# HG changeset patch
# User Steve Losh <steve@stevelosh.com>
# Date 1321229561 18000
# Node ID 96cf3ead3c63f33166434540234a3e749a443b9a
# Parent  17fbafb16c45ecaaef2eeeed87e0348155136766
ftdetect

diff -r 17fbafb16c45 -r 96cf3ead3c63 chapters/44.markdown
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/chapters/44.markdown	Sun Nov 13 19:12:41 2011 -0500
@@ -0,0 +1,76 @@
+Detecting Filetypes
+===================
+
+Let's create a Potion file we can use as a sample as we're working on our
+plugin.  Create a `factorial.pn` file somewhere and put the following Potion
+code inside it:
+
+    factorial = (n):
+        total = 1
+        n to 1 (i):
+            total *= i.
+        total.
+
+    10 times (i):
+        i string print
+        '! is: ' print
+        factorial (i) string print
+        "\n" print.
+
+This code creates a simple factorial function and calls it ten times, printing
+the results each time.  Go ahead and run it with `potion factorial.pn`.  The
+output should look like this:
+
+    0! is: 0
+    1! is: 1
+    2! is: 2
+    3! is: 6
+    4! is: 24
+    5! is: 120
+    6! is: 720
+    7! is: 5040
+    8! is: 40320
+    9! is: 362880
+
+Detecting Potion Files
+----------------------
+
+Open `factorial.pn` in Vim and run the following command:
+
+    :set filetype?
+
+Vim will display `filetype=` because it doesn't know what a `.pn` file is yet.
+Let's fix that.
+
+Create `ftdetect/potion.vim` in your plugin's repo.  Put the following lines
+into it:
+
+    augroup potion_detect
+        au!
+        au BufNewFile,BufRead *.pn set filetype=potion
+    augroup END
+
+This creates an autocommand group with one autocommand inside: a command to set
+the filetype of `.pn` files to `potion`.  Pretty straightforward.
+
+Close the `factorial.pn` file and reopen it.  Now run the previous command
+again:
+
+    :set filetype?
+
+This time Vim displays `filetype=potion`.  When Vim started up it loaded the
+autocommand group inside `~/.vim/bundle/potion.vim`, and when it opened
+`factorial.pn` the autocommand fired, setting the `filetype` to `potion`.
+
+Now that we've taught Vim to recognize Potion files we can move on to actually
+creating some useful behavior in our plugin.
+
+Exercises
+---------
+
+Read `:help ft`.  Don't worry if you don't understand everything there.
+
+Read `:help setfiletype`.
+
+Modify the Potion plugin's `ftdetect/potion.vim` script to use `setfiletype`
+instead of `set filetype`.
diff -r 17fbafb16c45 -r 96cf3ead3c63 outline.org
--- a/outline.org	Sun Nov 13 18:35:19 2011 -0500
+++ b/outline.org	Sun Nov 13 19:12:41 2011 -0500
@@ -46,7 +46,7 @@
 ** DONE intro
 ** DONE plugin layout
 ** DONE pathogen
-** TODO ftdetect
+** DONE ftdetect
 ** TODO syntax
 ** TODO autoload
 ** TODO folding