/* 
   X11 underwaved text example by <address@hidden>
   Usage: gcc -lX11 underwave.c && ./a.out 
   Press ESC to quit, any other key to change the strings
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <X11/Xlib.h>
#include <X11/keysym.h>

#define RAND(min,max) (rand()%((max)-(min))+(min))

#define FONT_NAME    "-*-fixed-*-*-*-*-13-*-*-*-*-*-iso8859-*"
#define WAVE_COLOR   "red"
#define WAVE_HEIGHT  2
#define WAVE_THICK   1

Window win;
Display* dpy;
GC gc;
int screen;
int width, height;
XFontStruct* font_info;
char* font_name = FONT_NAME;
int font_height;
int seed = 42;
unsigned long undercolor, black;

void init (int w, int h)
{
    XColor color;
    Colormap cmap;
    unsigned int line_width = WAVE_THICK;
    int line_style = LineSolid;
    int cap_style = CapButt;
    int join_style = JoinBevel;

    width = w, height = h;
    
    dpy = XOpenDisplay(NULL);

    if(!dpy)
        puts("err: XOpenDisplay"), exit(1);

    screen = XDefaultScreen(dpy);
    win = XCreateSimpleWindow(dpy, RootWindow(dpy, screen),
                              100, 100, width, height, 0,
                              BlackPixel(dpy, screen),
                              WhitePixel(dpy, screen));

    cmap = XDefaultColormap(dpy, screen);
    black = BlackPixel(dpy, screen);
    XAllocNamedColor(dpy, cmap, WAVE_COLOR, &color, &color);
    undercolor = color.pixel;
    
    gc = XCreateGC(dpy, win, 0, NULL);
    XSetForeground(dpy, gc, BlackPixel(dpy, screen));
    XSetBackground(dpy, gc, WhitePixel(dpy, screen));
    XSetLineAttributes(dpy, gc, line_width, line_style, cap_style, join_style);

    font_info = XLoadQueryFont(dpy, font_name);
    XSetFont(dpy, gc, font_info->fid);
    font_height = font_info->ascent + font_info->descent;
}

void draw_wave (int x0, int y0, int w)
{
    int dx = WAVE_HEIGHT;
    int dy = dx/2;
    int x1, y1, x2, y2, i, times = w/dx;

    for(i = 0; i < times; i++) {
        x1 = x0 + i*dx;
        y1 = y0 + (i%2 ? 1 : -1) * dy;
        x2 = x0 + (i+1)*dx;
        y2 = y0 + ((i+1)%2 ? 1 : -1) * dy;
        XDrawLine(dpy, win, gc, x1, y1, x2, y2);
    }
}

void draw_underwave_string (char* str, int y)
{
    int len = strlen(str);
    int w = XTextWidth(font_info, str, len);
    int x = (width-w)/2;

    XSetForeground(dpy, gc, black);
    XDrawString(dpy, win, gc, x, y+font_info->ascent, str, len);
    XSetForeground(dpy, gc, undercolor);
    draw_wave(x, y+font_height, w);
}

void draw (void)
{
    char buf[256];
    int i, j, y, n = 20;

    srand(seed);
    XClearWindow(dpy, win);

    for(i = 1; i <= n; i++) {
        y = (height-font_height*1.5*n)/2+font_height*1.5*i;

        /* random ascii string */
        memset(buf, 0, sizeof buf);
        for(j = 0; j < i; j++)
            buf[j] = RAND(32, 126);
        buf[j] = 0;

        draw_underwave_string(buf, y);
    }
}

int main (void)
{
    int done = 0;
    XEvent e;
    int mask = ExposureMask | KeyPressMask | StructureNotifyMask;

    init(300, 300);

    XSelectInput(dpy, win, mask);
    XMapWindow(dpy, win);

    while (!done) {
        XNextEvent(dpy, &e);
        switch (e.type) {
        case Expose:
                draw();
            break;
        case ConfigureNotify:
            width = e.xconfigure.width;
            height = e.xconfigure.height;
            draw();
            break;
        case KeyPress:
            if(XLookupKeysym(&e.xkey, 0) == XK_Escape)
                done = 1;
            else {
                seed = time(NULL)+rand();
                draw();
            }
            break;
        }
    }

    XFreeGC(dpy, gc);
    XCloseDisplay(dpy);

    return 0;
}