On 06/28/2012 05:31 PM, David Seikel wrote:
Coming late to this party, but..
More importantly, the infrastructure is taking shape well. So right
now making a really cut down microemacs, wordstar, nano, or whatever is
as simple as providing a different key to command mapping array, then
calling the editLine() function. New commands for a more feature full
editor should be easy to add.
I wonder if it's really that simple? Most of the discussion I've seen
here seems to focus on how you display the text on screen, but that's
only part of the issue. Pagers like less simply read files from disk
and put the results on screen, letting you scroll forward and backward.
Less was popular when it first came out because it simply started to
read from disk and put up what it had, which could be a lot faster than
using an editor like vi in read-only mode and needing to wait for the
whole file to load.
But when you want to *edit* files, you start running into questions of
how you will store the text to be edited in memory. Storing it as one
big blob may not be feasible when you are dealing with large files, and
you have issues of how you handle things like copying, moving or
deleting blocks.
Some editors have used linked lists or doubly linked lists, where the
list is an array of lines. What happens if the file you want to edit is
one *very* long line? Current practice seems to be using the "buffer
gap" technique. An outfit called Blue Mug software did a research paper
on writing a word processor for handheld devices that might be a useful
reference. See http://goo.gl/bJtPt
Additional documentation that might be useful is here:
http://texteditors.org/cgi-bin/wiki.pl?DesigningTextEditors
Something else to look at might be Albrecht Kliene's e3 editor. e3 is
open source and cross platform, with X86 versions available for Linux,
FreeBSD, NetBSD, OpenBSD, Win9x, QNX, Atheos, BeOS(TM), DOS and ELKS,
and a version for ARM as well. Significantly, they're written in NASM
Assembler. There is also a generic C version for other platforms.
e3 emulates a subset of the emacs, nedit, pico, vi, and WordStar command
sets. Which emulation it uses is determined by the name it is called
by, and the usual installation practice is to hard link or symlink it to
the desired names. The 64 bit Linux executable is a whopping 17K in
size here.
(Under DOS/Windows, there is a 4K stub and a 20K overlay. On a 16 bit
system it's possible to use just the 4K stub, which has WS keybindings
and a 64K file size limit.)
e3 is at https://sites.google.com/site/e3editor/
Key bindings in vi mode:
<ESC> enter cmd mode
h,j,k,l,+,-,<Ret>,<SPC> move by chars&lines
^B,^F,^D,^U move by [half]page
$,0,^,w,b,e,H,L,M,z. move in line/screen
/,?,G srch fwd/bwd, go EOF
ma,'a set/go marker a
x,X,<Del>,dw,D dele chr,word,EOL
S,C,dd,d'a,yy,y'a subst,change,dele,yank
p,P paste
A,a,I,i,<Ins>,O,o enter ins.mode
R,r enter ovw.mode,ovw.chr
J join lines
ZZ,^Z, u save&quit,suspend, undo!
;,# E3 SPECIAL: set edit mode,calculate
:w,:wq,:x,:q,:q!,:e ex mode:save,quit,save_as,edit other
:0,:$,:<line#> ex mode:go BOF,EOF,line
:h ex mode:help
:<other cmd> pipe buffer thru 'sed'
Key bindings in WS mode:
Files: ^KR Insert ^KS Save ^KX Save&Exit ^KQ Abort&Exit
^KD Save&Load ^KP Pipe buffer thru 'sed'
Blocks: ^KB Start ^KK End ^KC Copy ^KY Del
^KV Move ^KW Write
Search: ^QF Find ^L Repeat ^QA Srch&Repl
Move: ^E Up ^X Down ^S Left ^D Right
^R Page Up ^C Page Dn ^W Scroll Up ^Z Scroll Dn
Quick- ^QE Wnd Top ^QX Wnd Bott ^QS Home ^QD End
-Move: ^QR BOF ^QC EOF ^QB Blk Begin ^QK Blk End
^F Next Word ^A Prev Word ^QI Line# ^QV Last Find
Delete: ^T Word ^Y Line ^H Left ^G Chr
^QY Line End ^QDel,^QH Line Beg
Other: ^KM Set mode ^KN Numerics ^KZ Suspend ^U Undo
Key bindings in EMACS mode:
Files: ^X^C Exit ^XI Insert ^X^S Save ^X^F Load New
^X^W Write new ^X^H Help ^X^P Pipe buffer thru 'sed'
Move: ^P Up ^N Down ^B Left ^F Right
altV Pg up ^V Pg down altB Left word altF Right word
^A Home ^E End alt< BOF alt> EOF
altG Go line# ^L Center Pos
Search: ^S Find fwd ^R Find bwd alt% Search&Replace like WS
Buffer: altW Copy ^Y Yank ^<SPC> Mark ^X^X Xchg Mark/Pt
Delete: ^K Line ^W Region ^H Left Chr ^D This Chr
Other: ^O Open line ^I Ins Tab ^Q Quoted Ins
^M NL ^J NL+indent altX Set edit mode
^X^N Calculate ^Z Suspend ^_ Undo
Key bindings in PICO mode:
Files: ^XN ExitNoSave ^XY Exit+Save ^XL Save+Load New File
^O Save ^S Save as ^R Read
Move: ^P Up ^N Down ^B Left ^F Right
^Y Page up ^V Page down ^QN Next word ^QP Previous word
^A Home ^E End ^QS Start ^QE EOF
^QT Top screen ^QB Bottom scr ^QL Line # ^QF last Find
Search: ^W Where is ^T Search&Repl ^JT Repeat Search & Replace
Delete: ^H Left char ^D This char ^K Kill line/region
^JW Word ^JL Line end ^JH Line begin
Other: ^U Unkill ^G Help ^^,^L,^<SPC> Mark region
^QM Set Edit Mode ^JP Pipe buffer thru 'sed'
^QC Calculate ^Z Suspend ^QU Undo
Key bindings in NEDIT mode:
Files: ^QN Exit_NoSave ^QY Exit&Save ^QL Save&Load new
^S Save ^W WriteTo=SaveAs
Move: ^L Line#
^F Find ^R Search&Replace (like WS)
^G Go repeat last ^F,^R
Select: ^<SPACE> begin&extend by cursor keys (like Emacs)
^A All buffer
^X Cut ^C Copy ^V Paste
Other: ^E Set edit mode
^K Calculate
altH Help ^Z Suspend ^U Undo
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