The event.x and event.y are relative to the container, and are computed using d3.pointer. Use event.sourceEvent to access the initiating input event and event.identifier to access the touch identifier. During the evaluation of the subject accessor, event is a beforestart drag event. The subject accessor is invoked with the same context and arguments as selection.on listeners: the current event ( event) and datum d, with the this context as the current DOM element. The subject of a drag gesture may not be changed after the gesture starts. If the subject is null or undefined, no drag gesture is started for this pointer however, other starting touches may yet start drag gestures. The returned subject should be an object that exposes x and y properties, so that the relative position of the subject and the pointer can be preserved during the drag gesture. (If necessary, the above can be accelerated using quadtree.find, simulation.find or delaunay.find.) For example, to instantiate a drag behavior and apply it to a selection:įunction subject ( event ) This function is typically not invoked directly, and is instead invoked via selection.call. The returned behavior, drag, is both an object and a function, and is typically applied to selected elements via selection.call.Īpplies this drag behavior to the specified selection. ⁵ Ignored if within 500ms of a touch gesture ending assumes click emulation.Ĭreates a new drag behavior. ⁴ Necessary to allow click emulation on touch input see #9. ³ Only applies immediately after some mouse-based gestures see drag.clickDistance. ² Only applies during an active, mouse-based gesture see #9. ¹ Necessary to capture events outside an iframe see #9. If you want to prevent some events from initiating a drag gesture, use drag.filter. The propagation of all consumed events is immediately stopped. This table describes how the drag behavior interprets native events: Event For vanilla HTML in modern browsers, import d3-drag from Skypack: DRAG AND DROP CIRCLES ANGULAR DOWNLOADYou can also download the latest release on GitHub. When Pointer Events are more widely available, the drag behavior will support those, too. The drag behavior is agnostic about the DOM, so you can use it with SVG, HTML or even Canvas! And you can extend it with advanced selection techniques, such as a Voronoi overlay or a closest-target search:īest of all, the drag behavior automatically unifies mouse and touch input, and avoids browser idiosyncrasies. The drag behavior can be combined with other behaviors, such as d3-zoom for zooming. For example, you can use it to lasso elements in a scatterplot, or to paint lines on a canvas: But the drag behavior isn’t just for moving elements around there are a variety of ways to respond to a drag gesture. You can also use d3-drag to implement custom user interface elements, such as a slider. For example, you can use d3-drag to facilitate interaction with a force-directed graph, or a simulation of colliding circles: D3’s drag behavior provides a convenient but flexible abstraction for enabling drag-and-drop interaction on selections. Drag-and-drop is a popular and easy-to-learn pointing gesture: move the pointer to an object, press and hold to grab it, “drag” the object to a new location, and release to “drop”.
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