On Sat 2024.04.06 at 15:40 +0000, ZenitDS wrote:
> Hello,
>
> I sent this patch two months ago but got no response. I send it
> again just in case.
> Some kind of response like, "ok, we have seen it but dont want to
> merge or mess with this", would be nice.
Hi - I saw this and was at first confused.
> When running cwm you can destroy the client window while
> you are moving or resizing it, leading to crash of the WM
> when the prop window is accessed (the one at the top-left that
> indicates the position/scale).
>
> I include a demonstration for the crash and also a patch that
> fixes it. Hopefully someone with more experience here can implement
> a better solution.
Looking again, I'm still confused as to why this sample is essentialy
pulling events from the x event queue, rather than using XWindowEvent();
it seems a contrived example. What is the use-case outside of this example?
Best regards,
Okan
> Demonstration code for the crash:
>
> #include <X11/Xlib.h>
>
> #include <err.h>
> #include <unistd.h>
>
> int
> main(void)
> {
> Display *dpy;
> Window win;
> int scr;
> XEvent ev;
>
> dpy = XOpenDisplay(NULL);
> if (!dpy)
> err(1, "XOpenDisplay");
>
> scr = DefaultScreen(dpy);
>
> win = XCreateSimpleWindow(dpy, RootWindow(dpy, scr), 0, 0, 500, 500, 0,
> 0, WhitePixel(dpy, scr));
> if (!win)
> err(1, "XCreateSimpleWindow");
>
> XSelectInput(dpy, win, StructureNotifyMask | SubstructureNotifyMask |
> ExposureMask);
> XMapRaised(dpy, win);
>
> while (1) {
> XNextEvent(dpy, &ev);
> switch (ev.type) {
> case CreateNotify:
> goto end;
> case Expose:
> XClearWindow(dpy, win);
> break;
> default:
> break;
> }
> }
> end:
> XDestroyWindow(dpy, win);
>
> XCloseDisplay(dpy);
>
> return 0;
> }
>
> Here is the patch:
>
> Index: calmwm.h
> ===================================================================
> RCS file: /cvs/xenocara/app/cwm/calmwm.h,v
> retrieving revision 1.379
> diff -u -p -r1.379 calmwm.h
> --- calmwm.h 20 Jul 2023 14:39:34 -0000 1.379
> +++ calmwm.h 6 Apr 2024 15:26:37 -0000
> @@ -481,7 +481,7 @@ struct geom screen_area(struct screen_
> struct screen_ctx *screen_find(Window);
> void screen_init(int);
> void screen_prop_win_create(struct screen_ctx *, Window);
> -void screen_prop_win_destroy(struct screen_ctx *);
> +void screen_prop_win_destroy(struct screen_ctx *, int);
> void screen_prop_win_draw(struct screen_ctx *,
> const char *, ...)
> __attribute__((__format__ (printf, 2, 3)))
> @@ -558,6 +558,7 @@ void conf_screen(struct screen_ctx
> *)
> void conf_group(struct screen_ctx *);
>
> void xev_process(void);
> +void xev_process_ev(XEvent *);
>
> int xu_get_prop(Window, Atom, Atom, long, unsigned char
> **);
> int xu_get_strprop(Window, Atom, char **);
> Index: kbfunc.c
> ===================================================================
> RCS file: /cvs/xenocara/app/cwm/kbfunc.c,v
> retrieving revision 1.174
> diff -u -p -r1.174 kbfunc.c
> --- kbfunc.c 20 Jul 2023 14:39:34 -0000 1.174
> +++ kbfunc.c 6 Apr 2024 15:26:37 -0000
> @@ -169,8 +169,8 @@ kbfunc_client_move_mb(void *ctx, struct
>
> screen_prop_win_create(sc, cc->win);
> screen_prop_win_draw(sc, "%+5d%+5d", cc->geom.x, cc->geom.y);
> - while (move) {
> - XMaskEvent(X_Dpy, MOUSEMASK, &ev);
> + while (move > 0) {
> + XMaskEvent(X_Dpy, MOUSEMASK | SubstructureNotifyMask, &ev);
> switch (ev.type) {
> case MotionNotify:
> /* not more than 60 times / second */
> @@ -197,11 +197,27 @@ kbfunc_client_move_mb(void *ctx, struct
> case ButtonRelease:
> move = 0;
> break;
> + /* check for destroy events, in case the client window
> + * gets destroyed, which forcefully closes the prop window.
> + */
> + case DestroyNotify:
> + /* set move to -1 to specify abrupt exit */
> + if (ev.xdestroywindow.window == cc->win) {
> + screen_prop_win_destroy(sc, 1);
> + move = -1;
> + } else if (ev.xdestroywindow.window == sc->prop.win) {
> + screen_prop_win_destroy(sc, 0);
> + move = -1;
> + }
> + default: /* process event anyway */
> + xev_process_ev(&ev);
> }
> }
> - if (ltime)
> - client_move(cc);
> - screen_prop_win_destroy(sc);
> + if (move != -1) {
> + if (ltime)
> + client_move(cc);
> + screen_prop_win_destroy(sc, 1);
> + }
> XUngrabPointer(X_Dpy, CurrentTime);
> }
>
> @@ -258,7 +274,7 @@ kbfunc_client_resize_mb(void *ctx, struc
>
> screen_prop_win_create(sc, cc->win);
> screen_prop_win_draw(sc, "%4d x %-4d", cc->dim.w, cc->dim.h);
> - while (resize) {
> + while (resize > 0) {
> XMaskEvent(X_Dpy, MOUSEMASK, &ev);
> switch (ev.type) {
> case MotionNotify:
> @@ -277,11 +293,26 @@ kbfunc_client_resize_mb(void *ctx, struc
> case ButtonRelease:
> resize = 0;
> break;
> + /* check for destroy events, in case the client window
> + * gets destroyed, which forcefully closes the prop window.
> + */
> + case DestroyNotify:
> + if (ev.xdestroywindow.window == cc->win) {
> + screen_prop_win_destroy(sc, 1);
> + resize = -1;
> + } else if (ev.xdestroywindow.window == sc->prop.win) {
> + screen_prop_win_destroy(sc, 0);
> + resize = -1;
> + }
> + default: /* process event anyway */
> + xev_process_ev(&ev);
> }
> }
> - if (ltime)
> - client_resize(cc, 1);
> - screen_prop_win_destroy(sc);
> + if (resize != -1) {
> + if (ltime)
> + client_resize(cc, 1);
> + screen_prop_win_destroy(sc, 1);
> + }
> XUngrabPointer(X_Dpy, CurrentTime);
>
> /* Make sure the pointer stays within the window. */
> Index: screen.c
> ===================================================================
> RCS file: /cvs/xenocara/app/cwm/screen.c,v
> retrieving revision 1.98
> diff -u -p -r1.98 screen.c
> --- screen.c 27 Jan 2022 18:45:10 -0000 1.98
> +++ screen.c 6 Apr 2024 15:26:37 -0000
> @@ -278,10 +278,15 @@ screen_prop_win_create(struct screen_ctx
> }
>
> void
> -screen_prop_win_destroy(struct screen_ctx *sc)
> +screen_prop_win_destroy(struct screen_ctx *sc, int destroy_window)
> {
> XftDrawDestroy(sc->prop.xftdraw);
> - XDestroyWindow(X_Dpy, sc->prop.win);
> + /*
> + * In case the window was already destroyed
> + * (i.e. DestroyNotify event)
> + */
> + if (destroy_window)
> + XDestroyWindow(X_Dpy, sc->prop.win);
> }
>
> void
> Index: xevents.c
> ===================================================================
> RCS file: /cvs/xenocara/app/cwm/xevents.c,v
> retrieving revision 1.150
> diff -u -p -r1.150 xevents.c
> --- xevents.c 24 Mar 2020 14:47:29 -0000 1.150
> +++ xevents.c 6 Apr 2024 15:26:37 -0000
> @@ -485,9 +485,15 @@ xev_process(void)
>
> while (XPending(X_Dpy)) {
> XNextEvent(X_Dpy, &e);
> - if ((e.type - Conf.xrandr_event_base) == RRScreenChangeNotify)
> - xev_handle_randr(&e);
> - else if ((e.type < LASTEvent) && (xev_handlers[e.type] != NULL))
> - (*xev_handlers[e.type])(&e);
> + xev_process_ev(&e);
> }
> +}
> +
> +void
> +xev_process_ev(XEvent *ev)
> +{
> + if ((ev->type - Conf.xrandr_event_base) == RRScreenChangeNotify)
> + xev_handle_randr(ev);
> + else if ((ev->type < LASTEvent) && (xev_handlers[ev->type] != NULL))
> + (*xev_handlers[ev->type])(ev);
> }
>
