/* Copyright 2013 Rob Wu <rob@robwu.nl>
* https://github.com/Rob--W/grab-to-pan.js
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Construct a GrabToPan instance for a given HTML element.
* @param options.element {Element}
* @param options.ignoreTarget {function} optional. See `ignoreTarget(node)`
* @param options.onActiveChanged {function(boolean)} optional. Called
* when grab-to-pan is (de)activated. The first argument is a boolean that
* shows whether grab-to-pan is activated.
*/
function GrabToPan(options) {
this.element = options.element
this.document = options.element.ownerDocument
if (typeof options.ignoreTarget === 'function') {
this.ignoreTarget = options.ignoreTarget
}
this.onActiveChanged = options.onActiveChanged
// Bind the contexts to ensure that `this` always points to
// the GrabToPan instance.
this.activate = this.activate.bind(this)
this.deactivate = this.deactivate.bind(this)
this.toggle = this.toggle.bind(this)
this._onmousedown = this._onmousedown.bind(this)
this._onmousemove = this._onmousemove.bind(this)
this._endPan = this._endPan.bind(this)
// This overlay will be inserted in the document when the mouse moves during
// a grab operation, to ensure that the cursor has the desired appearance.
const overlay = (this.overlay = document.createElement('div'))
overlay.className = 'grab-to-pan-grabbing'
}
GrabToPan.prototype = {
/**
* Class name of element which can be grabbed
*/
CSS_CLASS_GRAB: 'grab-to-pan-grab',
/**
* Bind a mousedown event to the element to enable grab-detection.
* @type {() => void}
*/
activate: function GrabToPan_activate() {
if (!this.active) {
this.active = true
this.element.addEventListener('mousedown', this._onmousedown, true)
this.element.classList.add(this.CSS_CLASS_GRAB)
if (this.onActiveChanged) {
this.onActiveChanged(true)
}
}
},
/**
* Removes all events. Any pending pan session is immediately stopped.
* @type {() => void}
*/
deactivate: function GrabToPan_deactivate() {
if (this.active) {
this.active = false
this.element.removeEventListener('mousedown', this._onmousedown, true)
this._endPan()
this.element.classList.remove(this.CSS_CLASS_GRAB)
if (this.onActiveChanged) {
this.onActiveChanged(false)
}
}
},
toggle: function GrabToPan_toggle() {
if (this.active) {
this.deactivate()
} else {
this.activate()
}
},
/**
* Whether to not pan if the target element is clicked.
* Override this method to change the default behaviour.
*
* @param node {Element} The target of the event
* @returns {boolean} Whether to not react to the click event.
*/
ignoreTarget: function GrabToPan_ignoreTarget(node) {
// Use matchesSelector to check whether the clicked element
// is (a child of) an input element / link
return node[matchesSelector](
'a[href], a[href] *, input, textarea, button, button *, select, option'
)
},
/**
* @private
*/
_onmousedown: function GrabToPan__onmousedown(event) {
if (event.button !== 0 || this.ignoreTarget(event.target)) {
return
}
if (event.originalTarget) {
try {
// eslint-disable-next-line no-unused-expressions
event.originalTarget.tagName
} catch (e) {
// Mozilla-specific: element is a scrollbar (XUL element)
return
}
}
this.scrollLeftStart = this.element.scrollLeft
this.scrollTopStart = this.element.scrollTop
this.clientXStart = event.clientX
this.clientYStart = event.clientY
this.document.addEventListener('mousemove', this._onmousemove, true)
this.document.addEventListener('mouseup', this._endPan, true)
// When a scroll event occurs before a mousemove, assume that the user
// dragged a scrollbar (necessary for Opera Presto, Safari and IE)
// (not needed for Chrome/Firefox)
this.element.addEventListener('scroll', this._endPan, true)
event.preventDefault()
event.stopPropagation()
const focusedElement = document.activeElement
if (focusedElement && !focusedElement.contains(event.target)) {
focusedElement.blur()
}
},
/**
* @private
*/
_onmousemove: function GrabToPan__onmousemove(event) {
this.element.removeEventListener('scroll', this._endPan, true)
if (isLeftMouseReleased(event)) {
this._endPan()
return
}
const xDiff = event.clientX - this.clientXStart
const yDiff = event.clientY - this.clientYStart
const scrollTop = this.scrollTopStart - yDiff
const scrollLeft = this.scrollLeftStart - xDiff
if (this.element.scrollTo) {
this.element.scrollTo({
top: scrollTop,
left: scrollLeft,
behavior: 'instant',
})
} else {
this.element.scrollTop = scrollTop
this.element.scrollLeft = scrollLeft
}
if (!this.overlay.parentNode) {
document.body.appendChild(this.overlay)
}
},
/**
* @private
*/
_endPan: function GrabToPan__endPan() {
this.element.removeEventListener('scroll', this._endPan, true)
this.document.removeEventListener('mousemove', this._onmousemove, true)
this.document.removeEventListener('mouseup', this._endPan, true)
// Note: ChildNode.remove doesn't throw if the parentNode is undefined.
this.overlay.remove()
},
}
// Get the correct (vendor-prefixed) name of the matches method.
let matchesSelector
;['webkitM', 'mozM', 'msM', 'oM', 'm'].some(function (prefix) {
let name = prefix + 'atches'
if (name in document.documentElement) {
matchesSelector = name
}
name += 'Selector'
if (name in document.documentElement) {
matchesSelector = name
}
return matchesSelector // If found, then truthy, and [].some() ends.
})
// Browser sniffing because it's impossible to feature-detect
// whether event.which for onmousemove is reliable
const isNotIEorIsIE10plus = !document.documentMode || document.documentMode > 9
const chrome = window.chrome
const isChrome15OrOpera15plus = chrome && (chrome.webstore || chrome.app)
// ^ Chrome 15+ ^ Opera 15+
const isSafari6plus =
/Apple/.test(navigator.vendor) &&
/Version\/([6-9]\d*|[1-5]\d+)/.test(navigator.userAgent)
/**
* Whether the left mouse is not pressed.
* @param event {MouseEvent}
* @returns {boolean} True if the left mouse button is not pressed,
* False if unsure or if the left mouse button is pressed.
*/
function isLeftMouseReleased(event) {
if ('buttons' in event && isNotIEorIsIE10plus) {
// http://www.w3.org/TR/DOM-Level-3-Events/#events-MouseEvent-buttons
// Firefox 15+
// Internet Explorer 10+
return !(event.buttons & 1)
}
if (isChrome15OrOpera15plus || isSafari6plus) {
// Chrome 14+
// Opera 15+
// Safari 6.0+
return event.which === 0
}
return false
}
export { GrabToPan }