Finish up ep13

docs/videos.org

@@ -778,4 +778,106 @@ We can clone a library somewhere on the disk and add the path to it to the =load
 and load the library files.
 
 But that would be tedious to do so for all the libraries. That's why we use a package manager
-* Episode 13 - Hooks
+* Episode 13 - Editing Modes, Part 1
+Emacs provides a concept called ~editing mode~ that allows
+us to control different aspect of the editor.
+
+** Major Modes
+Major modes are mutually exclusive, so each Buffer has exactly on
+major mode and just one major mode can be active at any given
+time. So, it is possible to switch between different major modes.
+
+Major modes control the main behaviour of your editor for each buffer.
+For example, The active major mode might:
+
+- Provide syntax highlighter
+- Control the indentation
+- Provide a local =keymap=
+- ...
+
+To put it simply, major modes are specialized to handle certain files
+and buffers.
+
+*** Naming Convenstion
+Usually, the name of a major mode is like =<major-mode-name>-mode= which is
+an interactive function that we can call either directly or via =M-x= interface.
+For example:
+
+- python-mode
+- fundamental-mode
+- emacs-lisp-mode
+- ...
+
+**** Keymap
+*We will take about Keymaps in the future*
+
+Major modes usually have a keymap to hold their local keybindings that has the
+the =-map= suffix.
+
+**** Hooks
+*We will take about Hooks in the future*
+
+Hooks are lists of functions that can be called on certain occasions. For example,
+after a major mode activates.
+
+Usually major modes come with at least one hook called =<major-mode-name>-hook= that
+runs after the major mode activates. E.g. =emacs-lisp-mode-hook= or =python-mode-hook=.
+
+*** How Emacs choose a major mode for a buffer?
+When we open a file, Emacs goes through some hoops to figure out what major mode
+should it choose for that buffer.
+
+To put it simply and avoid a lot of details, Emacs will try to match the buffer name
+against the keys in ~auto-mode-alist~ and uses the mode provided by that key as a value.
+
+#+BEGIN_SRC emacs-lisp
+  (("\\`/tmp/fol/" . text-mode)
+   ("\\.texinfo\\'" . texinfo-mode)
+   ("\\.texi\\'" . texinfo-mode)
+
+   ("\\.el\\'" . emacs-lisp-mode)
+   ("\\.c\\'" . c-mode)
+   ("\\.h\\'" . c-mode)
+   …)
+#+END_SRC
+
+For more info check out:
+https://www.gnu.org/software/emacs/manual/html_node/elisp/Auto-Major-Mode.html
+
+*** How to switch the major mode
+Just call the other mode or
+- ~major-mode-suspend~: Kills all the buffer local variables and record them
+- ~major-mode-restore~: This function restores the major mode recorded by ~major-mode-suspend~
+
+For more info:
+https://www.gnu.org/software/emacs/manual/html_node/elisp/Major-Modes.html
+
+** Minor Modes
+A minor mode provides optional features that users may enable or disable independently of
+the choice of major mode. Minor modes can be enabled individually or in combination.
+
+The main difference with major modes is that minor modes are not mutually exclusive and
+are not tied to buffers. They can operate globally or local to buffers.
+
+*** How to enable/disable minor modes?
+In order to toggle a minor mode we just have to call its function with no argument
+*interactively*. In order to disable a minor mode we can pass a negative integer,
+and to enable it we can pass a positive integer.
+
+
+#+BEGIN_SRC emacs-lisp
+  ;; Enable
+  (blah-mode 1)
+
+  ;; Disable
+  (blah-mode -1)
+#+END_SRC
+
+** Useful functions and variables
+- ~describe-mode~: Display documentation of current major mode and minor modes and a brief
+  summary of the state of the current buffer.
+- ~local-minor-modes~: This buffer-local variable lists the currently enabled minor modes
+  in the current buffer, and is a list of symbols.
+- ~global-minor-modes~: This variable lists the currently enabled global minor modes,
+  and is a list of symbols.
+- ~minor-mode-list~: The value of this variable is a list of all minor mode commands.