Move window event on X11 window

Question

I currently have 2 X11 windows that I want to keep in sync. One overlays a transparent graphic while the other one shows video. I currently have the one that overlays graphic to be always on top of the one of the video, but I am having trouble making sure both windows are at the same places when moved. I am looking for a window move event in the X11 documentation, but I can't seem to find one.

In addition, in my event handle loop, I have tried to get the location of one of my windows and to move the other window to that location. This has failed whenever XGetWindowAttributes is called it always returns x=0 and y=0 even though the window is moved.

Window   win;
int nxvisuals = 0;
XVisualInfo visual_template;
XVisualInfo *visual_list;
XVisualInfo vinfo;
Visual *visual;
int depth;
Atom wm_state;
(void)wm_state;

x_display = XOpenDisplay ( NULL );   // open the standard display (the primary screen)

visual_template.screen = DefaultScreen(x_display);
visual_list = XGetVisualInfo(x_display, VisualScreenMask, &visual_template, &nxvisuals);

XMatchVisualInfo(x_display, XDefaultScreen(x_display), 32, TrueColor, &vinfo)

Window parent = XDefaultRootWindow(x_display);
XSync(x_display, True);
visual = vinfo.visual;
depth = vinfo.depth;

XSetWindowAttributes  swa;
swa.event_mask = ExposureMask | PointerMotionMask | KeyPressMask;
swa.colormap = XCreateColormap(x_display, XDefaultRootWindow(x_display), visual, AllocNone);
swa.background_pixel = 0;
swa.border_pixel = 0;

win = XCreateWindow (   // create a window with the provided parameters
          x_display, parent,
          0, 0, 1024, 576, 0,
          depth, InputOutput,
          visual, CWEventMask | CWBackPixel | CWColormap | CWBorderPixel,
          &swa );

XSync(x_display, True);

XSetWindowAttributes  xattr;

xattr.override_redirect = False;
XChangeWindowAttributes ( x_display, win, CWOverrideRedirect, &xattr );

XWMHints hints;
hints.input = True;
hints.flags = InputHint;
XSetWMHints(x_display, win, &hints);

XSizeHints *size_hints = XAllocSizeHints();
size_hints->flags = PMinSize | PMaxSize | PSize;
size_hints->min_width = 1024;
size_hints->max_width = 1024;
size_hints->min_height = 576;
size_hints->max_height = 576;
XSetNormalHints(x_display, win, size_hints);
XSetWMSizeHints(x_display,win , size_hints, PSize | PMinSize | PMaxSize);

XMapWindow ( x_display , win );                   // make the window visible on the screen
XStoreName ( x_display , win , "OpenGL" ); // give the window a name

/* Second window starts here */
int cnxvisuals = 0;
XVisualInfo cvisual_template;
XVisualInfo *cvisual_list;
XVisualInfo cvinfo;
Visual *cvisual;
int cdepth;

cvisual_template.screen = DefaultScreen(x_display);
cvisual_list = XGetVisualInfo(x_display, VisualScreenMask, &cvisual_template, &cnxvisuals);

XMatchVisualInfo(x_display, XDefaultScreen(x_display), 24, TrueColor, &cvinfo)

Window child = XDefaultRootWindow(x_display);
XSync(x_display, True);
cvisual = cvinfo.visual;
cdepth = cvinfo.depth;

XSetWindowAttributes  cswa;
cswa.event_mask = PointerMotionMask | KeyPressMask;
cswa.colormap = XCreateColormap(x_display, XDefaultRootWindow(x_display), cvisual, AllocNone);
cswa.background_pixel = 0;
cswa.border_pixel = 0;

child = XCreateWindow (   // create a window with the provided parameters
          x_display, parent,
          0, 0, 1024, 576, 0,
          cdepth, InputOutput,
          cvisual, CWEventMask | CWBackPixel | CWColormap | CWBorderPixel,
          &cswa );

XSync(x_display, True);

XSetWindowAttributes  xcattr;

xcattr.override_redirect = False;
XChangeWindowAttributes ( x_display, child, CWOverrideRedirect, &xcattr );

XWMHints chints;
chints.input = True;
chints.flags = InputHint;
XSetWMHints(x_display, child, &chints);

XSetNormalHints(x_display, child, size_hints);
XSetWMSizeHints(x_display,child , size_hints, PSize | PMinSize | PMaxSize);

XMapWindow ( x_display , child );                   // make the window visible on the screen
XStoreName ( x_display , child , "video" ); // give the window a name

XSelectInput(x_display, child, ExposureMask | FocusChangeMask);

int id = pthread_create(&x11loop, NULL,x11_handle_events,this);

Here is my handle events call

void* x11_handle_events(void *void_ptr)
{
    Renderer* renderer = static_cast<Renderer*>(void_ptr);
    renderer->stop = false;
    XEvent event;
    XWindowAttributes opengl_attrs;
    while(!renderer->stop)
    {
        XNextEvent(renderer->x_display, &event);
        switch(event.type)
        {
            case Expose:
            if (event.xexpose.window == renderer->child)
            {
                XRaiseWindow(renderer->x_display, renderer->win);
            }
            break;

            case FocusIn:
           if (event.xfocus.window == renderer->child)
            {
                XRaiseWindow(renderer->x_display, renderer->win);
            }
            break;

        }

        // Make sure both windows are in the same location
        XGetWindowAttributes(renderer->x_display, renderer->child, &opengl_attrs);
        XMoveWindow(renderer->x_display, renderer->win, opengl_attrs.x, opengl_attrs.y);
    }


    pthread_exit(0);
    return NULL;
}

Answer 1

The event you're looking for is ConfigureNotify

http://tronche.com/gui/x/xlib/events/window-state-change/configure.html

The X server can report ConfigureNotify events to clients wanting information about actual changes to a window's state, such as size, position, border, and stacking order. The X server generates this event type whenever one of the following configure window requests made by a client application actually completes:

snip

A window is moved by calling XMoveWindow().

The x and y members are set to the coordinates relative to the parent window's origin and indicate the position of the upper-left outside corner of the window. The width and height members are set to the inside size of the window, not including the border. The border_width member is set to the width of the window's border, in pixels.

The event mask is iirc StructureNotifyMask.

The window manager might disagree with your moving around though... but if it still doesn't work, leave a comment and we'll look deeper.