matemat/static/js/touchkey.js

268 lines
12 KiB
JavaScript

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