Wikipedia:Reference desk/Archives/Computing/2014 October 27

= October 27 =

How to build GRUB2
I'm currently running Ubuntu 14.10 Minimal from inside a virtual machine. I ran  and unzipped the Debian tarball. Inside it, however, there are no makefiles or configuration scripts. How in the world would this build system work? — Melab±1 &#9742; 01:55, 27 October 2014 (UTC)


 * I don't know what Canonical (or whomever maintains the APT repository) provided you when you ran the apt-get source command. But if you get GRUB2 from its official distribution channel - https://www.gnu.org/software/grub - it comes with a set of scripts that work with autotools.  The official documentation also has a link to a tutorial and build instructions from the Linux From Scratch website.
 * Try:

git clone git://git.savannah.gnu.org/grub.git
 * ...and take a look at the conf scripts. If you aren't familiar with GNU autotools, our article is a good introduction.
 * Nimur (talk) 02:45, 27 October 2014 (UTC)
 * I'm not sure how easily the GNU version will build though. I might need to make changes to it and all and the APT version doesn't provide a diff file. — Melab±1 &#9742; 03:41, 27 October 2014 (UTC)
 * You can diff -rq the GNU grub folder and the apt-get grub folder to see the differences. Chances are pretty high that grub itself is no different from mainline.  Debian and Ubuntu (and other "distributions") probably provide a complicated variant of the menu.lst configuration (or whatever the equivalent is, now that we've got GRUB2); but there's little reason for them to significantly modify the GRUB source itself.  Nimur (talk) 03:57, 27 October 2014 (UTC)

MS outlook & address book transfer with containing folder integrity
Is there a way to transfer MS outlook/outlook express and MS addressbook w/o loosing folder integrity? I used to transfer outlook and address book by transferring the containing folder to another computer but folders from the original PC are lost this way.TMCk (talk) 02:11, 27 October 2014 (UTC)


 * This might help: How to back up and to restore Outlook Express data. Mitch Ames (talk) 12:20, 27 October 2014 (UTC)


 * Thanks. Next time I'll try it with an .csv file instead of wab. Guess that should work :) TMCk (talk) 16:52, 27 October 2014 (UTC)

Why does Android not use X11
Why does Android not use X11 for graphics? Is Android's graphics system superior to X11 for mobile devices? --RM — Preceding unsigned comment added by 121.247.216.191 (talk) 11:33, 27 October 2014 (UTC)


 * I'm no expert on X or on modern GUI API's, so this is a pretty ill-informed response, but I think the answer is basically, yes, the new graphics systems are superior. X strikes me as being pretty old and obsolete; if it weren't for graphical Linux I don't think anybody would be seriously using it.  More importantly, modern GUIs have lots of must-have bells and whistles -- transparency, whiz-bang animations, etc. -- that I suspect are only reasonably achievable with heavy ingrained support all through the infrastructure.


 * (I've probably been grossly unfair to X11 in this response, but perhaps my heresy will goad someone who knows into providing the counterargument.) —Steve Summit (talk) 18:36, 27 October 2014 (UTC)
 * Why does Android do anything? Because Google so decrees.  To first order, Google has performed a technical evaluation and made decision that X11 is not part of their Android strategy.  In this particular instance, some of their justifications are made public; and some of their reasoning must be surmised by observing industry trends at large.
 * Start by reading the official Android Graphics Design Overview. If you're a little bit more technical, Google hosts an "unofficial" deep-dive presentation on Android Graphics Architecture.  Android has taken the approach of encouraging graphical applications to write data directly into a frame buffer.  Frame-buffers are wrangled by a very minimalistic compositing architecture, suitable for hardware with severe constraints.  This is conducive to hardware acceleration, but it is antithetical to a multi-tasking style "window manager" - and because X11 was structured to encourage multiple simultaneous clients all sharing a small part of a giant frame-buffer, the chief advantages are not useful for these kinds of platforms.
 * Read about X11. X11 is a protocol - and in order to correctly satisfy that protocol, the display client must necessarily perform some very inefficient bitmap-based operations.  In exchange, the work of graphical composition is highly abstracted - it's great for inter-platform operability, because almost all the graphical work is very generalized.  It's great for running multiple applications - even if the source-data for several of those operations is provided over a network layer.  X11 is terrible for things like memory-efficiency or avoiding expensive deep-copies of redundant data.  As a design-decision, think about how often you would want your Android telephone to render graphical application-data from an HP-UX server - and how much performance you'd trade off for that feature!
 * X11 can run on Android: but X11 doesn't take advantage of modern hardware capabilities.
 * Even on desktop platforms, many modern operating systems are moving away from X windowing. Most Linux distributions are moving towards Wayland or Mir.  OS X has moved to a totally different graphics architecture, to the extent that Xquartz is no longer distributed with the operating system.  Other Unix platforms - those few that are left! - are becoming more rare; and they probably continue to run X with Gnome or with some of the more insular window managers; but these platforms rarely get major overhauls - they'll probably stick with whatever worked in 1997, until it becomes cost-prohibitive to replace those dinosaur hardwares that run mission-critical systems.  A while back, I toured an air traffic control facility, and those folks were running some kind of SGI workstations with the logos covered by sticker-labels from a major aerospace conglomerate!  Full color graphics workstations that will keep ticking for fifty-odd years...
 * So, I won't say that X11 is dead - but it's widely acknowledged that new graphical systems are using newer software technology that takes advantage of a lot of lessons-learned with regard to platform-portability and hardware optimization.
 * Nimur (talk) 18:38, 27 October 2014 (UTC)


 * Readers of Steve's and Nimur's answers, with which I entirely agree, might be struck with a tad of cognitive dissonance - if X is so clunky, how come it's still used? As Steve says, it's chiefly Linux now, and as Nimur says, they're moving away too. But applications on Linux, which run on the X desktop, mostly don't explicitly use X itself any more - which will mean the transition to post-X display management (Wayland, Mir) won't be super hard.  In the olden days of Unix(alike) GUI programming, one did write programs which used the X libraries directly, and if one used a (slightly) higher level toolkit library like Xaw/Xt and Xm (motif) one still made X calls too. But programs that work like that are pretty thin on the ground, at least on the Linux desktop. Most are written to more capable toolkits (of which GTK+ and Qt are have between them the lion's share); these toolkits are written to be platform agnostic, which forces them to be complete (that is, programs never have to explicitly call the underlying GUI system - X on Unix, GDI et al on Windows, etc.). They're more than a thin layer over X - they do most of the work themselves. X is lacking in many areas - e.g. its own drawing system is pretty rudimentary, lacking a modern rich drawing toolkit with Porter-Duff, anti-aliasing, and decent font rendering. A modern program like Firefox does the rendering client-side, with Pango/Freetype for text rendering and a library like Cairo for high-quality drawing. They then blit that completed image to the X window wholesale. Video games use another path - they typically write with OpenGL into a buffer given them by the video driver, again with no X calls being made. Right now X still owns the screen and all the input devices, so the bottom surface of toolkits running on X still have to make X calls to pump events, create windows, and blit chunks of display around. The migration to Mir or Wayland removes X from this central role (the Mir or Wayland server will do that instead). An X server will work, but it will be subordinate to the real display server (the way an X server on OS-X or Windows already is), and will survive (for a time, I guess) to support legacy applications and remoting. -- Finlay McWalterᚠTalk 13:05, 28 October 2014 (UTC)

Returning old dock appearance in Yosemite
I Just upgraded to Yosemite. Looks like they fixed the terrible Maverick menu problems! Question: Is there any way to return to the old dock appearance? The new light brown dock is quite a downgrade.--71.167.166.18 (talk) 13:37, 27 October 2014 (UTC)
 * There doesn't seem to be any way to revert to the 3D dock appearance (a la Leopard to Mavericks), however it if is the color you don't like, I believe that is based on a heavily blurred translucency effect on the desktop wallpaper, see samples in the Ars Technica review. --Canley (talk) 03:27, 29 October 2014 (UTC)

Is Windiff a better diff tool?
For example, to compare the text as follows

old text  new text aaa       ccc bbb       bbb ccc       aaa

it seems that Windiff can find out that "aaa" and "ccc" are swapped and give output similar to this (note that the lines are cross! See this too)

But I have never seen other diff tool can do that. Instead, they output like this

(I don't have Windiff installed on my "Linux" box)

So my questions are:
 * 1. Does Windiff really have that kind of ability?
 * 2. If so, what is the alternative tool for Linux?

Justin545 (talk) 13:58, 27 October 2014 (UTC)


 * I recently discovered Meld, http://meldmerge.org/, which has a Windows version which does a far better job than windiff. It is excellent for getting two versions of a file that have diverged slightly back in sync. It is a standard Linux tool. You may want to try it. It passes your test. --NorwegianBluetalk 19:05, 28 October 2014 (UTC) EDIT: The image you linked to appears to have been created with Meld. --NorwegianBluetalk 19:10, 28 October 2014 (UTC)


 * Yes, the image I linked was created by Meld installed on my own Linux machine. Meld may have better graphical presentation than Windiff, but my concern is the diff algorithm they use. In the case above when the positions of two text blocks are swapped, Windiff seems able to find out two swapped text blocks and correctly show their relation (that is, it could detect text move correctly even if two text blocks are swapped in position). On the other hand, Meld only shows me that the text block is first get deleted and then re-inserted at the other place, which means the diff algorithm Meld uses fail to detect text block move when text blocks are swapped! - Justin545 (talk) 02:09, 29 October 2014 (UTC)


 * Comparison of file comparison tools may be helpful. That article says that Meld can detect moved lines, but I wasn't able to coerce it into doing so in a simple test like yours. (edit: I changed the article.) WinMerge does detect moved blocks (if you enable that in the Options dialog), but only by using a different background color for those blocks. It doesn't draw a line to the location in the other file like Windiff does, though I've never found those lines useful since they end up as spaghetti in all but the simplest cases. -- BenRG (talk) 23:17, 29 October 2014 (UTC)

Facebook group and search ?
what is suggested groups in facebook and how is the suggested groups list created, what is the algorithm behind it .I see that a person whose timeline i am frequently visitng and who was never my friend on fb and do not share any common friend with me that is a member of public but the groups to which that belong are appearing in my suggested groups list how and why is this happening.I have graph search enabled or turned on.Can that person sense somehow directly/indirectly that i am very frequently visiting that guys page whenever i type the first letter of his name in search box on top i am getting his name with profile and pic as suggested searck although he is a member of public in fb terms whats the reason for this and how is it so what is the significance.117.248.136.24 (talk) 14:56, 27 October 2014 (UTC)

matrix in latex conflict with packages
In preparing my presentation I have a problem in writing a matrix Array, tabular are not working gives an error message .I m using the following packages: \usepackage[screen,panelright,gray,paneltoc,sectionbreak]{pdfscreen}%È±Ê¡×´Ì¬ÎªBlue,Ñ§Êõ±¨¸æÍÆ¼ö²ÉÓÃ"gray"¡£ \usepackage{xspace,colortbl} \usepackage{fancyvrb} \usepackage{graphicx} \usepackage{CJK} \usepackage{color} \usepackage{times} \usepackage{type1cm} \usepackage{tabls} \usepackage{background} \usepackage{geometry} \usepackage{hyperref} \usepackage[display]{texpower} \usepackage{manfnt} \usepackage{hypbmsec} \usepackage{pause} \usepackage{amssymb, latexcad, lgrind} \usepackage{tikz} \usepackage{amsmath} — Preceding unsigned comment added by 182.187.55.132 (talk) 23:40, 27 October 2014 (UTC)


 * There really isn't enough info here, unless someone happens to have had the exact same problem (unlikely). Please try to give us a complete minimal example of your problem, as described here . Often the process of making the minimal example will help you solve your own problem. If not, then at least it helps us help you. Also you could post the exact error message. You might also try asking this question at latex.stackexchange.com. If you are getting an error message and the code is not compiling, it could be a package conflict, but it is more likely a syntax error. Pending any more information from you, I'd recommend trying the Beamer_(LaTeX) package for presentations. It plays well with most other packages, but gives completely useless error logs :) SemanticMantis (talk) 15:38, 28 October 2014 (UTC)

It is not a syntax error, and surly a package conflict. Same code works when pasted in an other tex file with different package. I think userpackage CJK, hyperref or background are creating problems. I want to write a some command for matrix which run with these packages. — Preceding unsigned comment added by 39.35.166.197 (talk) 16:10, 29 October 2014 (UTC)
 * Ok, well you might check into these alternative for 'array' [], or look for alternatives to the package(s) that are causing problems. That's all the help I can give without a minimal example. Good luck! SemanticMantis (talk) 16:40, 29 October 2014 (UTC)

Any of this do not work, with error message "missing $ inserted a\begin{Vmatrix}". If I use $ sign or \[, then error message is ,"Extra } or forgotten $\alpha\beta^{*}\\". Also I want to tell u that, the command \begin{figure} do not work.\begin{tikzpicture} goes well, but  \Line do not work, but \draw works well. — Preceding unsigned comment added by 182.187.11.98 (talk) 21:41, 29 October 2014 (UTC)
 * \begin{figure} should work with every package! So I suspect that that one of your packages is rather badly written. You could consider filing a bug report at CTAN. If you didn't get the package from CTAN, that's a bit of a bad sign at the start. In Beamer, the figure environment is re-defined so that it is not a 'float', so that you can place each figure exactly where you want to (not the normal case for figures in LaTeX). My guess is that your presentation package is re-defining the figure environment in a way that makes it unusable with some of the other packages. If you have a deadline for your presentation, I encourage you to seek alternate packages or simply drop some (e.g. do you really need background images?) in order to get your work to compile. Bug hunting is not as fun as the work you want to present! Anyway, if you post a small complete file that fails (all headers, a few commands, end document), I might be able to help, but not without that. If you do post that, you can type in '' to notify me, otherwise I will probably miss it. SemanticMantis (talk) 14:41, 30 October 2014 (UTC)

Thank u, I have found the package by creating an other latex file containing only a table and compiling by exluding one one package. The package which is creating problem is \usepackage{colortbl}. — Preceding unsigned comment added by 39.35.46.26 (talk) 16:08, 30 October 2014 (UTC)