#include <unistd.h>
#include <X11/Xlib.h>
#include <X11/extensions/Xrender.h>

int main(void)
{
    int event_base, error_base;
    Display *display;
    Screen *screen;
    Window root;
    XSetWindowAttributes attr;
    const int w1 = 400, h1 = 300, w2 = 300, h2 = 400;
    Window window1, window2;
    XRenderPictFormat *format;
    Picture pict1, pict2;
    XTransform xform;
    static const XRenderColor green = { 0, 0xffff, 0, 0xffff };

    display = XOpenDisplay(NULL);
    if (display == NULL)
    {
	return 1;
    }

    if (!XRenderQueryExtension(display, &event_base, &error_base))
    {
	XCloseDisplay(display);
	return 1;
    }

    screen = DefaultScreenOfDisplay(display);
    root = RootWindowOfScreen(screen);
    attr.override_redirect = True;
    window1 = XCreateWindow(display, root, w2 / 2, h2 / 2, w1, h1, 0, CopyFromParent, InputOutput, CopyFromParent, CWOverrideRedirect, &attr);
    window2 = XCreateWindow(display, root, w1 + w2 / 2, 0, w2, h2, 0, CopyFromParent, InputOutput, CopyFromParent, CWOverrideRedirect, &attr);
    XMapWindow(display, window1);
    XMapWindow(display, window2);

    format = XRenderFindVisualFormat(display, DefaultVisualOfScreen(screen));
    pict1 = XRenderCreatePicture(display, window1, format, 0, NULL);
    pict2 = XRenderCreatePicture(display, window2, format, 0, NULL);

    xform.matrix[0][0] = (w1 << 16) / w2;
    xform.matrix[0][1] = 0;
    xform.matrix[0][2] = 0;
    xform.matrix[1][0] = 0;
    xform.matrix[1][1] = (h1 << 16) / h2;
    xform.matrix[1][2] = 0;
    xform.matrix[2][0] = 0;
    xform.matrix[2][1] = 0;
    xform.matrix[2][2] = 0;
    XRenderSetPictureTransform(display, pict1, &xform);

    XRenderFillRectangle(display, PictOpSrc, pict1, &green, 0, 0, w1, h1);
    XRenderComposite(display, PictOpSrc, pict1, None, pict2, 0, 0, 0, 0, 0, 0, w2, h2);
    XFlush(display);
    sleep(5);

    XDestroyWindow(display, window1);
    XDestroyWindow(display, window2);
    XCloseDisplay(display);
    return 0;
}