Created
December 3, 2012 02:26
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Get cursor or text position in pixels for input element
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// @author Rob W http://stackoverflow.com/users/938089/rob-w | |
// @name getTextBoundingRect | |
// @param input Required HTMLElement with `value` attribute | |
// @param selectionStart Optional number: Start offset. Default 0 | |
// @param selectionEnd Optional number: End offset. Default selectionStart | |
// @param debug Optional boolean. If true, the created test layer | |
// will not be removed. | |
function getTextBoundingRect(input, selectionStart, selectionEnd, debug) { | |
// Basic parameter validation | |
if(!input || !('value' in input)) return input; | |
if(typeof selectionStart == "string") selectionStart = parseFloat(selectionStart); | |
if(typeof selectionStart != "number" || isNaN(selectionStart)) { | |
selectionStart = 0; | |
} | |
if(selectionStart < 0) selectionStart = 0; | |
else selectionStart = Math.min(input.value.length, selectionStart); | |
if(typeof selectionEnd == "string") selectionEnd = parseFloat(selectionEnd); | |
if(typeof selectionEnd != "number" || isNaN(selectionEnd) || selectionEnd < selectionStart) { | |
selectionEnd = selectionStart; | |
} | |
if (selectionEnd < 0) selectionEnd = 0; | |
else selectionEnd = Math.min(input.value.length, selectionEnd); | |
// If available (thus IE), use the createTextRange method | |
if (typeof input.createTextRange == "function") { | |
var range = input.createTextRange(); | |
range.collapse(true); | |
range.moveStart('character', selectionStart); | |
range.moveEnd('character', selectionEnd - selectionStart); | |
return range.getBoundingClientRect(); | |
} | |
// createTextRange is not supported, create a fake text range | |
var offset = getInputOffset(), | |
topPos = offset.top, | |
leftPos = offset.left, | |
width = getInputCSS('width', true), | |
height = getInputCSS('height', true); | |
// Styles to simulate a node in an input field | |
// use pre-wrap instead of wrap for white-space to support wrapping in textareas | |
var cssDefaultStyles = "white-space:pre-wrap;padding:0;margin:0;", | |
listOfModifiers = ['direction', 'font-family', 'font-size', 'font-size-adjust', 'font-variant', 'font-weight', 'font-style', 'letter-spacing', 'line-height', 'text-align', 'text-indent', 'text-transform', 'word-wrap', 'word-spacing']; | |
topPos += getInputCSS('padding-top', true); | |
topPos += getInputCSS('border-top-width', true); | |
leftPos += getInputCSS('padding-left', true); | |
leftPos += getInputCSS('border-left-width', true); | |
leftPos += 1; //Seems to be necessary | |
for (var i=0; i<listOfModifiers.length; i++) { | |
var property = listOfModifiers[i]; | |
cssDefaultStyles += property + ':' + getInputCSS(property) +';'; | |
} | |
// End of CSS variable checks | |
var text = input.value, | |
textLen = text.length, | |
fakeClone = document.createElement("div"); | |
if(selectionStart > 0) appendPart(0, selectionStart); | |
var fakeRange = appendPart(selectionStart, selectionEnd); | |
if(textLen > selectionEnd) appendPart(selectionEnd, textLen); | |
// Styles to inherit the font styles of the element | |
fakeClone.style.cssText = cssDefaultStyles; | |
// Styles to position the text node at the desired position | |
fakeClone.style.position = "absolute"; | |
fakeClone.style.top = topPos + "px"; | |
fakeClone.style.left = leftPos + "px"; | |
fakeClone.style.width = width + "px"; | |
fakeClone.style.height = height + "px"; | |
document.body.appendChild(fakeClone); | |
var returnValue = fakeRange.getBoundingClientRect(); //Get rect | |
if (!debug) fakeClone.parentNode.removeChild(fakeClone); //Remove temp | |
return returnValue; | |
// Local functions for readability of the previous code | |
function appendPart(start, end){ | |
var span = document.createElement("span"), | |
tmpText = text.substring(start, end); | |
span.style.cssText = cssDefaultStyles; //Force styles to prevent unexpected results | |
// add a space if it ends in a newline | |
if (/[\n\r]$/.test(tmpText)) { | |
tmpText += ' '; | |
} | |
span.textContent = tmpText; | |
fakeClone.appendChild(span); | |
return span; | |
} | |
// Computing offset position | |
function getInputOffset(){ | |
var body = document.body, | |
win = document.defaultView, | |
docElem = document.documentElement, | |
box = document.createElement('div'); | |
box.style.paddingLeft = box.style.width = "1px"; | |
body.appendChild(box); | |
var isBoxModel = box.offsetWidth == 2; | |
body.removeChild(box); | |
box = input.getBoundingClientRect(); | |
var clientTop = docElem.clientTop || body.clientTop || 0, | |
clientLeft = docElem.clientLeft || body.clientLeft || 0, | |
scrollTop = win.pageYOffset || isBoxModel && docElem.scrollTop || body.scrollTop, | |
scrollLeft = win.pageXOffset || isBoxModel && docElem.scrollLeft || body.scrollLeft; | |
return { | |
top : box.top + scrollTop - clientTop, | |
left: box.left + scrollLeft - clientLeft}; | |
} | |
function getInputCSS(prop, isnumber){ | |
var val = document.defaultView.getComputedStyle(input, null).getPropertyValue(prop); | |
return isnumber ? parseFloat(val) : val; | |
} | |
} |
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