Change Xlib window background color with C++

Question

This is Linux. I have created a window and I want to change its background color to green. This is how my code looks like:

Window xwin = XCreateSimpleWindow(dis, 
                                  DefaultRootWindow(dis), 
                                  0, 0, 
                                  500, 300, 
                                  0,
                                  WhitePixel(dis, 0),
                                  WhitePixel(dis, 0));
GC gc = XCreateGC(dis, xwin, 0, NULL);
XColor color;
Colormap colormap;
char green[] = "#00FF00";

colormap = DefaultColormap(dis, 0);
XParseColor(dis, colormap, green, &color);
XAllocColor(dis, colormap, &color);

XSetBackground(dis, gc, color.pixel);

XMapWindow(dis, xwin);
XFlush(dis);

The window that I see is white. Is it possible to change window background color in Linux, using X11? Thanks!

Answer 1

If you just want a green background, the last argument of XCreateSimpleWindow is the background colour so ...

  XColor color;
  Colormap colormap;
  char green[] = "#00FF00";

  colormap = DefaultColormap(dis, 0);
  XParseColor(dis, colormap, green, &color);
  XAllocColor(dis, colormap, &color);


  Window xwin = XCreateSimpleWindow(dis, 
                   DefaultRootWindow(dis), 
                   0, 0, 
                   500, 300, 
                   0,
                   WhitePixel(dis, 0),
                   color.pixel);

XMapWindow(dis, xwin);
XFlush(dis);