For typesetting mathematics, I am used to use the LaTeX document preparation system with the AUCTeX package for the GNU Emacs editor, and the GNOME Evince viewer, provided by Debian. Here is my modest init file: dot-emacs.el. It features synctex forward and inverse search (without focus problems) and many other goodies. Feel free to use it and to improve it!
Wikipedia provides a rich list of LaTeX editors. By curiosity, you may try from time to time some of these editors. Even if they have made huge progresses, I still believe personally that Emacs is the best to date, due to its versatility: within the editor, one can open a remote file using SSH, one can search for bibtex entries from arXiv or MathSciNet, one can play with Octave, etc.
PS: EMACSulation is the name of an old series of articles by Eric Marsden in the Linux Gazette.
;;;
;;; Djalil's GNU Emacs .emacs.el init file, dated 2013-05.
;;; Tested with Emacs 23 and 24, Auctex 11.86, Evince 3.4
;;; With Auctex 11.87, reverse/forward search is almost built-in (with bugs)
;;; Debian: apt-get install wmctrl auctex preview-latex
;;;
(add-to-list 'load-path "~/S/elisp")
(setq custom-file "~/.emacs.cu")
;;;
(setq locale-coding-system 'utf-8)
(set-selection-coding-system 'utf-8)
(prefer-coding-system 'utf-8)
(set-default-font "DejaVu Sans Mono-16")
;;;
(require 'jka-compr) ; Read compressed files
(require 'paren) ; Visual matching () {} []
;; s-region.el and pc-select are obsolete.
;; They are superseded by shift-select-mode enabled by default in 23.1.
;(require 's-region) ; Copy/Cut/Paste with Shift/Delete/Insert
;;;
(put 'eval-expression 'disabled nil)
(put 'erase-buffer 'disabled nil)
(put 'narrow-to-region 'disabled nil)
;;;
(custom-set-variables
'(column-number-mode t)
'(default-major-mode 'text-mode)
'(delete-selection-mode t)
'(dired-listing-switches "-alF")
'(dired-ls-program "/bin/ls")
'(fill-column 78)
'(global-font-lock-mode t)
'(indent-tabs-mode nil)
'(iso-accents-customize french)
'(line-number-mode t)
'(resize-minibuffer-mode t)
'(search-highlight t)
'(sentence-end-double-space nil)
'(show-paren-mode t)
'(show-paren-ring-bell-on-mismatch t)
'(show-paren-style 'mixed)
'(tab-width 4)
'(tool-bar-mode nil)
'(transient-mark-mode t)
)
;;;
;;; I don't remember who wrote this useful function...
;;;
(defun match-paren (arg)
" Go to the matching parenthesis if on parenthesis otherwise insert %."
(interactive "p")
(cond ((looking-at "\\s\(") (forward-list 1) (backward-char 1))
((looking-at "\\s\)") (forward-char 1) (backward-list 1))
(t (self-insert-command (or arg 1)))))
;;;
;;; Keys
;;;
(define-key global-map [(%)] 'match-paren)
(define-key global-map [(f1)] 'help)
(define-key global-map [(f2)] 'run-octave)
(define-key global-map [(f3)] 'font-lock-mode)
(define-key global-map [(f4)] 'ispell-change-dictionary)
(define-key global-map [(next)] '(lambda ()(interactive)(scroll-up 25)))
(define-key global-map [(prior)] '(lambda ()(interactive)(scroll-down 25)))
(define-key global-map [(control home)] 'beginning-of-buffer)
(define-key global-map [(control end)] 'end-of-buffer)
(define-key global-map [(meta backspace)] 'undo)
(define-key global-map [(meta return)] 'eshell)
;(define-key global-map [(delete)] 'delete-char)
;;;
;;; Bibretrieve allows to fetch Bibtex entries from MathSciNet or arXiv
;;; Get if from http://www.emacswiki.org/emacs/download/bibretrieve.el
;;;
(autoload 'bibretrieve "bibretrieve" "Search for BibTeX entries on the web" t)
(setq bibretrieve-backends '(("mrl" . 10) ("arxiv" . 5)))
;;;
;;; LaTeX: AUCTeX, Bibcite, RefTeX, etc
;;;
(require 'tex-site)
(load-library "auctex")
(load-library "preview-latex")
(load "server")
(unless (server-running-p) (server-start))
(if window-system (require 'font-latex))
(autoload 'turn-on-bib-cite "bib-cite")
(custom-set-variables
'(TeX-auto-save t)
'(TeX-master nil)
'(TeX-parse-self t)
'(TeX-source-specials-mode t)
'(bib-cite-use-reftex-view-crossref t)
'(reftex-enable-partial-scans t)
'(reftex-insert-label-flags (quote (t t)))
'(reftex-plug-into-AUCTeX t)
'(reftex-save-parse-info t)
'(reftex-label-alist
(quote (("thm" ?h "th:" "~\\ref{%s}" nil ("thm" "th."))
("defn" ?d "def:" "~\\ref{%s}" nil ("defn" "def."))
("lem" ?l "lem:" "~\\ref{%s}" t ("lem" "lem.")))))
'(reftex-use-multiple-selection-buffers t))
(add-hook 'LaTeX-mode-hook 'turn-on-auto-fill)
(add-hook 'LaTeX-mode-hook 'turn-on-bib-cite)
(add-hook 'LaTeX-mode-hook 'turn-on-reftex)
(add-hook 'LaTeX-mode-hook 'font-lock-mode)
(add-hook 'LaTeX-mode-hook 'imenu-add-menubar-index)
(add-hook 'LaTeX-mode-hook 'my-LaTeX-keys)
(defun my-LaTeX-keys ()
(define-key LaTeX-mode-map [down-mouse-3] 'imenu)
(define-key LaTeX-mode-map [(f7)] 'preview-buffer)
(define-key LaTeX-mode-map [(f8)] 'preview-clearout-buffer)
(define-key LaTeX-mode-map [(f9)] 'TeX-command-master)
(define-key LaTeX-mode-map [(f10)] 'TeX-next-error)
(define-key LaTeX-mode-map [(f12)] 'TeX-toggle-debug-bad-boxes)
(define-key LaTeX-mode-map [(print)] 'preview-buffer)
(define-key LaTeX-mode-map [(control B)] 'bibretrieve)
(define-key LaTeX-mode-map [(control C)] 'reftex-citation)
(define-key LaTeX-mode-map [(control R)] 'reftex-reference))
(add-hook 'server-switch-hook 'raise-frame)
;;
;; Forward/inverse search using Evince (based on dbus, needs also wmctrl)
;; Forward: C-c C-v
;; Inverse: Ctrl - Left Mouse Button
;;
(add-hook 'LaTeX-mode-hook 'TeX-PDF-mode)
(setq TeX-source-correlate-method 'synctex) ; instead of source-specials
(add-hook 'LaTeX-mode-hook 'TeX-source-correlate-mode)
;;
;; Forward search.
;;
(defun un-urlify (fname-or-url)
"Transform file:///absolute/path into /absolute/path"
;; Limited support for special characters"
(if (string= (substring fname-or-url 0 8) "file:///")
(url-unhex-string (substring fname-or-url 7))
fname-or-url))
;;
(defun urlify-escape-only (path)
"Handle special characters for urlify"
(replace-regexp-in-string " " "%20" path))
;;
(defun urlify (absolute-path)
"Transform /absolute/path to file:///absolute/path"
;; Limited support for special characters"
(urlify-escape-only
(concat "file://"
(file-truename
(concat default-directory absolute-path)))))
;;
(if (require 'dbus "dbus" t)
(progn
;; universal time, need by evince
(defun utime ()
(let ((high (nth 0 (current-time)))
(low (nth 1 (current-time))))
(+ (* high (lsh 1 16) ) low)))
;;
(defun auctex-evince-forward-sync (pdffile texfile line)
(let ((dbus-name
(dbus-call-method
:session
"org.gnome.evince.Daemon" ; service
"/org/gnome/evince/Daemon" ; path
"org.gnome.evince.Daemon" ; interface
"FindDocument"
(urlify pdffile)
t ; Open a new win if file not opened.
)))
(dbus-call-method
:session
dbus-name
"/org/gnome/evince/Window/0"
"org.gnome.evince.Window"
"SyncView"
(urlify-escape-only texfile)
(list :struct :int32 line :int32 1)
(utime)))
;DC: bring the window to the foreground and give it the focus
(call-process "wmctrl" nil nil nil "-R" pdffile))
;;
(defun auctex-evince-view ()
(let ((pdffile (concat (TeX-master-file TeX-output-extension)))
(texfile (buffer-file-name))
(line (line-number-at-pos)))
(auctex-evince-forward-sync pdffile texfile line)))
;; New view entry: Evince via D-bus.
(setq TeX-view-program-list '())
(add-to-list 'TeX-view-program-list
'("EvinceDbus" auctex-evince-view))
;; Prepend Evince via D-bus to program selection list
;; overriding other settings for PDF viewing.
(setq TeX-view-program-selection '())
(add-to-list 'TeX-view-program-selection
'(output-pdf "EvinceDbus"))))
;;
;; Inverse search.
;;
(if (require 'dbus "dbus" t)
(progn
;;
(defadvice raise-frame (after make-it-work (&optional frame) activate)
"Work around some bug? in raise-frame/Emacs/GTK/Metacity/something.
Katsumi Yamaoka http://article.gmane.org/gmane.emacs.devel:39702"
(call-process
"wmctrl" nil nil nil "-i" "-R"
(frame-parameter (or frame (selected-frame)) 'outer-window-id)))
;;
(defun auctex-evince-inverse-sync (file linecol timestamp)
(let ((buf (get-file-buffer (un-urlify file)))
(line (car linecol))
(col (cadr linecol)))
(if (null buf)
(message "Sorry, %s is not opened..." file)
(switch-to-buffer buf)
(goto-line (car linecol))
(unless (= col -1)
(move-to-column col))
(raise-frame))))
;;
(dbus-register-signal
:session
nil
"/org/gnome/evince/Window/0"
"org.gnome.evince.Window"
"SyncSource"
'auctex-evince-inverse-sync)))
;;;
;;; Tramp
;;;
(require 'tramp)
(setq tramp-default-method "scp")
;;;
;;; Octave mode
;;;
(autoload 'octave-mode "octave-mod" nil t)
(setq auto-mode-alist
(cons '("\\.m$" . octave-mode) auto-mode-alist))
(add-hook 'octave-mode-hook
(lambda ()
(abbrev-mode 1)
(auto-fill-mode 1)
(if (eq window-system 'x)
(font-lock-mode 1))))
(add-hook 'inferior-octave-mode-hook
(lambda ()
(turn-on-font-lock)
(define-key inferior-octave-mode-map [up]
'comint-previous-input)
(define-key inferior-octave-mode-map [down]
'comint-next-input)))
;;;
;;
;; Credits
;;
;; http://dud.inf.tu-dresden.de/~ben/evince_synctex.tar.gz
;; http://tex.stackexchange.com/questions/29813/setup-synctex-with-emacs
;; http://coderuins.wordpress.com/2011/10/04/using-synctex-with-emacs-and-evince-3-2/
;; http://www.mail-archive.com/auctex@gnu.org/msg04175.html
;;
;;; EOF.
Updated on May 1st, 2013 with corrections for Emacs 24.