Drawing to an X window

As an example of using the X11/Xlib interface, let's create an X window and write some text on it.

hello_world_xlib.cpp

#include "hershey.hpp"
#include "hershey_xlib.hpp"
 
void close_x(Display *display, Window win, GC gc) {
    XFreeGC(display, gc);
    XDestroyWindow(display, win);
    XCloseDisplay(display);
    exit(1);
}
 
int main(int argc, char *argv[]) {
 
    Hershey::Font roman("simplexroman");
    Hershey::Font italic("complexitalic");
 
    Hershey::String substr1(roman, "Hello, ");
    Hershey::String substr2(italic, "world!");
    Hershey::String text_to_display = substr1 + substr2;
 
    Display *display;
    int screen;
    Window win;
    GC gc;
 
    unsigned long black, white;
    XEvent event;
    KeySym key;
    char text[255];
 
    display = XOpenDisplay((char *)0);
    if(display == NULL) {
        std::cout << "Error connecting to X server" << '\n';
        exit(-1);
    }
 
    screen = DefaultScreen(display);
    black = BlackPixel(display, screen);
    white = WhitePixel(display, screen);
 
    win = XCreateSimpleWindow(
        display, XDefaultRootWindow(display), 0, 0, 1440, 720, 4, black, white
    );
 
    XMapWindow(display, win);
    XSelectInput(display, win, KeyPressMask | ButtonPressMask | ExposureMask);
 
    gc = XCreateGC(display, win, 0, 0);
    XSetLineAttributes(display, gc, 1, LineSolid, CapRound, JoinRound);
 
    while(1) {
        XNextEvent(display, &event);
        if(event.type == Expose && !event.xexpose.count) {
            draw_glyphs(display, &win, &gc, text_to_display, 360, 360, 4);
        }
        if(event.type == KeyPress && XLookupString(&event.xkey, text, 255, &key, 0)) {
            if(text[0] == 'q') {
                close_x(display, win, gc);
            }
        }
    }
 
    return 0;
}

Note that the majority of the code here is Xlib boilerplate for creating the window to draw on, as well as the colours, line style and width to draw with.

The statements using the Hershey fonts are simply:

// Load the fonts we wish to use
Hershey::Font roman("simplexroman");
Hershey::Font italic("complexitalic");
 
// Create two strings of glyphs to draw, each with a different font
Hershey::String substr1(roman, "Hello, ");
Hershey::String substr2(italic, "world!");
 
// Concatenate the strings
Hershey::String text_to_display = substr1 + substr2;
 
// Draw the text starting at x=y=360, glyph sizes scaled x4
draw_glyphs(display, &win, &gc, text_to_display, 360, 360, 4);

Compile, e.g.

g++ -o hello_world_xlib -lX11 -I./include/ src/hello_world_xlib.cpp src/glyph.cpp src/font.cpp src/string.cpp src/hershey_xlib.cpp

Run, e.g.

./hello_world_xlib