DataTransfer: setDragImage() method
When a drag occurs, a translucent image is generated from the drag target (the element
the dragstart
event is fired at), and follows the mouse pointer during the
drag. This image is created automatically, so you do not need to create it yourself.
However, if a custom image is desired, the
DataTransfer.setDragImage()
method can be used to set the
custom image to be used. The image will typically be an <img>
element
but it can also be a <canvas>
or any other visible element.
The method's x
and y
coordinates define how the image should
appear relative to the mouse pointer. These coordinates define the offset into the image
where the mouse cursor should be. For instance, to display the image so that the pointer
is at its center, use values that are half the width and height of the image.
This method must be called in the dragstart
event handler.
Syntax
js
setDragImage(imgElement, xOffset, yOffset)
Parameters
imgElement
-
An image
Element
element to use for the drag feedback image.If
Element
is an img element, then set the drag data store bitmap to the element's image (at its intrinsic size); otherwise, set the drag data store bitmap to an image generated from the given element (the exact mechanism for doing so is not currently specified).Note: If the
Element
is an existingHTMLElement
it needs to be visible in the viewport in order to be shown as a drag feedback image. Alternatively, you can create a new DOM element that might be off-screen specifically for this purpose. xOffset
-
A
long
indicating the horizontal offset within the image. yOffset
-
A
long
indicating the vertical offset within the image.
Return value
None (undefined
).
Examples
This example shows how to use the setDragImage()
method. Note the example
refers to an image file named example.gif
. If that file is present, it will
be used as the drag image and if that file is not present, the browser will use its
default drag image.
html
<!DOCTYPE html>
<html lang="en">
<head>
<title>Example of DataTransfer.setDragImage()</title>
<meta name="viewport" content="width=device-width" />
<style>
div {
margin: 0em;
padding: 2em;
}
#source {
color: blue;
border: 1px solid black;
}
#target {
border: 1px solid black;
}
</style>
<script>
function dragStartHandler(ev) {
console.log("dragStart");
// Set the drag's format and data. Use the event target's id for the data
ev.dataTransfer.setData("text/plain", ev.target.id);
// Create an image and use it for the drag image
// NOTE: change "example.gif" to an existing image or the image will not
// be created and the default drag image will be used.
const img = new Image();
img.src = "example.gif";
ev.dataTransfer.setDragImage(img, 10, 10);
}
function dragOverHandler(ev) {
console.log("dragOver");
ev.preventDefault();
}
function dropHandler(ev) {
console.log("Drop");
ev.preventDefault();
// Get the data, which is the id of the drop target
const data = ev.dataTransfer.getData("text");
ev.target.appendChild(document.getElementById(data));
}
</script>
</head>
<body>
<h1>Example of <code>DataTransfer.setDragImage()</code></h1>
<div>
<p id="source" ondragstart="dragStartHandler(event);" draggable="true">
Select this element, drag it to the Drop Zone and then release the
selection to move the element.
</p>
</div>
<div
id="target"
ondrop="dropHandler(event);"
ondragover="dragOverHandler(event);">
Drop Zone
</div>
</body>
</html>
Specifications
Specification |
---|
HTML Standard # dom-datatransfer-setdragimage-dev |
Browser compatibility
BCD tables only load in the browser