import sometimes incorrectly handles X11 window hierarchy, output garbled

Hello,

  ImageMagick bug report
  Platform: Linux, X11
  Version: 6.0.7.1

We found that sometimes the "import" utility does not correctly handle
a hierarchy of subwindows under X11.  First we have seen this with
windows using the OpenMotif NotePage widget.  But it is easy to
reproduce with just a small window hierarchy.  A small test program to
show the problem is attached.  Please compile and run with

% cc -o wintree wintree.c -lX11
% ./wintree
Main Window = 0xc400001

A white window appears, and the main window's id is printed.  Now run
the import utility as follows:

% import -frame -window <window-id> /tmp/wrong.png

With "display", you will see that import did include some garbage in
the generated PNG file.

% display /tmp/wrong.png

The reason for this is that the XGetWindowImage() function in
magick/xwindow.c does not correctly compute the bounds or crop
rectangles when descending the window hierarchy.

A patch would be appreciated.
Kind regards,
-- 
Andreas Luik

Barco Orthogon GmbH
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#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>

static struct {
    int x;
    int y;
    unsigned int width;
    unsigned int height;
    unsigned int bw;
} winlist[] = {
    {  100,  100, 550, 528, 0 },
    {    0,   28, 550, 500, 0 },
    {   10,   10, 540, 340, 0 },
    { -540, -340, 540, 340, 0 },
    {    0,  190, 538, 114, 0 },
};

int main()
{
    int i;
    Display *dpy;
    Window parent;
    Window mainw;
    Window w;

    if ((dpy = XOpenDisplay(0)) == NULL) {
	fprintf(stderr, "failed to open display\n");
	exit(1);
    }

    parent = DefaultRootWindow(dpy);
    for (i = 0; i < sizeof(winlist) / sizeof(winlist[0]); i++) {
	w = XCreateSimpleWindow(dpy, parent,
				winlist[i].x, winlist[i].y,
				winlist[i].width, winlist[i].height,
				winlist[i].bw,
				BlackPixel(dpy, DefaultScreen(dpy)),
				WhitePixel(dpy, DefaultScreen(dpy)));
	parent = w;
	if (i == 0) {
	    mainw = w;
	    XSelectInput(dpy, mainw, ButtonPressMask);
	}
	XMapWindow(dpy, w);
    }

    printf("Main Window = %#lx\n", mainw);

    while (1) {
	XEvent event;
	
	XNextEvent(dpy, &event);
	
	switch (event.type) {
	  case ButtonPress:
	    exit(0);
	    break;
	}
    }
}