在 contenteditable 中精确拖放

Question

The Setup

So, I have a contenteditable div -- I'm making a WYSIWYG editor: bold, italics, formatting, whatever, and most lately: inserting fancy images (in a fancy box, with a caption).

<a class="fancy" href="i.jpg" target="_blank">
    <img alt="" src="i.jpg" />
    Optional Caption goes Here!
</a>

The user adds these fancy images with a dialog I present them with: they fill out the details, upload the image, and then much like the other editor functions, I use document.execCommand('insertHTML',false,fancy_image_html); to plop it in at the user's selection.

Desired Functionality

So, now that my user can plop in a fancy image -- they need to be able to move it around. The user needs to be able to click and drag the image (fancy box and all) to place it anywhere that they please within the contenteditable. They need to be able to move it between paragraphs, or even within paragraphs -- between two words if they want.

What gives me hope

Keep in mind -- in a contenteditable, plain old <img> tags are already blessed by the user-agent with this lovely drag-and-drop capability. By default, you can drag and drop <img> tags around wherever you please; the default drag-and-drop operation behaves as one would dream.

So, considering how this default behavior already works so smashingly on our <img> buddies -- and I only want to extend this behaviour a little bit to include a tad more HTML -- this seems like something that should be easily possible.

My Efforts Thus Far

First, I set up my fancy <a> tag with the draggable attribute, and disabled contenteditable (not sure if that's necessary, but it seems like it may as well be off):

<a class="fancy" [...] draggable="true" contenteditable="false">

Then, because the user could still drag the image out of the fancy <a> box, I had to do some CSS. I'm working in Chrome, so I'm only showing you the -webkit- prefixes, though I used the others too.

.fancy {
    -webkit-user-select:none;
    -webkit-user-drag:element; }
    .fancy>img {
        -webkit-user-drag:none; }

Now the user can drag the whole fancy box, and the little partially-faded click-drag representation image reflects this -- I can see that I'm picking up the entire box now :)

I've tried several combinations of different CSS properties, the above combo seems to make sense to me, and seems to work best.

I was hoping that this CSS alone would be enough for the browser to use the entire element as the draggable item, automagically granting the user the functionality I've been dreaming of... It does however, appear to be more complicated than that.

HTML5's JavaScript Drag and Drop API

This Drag and Drop stuff seems more complicated than it needs to be.

So, I started getting deep into DnD api docs, and now I'm stuck. So, here's what I've rigged up (yes, jQuery):

$('.fancy')
    .bind('dragstart',function(event){
        //console.log('dragstart');
        var dt=event.originalEvent.dataTransfer;
        dt.effectAllowed = 'all';
        dt.setData('text/html',event.target.outerHTML);
    });

$('.myContentEditable')
    .bind('dragenter',function(event){
        //console.log('dragenter');
        event.preventDefault();
    })
    .bind('dragleave',function(event){
        //console.log('dragleave');
    })
    .bind('dragover',function(event){
        //console.log('dragover');
        event.preventDefault();
    })
    .bind('drop',function(event){
        //console.log('drop');      
        var dt = event.originalEvent.dataTransfer;
        var content = dt.getData('text/html');
        document.execCommand('insertHTML',false,content);
        event.preventDefault();
    })
    .bind('dragend',function(event){ 
        //console.log('dragend');
    });

So here's where I'm stuck: This almost completely works. Almost completely. I have everything working, up until the very end. In the drop event, I now have access to the fancy box's HTML content that I'm trying to have inserted at the drop location. All I need to do now, is insert it at the correct location!

The problem is I can't find the correct drop location, or any way to insert to it. I've been hoping to find some kind of 'dropLocation' object to dump my fancy box into, something like dropEvent.dropLocation.content=myFancyBoxHTML; , or perhaps, at least, some kind of drop location values with which to find my own way to put the content there? Am I given anything?

Am I doing it completely wrong? Am I completely missing something?

I tried to use document.execCommand('insertHTML',false,content); like I expected I should be able to, but it unfortunately fails me here, as the selection caret is not located at the precise drop location as I'd hope.

I discovered that if I comment out all of the event.preventDefault(); 's, the selection caret becomes visible, and as one would hope, when the user prepares to drop, hovering their drag over the contenteditable, the little selection caret can be seen running along between characters following the user's cursor and drop operation -- indicating to the user that the selection caret represents the precise drop location. I need the location of this selection caret.

With some experiments, I tried execCommand-insertHTML'ing during the drop event, and the dragend event -- neither insert the HTML where the dropping-selection-caret was, instead it uses whatever location was selected prior to the drag operation.

Because the selection caret is visible during dragover, I hatched a plan.

For awhile, I was trying, in the dragover event, to insert a temporary marker, like <span class="selection-marker">|</span> , just after $('.selection-marker').remove(); , in an attempt for the browser to constantly (during dragover) be deleting all selection markers and then adding one at the insertion point -- essentially leaving one marker wherever that insertion point is, at any moment. The plan of course, was to then replace this temporary marker with the dragged content which I have.

None of this worked, of course: I couldn't get the selection-marker to insert at the apparently visible selection caret as planned -- again, the execCommand-insertedHTML placed itself wherever the selection caret was, prior to the drag operation.

Huff. So what have I missed? How is it done?

How do I obtain, or insert into, the precise location of a drag-and-drop operation? I feel like this is, obviously, a common operation among drag-and-drops -- surely I must have overlooked an important and blatant detail of some kind? Did I even have to get deep into JavaScript, or maybe there's a way to do this just with attributes like draggable, droppable, contenteditable, and some fancydancy CSS3?

I'm still on the hunt -- still tinkering around -- I'll post back as soon as I find out what I've been failing at :)

---

The Hunt Continues (edits after original post)

---

Farrukh posted a good suggestion -- use:

console.log( window.getSelection().getRangeAt(0) );

To see where the selection caret actually is. I plopped this into the dragover event, which is when I figure the selection caret is visibily hopping around between my editable content in the contenteditable.

Alas, the Range object that is returned, reports offset indices that belong to the selection caret prior to the drag-and-drop operation.

It was a valiant effort. Thanks Farrukh.

So what's going on here? I am getting the sensation that the little selection caret I see hopping around, isn't the selection caret at all! I think it's an imposter!

Upon Further Inspection!

Turns out, it is an imposter! The real selection caret remains in place during the entire drag operation! You can see the little bugger!

I was readingMDN Drag and Drop Docs , and found this:

Naturally, you may need to move the insertion marker around a dragover event as well. You can use the event's clientX and clientY properties as with other mouse events to determine the location of the mouse pointer.

Yikes, does this mean I'm supposed to figure it out for myself, based on clientX and clientY ?? Using mouse coordinates to determine the location of the selection caret myself? Scary!!

I'll look into doing so tomorrow -- unless myself, or somebody else here reading this, can find a sane solution :)

Answer 1

Dragon Drop

I've done a ridiculous amount of fiddling. So, so much jsFiddling.

This is not a robust, or complete solution; I may never quite come up with one. If anyone has any better solutions, I'm all ears -- I didn't want to have to do it this way, but it's the only way I've been able to uncover so far. The following jsFiddle, and the information I am about to vomit up, worked for me in this particular instance with my particular versions of Firefox and Chrome on my particular WAMP setup and computer. Don't come crying to me when it doesn't work on your website. This drag-and-drop crap is clearly every man for himself.

jsFiddle: Chase Moskal's Dragon Drop

So, I was boring my girlfriend's brains out, and she thought I kept saying "dragon drop" when really, I was just saying "drag-and-drop". It stuck, so that's what I call my little JavaScript buddy I've created for handling these drag-and-drop situations.

Turns out -- it's a bit of a nightmare. The HTML5 Drag-and-Drop API even at first glance, is horrible. Then, you almost warm up to it, as you start to understand and accept the way it's supposed to work.. Then you realize what a terrifying nightmare it actually is, as you learn how Firefox and Chrome go about this specification in their own special way, and seem to completely ignore all of your needs. You find yourself asking questions like: "Wait, what element is even being dragged right now? How to do I get that information? How do I cancel this drag operation? How can I stop this particular browser's unique default handling of this situation?"... The answers to your questions: "You're on your own, LOSER! Keep hacking things in, until something works!".

So, here's how I accomplished Precise Drag and Drop of Arbitrary HTML Elements within, around, and between multiple contenteditable's. (note: I'm not going fully in-depth with every detail, you'll have to look at the jsFiddle for that -- I'm just rambling off seemingly relevant details that I remember from the experience, as I have limited time)

My Solution

• First, I applied CSS to the draggables (fancybox) -- we needed user-select:none; user-drag:element; user-select:none; user-drag:element; on the fancy box, and then specifically user-drag:none; on the image within the fancy box (and any other elements, why not?). Unfortunately, this was not quite enough for Firefox, which required attribute draggable="false" to be explicitly set on the image to prevent it from being draggable.
• Next, I applied attributes draggable="true" and dropzone="copy" onto the contenteditables.

To the draggables (fancyboxes), I bind a handler for dragstart . We set the dataTransfer to copy a blank string of HTML ' ' -- because we need to trick it into thinking we are going to drag HTML, but we are cancelling out any default behavior. Sometimes default behavior slips in somehow, and it results in a duplicate (as we do the insertion ourselves), so now the worst glitch is a ' ' (space) being inserted when a drag fails. We couldn't rely on the default behavior, as it would fail to often, so I found this to be the most versatile solution.

DD.$draggables.off('dragstart').on('dragstart',function(event){
    var e=event.originalEvent;
    $(e.target).removeAttr('dragged');
    var dt=e.dataTransfer,
        content=e.target.outerHTML;
    var is_draggable = DD.$draggables.is(e.target);
    if (is_draggable) {
        dt.effectAllowed = 'copy';
        dt.setData('text/plain',' ');
        DD.dropLoad=content;
        $(e.target).attr('dragged','dragged');
    }
});

To the dropzones, I bind a handler for dragleave and drop . The dragleave handler exists only for Firefox, as in Firefox, the drag-drop would work (Chrome denies you by default) when you tried to drag it outside the contenteditable, so it performs a quick check against the Firefox-only relatedTarget . Huff.

Chrome and Firefox have different ways of acquiring the Range object, so effort had to be put in to do it differently for each browser in the drop event. Chrome builds a range based on mouse-coordinates (yup that's right) , but Firefox provides it in the event data. document.execCommand('insertHTML',false,blah) turns out to be how we handle the drop. OH, I forgot to mention -- we can't use dataTransfer.getData() on Chrome to get our dragstart set HTML -- it appears to be some kind of weird bug in the specification. Firefox calls the spec out on it's bullcrap and gives us the data anyways -- but Chrome doesn't, so we bend over backwards and to set the content to a global, and go through hell to kill all the default behavior...

DD.$dropzones.off('dragleave').on('dragleave',function(event){
    var e=event.originalEvent;

    var dt=e.dataTransfer;
    var relatedTarget_is_dropzone = DD.$dropzones.is(e.relatedTarget);
    var relatedTarget_within_dropzone = DD.$dropzones.has(e.relatedTarget).length>0;
    var acceptable = relatedTarget_is_dropzone||relatedTarget_within_dropzone;
    if (!acceptable) {
        dt.dropEffect='none';
        dt.effectAllowed='null';
    }
});
DD.$dropzones.off('drop').on('drop',function(event){
    var e=event.originalEvent;

    if (!DD.dropLoad) return false;
    var range=null;
    if (document.caretRangeFromPoint) { // Chrome
        range=document.caretRangeFromPoint(e.clientX,e.clientY);
    }
    else if (e.rangeParent) { // Firefox
        range=document.createRange(); range.setStart(e.rangeParent,e.rangeOffset);
    }
    var sel = window.getSelection();
    sel.removeAllRanges(); sel.addRange(range);

    $(sel.anchorNode).closest(DD.$dropzones.selector).get(0).focus(); // essential
    document.execCommand('insertHTML',false,'<param name="dragonDropMarker" />'+DD.dropLoad);
    sel.removeAllRanges();

    // verification with dragonDropMarker
    var $DDM=$('param[name="dragonDropMarker"]');
    var insertSuccess = $DDM.length>0;
    if (insertSuccess) {
        $(DD.$draggables.selector).filter('[dragged]').remove();
        $DDM.remove();
    }

    DD.dropLoad=null;
    DD.bindDraggables();
    e.preventDefault();
});

Okay, I'm sick of this. I've wrote all I want to about this. I'm calling it a day, and might update this if I think of anything important.

Thanks everybody. //Chase.

Answer 2

Since I wanted to see this in a native JS solution I worked a bit to remove all jQuery dependencies. Hopefully it can help someone.

First the markup

    <div class="native_receiver" style="border: 2px solid red;padding: 5px;" contenteditable="true" >
      WAITING  FOR STUFF
    </div>
    <div class="drawer" style="border: 2px solid #AAE46A; padding: 10px">
      <span class="native_drag" data-type="dateselector" contenteditable="false" draggable="true" style="border: 2px solid rgba(0,0,0,0.2);padding:4px; margin:2px">
        Block 1
      </span>
      <span class="native_drag" data-type="dateselector" contenteditable="false" draggable="true" style="border: 2px solid rgba(0,0,0,0.2);padding:4px; margin:2px">
        Second Blk
      </span>
    </div>

Then some helpers

    function addClass( elem, className ){
        var classNames = elem.className.split( " " )
        if( classNames.indexOf( className ) === -1 ){
            classNames.push( className )
        }
        elem.className = classNames.join( " " )
    }
    function selectElem( selector ){
        return document.querySelector( selector )
    }
    function selectAllElems( selector ){
        return document.querySelectorAll( selector )
    }
    function removeElem( elem ){
         return elem ? elem.parentNode.removeChild( elem ) : false
    }

Then the actual methods

    function nativeBindDraggable( elems = false ){
        elems = elems || selectAllElems( '.native_drag' );
        if( !elems ){
            // No element exists, abort
            return false;
        }else if( elems.outerHTML ){
            // if only a single element, put in array
            elems = [ elems ];
        }
        // else it is html-collection already (as good as array)

        for( let i = 0 ; i < elems.length ; i++ ){
            // For every elem in list, attach or re-attach event handling
            elems[i].dataset.transferreference = `transit_${ new Date().getTime() }`;
            elems[i].ondragstart = function(e){
                if (!e.target.id){
                    e.target.id = (new Date()).getTime();
                }

                window.inTransferMarkup = e.target.outerHTML;
                window.transferreference = elems[i].dataset.transferreference;
                addClass( e.target, 'dragged');
            };
        };
    }

    function nativeBindWriteRegion( elems = false ){
        elems = elems || selectAllElems( '.native_receiver' );
        if( !elems ){
            // No element exists, abort
            return false;
        }else if( elems.outerHTML ){
            // if only a single element, put in array
            elems = [ elems ];
        }
        // else it is html-collection

        for( let i = 0 ; i < elems.length ; i++ ){
            elems[i].ondragover = function(e){
                e.preventDefault();
                return false;
            };
            elems[i].ondrop = function(e){
                receiveBlock(e);
            };
        }
    }

    function receiveBlock(e){
        e.preventDefault();
        let content = window.inTransferMarkup;

        window.inTransferMarkup = "";

        let range = null;
        if (document.caretRangeFromPoint) { // Chrome
            range = document.caretRangeFromPoint(e.clientX, e.clientY);
        }else if (e.rangeParent) { // Firefox
            range = document.createRange();
            range.setStart(e.rangeParent, e.rangeOffset);
        }
        let sel = window.getSelection();
        sel.removeAllRanges(); 
        sel.addRange( range );
        e.target.focus();

        document.execCommand('insertHTML',false, content);
        sel.removeAllRanges();

        // reset draggable on all blocks, esp the recently created
        nativeBindDraggable(
          document.querySelector(
            `[data-transferreference='${window.transferreference}']`
          )
        );
        removeElem( selectElem( '.dragged' ) );
        return false;
    }

And lastly instantiate

nativeBindDraggable();
nativeBindWriteRegion();

Below is the functioning snippet

 function addClass( elem, className ){ var classNames = elem.className.split( " " ) if( classNames.indexOf( className ) === -1 ){ classNames.push( className ) } elem.className = classNames.join( " " ) } function selectElem( selector ){ return document.querySelector( selector ) } function selectAllElems( selector ){ return document.querySelectorAll( selector ) } function removeElem( elem ){ return elem ? elem.parentNode.removeChild( elem ) : false } function nativeBindDraggable( elems = false ){ elems = elems || selectAllElems( '.native_drag' ); if( !elems ){ // No element exists, abort return false; }else if( elems.outerHTML ){ // if only a single element, put in array elems = [ elems ]; } // else it is html-collection already (as good as array) for( let i = 0 ; i < elems.length ; i++ ){ // For every elem in list, attach or re-attach event handling elems[i].dataset.transferreference = `transit_${ new Date().getTime() }`; elems[i].ondragstart = function(e){ if (!e.target.id){ e.target.id = (new Date()).getTime(); } window.inTransferMarkup = e.target.outerHTML; window.transferreference = elems[i].dataset.transferreference; addClass( e.target, 'dragged'); }; }; } function nativeBindWriteRegion( elems = false ){ elems = elems || selectAllElems( '.native_receiver' ); if( !elems ){ // No element exists, abort return false; }else if( elems.outerHTML ){ // if only a single element, put in array elems = [ elems ]; } // else it is html-collection for( let i = 0 ; i < elems.length ; i++ ){ elems[i].ondragover = function(e){ e.preventDefault(); return false; }; elems[i].ondrop = function(e){ receiveBlock(e); }; } } function receiveBlock(e){ e.preventDefault(); let content = window.inTransferMarkup; window.inTransferMarkup = ""; let range = null; if (document.caretRangeFromPoint) { // Chrome range = document.caretRangeFromPoint(e.clientX, e.clientY); }else if (e.rangeParent) { // Firefox range = document.createRange(); range.setStart(e.rangeParent, e.rangeOffset); } let sel = window.getSelection(); sel.removeAllRanges(); sel.addRange( range ); e.target.focus(); document.execCommand('insertHTML',false, content); sel.removeAllRanges(); // reset draggable on all blocks, esp the recently created nativeBindDraggable( document.querySelector( `[data-transferreference='${window.transferreference}']` ) ); removeElem( selectElem( '.dragged' ) ); return false; } nativeBindDraggable(); nativeBindWriteRegion(); 

  <div class="native_receiver" style="border: 2px solid red;padding: 5px;" contenteditable="true" > WAITING FOR STUFF </div> <div class="drawer" style="border: 2px solid #AAE46A; padding: 10px"> <span class="native_drag" data-type="dateselector" contenteditable="false" draggable="true" style="border: 2px solid rgba(0,0,0,0.2);padding:4px; margin:2px"> Block 1 </span> <span class="native_drag" data-type="dateselector" contenteditable="false" draggable="true" style="border: 2px solid rgba(0,0,0,0.2);padding:4px; margin:2px"> Second Blk </span> </div> 

Answer 3

1. event dragstart; dataTransfer.setData("text/html", "<div class='whatever'></div>");
2. event drop: var me = this; setTimeout(function () { var el = me.element.getElementsByClassName("whatever")[0]; if (el) { //do stuff here, el is your location for the fancy img } }, 0); var me = this; setTimeout(function () { var el = me.element.getElementsByClassName("whatever")[0]; if (el) { //do stuff here, el is your location for the fancy img } }, 0);

Answer 4

To summarise above answers, the keys are event.parentNode and event.rangeOffset (firefox) and caretRangeFromPoint(event.clientX, event.clientY) (chrome). Here is a minimal example:

 span { border: 1px solid red; } span:before { content: "grab "; background-color: #0f0; }

 <p contenteditable="true" ondrop="sel = window.getSelection(); if (document.caretRangeFromPoint) range = document.caretRangeFromPoint(event.clientX, event.clientY) else { sel.collapse(event.rangeParent,event.rangeOffset) range = sel.getRangeAt(0) } range.insertNode(sp1)" ondragover=" return false" >This is a contenteditable paragraph. Grab the green field in the following span <span draggable="True" id="sp1" ondragstart=" event.dataTransfer.setData('text/plain', this.innerText)">span</span> and drag it inside this paragraph. </p>