {225, random_cell},
    {240, random_cell}
};

struct color_pair {
    /* The type 'unsigned short' comes from the XColor struct definition,     */
    /* reproduced below.                                                      */
    /*                                                                        */
    /*      typedef struct {                                                  */
    /*          unsigned long pixel;                                          */
    /*          unsigned short red, green, blue;                              */
    /*          char flags;                                                   */
    /*          char pad;                                                     */
    /*      } XColor;                                                         */
    /*                                                                        */
    /* The red, green, and blue values are always in the range 0 to 65535     */
    /* inclusive, independent of the number of bits actually used in the      */
    /* display hardware. The server scales these values to the range used     */
    /* by the hardware. Black is represented by (0,0,0), and white is         */
    /* represented by (65535,65535,65535).                                    */
    unsigned short fg_red, fg_green, fg_blue;
    unsigned short bg_red, bg_green, bg_blue;
};

static const struct color_pair color_list[] = {
    /* For mapping X11 color names to RGB values:                                           */
    /*      https://www.ehdp.com/methods/x11-color-names-rgb-values.htm                     */
    /* Remember that our values range from 0-65535 inclusive, so scale the                  */
    /* usual 0-255 range accordingly.                                                       */
    /*                                                                                      */
    /* +---------------------------------------+                                            */
    /* |   foreground    |   |    background   |                                            */
    /* |  red,green,blue |   |  red,green,blue |                                            */
       {65535,    0,    0,        0,    0,    0}, /* {"red",             "black"},          */
       {32767,32767,    0,        0,    0,    0}, /* {"olive",           "black"},          */
       {    0,32767,32767,        0,    0,    0}, /* {"teal",            "black"},          */
       {27524,22937,52428,        0,    0,    0}, /* {"slateblue",       "black"},          */
       {60947,33422,60947,        0,    0,    0}, /* {"violet",          "black"},          */
       {41287, 8519,61602,        0,    0,    0}, /* {"purple",          "black"},          */
       {65535,65535,65535,        0,    0,    0}, /* {"white",           "black"},          */
       {65535,65535,65535,        0,25558,    0}, /* {"white",           "darkgreen"},      */
       {65535,65535,65535,    36044,    0,36044}, /* {"white",           "darkmagenta"},    */
       {65535,65535,65535,    36044,    0,    0}, /* {"white",           "darkred"},        */
       {65535,65535,65535,        0,    0,36044}, /* {"white",           "darkblue"},       */
       {11796,20315,20315,    36494,65535,65535}, /* {"darkslategray",   "darkslategray1"}, */
       {45219,50461,57015,    11796,20315,20315}, /* {"lightsteelblue",  "darkslategray"},  */
       {10023,16448,35723,    16383,26869,57670}, /* {"royalblue4",      "royalblue"},      */
       {61166,57311,52428,    35723,33667,30840}, /* {"antiquewhite2",   "antiquewhite4"},  */
       {51914,65535,28784,    21626,27524,11796}, /* {"darkolivegreen1", "darkolivegreen"}, */
       {49601,65535,49601,    26985,35723,26985}, /* {"darkseagreen1",   "darkseagreen4"},  */
       {65535,49151,52428,    36044,    0,    0}, /* {"pink",            "darkred"},        */
       {44563,55704,58981,        0,25558,    0}, /* {"lightblue",       "darkgreen"},      */
       {65535,    0,    0,        0,    0,65535}, /* {"red",             "blue"},           */
       {65535,    0,    0,        0,25558,    0}, /* {"red",             "darkgreen"},      */
       {    0,65535,65535,        0,32767,32767}, /* {"aqua",            "teal"},           */
       {    0,    0,36044,        0,32767,32767}, /* {"darkblue",        "teal"},           */
       {61602,58981,32767,    11796,36044,22281}, /* {"khaki",           "seagreen"},       */
       {61602,58981,32767,    21626,27524,11796}, /* {"khaki",           "darkolivegreen"}, */
       {30801,34733,39321,    11796,20315,20315}, /* {"lightslategray",  "darkslategray"},  */
       {65535,25558,18349,    11796,20315,20315}, /* {"tomato",          "darkslategray"},  */
       {65535,25558,18349,        0,36044,36044}  /* {"tomato",          "darkcyan"}        */
};

/* -------------------------------------------------------------------------- */
/* Helper Functions                                                           */
/* -------------------------------------------------------------------------- */

static void
generate_random_seed(struct state * state)
{
    int i;
    for (i = 0; i < state->number_of_cells; i++) {
        state->current_generation[i] = ((random() % 100) < state->population_density) ? True : False;
    }
}

/* This function sanitizes the index used to access cells in a generation.    */
/* Specifically, it wraps the index, creating a circular universe for the     */
/* cells and ensuring every cell has two neighbors.                           */
static size_t
sindex(struct state * state, int index)
{
    while (index < 0) {
        index += state->number_of_cells;
    }
    while (index >= state->number_of_cells) {
        index -= state->number_of_cells;
    }
    return (size_t) index;
}

/* For more information on the encoding used for state->rule_number and on    */
/* the method used to apply it: https://en.wikipedia.org/wiki/Wolfram_code    */
static Bool
calculate_cell(struct state * state, int cell_id)
{
    uint8_t cell_pattern = 0;
    int i;
    for (i = -1; i < 2; i++) {
        cell_pattern = cell_pattern << 1;
        if (state->current_generation[sindex(state, cell_id+i)] == True) {
            cell_pattern |= 1;
        }
    }
    if ((state->rule_number >> cell_pattern) & 1) {
        return True;
    } else {
        return False;
    }
}

static void
render_current_generation(struct state * state)
{
    size_t xpos;
    for (xpos = 0; xpos < state->number_of_cells; xpos++) {
        if (state->current_generation[xpos] == True) {
            XFillRectangle(state->dpy, state->evolution_history, state->gc, xpos*state->cell_size, state->ypos, state->cell_size, state->cell_size);
        } else {
            XSetForeground(state->dpy, state->gc, state->bg);
            XFillRectangle(state->dpy, state->evolution_history, state->gc, xpos*state->cell_size, state->ypos, state->cell_size, state->cell_size);
            XSetForeground(state->dpy, state->gc, state->fg);
        }
    }
}

/* -------------------------------------------------------------------------- */
/* Screenhack API Functions                                                   */
/* -------------------------------------------------------------------------- */

static Bool
WolframAutomata_event(Display * dpy, Window win, void * closure, XEvent * event)
{
    return False;
}

static void
WolframAutomata_free(Display * dpy, Window win, void * closure)
{
    struct state * state = closure;
    XFreeGC(state->dpy, state->gc);
    XFreePixmap(state->dpy, state->evolution_history);
    free(state->current_generation);
    free(state);
}

static void *
WolframAutomata_init(Display * dpy, Window win)
{
    struct state * state = calloc(1, sizeof(*state));
    if (!state) {
        fprintf(stderr, "ERROR: Failed to calloc() for state struct in WolframAutomata_init().\n");
        exit(EXIT_FAILURE);
    }

    XGCValues gcv;
    XWindowAttributes xgwa;
    const struct curated_ruleset * curated_ruleset = NULL;

    state->dpy = dpy;
    state->win = win;

    XGetWindowAttributes(state->dpy, state->win, &xgwa);
    state->dpy_width = xgwa.width;
    state->dpy_height = xgwa.height;
    state->ypos = 0;

    state->admiration_delay = get_integer_resource(state->dpy, "admiration-delay", "Integer");
    state->admiration_in_progress = False;

    /* Set foreground and background colors for active/inactive cells. Either */
    /* the user provided an index into the pre-defined color_list[] or a      */
    /* random entry from that same array should be selected.                  */
    size_t color_index = get_integer_resource(state->dpy, "color-index", "Integer");
    if (color_index == -1) {
        color_index = random() % sizeof(color_list)/sizeof(color_list[0]);
    } else if (color_index >= sizeof(color_list)/sizeof(color_list[0])) {
        fprintf(stderr, "WARNING: Color index out of range.\n");
        color_index = 0;
    }
    XColor fg, bg;
    fg.red   = color_list[color_index].fg_red;
    fg.green = color_list[color_index].fg_green;
    fg.blue  = color_list[color_index].fg_blue;
    bg.red   = color_list[color_index].bg_red;
    bg.green = color_list[color_index].bg_green;
    bg.blue  = color_list[color_index].bg_blue;
    /* TODO: Since I 'alloc', presumably I must also 'free' these colors  */
    /* at some point. Where/how? I don't want to eventually crash my      */
    /* X server after months of use.                                      */
    XAllocColor(state->dpy, xgwa.colormap, &fg);
    XAllocColor(state->dpy, xgwa.colormap, &bg);
    state->fg = gcv.foreground = fg.pixel;
    state->bg = gcv.background = bg.pixel;

    state->gc = XCreateGC(state->dpy, state->win, GCForeground, &gcv);

    /* Set the size of each simulated cell to NxN pixels for cell_size=N.     */
    if (get_boolean_resource(state->dpy, "random-cell-size", "Boolean")) {
        /* Although we are choosing the pixel size 'randomly', a truly random */
        /* selection would bias toward large numbers since there are more of  */
        /* them. To avoid this, we select a random number for a bit shift,    */
        /* resulting in a pixel size of 1, 2, 4, 8, 16 or 32, equally likely. */
        state->cell_size = 1 << (random() % 6);
    } else {
        state->cell_size = get_integer_resource(state->dpy, "cell-size", "Integer");
    }
    if (state->cell_size < 1) state->cell_size = 1;
    if (state->cell_size > state->dpy_width) state->cell_size = state->dpy_width;

    /* Larger cell sizes won't always evenly divide the number of pixels in   */
    /* our window. In order to avoid a black stripe down the edge, '+1' here  */
    /* to ensure we are slightly oversize rather than undersize.              */
    state->number_of_cells = (state->dpy_width / state->cell_size) + 1;

    /* Set the delay (in microseconds) between simulation of each generation  */
    /* of the simulation, also known as the delay between calls to            */
    /* WolframAutomata_draw(), which simulates one generation per call.       */
    if (get_boolean_resource(state->dpy, "random-delay", "Boolean")) {
        /* When randomly setting the delay, the problem is to avoid being too */
        /* fast or too slow, as well as ensuring slower speeds are chosen     */
        /* with the same likelihood as faster speeds, as perceived by a       */
        /* human. By empirical observation, we note that for 1x1 up to 4x4    */
        /* pixel cell sizes, values for state->delay_microsec between         */
        /* 2048 (2^11) and 16556 (2^14) produce pleasant scroll rates. To     */
        /* maintain this appearance, we bitshift state->cell_size down until  */
        /* it is a maximum of 4x4 pixels in size, record how many bitshifts   */
        /* took place, and then shift our valid window for                    */
        /* state->delay_microsec up by an equal number of bitshifts. For      */
        /* example, if state->cell_size=9, then it takes one right shift to   */
        /* reach state->cell_size=4. Thus, the valid window for               */
        /* state->delay_microsec becomes 4096 (2^12) up to 32768 (2^15).      */
        size_t pixel_shift_range = 1;
        size_t cell_size_temp = state->cell_size;
        while (cell_size_temp > 4) {
            cell_size_temp >>= 1;
            pixel_shift_range++;
        }
        /* In the below line, '3' represents the total range, namely '14-11'  */
        /* from '2^14' and '2^11' as the endpoints. Similarly, the '11' in    */
        /* the below line represents the starting point of this range, from   */
        /* the exponent in '2^11'.                                            */
        state->delay_microsec = 1 << ((random() % 3) + 11 + pixel_shift_range);
    } else {
        state->delay_microsec = get_integer_resource(state->dpy, "delay-usec", "Integer");
    }
    if (state->delay_microsec < 0) state->delay_microsec = 0;

    /* Set the number of generations to simulate before wiping the simulation */
    /* and re-running with new settings.                                      */
    if (get_boolean_resource(state->dpy, "random-num-generations", "Boolean")) {
        /* By empirical observation, keep the product                         */
        /*      state->num_generations * state->cell_size                     */
        /* below 10,000 to avoid BadAlloc errors from the X server due to     */
        /* requesting an enormous pixmap. This value works on both a 12 core  */
        /* Xeon with 108 GiB of RAM and a Sun Ultra 2 with 2 GiB of RAM.      */
        state->num_generations = random() % (10000 / state->cell_size);
        /* Ensure selected value is large enough to at least fill the screen. */
        /* Cast to avoid overflow.                                            */
        if ((long)state->num_generations * (long)state->cell_size < state->dpy_height) {
            state->num_generations = (state->dpy_height / state->cell_size) + 1;
        }
    } else {
        state->num_generations = get_integer_resource(state->dpy, "num-generations", "Integer");
    }
    /* The minimum number of generations is 2 since we must allocate enough   */
    /* space to hold the seed generation and at least one pass through        */
    /* WolframAutomata_draw(), which is where we check whether or not we've   */
    /* reached the end of the pixmap.                                         */
    if (state->num_generations < 0) state->num_generations = 2;
    /* The maximum number of generations is cell_size dependent. This is a    */
    /* soft limit and may be increased if you have plenty of RAM (and a       */
    /* cooperative X server). The value 10,000 was determined empirically.    */
    if ((long)state->num_generations * (long)state->cell_size > 10000) {
        state->num_generations = 10000 / state->cell_size;
    }

    /* Time to figure out which rule to use for this simulation.              */
    /* We ignore any weirdness resulting from the following cast since every  */
    /* bit pattern is also a valid rule; if the user provides weird input,    */
    /* then we'll return weird (but well-defined!) output.                    */
    state->rule_requested = (uint8_t) get_integer_resource(state->dpy, "rule-requested", "Integer");
    state->rule_random = get_boolean_resource(state->dpy, "rule-random", "Boolean");
    /* Through the following set of branches, we enforce CLI flag precedence. */
    if (state->rule_random) {
        /* If this flag is set, the user wants truly random rules rather than */
        /* random rules from a curated list.                                  */
        state->rule_number = (uint8_t) random();
    } else if (state->rule_requested != 0) {
        /* Rule 0 is terribly uninteresting, so we are reusing it as a 'null' */
        /* value and hoping nobody notices. Finding a non-zero value means    */
        /* the user requested a specific rule. Use it.                        */
        state->rule_number = state->rule_requested;
    } else {
        /* No command-line options were specified, so select rules randomly   */
        /* from a curated list.                                               */
        size_t number_of_array_elements = sizeof(curated_ruleset_list)/sizeof(curated_ruleset_list[0]);
        curated_ruleset = &curated_ruleset_list[random() % number_of_array_elements];
        state->rule_number = curated_ruleset->rule;
    }

    /* Time to construct the seed generation for this simulation.             */
    state->population_single = get_boolean_resource(state->dpy, "population-single", "Boolean");
    state->population_density = get_integer_resource(state->dpy, "population-density", "Integer");
    if (state->population_density < 0 || state->population_density > 100) state->population_density = 50;
    state->current_generation = calloc(1, sizeof(*state->current_generation)*state->number_of_cells);
    if (!state->current_generation) {
        fprintf(stderr, "ERROR: Failed to calloc() for cell generation in WolframAutomata_init().\n");
        exit(EXIT_FAILURE);
    }
    if (curated_ruleset) {
        /* If we're using a curated ruleset, ignore any CLI flags related to  */
        /* setting the seed generation, instead drawing that information from */
        /* the curated ruleset.                                               */
        switch (curated_ruleset->seed) {
            case random_cell: generate_random_seed(state);                                break;
            case middle_cell: state->current_generation[state->number_of_cells/2] = True; break;
            case edge_cell  : state->current_generation[0] = True;                        break;
        }
    } else {
        /* If we're not using a curated ruleset, process any relevant flags   */
        /* from the user, falling back to a random seed generation if nothing */
        /* else is specified.                                                 */
        if (state->population_single) {
            state->current_generation[0] = True;
        } else {
            generate_random_seed(state);
        }
    }

    state->evolution_history = XCreatePixmap(state->dpy, state->win, state->dpy_width, state->num_generations*state->cell_size, xgwa.depth);
    /* Pixmap contents are undefined after creation. Explicitly set a black   */
    /* background by drawing a black rectangle over the entire pixmap.        */
    XColor blackx, blacks;
    XAllocNamedColor(state->dpy, DefaultColormapOfScreen(DefaultScreenOfDisplay(state->dpy)), "black", &blacks, &blackx);
    XSetForeground(state->dpy, state->gc, blacks.pixel);
    XFillRectangle(state->dpy, state->evolution_history, state->gc, 0, 0, state->dpy_width, state->num_generations*state->cell_size);
    XSetForeground(state->dpy, state->gc, state->fg);
    render_current_generation(state);
    state->ypos += state->cell_size;

    return state;
}

static unsigned long
WolframAutomata_draw(Display * dpy, Window win, void * closure)
{
    struct state * state = closure;
    int xpos;
    int window_y_offset;

    /* Calculate and record new generation.                                   */
    Bool new_generation[state->dpy_width];
    for (xpos = 0; xpos < state->number_of_cells; xpos++) {
        new_generation[xpos] = calculate_cell(state, xpos);
    }
    for (xpos = 0; xpos < state->number_of_cells; xpos++) {
        state->current_generation[xpos] = new_generation[xpos];
    }
    render_current_generation(state);

    /* Check for end of simulation.                                           */
    if (state->ypos/state->cell_size < state->num_generations-1) {
        /* Life continues.                                                    */
        state->ypos += state->cell_size;
    } else {
        /* We have reached the end of this simulation. Give the user a moment */
        /* to bask in the glory of our output, then reset.                    */
        if (state->admiration_in_progress) {
            WolframAutomata_free(dpy, win, state);
            closure = WolframAutomata_init(dpy, win);
        } else {
            state->admiration_in_progress = True;
            return 1000000 * state->admiration_delay;
        }
    }

    /* Calculate vertical offset of current 'window' into the CA's history.   */
    /* After the CA evolution exceeds our display extents, make window track  */
    /* current generation, scrolling display to follow newest generation.     */
    if (state->ypos < state->dpy_height) {
        window_y_offset = 0;
    } else {
        window_y_offset = state->ypos - (state->dpy_height - 1);
    }

    /* Render a window into the CA history.                                   */
    XCopyArea(state->dpy, state->evolution_history, state->win, state->gc, 0, window_y_offset, state->dpy_width, state->dpy_height, 0, 0);

    return state->delay_microsec;
}

static const char * WolframAutomata_defaults[] = {
    "*delay-usec:         25000",
    "*admiration-delay:   5",
    "*num-generations:    5000",
    "*cell-size:          2",
    "*color-index:        -1",
    "*population-density: 50",
    "*population-single:  False",
    "*random-cell-size:   False",
    "*random-delay:       False",
    "*random-length:      False",
    "*random-rule:        False",
    "*rule-requested:     0",
    0
};

static XrmOptionDescRec WolframAutomata_options[] = {
    { "-delay-usec",         ".delay-usec",             XrmoptionSepArg, 0      },
    { "-admiration-delay",   ".admiration-delay",       XrmoptionSepArg, 0      },
    { "-num-generations",    ".num-generations",        XrmoptionSepArg, 0      },
    { "-cell-size",          ".cell-size",              XrmoptionSepArg, 0      },
    { "-color-index",        ".color-index",            XrmoptionSepArg, 0      },
    { "-population-density", ".population-density",     XrmoptionSepArg, 0      },
    { "-population-single",  ".population-single",      XrmoptionNoArg,  "True" },
    { "-random-cell-size",   ".random-cell-size",       XrmoptionNoArg,  "True" },
    { "-random-delay",       ".random-delay",           XrmoptionNoArg,  "True" },
    { "-random-length",      ".random-num-generations", XrmoptionNoArg,  "True" },
    { "-random-rule",        ".rule-random",            XrmoptionNoArg,  "True" },
    { "-rule",               ".rule-requested",         XrmoptionSepArg, 0      },
    { 0, 0, 0, 0 }
};

static void
WolframAutomata_reshape(Display * dpy, Window win, void * closure, unsigned int w, unsigned int h)
{
    struct state * state = closure;
    XWindowAttributes xgwa;
    XGetWindowAttributes(state->dpy, state->win, &xgwa);

    /* Only restart the simulation if the window changed size.                */
    if (state->dpy_width != xgwa.width || state->dpy_height != xgwa.height) {
        WolframAutomata_free(dpy, win, closure);
        closure = WolframAutomata_init(dpy, win);
    }
}

XSCREENSAVER_MODULE ("1D Nearest-Neighbor Cellular Automata", WolframAutomata)