Evil Mode hack for a colorful mode line

Intro

After trying out Spacemacs for about a week (and failing - too much old configuration to "convert") I am trying out Evil Mode by itself. It goes forward, slowly, step by step.

One thing I have been a bit annoyed with was how the different states are visualized. Being a Evil/Vim newbie I want to see, clearly, in which state/mode I am in.

Today I decided to do something about it and here is how my Emacs looks now:

Normal state

Insert state

Emacs state

How it was done

I could not find any good entry points for customizing the mode line with respect to the Evil Mode states, but I found the function (evil-generate-mode-line-tag) that generates the part of the mode line that comes from Evil Mode. I simply made a copy of it and changed it to add also a face attribute to the mode line, and let the face be different depending on the mode.

The code

Copy the code below and save it in a file called my-evil-hacks.el.

After this you need to make sure to load this file after you have loaded Evil mode for the first time. One way to achieve this is to put the following snippet in your .emacs or init.el file:

(with-eval-after-load "evil"
  (load "my-evil-hacks"))

Enjoy!

Evaluating elisp expressions from a web page with a custom URI scheme

Intro

Very boring title, eh? :) Well, this is kinda neat...

Some of you might already know that you can install a custom URI scheme handler in most operating system. Today I did an experiment with that together with Emacs and it turned out quite nicely. I did
this in Windows but it should work in GNU/Linux and OS X as well.

So, what is an URI scheme?

Briefly explained, the URI scheme is the "http" part in URLs that we all use everyday. Other examples are "ftp" and "file". The most common ones are handled by your web browser but you can also have another program on your computer handle a certain URI scheme. You can register your own URI schemes as well and in this post we will experiment with a new URI scheme that we name "emacs", for evaluating expressions/executing commands in Emacs.

A warning

If you decide to do this, you should be very careful, since it could be a big security risk. Either you let the warning from your web browser always be there to warn you (it can be supressed easily, for a
better user experience) or you register a secret URI scheme (like "myverysecretemacsurischeme") that no one else knows about. Otherwise, bad people can do very nasty things with your computer...

Okay, with that aside, let's go!

Step 1 - Registering a new URI scheme

In Windows you register a new URI scheme in the Windows registry (where else...). Basically you have to create the following key/folder structure under the HKEY_CLASSES_ROOT hive:

<name of URI scheme handler>
  shell
    open
      command

Lastly, the "command" key's Default value (right hand side) should have the path to the program handling the request, and %1 should be there to, to send in the parameters from the URL to the program.

If you dare, you can save the following snippet of text as something.reg on your PC, and double click that file. It will add an URI scheme handler for the "emacs" scheme for you. You have to change the path to the program afterwards:

Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\emacs]"URL Protocol"=""
[HKEY_CLASSES_ROOT\emacs\shell]
[HKEY_CLASSES_ROOT\emacs\shell\open]
[HKEY_CLASSES_ROOT\emacs\shell\open\command]@="f:\\Dropbox\\home\\dat\\doc\\src\\bat\\emacsschemehandler.cmd \"%1\""

Step 2 - A script to handle the new URI scheme

To handle the new URI scheme I created a small cmd file that processes the arguments a bit and then starts emacsclient. It looks like this:

REM f:\Dropbox\home\dat\doc\src\bat\emacsschemehandler.cmd

@echo off

REM Pick up all arguments to the script (in case there are spaces)
set emacscommand=%*

REM Stript away the part we don't need...
set emacscommand=%emacscommand:emacs:=%

REM Start emacsclient
f:\Dropbox\home\pgm\emacs-24.3\bin\emacsclient -n -e %emacscommand%

Save the script above as a .cmd file on your computer and update the registry to reflect the path to the .cmd file on your system. Also update the path to where your emacsclient is.

The script is, as can be seen, very simple and basically it just trims off part of the argument from the web browser that we do not need and use the rest as an argument to emacsclient. If you decide to use
another name than "emacs" for your own experiments, make sure to update "emacs:" above to whatever name you picked (plus a colon).

Step 3 - Testing it from a web page

Now you only need a web page with some links to try it out. I have provided a couple of links below that you can try right now, if you decided to use the "emacs" URI scheme, that is. The code for the links looks like this (if you do not trust me, view the source code for this blog post):

<a href='emacs:(message """Hello, Emacs!""")'>Hello, Emacs!</a> <a href="emacs:(calendar)">Open Calendar</a><a href="emacs:(info-emacs-manual)">Open the Emacs manual</a>

Here are the links:

Hello, Emacs!
Open Calendar
Open the Emacs manual

The triple double quotes in the first example are needed in order to send strings from the cmd file to emacsclient. That is why I used single quotes around the href value, which I normally don't like.

Now, what do you wait for, try it! Go go go! :)

So, what can this be used for?

Well, not sure. For me it was mostly a nice experiment, but I can see some uses for people who work a lot in Emacs but also a lot in a web browser and where they need some kind of interaction between
those. Perhaps something nice can be done together with Org mode and documentation of code, where you view the documentation in a browser but let the user try out code in Emacs, or just jump to a particular section in the Org mode document there. I guess the possibilities are endless, as with most things Emacs... :)

Hope you enjoyed it!

C'ya!

My Emacs launcher makes me happy

Yeah, just wanted to say that.

Okay, maybe I should elaborate "a little" (...) Some time ago (more than four years I see now...) I got the idea to combine the power of Emacs and the excellent Emacs package Anything (as it was called then, now Helm) plus a keyboard shortcut into my own launcher. Before that I had created a couple of simple ones on my own: PyQe, which I used at home, under Ubuntu (but should in theory work on Windows since it uses basic Python stuff), and another one at work called Quick Execute, which is a small VB hack that turned out to be used by one of my colleagues more than me.

Anyway...

So, Emacs, yes! After some fiddling with the necessary elisp needed and dark (but brittle) voodoo magic configuring a bash script that send keystrokes using some tool I cannot remember the name of now, Anything Launcher was born. It turned out to be a big hit, to me at least (I don't know about anyone in the universe using it, although there were a few comment in the EmacsWiki page early on.)

More than four years later I still use it, several times per hour. What do I do with it? Anything! (of course...) I open important web bookmarks with it, I start programs, I open commonly used folders, I start searches in our intranet at work, I find bugs, cases and Jira issues with it and today I added a small hack to create alarms using the Windows scheduler in the background. And everything I do with it is under total control by me. Not only can I "start" predefined list of "things" (bookmarks etc as mentioned earlier), I can interact with it to give arguments to the "commands" in it.

Just as a more detailed example, if I want to open a bug in our in-house bug tracker, I launch the "Bug Search with prompt" command. It asks me for the bug id and opens the web based bug tracker with the correct bug selected. But, and here comes something that is probably not so easy to do in other configurable launchers (not as easily or quickly I would guess, I am very productive in elisp), it also looks at the clipboard and if it finds something like looks like a bug id, it suggests that as the default input. So, when I get some bug id in some e-mail, I copy that text, open my Emacs launcher (which is what I actually call it on my PC) using a keyboard shortcut, type "bu" to match the bug search command, and then press enter. I then press enter again to accept the bug id it found on the clip board (I could probably make it open the bug directly without me pressing enter, but I like to verify that it is in fact a bug id it found on the clipboard).

That type of command (written in elisp, of course, with all the powers that gives me) turns out to be a quite common pattern, so I have similar commands for cases (connected to bugs), Jira issues and other things where I can "guess" what stuff is placed on the clipboard. And, again, since I have full control and access to an implementation of the world most powerful programming language (Lisp, in case you missed that), I of course implement a command to create these commands. Just as an example on how it could look, here is that exact "bug search" command, from the control file to the launcher:

("Bug Search with prompt" . ("http://urltobugtracker?BUG_ID=%s" "Bug ID" "\\w\\([0-9]+\\)\\w"))

That's it! If I want a similar command for some other web site I just give it another URL (with %s as the placeholder for the input I enter), a prompt for me to understand what to do and the last string up there as regexp for matching stuff on clipboard. Bang! I have a new command that lets me open stuff fast.

The control file, by the way, is actually a normal Lisp list, which the launcher then just "reads". The launcher accepts certain type of "commands", from simple strings that are just started like commands in Windows, to lambda expressions which can do everything that Emacs can do, and Emacs can do A LOT together with external tools. The command above, which begins with a command name and contains as the CDR a list with something that looks like an URL, and some more strings, is also a command that the launcher is programmed to support, since it is such a common command type for me.

Since people like screenshots, here is just an example on how it could look while trying to launch something matching the string "ra":

(please don't make fun of the colours, they can be changed easily but I happen to like them)

So, if you also want to reach launcher nirvana, and just happen to have Emacs lying around, have a look at my Anything Launcher page at EmacsWiki. The information there is a bit old and there are no instructions for Windows, but if there is enough interest (comments here or on the wiki, or by sending me an e-mail or twitter thing or whatever) I might take the time to write down my exact current setup.

Oh, and yes. Some people might ask why I am not simply living inside Emacs all day long and starting things from there. Well, that is not far from the truth either, but sometimes I have to leave the safe haven of Emacs and use other scary programs which people (yet) have not integrated in Emacs and which I don't have the time and effort to integrate myself. So, I need it to be something I can start quickly when I am not inside Emacs (where I, of course, also use Anything to find files and buffers).

Happy launching!

Bookmarklet to open a Youtube video in a new window

Sometimes I want to work in some other window while watching a Youtube video. This little bookmarklet opens a new window/tab with the particular Youtube video on the current page, without any fluff around the video.

To install it, just drag this link to your bookmarks toolbar, or copy the link and make a new bookmark and paste the link content there. Here is the actual link content:

javascript:var url=document.location.href;if(url.match('http.?://(www.)?youtube|youtu\.be')){yid=url.split(/v\/|v=|youtu\.be\//)[1].split(/[?&]/)[0];window.open("http://www.youtube.com/v/" + yid + "&hl=en&fs=1");}else{alert("Could not find video ID")}

(you must include the "javascript:" part)

To use it, just click the bookmark when you have a Youtube page opened.

Enjoy!

Using Emacs and ediff as an external diff tool

At work we have a program where one can configure an external diff tool to diff source code changes. Since I am used to work with ediff in Emacs I wanted to use it from that program as well. I ended up making a wrapper cmd file for it and thought I should share it in case someone else wants to solve the same problem.

Here is the script:


@echo off
REM c:\batfiles\ediff.cmd
set file1=%1
set file2=%2
REM Must convert the backslashes to slashes, otherwise they will be
REM interpreted as escape characters in the elisp strings. One can
REM also replace each backlslash with two backslashes to solve the
REM problem, but I like slashes better. Looks less messy.
set file1=%file1:\=/%
set file2=%file2:\=/%
%PATHTOEMACS%\bin\emacsclientw.exe -n -e "(ediff-files ""%file1%"" ""%file2%"")"

Replace %PATHTOEMACS% above with the real path to where you have installed Emacs. After that it's just a matter of selecting this cmd script as the diff tool.

Enjoy!

Creating multiple shells in Emacs

Sometimes you want to have more than one shell going in Emacs. If you have tried that you know it does not work like you would have expected - you end up in the current shell buffer instead of getting a new one. So I created this small hack:

(defun new-shell (name)
  "Start a shell with name NAME, or a generated name if empty.
Returns the name of the new shell."
  (interactive "sName: ")
  (let ((shell-name          
         (if (not (string= "" name))
             (concat "*shell*<" name ">")
           (generate-new-buffer-name "*shell*"))))
    (shell shell-name)
    shell-name))

It prompts for a name for a new shell buffer. If none is given it will generate one for you. Naming shell buffers can be useful when you are doing a certain kind of work in a certain buffer and want to switch to that buffer easily using parts of the name.

Enjoy!