Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!spool.mu.edu!snorkelwacker.mit.edu!ai-lab!life!burley From: burley@albert.ai.mit.edu (Craig Burley) Newsgroups: comp.misc Subject: Re: AT&T owns X-windows ?? (was Re: Software Patents) Message-ID: Date: 1 Mar 91 16:32:19 GMT References: <820@puck.mrcu> <1804@pdxgate.UUCP> <1991Mar1.124740.26026@pmsmam.uucp> Sender: news@ai.mit.edu Organization: Free Software Foundation 545 Tech Square Cambridge, MA 02139 (617) 253-8568 Lines: 80 In-reply-to: wwm@pmsmam.uucp's message of 1 Mar 91 12:47:40 GMT In article <1991Mar1.124740.26026@pmsmam.uucp> wwm@pmsmam.uucp (Bill Meahan) writes: In article <1804@pdxgate.UUCP> berggren@eecs.cs.pdx.edu (Eric Berggren) writes: >paj@uk.co.gec-mrc (Paul Johnson) writes: > > > Well... well... well... It's nice to see we're all exercising our legal >rights. I never knew something as ridiculous as this even existed until >X Windows became property of AT&T. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ SAY WHAT?????????? I subscribe to a large number of trade rags and have seen NO mention of this whatsoever. Are you SURE about this or are you just spreading a rumor based on something like buying X for a particular computer model? He's exaggerating. AT&T has sent letters to many vendors of X Window implementations saying they must contact AT&T about how to license ($$) use of the backing store mechanism they "invented". A simple description of backing store: if you have two windows on the screen, one partially or fully on top of the other, then you move the top one off the bottom one or close the top one, the window manager must redraw what is "on" the bottom one that you previously couldn't see (it was "occluded"). Many windowing systems simply call on the "owner" (program) of the bottom window to redraw its window -- but backing store means the window manager itself (or, perhaps, the owner of the window) simply saved the pixels that previously were occluded by the top window away in memory somewhere so they may be copied back to the display-memory pixels, saving the time it can (sometimes) take to do the redrawing from data in the owner of the window. X Windows offers backing store as an "option" for windows. The Mac uses backing store for pull-down menus (the bits under the menu are simply saved, so the menus disappear "quickly" instead of leaving a blank space on the screen while the window underneath the menu redraws). Note that backing store isn't useful if the bottom window changes while it is occluded, unless the saved bitmap is changed as well, or discarded. I don't know whether AT&T's patent specifies how updates to occluded portions of a window are handled, and it doesn't really matter to this discussion. Backing store wasn't usually implemented for windowing systems because there usually wasn't enough memory to do it (or the windowing system couldn't count on it and couldn't reclaim it if necessary). In fact, this can be a problem for a Mac with a big menu on a color screen -- it might not actually have enough memory to save the bits. However, MIT used backing store in its Lisp Machine because a) it usually had enough memory, and b) (I think) if it didn't, reclaiming memory on the fly or handling the situation in some other way was possible. X offers backing store because the server might well have plenty of memory available, and also because it never promises backing store is available -- just allows an app to say "ok to use it for this window". In other words, AT&T has patented an industry-wide switch from time over space to space over time as applied to redrawing windows on a display. Further, it isn't yet clear what this means to organizations like MIT and the Free Software Foundation that distribute X implementations for free. Obviously it would be absurd for them to pay licensing fees on products they distribute for free; so, either AT&T will continue to let them distribute for free without requiring license fees, X will have backing store removed as a capability (slowing it down greatly in many cases, I guess), or it'll no longer be distributed for free. This is all actually good news, because it is beginning to finally convince many people that the League for Programming Freedom (league@prep.ai.mit.edu) is worth joining and supporting. Believe me, we're seeing only the tip of the iceberg in software patents and user-interface copyright affecting the viability of the industry as a whole -- which is why I'm an LPF member and a volunteer contributor to the Free Software Foundation. Everyone who objects to the AT&T patent should be the former, and certainly I recommend helping out the FSF or at least ordering GNU software from them or donating funds to them, to everyone concerned with software patents. Note that the latest concern isn't so much backing store, but whether the very idea of include files (as in #include in C, INCLUDE in Fortran, &c) is patented. No definitive word on that -- yet. -- James Craig Burley, Software Craftsperson burley@ai.mit.edu