tor-browser

indentation.js (5224B)

---

/*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

const EXPAND_TAB = "devtools.editor.expandtab";
const TAB_SIZE = "devtools.editor.tabsize";
const DETECT_INDENT = "devtools.editor.detectindentation";
const DETECT_INDENT_MAX_LINES = 500;

/**
* Get the number of indentation units to use to indent a "block"
* and a boolean indicating whether indentation must be done using tabs.
*
* @return {object} an object of the form {indentUnit, indentWithTabs}.
*        |indentUnit| is the number of indentation units to use
*        to indent a "block".
*        |indentWithTabs| is a boolean which is true if indentation
*        should be done using tabs.
*/
function getTabPrefs() {
 const indentWithTabs = !Services.prefs.getBoolPref(EXPAND_TAB);
 const indentUnit = Services.prefs.getIntPref(TAB_SIZE, 2);
 return { indentUnit, indentWithTabs };
}

/**
* Get the indentation to use in an editor, or return false if the user has
* asked for the indentation to be guessed from some text.
*
* @return {false | object}
*        Returns false if the "detect indentation" pref is set.
*        If the pref is not set, returns an object of the same
*        form as returned by getTabPrefs.
*/
function getIndentationFromPrefs() {
 const shouldDetect = Services.prefs.getBoolPref(DETECT_INDENT);
 if (shouldDetect) {
   return false;
 }

 return getTabPrefs();
}

/**
* Given a function that can iterate over some text, compute the indentation to
* use.  This consults various prefs to arrive at a decision.
*
* @param {Function} iterFunc A function of three arguments:
*        (start, end, callback); where |start| and |end| describe
*        the range of text lines to examine, and |callback| is a function
*        to be called with the text of each line.
*
* @return {object} an object of the form {indentUnit, indentWithTabs}.
*        |indentUnit| is the number of indentation units to use
*        to indent a "block".
*        |indentWithTabs| is a boolean which is true if indentation
*        should be done using tabs.
*/
function getIndentationFromIteration(iterFunc) {
 let indentWithTabs = !Services.prefs.getBoolPref(EXPAND_TAB);
 let indentUnit = Services.prefs.getIntPref(TAB_SIZE);
 const shouldDetect = Services.prefs.getBoolPref(DETECT_INDENT);

 if (shouldDetect) {
   const indent = detectIndentation(iterFunc);
   if (indent != null) {
     indentWithTabs = indent.tabs;
     indentUnit = indent.spaces ? indent.spaces : indentUnit;
   }
 }

 return { indentUnit, indentWithTabs };
}

/**
* A wrapper for @see getIndentationFromIteration which computes the
* indentation of a given string.
*
* @param {string} string the input text
* @return {object} an object of the same form as returned by
*                  getIndentationFromIteration
*/
function getIndentationFromString(string) {
 const iteratorFn = function (start, end, callback) {
   const split = string.split(/\r\n|\r|\n|\f/);
   split.slice(start, end).forEach(callback);
 };
 return getIndentationFromIteration(iteratorFn);
}

/**
* Detect the indentation used in an editor. Returns an object
* with 'tabs' - whether this is tab-indented and 'spaces' - the
* width of one indent in spaces. Or `null` if it's inconclusive.
*/
function detectIndentation(textIteratorFn) {
 // # spaces indent -> # lines with that indent
 const spaces = {};
 // indentation width of the last line we saw
 let last = 0;
 // # of lines that start with a tab
 let tabs = 0;
 // # of indented lines (non-zero indent)
 let total = 0;

 textIteratorFn(0, DETECT_INDENT_MAX_LINES, text => {
   if (text.startsWith("\t")) {
     tabs++;
     total++;
     return;
   }
   let width = 0;
   while (text[width] === " ") {
     width++;
   }
   // don't count lines that are all spaces
   if (width == text.length) {
     last = 0;
     return;
   }
   if (width > 1) {
     total++;
   }

   // see how much this line is offset from the line above it
   const indent = Math.abs(width - last);
   if (indent > 1 && indent <= 8) {
     spaces[indent] = (spaces[indent] || 0) + 1;
   }
   last = width;
 });

 // this file is not indented at all
 if (total == 0) {
   return null;
 }

 // mark as tabs if they start more than half the lines
 if (tabs >= total / 2) {
   return { tabs: true };
 }

 // find most frequent non-zero width difference between adjacent lines
 let freqIndent = null,
   max = 1;
 for (let width in spaces) {
   width = parseInt(width, 10);
   const tally = spaces[width];
   if (tally > max) {
     max = tally;
     freqIndent = width;
   }
 }
 if (!freqIndent) {
   return null;
 }

 return { tabs: false, spaces: freqIndent };
}

exports.EXPAND_TAB = EXPAND_TAB;
exports.TAB_SIZE = TAB_SIZE;
exports.DETECT_INDENT = DETECT_INDENT;
exports.getTabPrefs = getTabPrefs;
exports.getIndentationFromPrefs = getIndentationFromPrefs;
exports.getIndentationFromIteration = getIndentationFromIteration;
exports.getIndentationFromString = getIndentationFromString;