Re: DECW$SM fills up the disk---is this a known bug?

From: Martin Kirby (martinkirby12_at_yahoo.co.uk)
Date: 08/20/03 

Date: 20 Aug 2003 03:48:47 -0700

Phillip,

I can try and explain in more detail but I'm not sure how much success
I'll have :-).

When the session manager starts the screen saver it creates a window
that covers the whole screen and passes the window id of that to the
screen saver process. This is also how the style manager can run the
screen saver in a small example window. You can see this window if you
run DECW$UTILS:XLSWINS when the screen saver is displayed (having
logged in remotely). It has a name something like "Cover Dialog".

The screen saver does its screen output, bouncing lines, fireflies or
just a black area, to this window. If the window doesn't exist then it
gets repeated X window errors and just keeps trying to write to the
window (the fix is to exit after an error). The X errors are output to
the log file.

When the screen saver starts it creates an invisible window and sends
the identity of that to the session manager by sending an event to the
cover window. The session manager records the screen savers window id
and when the session manager unlocks it uses this to send an
XKillClient request, prior to deleting the cover window.

One race condition is that the session manager processing is:

1. Start processing event that caused unlock
2. Kill registered screen saver clients (multiple
       if have multi-screen)
3. Delete cover windows

If the screen-saver was just started and its processing sends the
event between (1) and (3) then the session manager never sees the
event because the window was deleted [event processing uses Xt and
that ignores events on windows the widgets of which have been deleted]
and the screen saver process is not terminated.

There are other race conditions, some of which are allowed for in the
code and some of which are not.

Hope that is some help,

Martin Kirby
DECwindows Engineering

Relevant Pages

  • Users on startup
    ... Open your Display Properties window (right click anywhere ... Screen Saver tab and within the Screen saver section you ... Accounts window will open. ...
    (microsoft.public.windowsxp.security_admin)
  • Re: Brining XP out of screen saver closes in focus application.
    ... change your screen saver if it is 3D related and/or set it to XP for testing ... When a window that does not have focus is updated by its program, ... Customize Auto Hide Taskbar Settings Right hand side ... > the "Save work before closing" prompt form Word. ...
    (microsoft.public.windowsxp.general)
  • Windows screen saver and toplevel -use option
    ... Windows calls the screen saver application with a "/p ... representation of the HWND for the small preview window shown in the ... The application is supposed to create a window ... set child [toplevel .child-use $parentID] ...
    (comp.lang.tcl)
  • Re: Uther card works on Apple IIplus with contiki
    ... >> browser and a screen saver. ... single C-Library assembler function available only for mousetext. ... Beside that the custom code does no window clipping. ...
    (comp.sys.apple2)
  • Re: DECW$SM fills up the disk---is this a known bug?
    ... OpenVMS V7.3-2/DECwindows V1.3-1. ... The problem occurs when the window the screen saver uses is deleted by ... the session manager but the screen saver is not terminated. ...
    (comp.os.vms)