enigma-bbs/core/multi_line_edit_text_view.js

/* jslint node: true */
'use strict';

const View          = require('./view.js').View;
const strUtil       = require('./string_util.js');
const ansi          = require('./ansi_term.js');
const wordWrapText  = require('./word_wrap.js').wordWrapText;
const ansiPrep      = require('./ansi_prep.js');

const assert        = require('assert');
const _             = require('lodash');

//  :TODO: Determine CTRL-* keys for various things
//  See http://www.bbsdocumentary.com/library/PROGRAMS/GRAPHICS/ANSI/bansi.txt
//  http://wiki.synchro.net/howto:editor:slyedit#edit_mode
//  http://sublime-text-unofficial-documentation.readthedocs.org/en/latest/reference/keyboard_shortcuts_win.html

/* Mystic
     [^B]  Reformat Paragraph            [^O]  Show this help file
       [^I]  Insert tab space              [^Q]  Enter quote mode
       [^K]  Cut current line of text      [^V]  Toggle insert/overwrite
       [^U]  Paste previously cut text     [^Y]  Delete current line


                            BASIC MOVEMENT COMMANDS

                  UP/^E       LEFT/^S      PGUP/^R      HOME/^F
                DOWN/^X      RIGHT/^D      PGDN/^C       END/^G
*/

//
//  Some other interesting implementations, resources, etc.
//
//  Editors - BBS
//  *   https://github.com/M-griffin/Enthral/blob/master/src/msg_fse.cpp
//
//
//  Editors - Other
//  *   http://joe-editor.sourceforge.net/
//  *   http://www.jbox.dk/downloads/edit.c
//  *   https://github.com/dominictarr/hipster
//
//  Implementations - Word Wrap
//  *   https://github.com/protomouse/synchronet/blob/93b01c55b3102ebc3c4f4793c3a45b8c13d0dc2a/src/sbbs3/wordwrap.c
//
//  Misc notes
//  * https://github.com/dominictarr/hipster/issues/15 (Deleting lines/etc.)
//
//  Blessed
//      insertLine: CSR(top, bottom) + CUP(y, 0) + IL(1) + CSR(0, height)
//      deleteLine: CSR(top, bottom) + CUP(y, 0) + DL(1) + CSR(0, height)
//  Quick Ansi -- update only what was changed:
//  https://github.com/dominictarr/quickansi

//
//  To-Do
//
//  * Index pos % for emit scroll events
//  * Some of this should be async'd where there is lots of processing (e.g. word wrap)
//  * Fix backspace when col=0 (e.g. bs to prev line)
//  * Add word delete (CTRL+????)
//  *


const SPECIAL_KEY_MAP_DEFAULT = {
    'line feed'     : [ 'return' ],
    exit            : [ 'esc' ],
    backspace       : [ 'backspace' ],
    delete          : [ 'delete' ],
    tab             : [ 'tab' ],
    up              : [ 'up arrow' ],
    down            : [ 'down arrow' ],
    end             : [ 'end' ],
    home            : [ 'home' ],
    left            : [ 'left arrow' ],
    right           : [ 'right arrow' ],
    'delete line'   : [ 'ctrl + y' ],
    'page up'       : [ 'page up' ],
    'page down'     : [ 'page down' ],
    insert          : [ 'insert', 'ctrl + v' ],
};

exports.MultiLineEditTextView   = MultiLineEditTextView;

function MultiLineEditTextView(options) {
    if(!_.isBoolean(options.acceptsFocus)) {
        options.acceptsFocus = true;
    }

    if(!_.isBoolean(this.acceptsInput)) {
        options.acceptsInput = true;
    }

    if(!_.isObject(options.specialKeyMap)) {
        options.specialKeyMap = SPECIAL_KEY_MAP_DEFAULT;
    }

    View.call(this, options);

    var self = this;

    //
    //  ANSI seems to want tabs to default to 8 characters. See the following:
    //  * http://www.ansi-bbs.org/ansi-bbs2/control_chars/
    //  * http://www.bbsdocumentary.com/library/PROGRAMS/GRAPHICS/ANSI/bansi.txt
    //
    //  This seems overkill though, so let's default to 4 :)
    //  :TODO: what shoudl this really be? Maybe 8 is OK
    //
    this.tabWidth           = _.isNumber(options.tabWidth) ? options.tabWidth : 4;

    this.textLines          = [ ];
    this.topVisibleIndex    = 0;
    this.mode               = options.mode || 'edit';   //  edit | preview | read-only

    if ('preview' === this.mode) {
        this.autoScroll = options.autoScroll || true;
        this.tabSwitchesView = true;
    } else {
        this.autoScroll = options.autoScroll || false;
        this.tabSwitchesView = options.tabSwitchesView || false;
    }
    //
    //  cursorPos represents zero-based row, col positions
    //  within the editor itself
    //
    this.cursorPos          = { col : 0, row : 0 };

    this.getSGRFor = function(sgrFor) {
        return {
            text : self.getSGR(),
        }[sgrFor] || self.getSGR();
    };

    this.isEditMode = function() {
        return 'edit' === self.mode;
    };

    this.isPreviewMode = function() {
        return 'preview' === self.mode;
    };

    //  :TODO: Most of the calls to this could be avoided via incrementRow(), decrementRow() that keeps track or such
    this.getTextLinesIndex = function(row) {
        if(!_.isNumber(row)) {
            row = self.cursorPos.row;
        }
        var index = self.topVisibleIndex + row;
        return index;
    };

    this.getRemainingLinesBelowRow = function(row) {
        if(!_.isNumber(row)) {
            row = self.cursorPos.row;
        }
        return self.textLines.length - (self.topVisibleIndex + row) - 1;
    };

    this.getNextEndOfLineIndex = function(startIndex) {
        for(var i = startIndex; i < self.textLines.length; i++) {
            if(self.textLines[i].eol) {
                return i;
            }
        }
        return self.textLines.length;
    };

    this.toggleTextCursor = function(action) {
        self.client.term.rawWrite(`${self.getSGRFor('text')}${'hide' === action ? ansi.hideCursor() : ansi.showCursor()}`);
    };

    this.redrawRows = function(startRow, endRow) {
        self.toggleTextCursor('hide');

        const startIndex    = self.getTextLinesIndex(startRow);
        const endIndex      = Math.min(self.getTextLinesIndex(endRow), self.textLines.length);
        const absPos        = self.getAbsolutePosition(startRow, 0);

        for(let i = startIndex; i < endIndex; ++i) {
            //${self.getSGRFor('text')}
            self.client.term.write(
                `${ansi.goto(absPos.row++, absPos.col)}${self.getRenderText(i)}`,
                false   //  convertLineFeeds
            );
        }

        self.toggleTextCursor('show');

        return absPos.row - self.position.row;  //  row we ended on
    };

    this.eraseRows = function(startRow, endRow) {
        self.toggleTextCursor('hide');

        const absPos        = self.getAbsolutePosition(startRow, 0);
        const absPosEnd     = self.getAbsolutePosition(endRow, 0);
        const eraseFiller   = ' '.repeat(self.dimens.width);//new Array(self.dimens.width).join(' ');

        while(absPos.row < absPosEnd.row) {
            self.client.term.write(
                `${ansi.goto(absPos.row++, absPos.col)}${eraseFiller}`,
                false   //  convertLineFeeds
            );
        }

        self.toggleTextCursor('show');
    };

    this.redrawVisibleArea = function() {
        assert(self.topVisibleIndex <= self.textLines.length);
        const lastRow = self.redrawRows(0, self.dimens.height);

        self.eraseRows(lastRow, self.dimens.height);
        /*

        //  :TOOD: create eraseRows(startRow, endRow)
        if(lastRow < self.dimens.height) {
            var absPos  = self.getAbsolutePosition(lastRow, 0);
            var empty   = new Array(self.dimens.width).join(' ');
            while(lastRow++ < self.dimens.height) {
                self.client.term.write(ansi.goto(absPos.row++, absPos.col));
                self.client.term.write(empty);
            }
        }
        */
    };

    this.getVisibleText = function(index) {
        if(!_.isNumber(index)) {
            index = self.getTextLinesIndex();
        }
        return self.textLines[index].text.replace(/\t/g, ' ');
    };

    this.getText = function(index) {
        if(!_.isNumber(index)) {
            index = self.getTextLinesIndex();
        }
        return self.textLines.length > index ? self.textLines[index].text : '';
    };

    this.getTextLength = function(index) {
        if(!_.isNumber(index)) {
            index = self.getTextLinesIndex();
        }
        return self.textLines.length > index ? self.textLines[index].text.length : 0;
    };

    this.getCharacter = function(index, col) {
        if(!_.isNumber(col)) {
            col = self.cursorPos.col;
        }
        return self.getText(index).charAt(col);
    };

    this.isTab = function(index, col) {
        return '\t' === self.getCharacter(index, col);
    };

    this.getTextEndOfLineColumn = function(index) {
        return Math.max(0, self.getTextLength(index));
    };

    this.getRenderText = function(index) {
        let text        = self.getVisibleText(index);
        const remain    = self.dimens.width - text.length;

        if(remain > 0) {
            text += ' '.repeat(remain + 1);
            //          text += new Array(remain + 1).join(' ');
        }

        return text;
    };

    this.getTextLines = function(startIndex, endIndex) {
        var lines;
        if(startIndex === endIndex) {
            lines = [ self.textLines[startIndex] ];
        } else {
            lines = self.textLines.slice(startIndex, endIndex + 1); //  "slice extracts up to but not including end."
        }
        return lines;
    };

    this.getOutputText = function(startIndex, endIndex, eolMarker, options) {
        const lines = self.getTextLines(startIndex, endIndex);
        let text    = '';
        const re    = new RegExp('\\t{1,' + (self.tabWidth) + '}', 'g');

        lines.forEach(line => {
            text += line.text.replace(re, '\t');

            if(options.forceLineTerms || (eolMarker && line.eol)) {
                text += eolMarker;
            }
        });

        return text;
    };

    this.getContiguousText = function(startIndex, endIndex, includeEol) {
        var lines = self.getTextLines(startIndex, endIndex);
        var text = '';
        for(var i = 0; i < lines.length; ++i) {
            text += lines[i].text;
            if(includeEol && lines[i].eol) {
                text += '\n';
            }
        }
        return text;
    };

    this.replaceCharacterInText = function(c, index, col) {
        self.textLines[index].text = strUtil.replaceAt(
            self.textLines[index].text, col, c);
    };

    /*
    this.editTextAtPosition = function(editAction, text, index, col) {
        switch(editAction) {
            case 'insert' :
                self.insertCharactersInText(text, index, col);
                break;

            case 'deleteForward' :
                break;

            case 'deleteBack' :
                break;

            case 'replace' :
                break;
        }
    };
    */

    this.updateTextWordWrap = function(index) {
        const nextEolIndex  = self.getNextEndOfLineIndex(index);
        const wrapped       = self.wordWrapSingleLine(self.getContiguousText(index, nextEolIndex), 'tabsIntact');
        const newLines      = wrapped.wrapped.map(l => { return { text : l }; } );

        newLines[newLines.length - 1].eol = true;

        Array.prototype.splice.apply(
            self.textLines,
            [ index, (nextEolIndex - index) + 1 ].concat(newLines));

        return wrapped.firstWrapRange;
    };

    this.removeCharactersFromText = function(index, col, operation, count) {
        if('delete' === operation) {
            self.textLines[index].text =
                self.textLines[index].text.slice(0, col) +
                self.textLines[index].text.slice(col + count);

            self.updateTextWordWrap(index);
            self.redrawRows(self.cursorPos.row, self.dimens.height);
            self.moveClientCursorToCursorPos();
        } else if ('backspace' === operation) {
            //  :TODO: method for splicing text
            self.textLines[index].text =
                self.textLines[index].text.slice(0, col - (count - 1)) +
                self.textLines[index].text.slice(col + 1);

            self.cursorPos.col -= (count - 1);

            self.updateTextWordWrap(index);
            self.redrawRows(self.cursorPos.row, self.dimens.height);

            self.moveClientCursorToCursorPos();
        } else if('delete line' === operation) {
            //
            //  Delete a visible line. Note that this is *not* the "physical" line, or
            //  1:n entries up to eol! This is to keep consistency with home/end, and
            //  some other text editors such as nano. Sublime for example want to
            //  treat all of these things using the physical approach, but this seems
            //  a bit odd in this context.
            //
            var isLastLine  = (index === self.textLines.length - 1);
            var hadEol      = self.textLines[index].eol;

            self.textLines.splice(index, 1);
            if(hadEol && self.textLines.length > index && !self.textLines[index].eol) {
                self.textLines[index].eol = true;
            }

            //
            //  Create a empty edit buffer if necessary
            //  :TODO: Make this a method
            if(self.textLines.length < 1) {
                self.textLines = [ { text : '', eol : true } ];
                isLastLine = false; //  resetting
            }

            self.cursorPos.col = 0;

            var lastRow = self.redrawRows(self.cursorPos.row, self.dimens.height);
            self.eraseRows(lastRow, self.dimens.height);

            //
            //  If we just deleted the last line in the buffer, move up
            //
            if(isLastLine) {
                self.cursorEndOfPreviousLine();
            } else {
                self.moveClientCursorToCursorPos();
            }
        }
    };

    this.insertCharactersInText = function(c, index, col) {
        const prevTextLength    = self.getTextLength(index);
        let editingEol          = self.cursorPos.col === prevTextLength;

        self.textLines[index].text = [
            self.textLines[index].text.slice(0, col),
            c,
            self.textLines[index].text.slice(col)
        ].join('');

        self.cursorPos.col += c.length;

        if(self.getTextLength(index) > self.dimens.width) {
            //
            //  Update word wrapping and |cursorOffset| if the cursor
            //  was within the bounds of the wrapped text
            //
            let cursorOffset;
            const lastCol           = self.cursorPos.col - c.length;
            const firstWrapRange    = self.updateTextWordWrap(index);
            if(lastCol >= firstWrapRange.start && lastCol <= firstWrapRange.end) {
                cursorOffset = self.cursorPos.col - firstWrapRange.start;
                editingEol = true;  //override
            } else {
                cursorOffset = firstWrapRange.end;
            }

            //  redraw from current row to end of visible area
            self.redrawRows(self.cursorPos.row, self.dimens.height);

            //  If we're editing mid, we're done here. Else, we need to
            //  move the cursor to the new editing position after a wrap
            if(editingEol) {
                self.cursorBeginOfNextLine();
                self.cursorPos.col += cursorOffset;
                self.client.term.rawWrite(ansi.right(cursorOffset));
            } else {
                //  adjust cursor after drawing new rows
                const absPos = self.getAbsolutePosition(self.cursorPos.row, self.cursorPos.col);
                self.client.term.rawWrite(ansi.goto(absPos.row, absPos.col));
            }
        } else {
            //
            //  We must only redraw from col -> end of current visible line
            //
            const absPos = self.getAbsolutePosition(self.cursorPos.row, self.cursorPos.col);
            const renderText = self.getRenderText(index).slice(self.cursorPos.col - c.length);

            self.client.term.write(
                `${ansi.hideCursor()}${self.getSGRFor('text')}${renderText}${ansi.goto(absPos.row, absPos.col)}${ansi.showCursor()}`,
                false   //  convertLineFeeds
            );
        }
    };

    this.getRemainingTabWidth = function(col) {
        if(!_.isNumber(col)) {
            col = self.cursorPos.col;
        }
        return self.tabWidth - (col % self.tabWidth);
    };

    this.calculateTabStops = function() {
        self.tabStops = [ 0 ];
        var col = 0;
        while(col < self.dimens.width) {
            col += self.getRemainingTabWidth(col);
            self.tabStops.push(col);
        }
    };

    this.getNextTabStop = function(col) {
        var i = self.tabStops.length;
        while(self.tabStops[--i] > col);
        return self.tabStops[++i];
    };

    this.getPrevTabStop = function(col) {
        var i = self.tabStops.length;
        while(self.tabStops[--i] >= col);
        return self.tabStops[i];
    };

    this.expandTab = function(col, expandChar) {
        expandChar = expandChar || ' ';
        return new Array(self.getRemainingTabWidth(col)).join(expandChar);
    };

    this.wordWrapSingleLine = function(line, tabHandling = 'expand') {
        return wordWrapText(
            line,
            {
                width       : self.dimens.width,
                tabHandling : tabHandling,
                tabWidth    : self.tabWidth,
                tabChar     : '\t',
            }
        );
    };

    this.setTextLines = function(lines, index, termWithEol) {
        if(0 === index && (0 === self.textLines.length || (self.textLines.length === 1 && '' === self.textLines[0].text) )) {
            //  quick path: just set the things
            self.textLines = lines.slice(0, -1).map(l => {
                return { text : l };
            }).concat( { text : lines[lines.length - 1], eol : termWithEol } );
        } else {
            //  insert somewhere in textLines...
            if(index > self.textLines.length) {
                //  fill with empty
                self.textLines.splice(
                    self.textLines.length,
                    0,
                    ...Array.from( { length : index - self.textLines.length } ).map( () => { return { text : '' }; } )
                );
            }

            const newLines = lines.slice(0, -1).map(l => {
                return { text : l };
            }).concat( { text : lines[lines.length - 1], eol : termWithEol } );

            self.textLines.splice(
                index,
                0,
                ...newLines
            );
        }
    };

    this.setAnsiWithOptions = function(ansi, options, cb) {

        function setLines(text) {
            text = strUtil.splitTextAtTerms(text);

            let index = 0;

            text.forEach(line => {
                self.setTextLines( [ line ], index, true);  //  true=termWithEol
                index += 1;
            });

            self.cursorStartOfDocument();

            if(cb) {
                return cb(null);
            }
        }

        if(options.prepped) {
            return setLines(ansi);
        }

        ansiPrep(
            ansi,
            {
                termWidth           : this.client.term.termWidth,
                termHeight          : this.client.term.termHeight,
                cols                : this.dimens.width,
                rows                : 'auto',
                startCol            : this.position.col,
                forceLineTerm       : options.forceLineTerm,
            },
            (err, preppedAnsi) => {
                return setLines(err ? ansi : preppedAnsi);
            }
        );
    };

    this.insertRawText = function(text, index, col) {
        //
        //  Perform the following on |text|:
        //  *   Normalize various line feed formats -> \n
        //  *   Remove some control characters (e.g. \b)
        //  *   Word wrap lines such that they fit in the visible workspace.
        //      Each actual line will then take 1:n elements in textLines[].
        //  *   Each tab will be appropriately expanded and take 1:n \t
        //      characters. This allows us to know when we're in tab space
        //      when doing cursor movement/etc.
        //
        //
        //  Try to handle any possible newline that can be fed to us.
        //  See http://stackoverflow.com/questions/5034781/js-regex-to-split-by-line
        //
        //  :TODO: support index/col insertion point

        if(_.isNumber(index)) {
            if(_.isNumber(col)) {
                //
                //  Modify text to have information from index
                //  before and and after column
                //
                //  :TODO: Need to clean this string (e.g. collapse tabs)
                text = self.textLines;

                //  :TODO: Remove original line @ index
            }
        } else {
            index = self.textLines.length;
        }

        text = strUtil.splitTextAtTerms(text);

        let wrapped;
        text.forEach(line => {
            wrapped = self.wordWrapSingleLine(line, 'expand').wrapped;

            self.setTextLines(wrapped, index, true);    //  true=termWithEol
            index += wrapped.length;
        });
    };

    this.getAbsolutePosition = function(row, col) {
        return {
            row : self.position.row + row,
            col : self.position.col + col,
        };
    };

    this.moveClientCursorToCursorPos = function() {
        var absPos = self.getAbsolutePosition(self.cursorPos.row, self.cursorPos.col);
        self.client.term.rawWrite(ansi.goto(absPos.row, absPos.col));
    };


    this.keyPressCharacter = function(c) {
        var index = self.getTextLinesIndex();

        //
        //  :TODO: stuff that needs to happen
        //  * Break up into smaller methods
        //  * Even in overtype mode, word wrapping must apply if past bounds
        //  * A lot of this can be used for backspacing also
        //  * See how Sublime treats tabs in *non* overtype mode... just overwrite them?
        //
        //

        if(self.overtypeMode) {
            //  :TODO: special handing for insert over eol mark?
            self.replaceCharacterInText(c, index, self.cursorPos.col);
            self.cursorPos.col++;
            self.client.term.write(c);
        } else {
            self.insertCharactersInText(c, index, self.cursorPos.col);
        }

        self.emitEditPosition();
    };

    this.keyPressUp = function() {
        if(self.cursorPos.row > 0) {
            self.cursorPos.row--;
            self.client.term.rawWrite(ansi.up());

            if(!self.adjustCursorToNextTab('up')) {
                self.adjustCursorIfPastEndOfLine(false);
            }
        } else {
            self.scrollDocumentDown();
            self.adjustCursorIfPastEndOfLine(true);
        }

        self.emitEditPosition();
    };

    this.keyPressDown = function() {
        var lastVisibleRow = Math.min(
            self.dimens.height,
            (self.textLines.length - self.topVisibleIndex)) - 1;

        if(self.cursorPos.row < lastVisibleRow) {
            self.cursorPos.row++;
            self.client.term.rawWrite(ansi.down());

            if(!self.adjustCursorToNextTab('down')) {
                self.adjustCursorIfPastEndOfLine(false);
            }
        } else {
            self.scrollDocumentUp();
            self.adjustCursorIfPastEndOfLine(true);
        }

        self.emitEditPosition();
    };

    this.keyPressLeft = function() {
        if(self.cursorPos.col > 0) {
            var prevCharIsTab = self.isTab();

            self.cursorPos.col--;
            self.client.term.rawWrite(ansi.left());

            if(prevCharIsTab) {
                self.adjustCursorToNextTab('left');
            }
        } else {
            self.cursorEndOfPreviousLine();
        }

        self.emitEditPosition();
    };

    this.keyPressRight = function() {
        var eolColumn = self.getTextEndOfLineColumn();
        if(self.cursorPos.col < eolColumn) {
            var prevCharIsTab = self.isTab();

            self.cursorPos.col++;
            self.client.term.rawWrite(ansi.right());

            if(prevCharIsTab) {
                self.adjustCursorToNextTab('right');
            }
        } else {
            self.cursorBeginOfNextLine();
        }

        self.emitEditPosition();
    };

    this.keyPressHome = function() {
        var firstNonWhitespace = self.getVisibleText().search(/\S/);
        if(-1 !== firstNonWhitespace) {
            self.cursorPos.col = firstNonWhitespace;
        } else {
            self.cursorPos.col = 0;
        }
        self.moveClientCursorToCursorPos();

        self.emitEditPosition();
    };

    this.keyPressEnd = function() {
        self.cursorPos.col = self.getTextEndOfLineColumn();
        self.moveClientCursorToCursorPos();
        self.emitEditPosition();
    };

    this.keyPressPageUp = function() {
        if(self.topVisibleIndex > 0) {
            self.topVisibleIndex = Math.max(0, self.topVisibleIndex - self.dimens.height);
            self.redraw();
            self.adjustCursorIfPastEndOfLine(true);
        } else {
            self.cursorPos.row = 0;
            self.moveClientCursorToCursorPos(); //  :TODO: ajust if eol, etc.
        }

        self.emitEditPosition();
    };

    this.keyPressPageDown = function() {
        var linesBelow = self.getRemainingLinesBelowRow();
        if(linesBelow > 0) {
            self.topVisibleIndex += Math.min(linesBelow, self.dimens.height);
            self.redraw();
            self.adjustCursorIfPastEndOfLine(true);
        }

        self.emitEditPosition();
    };

    this.keyPressLineFeed = function() {
        //
        //  Break up text from cursor position, redraw, and update cursor
        //  position to start of next line
        //
        var index           = self.getTextLinesIndex();
        var nextEolIndex    = self.getNextEndOfLineIndex(index);
        var text            = self.getContiguousText(index, nextEolIndex);
        const newLines      = self.wordWrapSingleLine(text.slice(self.cursorPos.col), 'tabsIntact').wrapped;

        newLines.unshift( { text : text.slice(0, self.cursorPos.col), eol : true } );
        for(var i = 1; i < newLines.length; ++i) {
            newLines[i] = { text : newLines[i] };
        }
        newLines[newLines.length - 1].eol = true;

        Array.prototype.splice.apply(
            self.textLines,
            [ index, (nextEolIndex - index) + 1 ].concat(newLines));

        //  redraw from current row to end of visible area
        self.redrawRows(self.cursorPos.row, self.dimens.height);
        self.cursorBeginOfNextLine();

        self.emitEditPosition();
    };

    this.keyPressInsert = function() {
        self.toggleTextEditMode();
    };

    this.keyPressTab = function() {
        var index = self.getTextLinesIndex();
        self.insertCharactersInText(self.expandTab(self.cursorPos.col, '\t') + '\t', index, self.cursorPos.col);

        self.emitEditPosition();
    };

    this.keyPressBackspace = function() {
        if(self.cursorPos.col >= 1) {
            //
            //  Don't want to delete character at cursor, but rather the character
            //  to the left of the cursor!
            //
            self.cursorPos.col -= 1;

            var index = self.getTextLinesIndex();
            var count;

            if(self.isTab()) {
                var col = self.cursorPos.col;
                var prevTabStop = self.getPrevTabStop(self.cursorPos.col);
                while(col >= prevTabStop) {
                    if(!self.isTab(index, col)) {
                        break;
                    }
                    --col;
                }

                count = (self.cursorPos.col - col);
            } else {
                count = 1;
            }

            self.removeCharactersFromText(
                index,
                self.cursorPos.col,
                'backspace',
                count);
        } else {
            //
            //  Delete character at end of line previous.
            //  * This may be a eol marker
            //  * Word wrapping will need re-applied
            //
            //  :TODO: apply word wrapping such that text can be re-adjusted if it can now fit on prev
            self.keyPressLeft();    //  same as hitting left - jump to previous line
            //self.keyPressBackspace();
        }

        self.emitEditPosition();
    };

    this.keyPressDelete = function() {
        const lineIndex = self.getTextLinesIndex();

        if(0 === self.cursorPos.col && 0 === self.textLines[lineIndex].text.length && self.textLines.length > 0) {
            //
            //  Start of line and nothing left. Just delete the line
            //
            self.removeCharactersFromText(
                lineIndex,
                0,
                'delete line'
            );
        } else {
            self.removeCharactersFromText(
                lineIndex,
                self.cursorPos.col,
                'delete',
                1
            );
        }

        self.emitEditPosition();
    };

    this.keyPressDeleteLine = function() {
        if(self.textLines.length > 0) {
            self.removeCharactersFromText(
                self.getTextLinesIndex(),
                0,
                'delete line');
        }

        self.emitEditPosition();
    };

    this.adjustCursorIfPastEndOfLine = function(forceUpdate) {
        var eolColumn = self.getTextEndOfLineColumn();
        if(self.cursorPos.col > eolColumn) {
            self.cursorPos.col = eolColumn;
            forceUpdate = true;
        }

        if(forceUpdate) {
            self.moveClientCursorToCursorPos();
        }
    };

    this.adjustCursorToNextTab = function(direction) {
        if(self.isTab()) {
            var move;
            switch(direction) {
                //
                //  Next tabstop to the right
                //
                case 'right' :
                    move = self.getNextTabStop(self.cursorPos.col) - self.cursorPos.col;
                    self.cursorPos.col += move;
                    self.client.term.rawWrite(ansi.right(move));
                    break;

                    //
                    //  Next tabstop to the left
                    //
                case 'left' :
                    move = self.cursorPos.col - self.getPrevTabStop(self.cursorPos.col);
                    self.cursorPos.col -= move;
                    self.client.term.rawWrite(ansi.left(move));
                    break;

                case 'up' :
                case 'down' :
                    //
                    //  Jump to the tabstop nearest the cursor
                    //
                    var newCol = self.tabStops.reduce(function r(prev, curr) {
                        return (Math.abs(curr - self.cursorPos.col) < Math.abs(prev - self.cursorPos.col) ? curr : prev);
                    });

                    if(newCol > self.cursorPos.col) {
                        move = newCol - self.cursorPos.col;
                        self.cursorPos.col += move;
                        self.client.term.rawWrite(ansi.right(move));
                    } else if(newCol < self.cursorPos.col) {
                        move = self.cursorPos.col - newCol;
                        self.cursorPos.col -= move;
                        self.client.term.rawWrite(ansi.left(move));
                    }
                    break;
            }

            return true;
        }
        return false;   //  did not fall on a tab
    };

    this.cursorStartOfDocument = function() {
        self.topVisibleIndex    = 0;
        self.cursorPos          = { row : 0, col : 0 };

        self.redraw();
        self.moveClientCursorToCursorPos();
    };

    this.cursorEndOfDocument = function() {
        self.topVisibleIndex    = Math.max(self.textLines.length - self.dimens.height, 0);
        self.cursorPos.row      = (self.textLines.length - self.topVisibleIndex) - 1;
        self.cursorPos.col      = self.getTextEndOfLineColumn();

        self.redraw();
        self.moveClientCursorToCursorPos();
    };

    this.cursorBeginOfNextLine = function() {
        //  e.g. when scrolling right past eol
        var linesBelow = self.getRemainingLinesBelowRow();

        if(linesBelow > 0) {
            var lastVisibleRow  = Math.min(self.dimens.height, self.textLines.length) - 1;
            if(self.cursorPos.row < lastVisibleRow) {
                self.cursorPos.row++;
            } else {
                self.scrollDocumentUp();
            }
            self.keyPressHome();    //  same as pressing 'home'
        }
    };

    this.cursorEndOfPreviousLine = function() {
        //  e.g. when scrolling left past start of line
        var moveToEnd;
        if(self.cursorPos.row > 0) {
            self.cursorPos.row--;
            moveToEnd = true;
        } else if(self.topVisibleIndex > 0) {
            self.scrollDocumentDown();
            moveToEnd = true;
        }

        if(moveToEnd) {
            self.keyPressEnd(); //  same as pressing 'end'
        }
    };

    /*
    this.cusorEndOfNextLine = function() {
        var linesBelow = self.getRemainingLinesBelowRow();

        if(linesBelow > 0) {
            var lastVisibleRow = Math.min(self.dimens.height, self.textLines.length) - 1;
            if(self.cursorPos.row < lastVisibleRow) {
                self.cursorPos.row++;
            } else {
                self.scrollDocumentUp();
            }
            self.keyPressEnd(); //  same as pressing 'end'
        }
    };
    */

    this.scrollDocumentUp = function() {
        //
        //  Note: We scroll *up* when the cursor goes *down* beyond
        //  the visible area!
        //
        var linesBelow = self.getRemainingLinesBelowRow();
        if(linesBelow > 0) {
            self.topVisibleIndex++;
            self.redraw();
        }
    };

    this.scrollDocumentDown = function() {
        //
        //  Note: We scroll *down* when the cursor goes *up* beyond
        //  the visible area!
        //
        if(self.topVisibleIndex > 0) {
            self.topVisibleIndex--;
            self.redraw();
        }
    };

    this.emitEditPosition = function() {
        self.emit('edit position',  self.getEditPosition());
    };

    this.toggleTextEditMode = function() {
        self.overtypeMode = !self.overtypeMode;
        self.emit('text edit mode', self.getTextEditMode());
    };

    this.insertRawText(''); //  init to blank/empty
}

require('util').inherits(MultiLineEditTextView, View);

MultiLineEditTextView.prototype.setWidth = function(width) {
    MultiLineEditTextView.super_.prototype.setWidth.call(this, width);

    this.calculateTabStops();
};

MultiLineEditTextView.prototype.redraw = function() {
    MultiLineEditTextView.super_.prototype.redraw.call(this);

    this.redrawVisibleArea();
};

MultiLineEditTextView.prototype.setFocus = function(focused) {
    this.client.term.rawWrite(this.getSGRFor('text'));
    this.moveClientCursorToCursorPos();

    MultiLineEditTextView.super_.prototype.setFocus.call(this, focused);
};

MultiLineEditTextView.prototype.setText = function(text, options = { scrollMode : 'default' } ) {
    this.textLines = [ ];
    this.addText(text, options);
    /*this.insertRawText(text);

    if(this.isEditMode()) {
        this.cursorEndOfDocument();
    } else if(this.isPreviewMode()) {
        this.cursorStartOfDocument();
    }*/
};

MultiLineEditTextView.prototype.setAnsi = function(ansi, options = { prepped : false }, cb) {
    this.textLines = [ ];
    return this.setAnsiWithOptions(ansi, options, cb);
};

MultiLineEditTextView.prototype.addText = function(text, options = { scrollMode : 'default' }) {
    this.insertRawText(text);

    switch(options.scrollMode) {
        case 'default' :
            if(this.isEditMode() || this.autoScroll) {
                this.cursorEndOfDocument();
            } else {
                this.cursorStartOfDocument();
            }
            break;

        case 'top' :
        case 'start' :
            this.cursorStartOfDocument();
            break;

        case 'end' :
        case 'bottom' :
            this.cursorEndOfDocument();
            break;
    }
};

MultiLineEditTextView.prototype.getData = function(options = { forceLineTerms : false } ) {
    return this.getOutputText(0, this.textLines.length, '\r\n', options);
};

MultiLineEditTextView.prototype.setPropertyValue = function(propName, value) {
    switch(propName) {
        case 'mode'         :
            this.mode = value;
            if('preview' === value && !this.specialKeyMap.next) {
                this.specialKeyMap.next = [ 'tab' ];
            }
            break;

        case 'autoScroll'   :
            this.autoScroll = value;
            break;

        case 'tabSwitchesView' :
            this.tabSwitchesView = value;
            this.specialKeyMap.next = this.specialKeyMap.next || [];
            this.specialKeyMap.next.push('tab');
            break;
    }

    MultiLineEditTextView.super_.prototype.setPropertyValue.call(this, propName, value);
};

const HANDLED_SPECIAL_KEYS = [
    'up', 'down', 'left', 'right',
    'home', 'end',
    'page up', 'page down',
    'line feed',
    'insert',
    'tab',
    'backspace', 'delete',
    'delete line',
];

const PREVIEW_MODE_KEYS = [
    'up', 'down', 'page up', 'page down'
];

MultiLineEditTextView.prototype.onKeyPress = function(ch, key) {
    const self = this;
    let handled;

    if(key) {
        HANDLED_SPECIAL_KEYS.forEach(function aKey(specialKey) {
            if(self.isKeyMapped(specialKey, key.name)) {

                if(self.isPreviewMode() && -1 === PREVIEW_MODE_KEYS.indexOf(specialKey)) {
                    return;
                }

                if('tab' !== key.name || !self.tabSwitchesView) {
                    self[_.camelCase('keyPress ' + specialKey)]();
                    handled = true;
                }
            }
        });
    }

    if(self.isEditMode() && ch && strUtil.isPrintable(ch)) {
        this.keyPressCharacter(ch);
    }

    if(!handled) {
        MultiLineEditTextView.super_.prototype.onKeyPress.call(this, ch, key);
    }
};

MultiLineEditTextView.prototype.scrollUp = function() {
    this.scrollDocumentUp();
};

MultiLineEditTextView.prototype.scrollDown = function() {
    this.scrollDocumentDown();
};

MultiLineEditTextView.prototype.deleteLine = function(line) {
    this.textLines.splice(line, 1);
};

MultiLineEditTextView.prototype.getLineCount = function() {
    return this.textLines.length;
};

MultiLineEditTextView.prototype.getTextEditMode = function() {
    return this.overtypeMode ? 'overtype' : 'insert';
};

MultiLineEditTextView.prototype.getEditPosition = function() {
    var currentIndex = this.getTextLinesIndex() + 1;

    return {
        row     : this.getTextLinesIndex(this.cursorPos.row),
        col     : this.cursorPos.col,
        percent : Math.floor(((currentIndex / this.textLines.length) * 100)),
        below   : this.getRemainingLinesBelowRow(),
    };
};