268 lines
12 KiB
JavaScript
268 lines
12 KiB
JavaScript
/**
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* Initialize the touchkey setup.
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*
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* Requires an empty SVG container, and a HTML input tag (recommended: type="hidden") to write the string representation
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* to. Can additionally be provided with the ID of a HTML form which should be auto-submitted after touchkey entry.
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*
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* Example:
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*
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* <form id="touchkey-form" method="post" action="/login">
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* <svg id="touchkey-svg"></svg>
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* <input type="hidden" name="touchkey" id="touchkey-field" />
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* </form>
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* <script>
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* initTouchkey(false, "touchkey-svg", "touchkey-form", "touchkey-field");
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* </script>
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*
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* @param {boolean} keepPattern: Whether to keep the pattern on screen, or to clear it after the end event.
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* @param {string} svgid: HTML id of the SVG container the touchkey is drawn in.
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* @param {string} formid: HTML id of the form that should be submitted after touchkey entry. null to disable
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* auto-submit.
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* @param {string} formfieldid: ID of the input object that should receive the entered touchkey as its value.
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*/
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initTouchkey = (keepPattern, svgid, formid, formfieldid) => {
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// Define forEach (iteration) and slice (abused for shallow copying) on HTMLCollections (reuse the Array methods)
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HTMLCollection.prototype.forEach = Array.prototype.forEach;
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HTMLCollection.prototype.slice = Array.prototype.slice;
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// Max. distance to a nodes center, before the path snaps to the node.
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// Expressed as inverse ratio of the container width
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const SNAPPING_SENSITIVITY = 12;
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// Get the DOM objects for the SVG, the form and the input field
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let svg = document.getElementById(svgid);
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let form;
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if (formid !== null) {
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form = document.getElementById(formid);
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}
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let formfield = document.getElementById(formfieldid);
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// Reference to the SVG line object that's currently being drawn by the user, or null, if none
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let currentStroke = null;
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// ID generator for the SVG line objects drawn by the user
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let strokeId = 0;
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// Set of touchkey pattern nodes that have already been visited by a users pattern, and may not be reused again
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let doneMap = {};
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// The string representation of the touchkey entered by the user.
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let enteredKey = '';
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/**
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* Helper function to create a new stroke after the user completed one stroke by connecting two pattern nodes.
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*
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* @param {number} fromX: X coordinate of the starting point of this line.
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* @param {number} fromY: Y coordinate of the starting point of this line.
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* @param {number} toX: X coordinate of the ending point of this line.
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* @param {number} toY: Y coordinate of the ending point of this line.
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* @returns {string} The ID of the generated line object.
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*/
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let drawLine = (fromX, fromY, toX, toY) => {
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// Create a new SVG line object
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let line = document.createElementNS('http://www.w3.org/2000/svg', 'line');
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// Generate and set an unique ID for the line object
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let id = 'touchkey-svg-stroke-' + (strokeId++);
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line.setAttribute('id', id);
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// Create and set the HTML class attribute
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line.setAttribute('class', 'touchkey-svg-stroke');
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// Create and set the coordinate attributes
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line.setAttribute('x1', fromX.toString());
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line.setAttribute('y1', fromY.toString());
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line.setAttribute('x2', toX.toString());
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line.setAttribute('y2', toY.toString());
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// Create and set the style attribute (grey, circular ends, 5% width)
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line.setAttribute('style', 'stroke: grey; stroke-width: 5%; stroke-linecap: round');
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// Add the line to the SVG
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svg.appendChild(line);
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// Return the previously generated ID to identify the line object by
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return id;
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};
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/**
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* Helper function used to remove the "trailing stroke" (i.e. after the user let go, there is a dangling stroke from
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* the node that was hit last to the mouse pointer/finger).
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*/
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let endPath = () => {
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// Remove the current stroke ...
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svg.removeChild(svg.getElementById(currentStroke));
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// ... and set its reference to null
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currentStroke = null;
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};
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/**
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* Helper function used to clear the touchkey pattern drawn by the user.
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*/
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let clearTouchkey = () => {
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// Reset the set of visited pattern nodes
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doneMap = {};
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// Reset the touchkey string representation
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enteredKey = '';
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// Remove all line objects. Create a shallow copy of the list first to retain deletion order.
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svg.getElementsByClassName('touchkey-svg-stroke').slice().forEach((line) => {
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svg.removeChild(line);
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});
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};
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/**
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* Helper function to read and convert the event coordinates of a MouseEvent or TouchEvent to coordinates relative
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* to the SVG's origin.
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*
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* @param {(MouseEvent|TouchEvent)} ev: The event to get the X and Y coordinates from.
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* @param {(ClientRect|DOMRect)} svgrect: Bounds rectangle of the SVG container.
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* @returns {Array} The X and Y coordinates relative to the SVG's origin.
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*/
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let getEventCoordinates = (ev, svgrect) => {
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// Check for existence of the "touches" property to distinguish between touch and mouse events
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// For a touch event, take the page coordinates of the first touch
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// For a mouse event, take the event coordinates
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// Then subtract the SVG's origin from the page-relative coordinates to obtain the translated coordinates
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const trX = (typeof ev.touches !== 'undefined' ? ev.touches[0].pageX : ev.x) - svgrect.left;
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const trY = (typeof ev.touches !== 'undefined' ? ev.touches[0].pageY : ev.y) - svgrect.top;
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return [trX, trY]
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};
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/**
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* Find the pattern node closest to a coordinate.
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*
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* @param {number} evX: X coordinate of the point to search the closest node for.
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* @param {number} evY: Y coordinate of the point to search the closest node for.
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* @param {(ClientRect|DOMRect)} svgrect: Bounds rectangle of the SVG container.
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* @returns {Array} The node's ID, the distance, the X and Y coordinate of the node's center.
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*/
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let getNearestPatternNode = (evX, evY, svgrect) => {
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// Initialize nearest neighbors search variables
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let minId = '';
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let minDist2 = Infinity; // Squared distance
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let minX = 0;
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let minY = 0;
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// Iterate the pattern nodes for nearest neighbors search
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document.getElementsByClassName('touchkey-svg-node').forEach((node) => {
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// Get the position of a node's center, converted from ratio into absolute pixel count
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let x = parseFloat(node.getAttribute('cx')) / 100.0 * svgrect.width;
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let y = parseFloat(node.getAttribute('cy')) / 100.0 * svgrect.height;
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// Compute the squared distance from the event coordinate to the node's center
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let dist2 = Math.pow(evX - x, 2) + Math.pow(evY - y, 2);
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// Keep the properties of the closest node
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if (dist2 < minDist2) {
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minDist2 = dist2;
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minId = node.dataset.stringRepresentation;
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minX = x;
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minY = y;
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}
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});
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return [minId, Math.sqrt(minDist2), minX, minY];
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};
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/**
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* Event handler for "mouse down" / "touch down" events.
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*
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* Selects an "anchor node", i.e. the node where the pattern path started, and draws a line from there to the event
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* coordinates.
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*/
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svg.ontouchstart = svg.onmousedown = (ev) => {
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// Remove any previous strokes that may still be there if "keepPattern" was set to true in the init call
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clearTouchkey();
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// Get the SVG container's rectangle
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const svgrect = svg.getBoundingClientRect();
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// Get the event coordinates relative to the SVG container's origin
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const [trX, trY] = getEventCoordinates(ev, svgrect);
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// Get the closest pattern node
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const [minId, _, minX, minY] = getNearestPatternNode(trX, trY, svgrect);
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// Create the line from the anchor node to the event position
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currentStroke = drawLine(minX, minY, trX, trY);
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// Mark the anchor node as visited
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doneMap[minId] = 1;
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// Add the anchor node's string representation to the touchkey string representation
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enteredKey += minId;
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};
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/**
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* Event handler for "mouse move" / "touch move" events.
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*/
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svg.ontouchmove = svg.onmousemove = (ev) => {
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// Only act if the user started is drawing a pattern (only relevant for mouse input)
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if (currentStroke != null) {
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// Get the SVG container's rectangle
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const svgrect = svg.getBoundingClientRect();
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// Get the event coordinates relative to the SVG container's origin
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const [trX, trY] = getEventCoordinates(ev, svgrect);
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// Get the closest pattern node
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const [minId, minDist, minX, minY] = getNearestPatternNode(trX, trY, svgrect);
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// If the closest node is not visited yet, and the event coordinate is less than from the node's
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// center, snap the current stroke to the node, and create a new stroke starting from this node
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if (minDist < (svgrect.width / SNAPPING_SENSITIVITY) && !(minId in doneMap)) {
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// Snap the current stroke to the node
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let line = svg.getElementById(currentStroke);
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line.setAttribute('x2', minX.toString());
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line.setAttribute('y2', minY.toString());
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// Create a new line object from the closest node to the event position
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currentStroke = drawLine(minX, minY, trX, trY);
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// Mark the closest node as visited
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doneMap[minId] = 1;
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// Append its string representation to the touchkey string representation
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enteredKey += minId;
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} else {
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// If the stroke was not snapped to the closest node, update its end position
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let line = svg.getElementById(currentStroke);
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line.setAttribute('x2', trX);
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line.setAttribute('y2', trY);
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}
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}
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};
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/**
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* Event handler for "mouse up" / "touch end" events.
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*
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* Sets the input object value, and optionally clears the SVG path and submits the form.
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*/
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svg.ontouchend = svg.onmouseup = () => {
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// Remove the trailing, unfinished stroke
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endPath();
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// Write the touchkey string representation to the input field
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formfield.value = enteredKey;
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// Erase the touchkey pattern, if requested in the init call
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if (keepPattern !== true) {
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clearTouchkey();
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}
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// Submit the HTML form, if requested in the init call
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if (formid !== null) {
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form.submit();
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}
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};
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/*
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* Create the SVG touchkey nodes
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*/
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// Node ID provider
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let touchkey_node_counter = 0;
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// Percentages for centers of quarters of the container's width and height
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['12.5%', '37.5%', '62.5%', '87.5%'].forEach((y) => {
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['12.5%', '37.5%', '62.5%', '87.5%'].forEach((x) => {
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// Create a new pattern node
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let node = document.createElementNS('http://www.w3.org/2000/svg', 'circle');
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// Generate a new ID (and the touchkey string representation from it)
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let id = touchkey_node_counter++;
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node.dataset.stringRepresentation = id.toString(16).toLowerCase();
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// Class
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node.setAttribute('class', 'touchkey-svg-node');
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// Center
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node.setAttribute('cx', x);
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node.setAttribute('cy', y);
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// Radius
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node.setAttribute('r', '10%');
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// Center color
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node.setAttribute('fill', 'white');
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// Circle color
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node.setAttribute('stroke', 'grey');
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// Circle width
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node.setAttribute('stroke-width', '2%');
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// Add the node to the SVG container
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svg.appendChild(node);
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});
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});
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};
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