Desktop window

painter.c

void
create_xlib_window(painter_t *painter)
{
    painter->_display = XOpenDisplay(config.output_display);
    if (!painter->_display) {
		fprintf(stderr, "Unable to open display: '%s'\n", XDisplayName(config.output_display));
		exit(EXIT_FAILURE);
    }

    int screen = DefaultScreen(painter->_display);
    Window root = RootWindow(painter->_display, screen);
    
    XVisualInfo vi;
    if (!XMatchVisualInfo(painter->_display, screen, 32, TrueColor, &vi)) {
        fprintf(stderr, "Failed to match a TrueColor visual for transparency support.\n"
                "This is usually caused by the absense of a compositor.\n");
        exit(EXIT_FAILURE);
    }

    XSetWindowAttributes attr;
    attr.colormap = XCreateColormap(painter->_display, root, vi.visual, AllocNone);
    attr.event_mask = ExposureMask | KeyPressMask | StructureNotifyMask;
    attr.border_pixel = 0;
    attr.background_pixmap = None;
    attr.background_pixel = 0;
    
    if (!(painter->_window = XCreateWindow(painter->_display, root,
                                           0, 0, config.output_width, config.output_height, 0,
                                           vi.depth, InputOutput, vi.visual,
                                           CWColormap | CWEventMask | CWBackPixmap | CWBorderPixel,
                                           &attr))) {
        fprintf(stderr, "XCreateWindow(): failed\n");
        exit(EXIT_FAILURE);
    }
    
    /* Set EWMH window type to desktop */
    /*
    Atom wtype = XInternAtom(painter->_display, "_NET_WM_WINDOW_TYPE", false);
    Atom desktop = XInternAtom(painter->_display, "_NET_WM_WINDOW_TYPE_DESKTOP", false);
    XChangeProperty(painter->_display, painter->_window, wtype,
                    XA_ATOM, 32, PropModeReplace, (unsigned char*) &desktop, 1);
    */

    /* Assign the newly created dektop to be visible on all workspaces (EWMH) */
    Atom dvis = XInternAtom(painter->_display, "_NET_WM_DESKTOP", false);
    unsigned long all_desktops = 0xFFFFFFFF;
    XChangeProperty(painter->_display, painter->_window, dvis,
                    XA_CARDINAL, 32, PropModeReplace, (unsigned char*) &all_desktops, 1);

    /* Disable window decoration (motif hints, respected by most WMs) */
    struct {
        unsigned long flags, functions, decorations;
        long input_mode;
        unsigned long status;
    } hints;

    hints.flags = 2;
    hints.decorations = 0;
        
    Atom motif = XInternAtom(painter->_display, "_MOTIF_WM_HINTS", false);
    XChangeProperty(painter->_display, painter->_window, motif, motif, 32, PropModeReplace,
                    (unsigned char*) &hints, sizeof(hints) / sizeof(long));

    /* Allow the window to be clicked through (requries XShape support from the WM) */
    int _ignored;
    if (XShapeQueryExtension(painter->_display, &_ignored, &_ignored)) {
        Region region;
        if ((region = XCreateRegion())) {
            XShapeCombineRegion(painter->_display, painter->_window, ShapeInput, 0, 0, region, ShapeSet);
            XDestroyRegion(region);
        }
    }
    
    /* Assign window name and class */
    static char *win_name = "pscircle-display", *win_class = "pscircle";
    XSetClassHint(painter->_display, painter->_window,
                  &((XClassHint) { .res_name = win_class, .res_class = win_class }));
    XStoreName(painter->_display, painter->_window, win_name);

    /* Assign window close behaviour */
    Atom dwin = XInternAtom(painter->_display, "WM_DELETE_WINDOW", false);
    XSetWMProtocols(painter->_display, painter->_window, &dwin, 1);
    
    painter->_pixmap = XCreatePixmap(painter->_display, painter->_window,
			config.output_width, config.output_height, 32);
    painter->_surface = cairo_xlib_surface_create(painter->_display,
			painter->_pixmap, vi.visual, config.output_width,
			config.output_height);
    painter->_gc = XCreateGC(painter->_display, painter->_pixmap, 0, 0);

	cairo_surface_set_user_data(painter->_surface, NULL, NULL, NULL);

	cairo_xlib_surface_set_size(painter->_surface,
			config.output_width, config.output_height);

    /* Make window visible */
    XMapWindow(painter->_display, painter->_window);
}