My question relates to a excellent javascript library called packery which I am using to create a masonry style layout. I am also using a sister script called draggabilly to allow the user to drag and drop (reorder) the items in the page. Currently I am doing something fairly similar to conventional usage:
http://codepen.io/desandro/pen/CKbkw
When you drag an item the interface leaves a space large enough for the element to be dropped. I wanted to place a div there temporarily to indicate that this is where the element will be dropped. All I really need is a way to get the x, y co-ordinates for where the dragged element will come to rest once released but I can't seem to figure out how to get that information.
and I am using a dragMove listener which is where I expect to display my div and provide it with the correct co-ordinates:
draggie.on( 'dragMove', function(draggieInstance, event, pointer) {
//code to display and position ghost div
});
Any assistance would be much appreciated.
Related
I am trying to create a drag and drop application when I can drop a marker on an image. While this is an Angular app I am using plain old JS API for the drag and drop do to issues with CDK.
I am able to move a 20x20 div around the image and drop it and set the location on the image by setting the top/left style of the div. However, the problem I am having is that the offset[XY] is the point of the mouse down. So if I grab the upper left corning my div lands where I expect. If I grab the div in the middle, then it is off by the drag point offset.
How can I correct for this offset of the draggable? Or is there a better solution?
One of my coworkers came up with a great solution. Subscribe to the mousedown event to find the offset and then do the math.
How can activate the drag -and-drop feature inside the canvas tag ?
As far as I know, there is no built-in drag and drop within a canvas, because a canvas is a literal context that you draw things on. Canvas-based games constantly refresh and redraw all elements.
Basically, a canvas requires a lot of manual, fine-tuned assembly of colors, though it can be performant under circumstances where you want that type of manual, decided control
When a user clicks on an object that seems to be within your canvas, you have to calculate where that mouse event's X and Y coordinates would fall, and determine which actions can be performed onclick on whichever thing is drawn there.
Normal DOM (not so in a canvas or iframe) will emit an event from the element you clicked, and will bubble up through all parent elements saying that some target element was clicked, and this fired event will have lots of data about that click event
A canvas is kinda like having a real painting: rather than an assembly of objects, there is nothing to drag, just a bunch of data about which pixels are which colors.
Normally, HTML elements have an attribute [draggable], but you would still need to manually reposition the element on mouseup or whatever, based off of the screen, or closest non-staticly placed parent. This question might be helpful: HTML5 Canvas Drag and Drop Item
You should search around instead of asking a question like this, in my opinion
I am developing a magnifying glass and I was hoping I could get some help figuring out how I am going to do a step.
What I am doing is I have a div with a higher z-index than the content. It is moveable and draggable. It also has a transparent background so one can see the content (images & text) behind/underneath it that has a lesser z-index.
Now the part that I need help with is this:
I want to figure out exactly what content is behind the div (let's give it an ID of #glass).
Then my plan was to append a <span> before and a closing one after and style it with CSS3 scale transforms to increase the size so it acts as if it is magnified.
If you have a better idea on how to 'magnify' the content please share it.
So what I am looking to do in a spot of pseudo-code is:
Get position of #glass.
Get content behind #glass.
Store that in a variable or give it a class or something to refer it to.
Append a span before and after.
Style it with scale-transform.
Undo and reset the above when #glass moves.
I would really appreciate any and all help with any of these steps, but especially number 2 and 3, As I have no idea on how to do those.
You can listen for the mousemove event on every element in the page. each time the event fires you update a variable with the latest node being hovered over.
So as you are dragging around the glass, the mousemove event should be getting fired on the elements behind the glass (since you are hovering over them). And you can then use your latest node variable to get the element behind it.
Here a is Jsfiddle demonstrating how this could be done:
http://jsfiddle.net/wWVuy/
I'm trying to build an interactive map and I'm looking for information on how to have a click and drag in one window, affect an image in its parent window.
As this is hard to explain if you visit http://liamg.co.uk/map/map.html you will see a small window/map in the top left, Id like to be able to drag a small window around the map and have that move the larger/zoomed in image, does this make sense?
Any information/help is greatly appreciated!
jquery supports drag n drop elements, see here: http://jqueryui.com/demos/draggable/
you have to set the right boundaries, and then add an event that performs on drop in which you will read the position of the dropped element and can then apply it to the map however you want to.
The right example you want is this: http://jqueryui.com/demos/draggable/constrain-movement.html
The first one in the box has the boundaries of the box.
And here you see how to react on the drop: http://jqueryui.com/demos/draggable/events.html
I think what you need is not exactly a drag event, you want a element moving only inside the little map, yeah?
Let me explain:
1- Add a listener to mouse down, up and move to that little map;
2- When flag mousedown is true, mousemove works changing a position of a square div around the little map (showing what portion of image the user is seeing). Use pageX and Y (coordinates);
3- Make the math by size of the portion div and size of the big overflowed with the full map to show the exactly zoomed portion of the map.
I belive drag is really implemented when your move a think around all the document, or using the drop event. But it's what I think.
I am simply looking for a way of using drag and drop without jquery or any other library. If a dragged object is dropped on another element the later element should start an event (in FF - better would be browser independent).
I know that drag and drop for JavaScript was discussed sometimes before but the previous postings didn't help me.
Although I found some examples it is not clear to me if there is a "drop" or "dragdrop" events exist but these things don't work:
<p ondrop='alert("It worked");'>Text</p>
<p ondragdrop='alert("It worked");'>Text</p>
How could this be done?
Many thanks in advance.
I agree with the other answers. A library will save you a lot of time and headache. This is coming from someone who just recently created a drag-and-drop control from scratch.
If you insist though this is what you'll need to do:
Bind a onmousedown event to the div you want to drag (div.onmousedown).
Change the div's position style to absolute (div.style.position = 'absolute')
Begin capturing mouse movement (document.onmousemove).
On mouse move update the div's position (div.style.top|left = '[location]px')
On the div's onmouseup event (or the document's) unbind all the handlers and do any other cleanup (null out position changes, etc).
Some problems a library will probably solve:
While dragging you will select text on the page (looks ugly).
Binding to events is different between browsers.
You have to calculate the size of the element being dragged if you want to show placeholders and to make it not "pop" when you begin dragging the control (since changing to absolute positioning will remove the element from flow).
You will probably want your dragged element to move fluidly so you will have to store some mouse offset when selecting the element or automatically center the element to the mouse.
If you want to drag an item in a list you'll have to write a ton more custom code for that list to accept the dragged item.
You'll have to take into consideration dragging when the window is scrolled and possibly dragging inside other elements that are positioned strangely.
I am simply looking for a way of using drag and drop without jquery or any other library.
I'm sorry, but there are no such thing as simply drag and drop without any library. You can write it all yourself, but that will be a lot of JS to make it work in all browsers.
Hmm. It's probably not that simple that you'd want to do it yourself, but I would look at Peter Michaux's FORK Javascript drag and drop library -- unlike JQuery or all those big libraries, FORK's modules are decoupled from each other, and are simple enough that you could probably look at Peter's source code and figure out the bits you need. (edit: I'd just use FORK.Drag as it's really small: 7.6KB total minified)
While I agree that library is the way to go, the answer you want is onmousedown, onmousemove, onmouseup. You have to handle those three events.
In onmousedown you'd find the target (event.target or similar in different browsers) and set draggedObject = event.target. You'd also start handling the onmousemove event.
Whenever the onmousemove event fired, you'd move the dragged element based on the difference in position since last time the onmousemove event fired.
In the onmouseup event, you'd clear your draggedObject variable and stop handling onmousemove.
It's not very crossbrowser, but it's the core of what you'd need to do for dragging and dropping.