Shallow Thoughts : tags : emacs

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Sun, 14 Sep 2014

Global key bindings in Emacs

Global key bindings in emacs. What's hard about that, right? Just something simple like

(global-set-key "\C-m" 'newline-and-indent)
and you're all set.

Well, no. global-set-key gives you a nice key binding that works ... until the next time you load a mode that wants to redefine that key binding out from under you.

For many years I've had a huge collection of mode hooks that run when specific modes load. For instance, python-mode defines \C-c\C-r, my binding that normally runs revert-buffer, to do something called run-python. I never need to run python inside emacs -- I do that in a shell window. But I fairly frequently want to revert a python file back to the last version I saved. So I had a hook that ran whenever python-mode loaded to override that key binding and set it back to what I'd already set it to:

(defun reset-revert-buffer ()
  (define-key python-mode-map "\C-c\C-r" 'revert-buffer) )
(setq python-mode-hook 'reset-revert-buffer)

That worked fine -- but you have to do it for every mode that overrides key bindings and every binding that gets overridden. It's a constant chase, where you keep needing to stop editing whatever you wanted to edit and go add yet another mode-hook to .emacs after chasing down which mode is causing the problem. There must be a better solution.

A web search quickly led me to the StackOverflow discussion Globally override key bindings. I tried the techniques there; but they didn't work.

It took a lot of help from the kind folks on #emacs, but after an hour or so they finally found the key: emulation-mode-map-alists. It's only barely documented -- the key there is "The “active” keymaps in each alist are used before minor-mode-map-alist and minor-mode-overriding-map-alist" -- and there seem to be no examples anywhere on the web for how to use it. It's a list of alists mapping names to keymaps. Oh, clears it right up! Right?

Okay, here's what it means. First you define a new keymap and add your bindings to it:

(defvar global-keys-minor-mode-map (make-sparse-keymap)
  "global-keys-minor-mode keymap.")

(define-key global-keys-minor-mode-map "\C-c\C-r" 'revert-buffer)
(define-key global-keys-minor-mode-map (kbd "C-;") 'insert-date)

Now define a minor mode that will use that keymap. You'll use that minor mode for basically everything.

(define-minor-mode global-keys-minor-mode
  "A minor mode so that global key settings override annoying major modes."
  t "global-keys" 'global-keys-minor-mode-map)

(global-keys-minor-mode 1)

Now build an alist consisting of a list containing a single dotted pair: the name of the minor mode and the keymap.

;; A keymap that's supposed to be consulted before the first
;; minor-mode-map-alist.
(defconst global-minor-mode-alist (list (cons 'global-keys-minor-mode
                                              global-keys-minor-mode-map)))

Finally, set emulation-mode-map-alists to a list containing only the global-minor-mode-alist.

(setf emulation-mode-map-alists '(global-minor-mode-alist))

There's one final step. Even though you want these bindings to be global and work everywhere, there is one place where you might not want them: the minibuffer. To be honest, I'm not sure if this part is necessary, but it sounds like a good idea so I've kept it.

(defun my-minibuffer-setup-hook ()
  (global-keys-minor-mode 0))
(add-hook 'minibuffer-setup-hook 'my-minibuffer-setup-hook)

Whew! It's a lot of work, but it'll let me clean up my .emacs file and save me from endlessly adding new mode-hooks.

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[ 16:46 Sep 14, 2014    More linux/editors | permalink to this entry | comments ]

Tue, 29 Apr 2014

The evil HTML double-dash problem in Emacs is still there

Long ago (in 2006!), I blogged on an annoying misfeature of Emacs when editing HTML files: you can't type double dashes. Emacs sees them as an SGML comment and insists on indenting all subsequent lines in strange ways.

I wrote about finding a fix for the problem, involving commenting out four lines in sgml-mode.el. That file had a comment at the very beginning suggesting that they know about the problem and had guarded against it, but obviously it didn't work and the variable that was supposed to control the behavior had been overridden by other hardwired behaviors.

That fix has worked well for eight years. But just lately, I've been getting a lot of annoying warnings when I edit HTML files: "Error: autoloading failed to define function sgml_lexical_context". Apparently the ancient copy of sgml-mode.el that I'd been using all these years was no longer compatible with ... something else somewhere inside emacs. I needed to update it.

Maybe, some time during the intervening 8 years, they'd actually fixed the problem? I was hopeful. I moved my old patched sgml-mode.el aside and edited some files. But the first time I tried typing a double dashes -- like this, with text inside that's long enough to wrap to a new line -- I saw that the problem wasn't fixed at all.

I got a copy of the latest sgml-mode.el -- on Debian, that meant:

apt-get install emacs23-el
cp /usr/share/emacs/23.4/lisp/textmodes/sgml-mode.el.gz ~/.emacs-lisp
gunzip ~/.emacs-lisp/sgml-mode.el.gz
Then I edited the file and started searching for strings like font-lock and comment.

Unfortunately, the solution I documented in my old blog post is no longer helpful. The code has changed too much, and now there are many, many different places where automatic comment handling happens. I had to comment out each of them bit by bit before I finally found the section that's now causing the problem. Commenting out these lines fixed it:

   (set (make-local-variable 'indent-line-function) 'sgml-indent-line)
   (set (make-local-variable 'comment-start) "")
   (set (make-local-variable 'comment-indent-function) 'sgml-comment-indent)
   (set (make-local-variable 'comment-line-break-function)
        'sgml-comment-indent-new-line)

I didn't have to remove any .elc files, like I did in 2006; just putting the sgml-mode.el file in my Emacs load-path was enough. I keep all my customized Emacs code in a directory called .emacs-lisp, and in my .emacs I make sure it's in my path:

(setq load-path (cons "~/.emacs-lisp/" load-path))
And now I can type double dashes again. Whew!

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[ 12:42 Apr 29, 2014    More linux/editors | permalink to this entry | comments ]

Wed, 05 Jun 2013

Stop Emacs from invoking a browser

After upgrading my OS (in this case, to Debian sid), I noticed that my browser window kept being replaced with an HTML file I was editing in emacs. I'd hit Back or close the tab, and the next time I checked, there it was again, my HTML source.

I'm sure it's a nice feature that emacs can show me my HTML in a browser. But it's not cool to be replacing my current page without asking. How do I turn it off? A little searching revealed that this was html-autoview-mode, which apparently at some point started defaulting to ON instead of OFF. Running M-x html-autoview-mode toggles it back off for the current session -- but that's no help if I want it off every time I start emacs.

I couldn't find any documentation for this, and the obvious (html-autoview-mode nil) in .emacs didn't work -- first, it gives a syntax error because the function isn't defined until after you've loaded html-mode, but even if you put it in your html-mode hook, it still doesn't work.

I had to read the source of sgml-mode.el. (M-x describe-function html-autoview-mode also would have told me, if I had already loaded html-mode, but I didn't realize that until later.) Turns out html-autoview-mode turns off if its argument is negative, not nil. So I added it to my html derived mode:

(define-derived-mode html-wrap-mode html-mode "HTML wrap mode"
  (auto-fill-mode)
  ;; Don't call an external browser every time you save an html file:
  (html-autoview-mode -1)
)

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[ 22:48 Jun 05, 2013    More linux/editors | permalink to this entry | comments ]

Sat, 12 Jan 2013

Integrating graphics with text in Emacs

I discussed Emacs's artist-mode a few days ago as a simple, but incomplete, solution to the problem of sketching graphs while taking notes during a math class. But I've found a much better way, one that allows for including any images -- drawings, photos, or screenshots. It took a little work and some custom .emacs code, but I love the result.

Iimage mode

[iimage-mode: images displayed inline in Emacs] The key is iimage-mode, which displays inline images. In this mode, you put a line in your buffer with a reference to your image file, something like this:

file://myimage.jpg
and Emacs will replace it with the contents of that image. Marvellous!

You can use other patterns for filenames as well, but I'm fine with using URLs. Note there are only two slashes in file:// -- it's a local file in the same directory as the text file being edited.

It's a little tricky to enable it. The docs are not entirely clear on the differences between iimage-mode, turn-on-iimage-mode and iimage-mode-buffer. I found I could get a file that already had existing images to display them with:

  (turn-on-iimage-mode)
  (iimage-mode-buffer t)

Very cool! But too much to type every time. And to use it for note-taking, I needed a way to say, "Create a new image here, let me edit it, then display the image I just edited inline."

Enabling iimage-mode automatically

First, I wanted iimage mode displayed automatically on files in my note-taking directories. I normally use text-mode for these files, with spell checking and line wrapping turned on (auto-fill mode). So I defined a new minor mode based on text-mode:

(define-derived-mode text-img-mode text-mode "Image display mode"
  (auto-fill-mode)
  (turn-on-iimage-mode)
  (iimage-mode-buffer t)
  )

Then I wanted this mode to be called whenever I'm editing a file in my classes directory. So I added it to my auto-mode-alist:

(setq auto-mode-alist
   ...
      (cons '("Docs/classes/" . text-img-mode)
   ...
      auto-mode-alist) )

Inserting a new image

Next, I needed a way to insert an image URL into the buffer and call up an image editor on it. I shouldn't have to type the filename twice and keep track of it; that's what computers are for.

And I needed a drawing program. As a longtime GIMP geek, most of my computer drawing has been in GIMP. But GIMP is overkill for calling up a quick sketch window. I was tempted to use TuxPaint; it's a good sketching app even if you're not five years old, and it's fun and easy to use. But by default, TuxPaint has some features that get in the way of note-taking, like distracting sound effects. I'm sure it's possible to turn those off, and I do plan to investigate that.

I saw a reference to pinta as a lightweight drawing app, but it required a boatload of Mono libraries that I don't otherwise need, and Krita has the same problem with KDE services. So I opted for MyPaint. It works okay, though it's rather slow to start up and has some other issues, so I'm still hoping to find a more lightweight sketching app.

In any case, I fiddled around with start-process until I figured out how to use it to start a program. Then I wrote a little function that lets the user pick a filename, inserts a URL to that filename into the buffer, then calls up mypaint on the file.

(defun img ()
  "Prompt for a filename, then call up mypaint to create an image"
  (interactive)
  (let ((imgfile (read-string "Filename? " "xxx.jpg" 'my-history)))
    (insert "\nfile://" imgfile "\n" )
    (start-process "mypaint" nil "/usr/bin/mypaint" imgfile)
  ))

Worked fine! I can run M-x img, be prompted for a filename, and get a mypaint window where I can make my sketch.

Noticing that a new image has been added

But wait. I finish sketching, write the file and quit mypaint ... and the buffer still shows something like file://xxx.jpg, even if it's showing other images inline. I needed a way to tell it to refresh and load any new images. (I considered having emacs wait for mypaint to exit, but decided I might sometimes want to keep editing while mypaint was still up.)

M-x eval-expression (iimage-mode-buffer t) will do that, but that's a lot of typing to do. Obviously, I needed a key binding.

Strangely enough, C-c i wasn't taken for text buffers, so that seemed like a natural. So I added a key binding to the end of the text-img-mode. iimage-mode-buffer requires that t argument -- it gives an error without it -- so the key binding looks a little more complicated than one that just calls a simple function. I added it to the end of my text-img-mode function.

(define-derived-mode text-img-mode text-mode "Image display mode"
 ...
  (local-set-key "\C-ci" 
    (lambda () (interactive) (iimage-mode-buffer t)))
  )

But after using it a bit, I discovered that this didn't reload images if I edited them a second time. Fortunately, vwood had the answer:

(defun refresh-iimages ()
  "Only way I've found to refresh iimages (without also recentering)"
  (interactive)
  (clear-image-cache nil)
  (iimage-mode nil)
  (iimage-mode t)
  (message "Refreshed images")
 )

I added the message at the end, since otherwise the function left a distracting "Toggling iimage-mode off; better pass an explicit argument" error.

Then the key binding in my text-img-mode became

(local-set-key "\C-ci" 'refresh-iimages)

Inserting a screenshot

Wait -- one more thing. As I actually used text-img-mode to take notes, I discovered that taking screenshots would actually be much more useful than making my own drawings. Then I could copy small sections of the slides and graphs into my notes at the appropriate place, without needing to copy equations at all.

Why not write a function to allow that? The unpleasantly named scrot program fills the bill nicely, and gives me a choice of clicking in a window or dragging out an area of the screen.

(defun screenshot ()
 "Prompt for a filename, then call up scrot to create an interactive screenshot"
  (interactive)
  (let ((imgfile (read-string "Filename? " "scr.jpg" 'my-history)))
    (insert "\nfile://" imgfile "\n" )
    (start-process "scrot" nil "/usr/bin/scrot" "-s" imgfile)
  ))

This turned out to be so useful that I added a key for it in text-img-mode:

(local-set-key "\C-cs" 'screenshot)

I'm so happy with the result! Iimage mode is working great, and having text and images together is turning out to be perfect for note-taking.

My only problem now -- okay, I admit it -- is a tendency to get so excited over inserting screenshots that I get distracted and forget to actually listen to the lecture. I'm sure I'll get over that, but for now, Thank goodness vlc is good at skipping back!

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[ 13:42 Jan 12, 2013    More linux/editors | permalink to this entry | comments ]

Thu, 10 Jan 2013

ASCII graphics in Emacs with Artist Mode

I found a cool package in Emacs the other day: Artist Mode. It lets you draw ASCII graphics in your text file.

I was actually looking for the solution to a different problem: taking notes in a math-intensive Coursera class. I've been taking notes in Emacs, but a text editor is awkward for equations and even more awkward for graphs.

What I really wanted was something like the old Claris Works (or so I'm told; I never used it myself) -- something that's primarily a text editor but lets you drawings, equations, and tables when you need to. In theory, word processors like LibreOffice could do that, but in practice they're not very good at switching modes, nor at integrating several types of media into one document. Texmacs is great for the equations and apparently it can do tables too, but it can't do freehand drawing.

And none of these programs is very configurable -- I can't use my fast, comfortable Emacs bindings while typing, and that's a deal-breaker for me, because being able to make corrections quickly makes a huge difference in my typing speed. LibreOffice's key bindings are only partially configurable, and after you've spent half a day chasing down all the action names you need (the ones that are actually available), you upgrade to a newer version and discover you have to do it all over again because there's no way to migrate configuration files. Even Texmacs, ironically, is no better: the documentation claims it's possible to configure key bindings, but it doesn't appear anyone has ever succeeded in figuring out how.

Anyway, ASCII graphics aren't the ultimate solution to note-taking. And I've found a better solution for that, while I'll write about separately. But for now, Artist Mode is just so cool I had to share it.

Enable it by running M-x artist-mode. You can immediately start drawing in your buffer with the mouse. Whatever you draw gets turned into ASCII graphics.

For note-taking, it's fine for scribbling the rough shape of a curve. It takes no time to mouse in a little sketch like

       |                               .. 20
       |                              ..
       |                            ...
    10 |.                          ..
       |..                       ...
       | ...                   ...
       |   ..              ....
       |    .....      .....
       |    ............
       |.....        .............
       +-------------------------------------

It even has primitives (middleclick to get a.menu) for things like lines, rectangles and circles, and for filling regions. When you're done drawing, M-x artist-mode goes back to whatever mode you were using before.

I probably won't use it very much for note taking. But there are times when I've wanted to draw ASCII graphics -- a laborious process in ordinary text modes -- and other times when it would just be fun to play around with my buffer. I'm happy to know about Artist Mode. I may not need it often, but it sure is fun to use now and then.

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[ 20:02 Jan 10, 2013    More linux/editors | permalink to this entry | comments ]

Wed, 02 Jan 2013

Customize the Emacs modeline color

[Emacs with colored mode lines]

I wrote last week about how to customize syntax highlighting colors in Emacs. And as part of that, I ditched the color theme I'd been using and let Emacs go back to its default colors.

Which mostly was fine, except that when I split the window into two windows, to look at two files at once or two different parts of the same file, the separator between the two windows -- the mode line -- was the same grey as Emacs's normal background, so it wasn't very obvious where the window split was.

A web search turned out lots of different ways to set the mode line color. Many of them involve color themes and are fairly complicated. Here's the simplest method I found:

(set-face-foreground 'modeline "white")
(set-face-background 'modeline "purple")
(set-face-background 'modeline-inactive "light blue")

You can set your active mode line to a pretty color, so it stands out a bit and makes it easy to tell which of the visible windows is the one you're actually typing in, and set the inactive mode lines -- windows that are visible but you arne't actually typing in -- to a less striking color.

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[ 13:50 Jan 02, 2013    More linux/editors | permalink to this entry | comments ]

Sun, 23 Dec 2012

Customizing syntax highlighting colors in Emacs

Emacs has wonderful syntax highlighting. Words will be displayed in different colors depending on their syntax and the mode of the current file -- for instance, in C code, keywords of the language are highlighted in one color, comments in another, strings in a third.

The problem comes when the colors aren't right. Like that awful gold color that the flyspell spell checker uses for some words. Against a light background it makes the words almost impossible to read. I've struggled for years trying to set up custom color schemes to get around that problem, but I finally learned a simpler way to handle it when you see something in a color you want to change.

The trick is to find out what face you need to change. "Face" to emacs means more than a font face like Sans or Lucida; it means a collection of information about how characters are displayed, including font face, weight, slant, color and other attributes.

[Emacs' customize-face screen] When you see something displayed in a color you don't want, place the cursor somewhere in the word. type C-u C-x = will get you the face used, along with all sorts of information about it and a handy Customize what to show link. Or you can go straight to the Customize screen with M-x customize-face -- hit return to customize the face at point (the cursor location).

In the customize-face screen, there's no GUI to choose colors, but you can edit color names. Emacs lists "red" as the foreground color; if you change it to "blue" you'll see a preview of how it will look. Color names come from /etc/X11/rgb.txt, and there are various programs like xcolorsel that will show them -- or better yet, see Wikipedia's X11 color names chart.

Once you've chosen a color, the Save for future sessions button will add a section to your .emacs file with the appropriate elisp code. Of course, you can move this code elsewhere as well. I have a somewhat complex .emacs setup, so I've moved the code into another file. Strangely, I found that my .Xdefaults background color setting no longer worked once I started using custom-set-faces, so I added a line for that as well.

(set-background-color "grey90")
(custom-set-faces
 '(flyspell-duplicate ((((class color)) (:foreground "red" :underline t :weight bold))))
 '(font-lock-comment-face ((((class color) (min-colors 88) (background light)) (:foreground "blue"))))
 )

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[ 13:59 Dec 23, 2012    More linux/editors | permalink to this entry | comments ]

Mon, 16 Jul 2012

Editing tab-separated files with Emacs

I wanted to keep maintenance records for my car in a local file. Things like the date and mileage of the last oil change, when the timing belt was replaced, stuff like that.

I didn't want to hassle with databases or spreadsheets -- a simple, human-readable file is a lot easier to deal with. But I also wanted it in a predictable format so it could potentially be parsed later: I might some day want to write a program that keeps track and reminds me when I need to do things. (You'd think this program would already exist, but curiously, I haven't found one.)

So, something like:

7/9/12 <TAB> 86306 <TAB> Oil change, filter
6/11/12<TAB> 84813 <TAB> Smog test

Simple, right? And super easy just to type in in a text editor.

Well ... in emacs, maybe not. As an editor oriented toward programmers, emacs tends to prefer spaces instead of tabs ... and that's normally the way I prefer it. Tabs are a bad idea in most software projects, unless everybody on the project has already agreed on a tab style and width. (The complete tabs-vs.spaces religious war is beyond the scope of this article, but take my word for it that they can be a problem.)

But this wasn't code, and I needed an easy way to get those tabs into the file. Of course, I could quote them directly: type Ctrl-Q TAB every time I wanted a tab. But I knew I wouldn't remember to do that every time.

So I needed a local variables line, sometimes called a modeline, to flag this file as different from any other file I edit -- in this one, I really do want a TAB when I hit the TAB key.

My first try put this as the first line of the file:

-*- Mode: Text; indent-tabs-mode: t -*-
(Actually, my first try omitted the -*- part and didn't work at all, but let's ignore that part.)

When I re-loaded the file, emacs loaded it in text mode, and indent-tabs-mode was set to t if I checked it with describe-variable. Great! I could add new lines at the end of the file, and when I hit TAB, emacs inserted tabs. But wait -- if I added a line at the beginning of the file, and typed something lke 7/9/12<TAB> ... it inserted a space, not a tab.

It turns out indent-tabs-mode isn't really documented. If you check the help, it says:

Indentation can insert tabs if this is non-nil
-- note that "can" insert, not "will" insert, a tab. So how could I get emacs to really insert a tab, every time I hit the tab key?

Well, of course, I could bind the TAB key to "self-insert". But I didn't want to change it for every file, only for this one. how could I make that happen as part of a local variables line? The local variables line documentation shows how to set variables or file modes, but it looks like you can't bind keys or run functions.

Well, you can't run functions, but you can define a new mode that runs functions. At the suggestion of some helpful people on the #emacs IRC channel, I defined a new mode in my .emacs, like this:

(define-derived-mode tabbed-mode text-mode "Tab separated mode"
  (local-set-key (kbd "TAB") 'self-insert-command)
  )

Then in the file, I put this line:

-*- Mode: Tabbed -*-

Now, every time I load the file, emacs turns on tabbed mode -- which is just text mode except that the TAB key always inserts a tab.

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[ 19:35 Jul 16, 2012    More linux/editors | permalink to this entry | comments ]

Thu, 14 Jul 2011

Using default-frame-alist to specify Emacs window size, position and font

Seems like every few years I need to change the way I specify my preferred emacs fonts and window sizes.

Historically this all used to happen from one file, ~/.Xdefaults, where you set up your defaults for all X programs. In a way that was nice, since you could set up defaults and see the same font everywhere. On the other hand, it made for a huge, somewhat hard to read file, and it's increasingly out of favor on modern desktops, with modern toolkits like GTK just ignoring it.

Emacs still reads Xdefaults -- but only sort of. A lot of the values I used to set there no longer work properly. Some time ago I commented out my various attempts at setting emacs font, like

Emacs*font: -*-clean-bold-*-*-*-13-*-*-*-c-*-*-*
Emacs*font: DejaVu Sans Mono-10:bold
Emacs*font: clean-13:bold
Wmacs*font: Liberation Mono-10:bold
Emacs.font: 7x13bold
Emacs.faceName: Dejavu-10:style=bold
since none of them worked, and worked out a way of setting fonts inside my .emacs file:
(set-face-attribute 'default nil :font "Terminus-12:bold")

That worked to set the font, but it had another annoying attribute: it doesn't happen at startup, so it messed up my window size. See, emacs would start up, see the size I specified in .Xdefaults:

Emacs*geometry: 80x45
and try to set that. But it hadn't read .emacs yet, so it was still using whatever its default font and size is, and that's huge -- so 45 lines made a window too tall to fit on my laptop screen. Emacs would then shrink its window to fit the screen (41 lines). Only then would it open .emacs, whereupon it would see the set-face-attribute, change the font, and resize the window again, much, smaller, still 41 lines.

What a pain!

The emacs manual, in addition to talking about these various Xdefaults properties and command-line options, does mention a couple of variables, set-screen-height and set-screen-width, that looked promising. I tried putting (set-screen-height 45) in my .emacs right after I set the font -- no dice. Apparently that doesn't work because by the time those are read, emacs has already decided that 41 lines is as big as the window can possibly be.

Here's the answer: another variable that goes inside .emacs, default-frame-alist, but this one can override that maximum-height decision that emacs has already made. Here's an example of it in some useful defaults for emacs, and based on that, I was able to come up with this:

(setq default-frame-alist
      '((top . 10) (left . 2)
        (width . 80) (height . 53)
        (font . "terminus-iso8859-1-bold-14")
        ))

Curiously, that height setting, 53, needs to be 3 more than what I actually want according to the size emacs reports to the window manager. So don't take the number too seriously; just try numbers a little bigger than what you actually want until you get the size you're after. The font setting is the X font specifier: I ran xlsfonts | grep -i terminus | grep 14 then picked one of the simpler of the lines it printed out, but you can use a full specifier like -xos4-terminus-bold-r-normal--14-140-72-72-c-80-iso8859-1 like you get from xfontsel, if you prefer.

Startup still isn't pretty -- emacs still shows a big window at one place on the screen, resizes it several times then jumps it over to the top/left coordinates I specified. Of course, I could tell my window manager to start it in the right place so the jumping-around would be minimized; but that wouldn't help the visible resizing. Just a minor irritation.

I'm sure there's lots more useful stuff buried in that sample emacs config file (it was suggested to me when I asked about this on the #emacs IRC channel), so I'll be reading it to see what else I can glean.

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[ 12:24 Jul 14, 2011    More linux/editors | permalink to this entry | comments ]

Wed, 25 May 2011

Vim/Emacs tip: use modelines for files that need special behavior

Most of the time when I edit a text file in vim, I want lines to wrap automatically as I type, at somewhere around 70 columns wide. So I set textwidth=70 in .vimrc.

But sometimes that isn't appropriate. For instance, I have a procmail rules file where I put common spam patterns that programs like spamassassin don't seem to be able to catch. So I might have lines like:

*^Subject:.*(Ink Cartridges|Hummingbird Vine|who's who of executives|Avandia|Botox|Your Email ID|Zoosk|Best airfares on the internet|UGG Boots|police training)
... and so on -- you get the idea. I can't have lines breaking in the middle, because then the procmail rule wouldn't work. So every time I add a new phrase, I have to :set tw=0 (or one of the other umpteen ways one can tell vim not to wrap lines) first.

But you can set special behavior for one specific file by adding a special comment called a "modeline" as the first line of the file.

Procmail treats any line starting with a hash, #, as a comment, and vim recognizes # as a comment. So I can add this as the first line of the procmail file:

# vim: set tw=0:
then vim will see that and un-set that default text width I specify in .vimrc.

Vim understands most common comment styles, so it should understand lines like /* vim: set tw=0: */ and // vim: set tw=0: and ; vim: set tw=0: as well.

But to make this work I had to do one more thing: in .vimrc, I had to add

set modeline

Apparently on some versions of vim this is on by default; in others it's turned off for security reasons (someone could put an evil modeline into a file which would make your vim do something when you edited it). Definitely something to be aware of, but if you mostly edit files you created yourself on your local machine, and no one else uses your machine, it's your choice whether to worry about it.

Emacs has modelines too

Emacs has mode lines too, though it calls them Local variables lines. For instance, C++ files in Mozilla's source tend to start with:

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

It's awfully handy to be able to define specific indentation style for the files within a project, making it easy for emacs users, at least, to follow your preferred coding style. If only all editors understood them!

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[ 21:26 May 25, 2011    More linux/editors | permalink to this entry | comments ]

Fri, 04 Feb 2011

Quick tip: Disabling version control in Emacs

For some time I've been mildly annoyed that whenever I start emacs and open a file that's under any sort of version control -- cvs, svn, git or whatever -- I can't start editing right away, because emacs has to pause for a while and load a bunch of version-control cruft I never use. Sometimes it also causes problems later, when I try to write to the file or if I update the directory.

It wasn't obvious what keywords to search for, but I finally found a combination, emacs prevent OR disable autoload vc (the vc was the important part), which led me to the solution (found on this page):

;; Disable all version control
(setq vc-handled-backends nil)

Files load much faster now!

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[ 13:11 Feb 04, 2011    More linux/editors | permalink to this entry | comments ]

Wed, 01 Dec 2010

Escaping HTML characters in Emacs (and how to do replaces in elisp)

Last week I found myself writing another article that includes code snippets in HTML.

So what, you ask? The problem is, when you're writing articles in HTML, every time you include a code snippet inside a <pre> tag you invariably forget that special characters like < > & have special meanings in HTML, and must be escaped. Every < has to change to &lt;, and so forth, after you paste the code.

In vi/vim, replacing characters is straightforward. But I usually write longer articles in emacs, for various unimportant reasons, and although emacs has global replace, it only works from wherever you are now (called "point" in emacs lingo) to the end of the file. So if you're trying to fix something you pasted in the middle of the article, you can't do it with normal emacs replace.

Surely this is a wheel that has already been re-invented a thousand times, I thought! But googling and asking emacs experts turned up nothing. Looks like I'd have to write it.

And that turned out to be more difficult than I expected, for the same reason: emacs replace-string works the same way from a program as it does interactively, and replaces from point to the end of the file, and there's no way to restrict it to a more limited range.

Several helpful people on #emacs chimed in with ideas, but most of them didn't pan out. But ggole knew a way to do it that was both clean and reliable (thanks!).

Here's the elisp function I ended up with. It uses save-excursion to put the cursor back where it started before you ran the function, narrow-to-region to make replace-string work only on the region, and save-restriction get rid of that narrow-to-region after we're done. Nice!

(defun unhtml (start end)
  (interactive "r")
  (save-excursion
    (save-restriction
      (narrow-to-region start end)
      (goto-char (point-min))
      (replace-string "&" "&amp;")
      (goto-char (point-min))
      (replace-string "<" "&lt;")
      (goto-char (point-min))
      (replace-string ">" "&gt;")
      )))

And yes, I used it just now on that elisp snippet.

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[ 20:08 Dec 01, 2010    More linux/editors | permalink to this entry | comments ]

Tue, 09 Feb 2010

Make scroll lock stop beeping in Emacs 23

I haven't been using the spare machine much lately. So I hadn't noticed until last week that since upgrading to the emacs 23.1.1 on Ubuntu Karmic koala, every time I press the Scroll Lock key -- the key my KVM uses to switch to the other computer -- with focus in an emacs window, emacs beeps and complains that the key is unbound.

That was a problem I thought I'd solved long ago, an easy fix in .emacs:

(global-set-key [scroll-lock] 'ignore)
But in emacs 23, it wasn't working any more. Emacs listed the key as "<Scroll_Lock>", but using that directly in global-set-key doesn't work.

The friendly and helpful (really!) crew at #emacs found me a solution, after some fiddling around.

(global-set-key (kbd "<Scroll_Lock>") 'ignore)

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[ 23:47 Feb 09, 2010    More linux/editors | permalink to this entry | comments ]

Wed, 13 Jan 2010

Taming Emacs' text mode wrapping and indenting

To wrap long lines, or not to wrap? It's always a dilemma. Automatic wrapping is great when you're hammering away typing lots of text. But it's infuriating when you're trying to format something yourself and the editor decides it wants to line-wrap a little too early.

Although of course you can set the wrapping width, Emacs has a tendency to wrap early -- especially when you hit return. All too often, I'll be typing away at a long line, get to the end of the sentence and paragraph with the last word on the same line with the rest -- then realize that as soon as I hit return, Emacs is going to move that last word to a line by itself. Drives me nuts!

And the solution turns out to be so simple. The Return key, "\C-m". was bound to the (newline) function (you can find out by typing M-x, then describe-key, then hitting Return). Apparently (newline) re-wraps the current line before inserting a line break. But I just wanted it to insert a line break.

No problem -- just bind "C-m" to (insert "\n").

But there's a second way, too, if you don't want to rebind: there's a magic internal emacs table you can change.

(set-char-table-range auto-fill-chars 10 nil)

But wait -- there's one other thing I want to fix in text mode.

Automatic indent is another one of those features that's very convenient ... except when it's not.

If I have some text like:

First point:
  - subpoint a
  - subpoint b
then it's handy if, when I hit Return after subpoint a, emacs indents to the right level for subpoint b. But what happens when I get to the end of that list?
First point:
  - subpoint a
  - subpoint b

Second point:
  - subpoint c

When I hit Return after subpoint b, Emacs quite reasonably indents two spaces. If I immediately type another Return, Emacs sensibly deletes the two spaces it just inserted, opens a new line -- but then it indents that new line another two spaces.

After a blank line, I always want to start at the beginning, not indented at all.

Here's how to fix that. Define a function that will be called whenever you hit return in text mode. That function tests whether the caret comes immediately after a blank line, or at the beginning of the file. It indents except in those two cases; and in neither case does it re-wrap the current line.

;; In text mode, I don't want it auto-indenting for the first
;; line in the file, or lines following blank lines.
;; Everywhere else is okay.
(defun newline-and-text-indent ()
  "Insert a newline, then indent the next line sensibly for text"
  (interactive)
  (cond
   ;; Beginning of buffer, or beginning of an existing line, don't indent:
   ((or (bobp) (bolp)) (newline))

   ;; If we're on a whitespace-only line,
   ((and (eolp)
         (save-excursion (re-search-backward "^\\(\\s \\)*$"
                                             (line-beginning-position) t)))
    ;; ... delete the whitespace, then add another newline:
    (kill-line 0)
    (newline))

   ;; Else (not on whitespace-only) insert a newline,
   ;; then add the appropriate indent:
   (t (insert "\n")
      (indent-according-to-mode))
   ))

Then tell emacs to call that function when it sees the Return key in text mode:

(defun text-indent-hook ()
  (local-set-key "\C-m" 'newline-and-text-indent)
  )
(setq text-mode-hook 'text-indent-hook)

Finally, this is great for HTML mode too, if you get irritated at not being able to put an <a href="longurl"> all on one line:

(defun html-hook ()
  (local-set-key "\C-m" (lambda () (interactive) (insert "\n")))
  )
(setq sgml-mode-hook 'html-hook)

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[ 11:29 Jan 13, 2010    More linux/editors | permalink to this entry | comments ]

Wed, 29 Jul 2009

Emacs: Insert tags in HTML Mode

Wouldn't it be nice if Emacs HTML mode had a way to insert HTML tags, so you didn't have to type <b></b> all the time? Sort of like what's described in this page -- except that page describes an HTML mode that clearly isn't the one that's installed on Ubuntu, since none of those bindings actually work?

I've been meaning to figure out a way to do that for ages, and finally got around to it. Turns out Emacs SGML mode (which is really what Ubuntu installs and uses for HTML files) doesn't have functions for specific HTML tags like <b>, but it does have a general tag-inserting function.

Type C-c C-t -- emacs prompts you for the tag, so type b or whatever, and hit return -- and you get the tag, with the cursor correctly positioned for you to type your new bold text.

But that's four keystrokes. What if you want shorter bindings for particular tags, like C-b C-b to insert a bold?

For that, you need to use a lambda and a mode hook. In your .emacs it looks like this:

;; Define keys for inserting tags in HTML mode:
(defun html-hook ()
  (local-set-key "\C-c\C-b" (lambda () (interactive) (sgml-tag "b")))
  )
(setq sgml-mode-hook 'html-hook)

There's apparently also supposed to be a command bound to C-c / that closes the current tag, but my version of sgml-mode doesn't bind anything to that key, and the only likely-looking function name, sgml-maybe-end-tag, doesn't end the current tag. Such is life!

But one more don't-miss feature that I'd missed all along is C-c C-n: type it before a special character like < or & and emacs will insert the appropriate &lt; or &amp; for you. Nice!

(Thanks to bojohan on #emacs for the tips!)

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[ 21:31 Jul 29, 2009    More linux/editors | permalink to this entry | comments ]

Fri, 27 Mar 2009

Emacs bookmarks -- a huge time-saver

Oh, wow. I can't believe I've used Emacs all these years without knowing about bookmarks.

I wanted something in Emacs akin to the "Open Recent" menu that a lot of GUI apps have. Except, well, I didn't want it to need a menu (I don't normally show a menubar in Emacs) and I didn't want it limited only to recently accessed files. So ... just like Open Recent, only completely different.

What I really wanted was a way to nickname files I access regularly, so I don't have to type ~/foo/bar/blaz/route-66/dufus/velociraptor/archaeopteryx/filename every time. Even with tab completion, remembering long paths gets old. Of course emacs must have a way to do that; it has everything. The trick was guessing what it might be called in order to search for it.

The answer is emacs bookmarks and they're super easy to use.

C-x r m sets a bookmark for the current location in the current file. It prompts for a bookmark name; give it a nickname, or hit return to default it to the current filename.

C-x r b bookmark-name jumps back to a bookmark, opening the file if it isn't already. Of course, tab completion works for the bookmark name.

Bookmarks are saved in ~/.emacs.bmk so they're persistent.

It's perfect. I just wish I'd thought to look for it years ago.

(Of course, Emacs can do recent files too.)

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[ 10:21 Mar 27, 2009    More linux/editors | permalink to this entry | comments ]

Mon, 19 Feb 2007

Emacs with Long Lines

I don't like composing text documents in word processors like Open Office. Call it a quirk if you like, but I find them intrusive: they take up a lot of CPU and memory, they take up a lot of window space for stuff I don't need while I'm writing (all those margins and rulers and toolbars and such) making it hard to compare two documents at once, and they tend to have intrusive focus behavior (like popping windows to the front when I didn't ask for it).

So when I need to write a paper (or a book), I prefer to compose in a text editor like vim or emacs, something that won't get in the way of my train of thought. When it's mostly written and ready to format, then I start up the big heavyweight word processor and import or paste the text into it.

(For those of you who think I'm insane and should just live in Open Office all day, the same problem comes up for people who do a lot of composing for web applications, such as an online blog, gmail, a web forum, or a wiki, and for people who want a choice of editor for their GUI mail app.)

Fine, but that introduces a problem. See, text editors have a fixed line width (typically 80 characters, though of course you can adjust this) and paragraphs are usually separated by blank lines (two newline characters together). Word processors expect each paragraph to be one long line for the whole paragraph, and line breaks are used as paragraph breaks (but you only want one of them, not two). How do you reconcile these two models in order to paste plaintext from an editor into a word processor?

Several years ago when I first encountered this problem, I investigated solutions in both vim and emacs (oddly enough, I'm an editor agnostic and equally happy in either one).

For vim, I never did find a solution to the problem, so that settled the editor choice for me. Perhaps some vim expert can let me know what I missed.

For emacs, I found longlines-mode, a hack which lets long lines appear to be wrapped while you're editing them even though they're really not. Apparently Wikipedia has this issue and some Wikipedia contributors use longlines-mode too. (That page also has brief notes on alternate solutions.)

I used longlines-mode for a long time, and it's more or less functional, but I was never really happy with it. It turns out to have some pretty annoying bugs which I was forever needing to work around, and it doesn't solve the blank-lines problem -- you still need to delete blank lines before or after pasting.

Yesterday I was working on an essay for a class I'm taking and decided I'd had enough of longlines-mode and wanted a better solution. I poked around and chatted with the nice folks on #emacs (hoping that someone had come up with a better solution, but no one knew of one) and based on some ideas they had, I came up with one of my own.

My new method is to edit the text file normally: line breaks where they look good, blank lines to separate paragraphs. When I'm finished writing and ready to paste, I run M-x wp-munge, which calls up a very simple function I wrote and added to my .emacs:

;; For composing in emacs then pasting into a word processor,
;; this un-fills all the paragraphs (i.e. turns each paragraph
;; into one very long line) and removes any blank lines that
;; previously separated paragraphs.
;;
(defun wp-munge () "un-fill paragraphs and remove blank lines" (interactive)
  (let ((save-fill-column fill-column))
    (set-fill-column 1000000)
    (mark-whole-buffer)
    (fill-individual-paragraphs (point-min) (point-max))
    (delete-matching-lines "^$")
    (set-fill-column save-fill-column) ))

So simple! Why didn't I think of doing it that way before?

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[ 21:10 Feb 19, 2007    More linux/editors | permalink to this entry | comments ]

Wed, 29 Mar 2006

Emacs: Typing dashes in html mode

What to do with a few extra hours in a boring motel with no net access? How about digging into fixing one of Emacs' more annoying misfeatures?

Whenever I edit an html file using emacs, I find I have to stay away from double dashes -- I can't add a phrase such as this one. If I forget and type a phrase with a double dash, then as soon as I get to the end of that line and emacs decides it's time to wrap to the next line, it "helpfully" treats the double dashes as a comment, and indents the next line to the level where the dashes were, adding another set of dashes. I've googled, I've asked on emacs IRC help channels, but there doesn't seem to be any way out. (I guess no one else ever uses double dashes in html files?)

It's frustrating: I like using double dashes now and then. And aside from the occasional boneheaded misfeature like this one, I like using emacs. But the dash problem been driving me nuts for a long time now. So I finally dug into the code to cure it.

First, the file is sgml-mode.el, so don't bother searching anything with html in the name. On my system it's /usr/share/emacs/21.4/lisp/textmodes/sgml-model.el. Edit that file and search for "--" and the first thing you'll find (well, after the file's preamble comments) is a comment in the definition of "sgml-specials" saying that if you include ?- in the list of specials, it will hork the typing of double dashes, so that's normally left out.

A clue! Perhaps some Debian or Ubuntu site file has changed sgml-specials for me, and all I need to do is change it back! So I typed

M-x describe-variable sgml-specials
to see the current setting.

Um ... it's set to "34". That's not very helpful. I haven't a clue how that translates to the list of characters I see in sgml-mode.el. Forget about that approach for now.

Searching through the file for the string "comment" got me a few more hits, and I tried commenting out various comment handling lines until the evil behavior went away. (I had to remove sgml-mode.elc first, otherwise emacs wouldn't see any changes I made to sgml-mode.el. If you haven't done much elisp hacking, the .el is the lisp source, while the .elc is a byte-compiled version which loads quicker but isn't intended to be edited by humans. For Java programmers, the .elc is sort of like a .class file.)

Commenting out these four lines did the trick:

  (set (make-local-variable 'font-lock-syntactic-keywords)
       '(("\\(<\\)! *--.*-- *\\(>\\)" (1 "!") (2 "!"))))
  ;; This will allow existing comments within declarations to be
  ;; recognized.
  (set (make-local-variable 'comment-start-skip) "\\(?:\\)?")

To regenerate the .elc file so sgml-mode will load faster, I ran emacs as root from the directory sgml-mode.el was in, and typed:

M-x byte-compile-file sgml-mode.el

All better! And now I know where to find documentation for all those useful-looking, but seemingly undocumented, keyboard shortcuts that go along with emacs' html mode. Just search in the file for html-mode-map, and you'll find all sorts of useful stuff.

For instance, that typing Ctrl-C Ctrl-C followed by various letters: u gets you an unordered list, h gets you an href tag, i an image tag, and so on, with the cursor positioned where you want to type next.

It doesn't seem to offer any basic inline formatting (like <i> or <em>), alas; but of course that's easy to add by editing the file (or maybe even in .emacs). To add an <em> tag, add this line to html-mode-map:

    (define-key map "\C-c\C-ce" 'html-em)
then add this function somewhere near where html-headline-1 and friends are defined:
(define-skeleton html-em
  "HTML emphasis tags."
  nil
  "" _ "")

Of course, you can define any set of tags you use often, not just <em>.

HTML mode in emacs should be much more fun and less painful now!

Update: If you don't want to modify the files as root, it also works fine to copy sgml-mode.el to wherever you keep personal elisp files. For instance, put them in a directory called ~/.emacs-lisp then add this to your .emacs:
(setq load-path (cons "~/.emacs-lisp/" load-path))

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[ 22:48 Mar 29, 2006    More linux/editors | permalink to this entry | comments ]

Sat, 19 Feb 2005

Tweaking Emacs' Text Indent: Don't Indent So Aggressively

Encouraged by my success a few days ago at finally learning how to disable vim's ctrl-spacebar behavior, the next day I went back to an emacs problem that's been bugging me for a while: in text mode, newline-and-indent always wants to indent the first line of a text file (something I almost never want), and skips blank lines when calculating indent (so starting a new paragraph doesn't reset the indent back to zero).

I had already googled to no avail, and had concluded that the only way was to write a new text-indent function which could be bound to the return key in the text mode hook.

This went fairly smoothly: I got a little help in #emacs with checking the pattern immediately before the cursor (though I turned out not to need that after all) and for the function called "bobp" (beginning of buffer predicate). Here's what I ended up with:

(defun newline-and-text-indent ()
  "Insert a newline, then indent the next line sensibly for text"
  (interactive)
  (if (or (bobp)
          (looking-at "^$"))
      (newline)
      (newline-and-indent)
  ))
(defun text-indent-hook ()
  (local-set-key "\C-m" 'newline-and-text-indent)
  )
(setq text-mode-hook 'text-indent-hook)

It seems to work fine. For the curious, here's my current .emacs

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[ 14:03 Feb 19, 2005    More linux/editors | permalink to this entry | comments ]

Thu, 03 Feb 2005

Emacs Color Themes

A nifty emacs trick I learned about today: ColorThemes.

Instead of the old hacked-together color collection I've been using in emacs, I can load color-theme.el and choose from lots of different color schemes.

I added these lines to .emacs:

(require 'font-lock)
(if (fboundp 'global-font-lock-mode) (global-font-lock-mode 1))
(load "~/.emacs-lisp/color-theme.el")
(color-theme-ramangalahy)  ;; pick a favorite theme

The disadvantage is that color-theme.el is fifteen thousand lines long! So I'll probably make a local version that strips out all but the theme I actually use (then I can customize that).

The (global-font-lock-mode 1) tells emacs to use syntax highlighting on every file, not just certain types. So now I get at least some highlighting even in html files, though it still doesn't seem to be able to highlight like vim does (e.g. different colors for text inside <b> or <b> tags).

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[ 18:57 Feb 03, 2005    More linux/editors | permalink to this entry | comments ]

Thu, 13 Jan 2005

Nifty emacs hack: how to wrap only certain files

For a long time I've wanted some, but not all, text and html files to line-wrap automatically in emacs. For instance, it drives me nuts when I edit a system configuration file and it wraps each long line, or when I edit an html file containing lots of long links and it keeps wrapping between the <a and the href=. But for files which are mostly text (such as these blog entries), I want line wrapping.

I'd been trying to do this with html-mode-hook and text-mode-hook, then checking the filename and calling (auto-fill-mode) if appropriate, but it wasn't working, because buffer-file-name isn't always defined at the time the mode hook is called. (No one seems to know why.) The buffer name seems to be defined at that point, but it doesn't contain path information so I can't say "Use wrapping for anything under ~/Docs" or "Don't wrap anything in /etc".

But with some help from sachac and the nice folks on #emacs I came up with a much better solution, and it's way simpler than the mode-hook approach: derived modes.

I set up two new modes, called html-wrap-mode and text-wrap-mode, which are the same as html-mode and text-mode except that they turn on auto-fill. Then I use the easy auto-mode-alist mechanism, which already does string matching on the filename, to call these modes, instead of the regular text and html modes, based on the extension or some other aspect of the file's pathname. Here's what I added to .emacs:

;; Want auto-fill-mode for some text and html files, but not all.
;; So define two derived modes for that, and we'll use auto-mode-alist
;; to choose them based on filename.
(define-derived-mode html-wrap-mode html-mode "HTML wrap mode"
  (auto-fill-mode))
(define-derived-mode text-wrap-mode text-mode "Text wrap mode"
  (auto-fill-mode))

(setq auto-mode-alist
      (cons '("\\.blx$" . html-wrap-mode)
      (cons '("Docs/.*.html$" . html-wrap-mode)
      (cons '("Docs/" . text-wrap-mode)
            auto-mode-alist) ) ) )

Here's my current .emacs.

I wonder if vim has a way to do this?

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[ 23:30 Jan 13, 2005    More linux/editors | permalink to this entry | comments ]

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