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index.js
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index.js
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/*
* Copyright (c) 2012 Adobe Systems Incorporated. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License. *
*/
var debounce = function(func, threshold, caller) {
var timeout, args = arguments;
caller = caller || null;
return function() {
if (timeout) {
clearTimeout(timeout);
}
timeout = setTimeout(function() {
func.apply(caller, args);
}, threshold || 250);
};
};
function height(elem) {
var elemStyles = window.getComputedStyle(elem);
var excludeHeight = 0;
excludeHeight += parseFloat(elemStyles.getPropertyValue('padding-top'));
excludeHeight += parseFloat(elemStyles.getPropertyValue('padding-bottom'));
return elem.offsetHeight - excludeHeight;
}
module.exports = (function(window, document) {
"use strict";
var style = document.documentElement.style,
hasTextWrap = (style.textWrap || style.WebkitTextWrap || style.MozTextWrap || style.MsTextWrap || style.OTextWrap),
wsMatches;
function NextWS_params() {
this.reset();
}
NextWS_params.prototype.reset = function () {
this.index = 0;
this.width = 0;
};
/**
* Returns true iff char at index is a space character outside of HTML < > tags.
*/
var isWS = function (txt, index) {
var re = /\s(?![^<]*>)/g,
match;
if (!wsMatches) {
// Only calc ws matches once per line
wsMatches = [];
while ((match = re.exec(txt)) !== null) {
wsMatches.push(match.index);
}
}
return wsMatches.indexOf(index) !== -1;
};
var removeTags = function (elem) {
var brTags = elem.querySelectorAll('br[data-owner="balance-text"]');
Array.prototype.slice.call(brTags).forEach(function(childElem) {
elem.replaceChild(document.createTextNode(" "), childElem);
});
var spans = elem.querySelectorAll('span[data-owner="balance-text"]');
if (spans.length > 0) {
var text = '';
Array.prototype.slice.call().forEach(function(childElem) {
text += childElem.textContent;
elem.removeChild(childElem);
});
elem.innerHTML = text;
}
};
/**
* Checks to see if we should justify the balanced text with the
* element based on the textAlign property in the computed CSS
*
* @param $el - $(element)
*/
var isJustified = function (elem) {
style = window.getComputedStyle(elem, null);
return (style.textAlign === 'justify');
};
/**
* Add whitespace after words in text to justify the string to
* the specified size.
*
* @param txt - text string
* @param conWidth - container width
*/
var justify = function (elem, txt, conWidth) {
txt = txt.trim();
var words = txt.split(' ').length;
txt = txt + ' ';
// if we don't have at least 2 words, no need to justify.
if (words < 2) {
return txt;
}
var tmp = document.createElement('span');
tmp.innerHTML = txt;
elem.appendChild(tmp);
var size = tmp.offsetWidth;
elem.removeChild(tmp);
// Figure out our word spacing and return the element
var wordSpacing = Math.floor((conWidth - size) / (words - 1));
tmp.style.wordSpacing = wordSpacing + 'px';
tmp.setAttribute('data-owner', 'balance-text');
var div = document.createElement('div');
div.appendChild(tmp);
return div.innerHTML;
};
/**
* In the current simple implementation, an index i is a break
* opportunity in txt iff it is 0, txt.length, or the
* index of a non-whitespace char immediately preceded by a
* whitespace char. (Thus, it doesn't honour 'white-space' or
* any Unicode line-breaking classes.)
*
* @precondition 0 <= index && index <= txt.length
*/
var isBreakOpportunity = function (txt, index) {
return ((index === 0) || (index === txt.length) ||
(isWS(txt, index - 1) && !isWS(txt, index)));
};
/**
* Finds the first break opportunity (@see isBreakOpportunity)
* in txt that's both after-or-equal-to index c in the direction dir
* and resulting in line width equal to or past clamp(desWidth,
* 0, conWidth) in direction dir. Sets ret.index and ret.width
* to the corresponding index and line width (from the start of
* txt to ret.index).
*
* @param $el - $(element)
* @param txt - text string
* @param conWidth - container width
* @param desWidth - desired width
* @param dir - direction (-1 or +1)
* @param c - char index (0 <= c && c <= txt.length)
* @param ret - return object; index and width of previous/next break
*
*/
var findBreakOpportunity = function(elem, txt, conWidth, desWidth, dir, c, ret) {
var w;
if (txt && typeof txt === 'string') {
for(;;) {
while (!isBreakOpportunity(txt, c)) {
c += dir;
}
elem.innerHTML = txt.substr(0, c);
// $el.html(txt.substr(0, c));
w = elem.offsetWidth;
if ((dir < 0)
? ((w <= desWidth) || (w <= 0) || (c === 0))
: ((desWidth <= w) || (conWidth <= w) || (c === txt.length))) {
break;
}
c += dir;
}
}
ret.index = c;
ret.width = w;
};
/**
* Detects the width of a non-breaking space character, given the height of
* the element with no-wrap applied.
*
* @param $el - $(element)
* @param h - height
*
*/
var getSpaceWidth = function (elem, h) {
var container = document.createElement('div');
container.style.display = "block";
container.style.position = "absolute";
container.style.bottom = 0;
container.style.right = 0;
container.style.width = 0;
container.style.height = 0;
container.style.margin = 0;
container.style.padding = 0;
container.style.visibility = "hidden";
container.style.overflow = "hidden";
var space = document.createElement('span');
space.style.fontSize = "2000px";
space.innerHTML = " ";
container.appendChild(space);
elem.appendChild(container);
var dims = space.getBoundingClientRect();
container.parentNode.removeChild(container);
var spaceRatio = dims.height / dims.width;
return (h / spaceRatio);
};
// Selectors to watch; calling balanceText() on a new selector adds it to this list.
var balancedElements = ['.balance-text'];
// Call the balanceText plugin on the elements with "balance-text" class. When a browser
// has native support for the text-wrap property, the text balanceText plugin will let
// the browser handle it natively, otherwise it will apply its own text balancing code.
var applyBalanceText = function () {
Array.prototype.slice.call(document.querySelectorAll(balancedElements.join(','))).forEach(function(elem) {
balanceText(elem, true);
});
};
var balanceText = function (elem, skipResize) {
if (hasTextWrap) {
// browser supports text-wrap, so do nothing
return;
}
// In a lower level language, this algorithm takes time
// comparable to normal text layout other than the fact
// that we do two passes instead of one, so we should
// be able to do without this limit.
var maxTextWidth = 5000;
removeTags(elem); // strip balance-text tags
// save settings
var oldWS = elem.style.whiteSpace;
var oldFloat = elem.style.float;
var oldDisplay = elem.style.display;
var oldPosition = elem.style.position;
var oldLH = elem.style.lineHeight;
// remove line height before measuring container size
elem.style.lineHeight = 'normal';
var containerWidth = elem.offsetWidth;
var containerHeight = height(elem);
elem.style.whiteSpace = 'nowrap';
elem.style.float = 'none';
elem.style.display = 'inline';
elem.style.position = 'static';
var nowrapWidth = elem.offsetWidth;
var nowrapHeight = height(elem);
// An estimate of the average line width reduction due
// to trimming trailing space that we expect over all
// lines other than the last.
var spaceWidth = ((oldWS === 'pre-wrap') ? 0 : getSpaceWidth(elem, nowrapHeight));
if (containerWidth > 0 && // prevent divide by zero
nowrapWidth > containerWidth && // text is more than 1 line
nowrapWidth < maxTextWidth) { // text is less than arbitrary limit (make this a param?)
var remainingText = elem.innerHTML;
var newText = "";
var lineText = "";
var shouldJustify = isJustified(elem);
var totLines = Math.round(containerHeight / nowrapHeight);
var remLines = totLines;
// Determine where to break:
while (remLines > 1) {
// clear whitespace match cache for each line
wsMatches = null;
var desiredWidth = Math.round((nowrapWidth + spaceWidth) / remLines - spaceWidth);
// Guessed char index
var guessIndex = Math.round((remainingText.length + 1) / remLines) - 1;
var le = new NextWS_params();
// Find a breaking space somewhere before (or equal to) desired width,
// not necessarily the closest to the desired width.
findBreakOpportunity(elem, remainingText, containerWidth, desiredWidth, -1, guessIndex, le);
// Find first breaking char after (or equal to) desired width.
var ge = new NextWS_params();
guessIndex = le.index;
findBreakOpportunity(elem, remainingText, containerWidth, desiredWidth, +1, guessIndex, ge);
// Find first breaking char before (or equal to) desired width.
le.reset();
guessIndex = ge.index;
findBreakOpportunity(elem, remainingText, containerWidth, desiredWidth, -1, guessIndex, le);
// Find closest string to desired length
var splitIndex;
if (le.index === 0) {
splitIndex = ge.index;
} else if ((containerWidth < ge.width) || (le.index === ge.index)) {
splitIndex = le.index;
} else {
splitIndex = ((Math.abs(desiredWidth - le.width) < Math.abs(ge.width - desiredWidth)) ? le.index : ge.index);
}
// Break string
lineText = remainingText.substr(0, splitIndex);
if (shouldJustify) {
newText += justify(elem, lineText, containerWidth);
} else {
newText += lineText.replace(/\s$/, "");
newText += '<br data-owner="balance-text" />';
}
remainingText = remainingText.substr(splitIndex);
// update counters
remLines--;
elem.innerHTML = remainingText;
nowrapWidth = elem.offsetWidth;//$this.width();
}
if (shouldJustify) {
elem.innerHTML = newText + justify(elem, remainingText, containerWidth);
} else {
elem.innerHTML = newText + remainingText;
}
}
// restore settings
elem.style.whiteSpace = oldWS;
elem.style.float = oldFloat;
elem.style.display = oldDisplay;
elem.style.position = oldPosition;
elem.style.lineHeight = oldLH;
};
// call on load and on resize
window.addEventListener('DOMContentLoaded', applyBalanceText);
window.addEventListener('resize', debounce(applyBalanceText));
return {
balanceText: balanceText,
balancedElements: balancedElements,
};
}(window, document));