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# svg.draggable.js A plugin for the [svgdotjs.github.io](https://svgdotjs.github.io/) library to make elements draggable. svg.draggable.js is licensed under the terms of the MIT License. ## Usage Install the plugin: ```sh npm install @svgdotjs/svg.js @svgdotjs/svg.draggable.js ``` Include this plugin after including the svg.js library in your html document. ```html ``` Or for esm just require it: ```js import { SVG } from '@svgdotjs/svg.js' import '@svgdotjs/svg.draggable.js' ``` To make an element draggable just call `draggable()` on the element ```javascript var draw = SVG().addTo('#canvas').size(400, 400) var rect = draw.rect(100, 100) rect.draggable() ``` Yes indeed, that's it! Now the `rect` is draggable. ## Events The Plugin fires 4 different events - beforedrag (cancelable) - dragstart - dragmove (cancelable) - dragend You can bind/unbind listeners to this events: ```javascript // bind rect.on('dragstart.namespace', function (event) { // event.detail.event hold the given data explained below // this == rect }) // unbind rect.off('dragstart.namespace') ``` ### event.detail `beforedrag`, `dragstart`, `dragmove` and `dragend` gives you the mouse / touch `event` and the `handler` which calculates the drag. The `dragmove` event also gives you the `dx` and `dy` values for your convenience. Except for `beforedrag` the events also give you `detail.box` which holds the initial or new bbox of the element before or after the drag. You can use this property to implement custom drag behavior as seen below. Please note that the bounding box is not what you would expect for nested svgs because those calculate their bbox based on their content and not their x, y, width and height values. Therefore stuff like constraints needs to be implemented a bit differently. ### Cancelable Events You can prevent the default action of `beforedrag` and `dragmove` with a call to `event.preventDefault()` in the callback function. The shape won't be dragged in this case. That is helpfull if you want to implement your own drag handling. ```javascript rect.draggable().on('beforedrag', (e) => { e.preventDefault() // no other events are bound // drag was completely prevented }) rect.draggable().on('dragmove', (e) => { e.preventDefault() e.detail.handler.move(100, 200) // events are still bound e.g. dragend will fire anyway }) ``` ### Custom Drag Behavior #### Constraints ```js // Some constraints (x, y, width, height) const constraints = new SVG.Box(100, 100, 400, 400) rect.on('dragmove.namespace', (e) => { const { handler, box } = e.detail e.preventDefault() let { x, y } = box // In case your dragged element is a nested element, // you are better off using the rbox() instead of bbox() if (x < constraints.x) { x = constraints.x } if (y < constraints.y) { y = constraints.y } if (box.x2 > constraints.x2) { x = constraints.x2 - box.w } if (box.y2 > constraints.y2) { y = constraints.y2 - box.h } handler.move(x - (x % 50), y - (y % 50)) }) ``` #### Snap to grid ```js rect.on('dragmove.namespace', (e) => { const { handler, box } = e.detail e.preventDefault() handler.move(box.x - (box.x % 50), box.y - (box.y % 50)) }) ``` ## Remove The draggable functionality can be removed calling draggable again with false as argument: ```javascript rect.draggable(false) ``` ## Restrictions - If your root-svg is transformed this plugin won't work properly in Firefox. Viewbox however is not affected. ## Dependencies This module requires svg.js >= v3.0.10