chart.js
Version:
Simple HTML5 charts using the canvas element.
215 lines (197 loc) • 6.04 kB
JavaScript
;
var helpers = require('./helpers.core');
/**
* @namespace Chart.helpers.canvas
*/
var exports = module.exports = {
/**
* Clears the entire canvas associated to the given `chart`.
* @param {Chart} chart - The chart for which to clear the canvas.
*/
clear: function(chart) {
chart.ctx.clearRect(0, 0, chart.width, chart.height);
},
/**
* Creates a "path" for a rectangle with rounded corners at position (x, y) with a
* given size (width, height) and the same `radius` for all corners.
* @param {CanvasRenderingContext2D} ctx - The canvas 2D Context.
* @param {Number} x - The x axis of the coordinate for the rectangle starting point.
* @param {Number} y - The y axis of the coordinate for the rectangle starting point.
* @param {Number} width - The rectangle's width.
* @param {Number} height - The rectangle's height.
* @param {Number} radius - The rounded amount (in pixels) for the four corners.
* @todo handle `radius` as top-left, top-right, bottom-right, bottom-left array/object?
*/
roundedRect: function(ctx, x, y, width, height, radius) {
if (radius) {
var rx = Math.min(radius, width / 2);
var ry = Math.min(radius, height / 2);
ctx.moveTo(x + rx, y);
ctx.lineTo(x + width - rx, y);
ctx.quadraticCurveTo(x + width, y, x + width, y + ry);
ctx.lineTo(x + width, y + height - ry);
ctx.quadraticCurveTo(x + width, y + height, x + width - rx, y + height);
ctx.lineTo(x + rx, y + height);
ctx.quadraticCurveTo(x, y + height, x, y + height - ry);
ctx.lineTo(x, y + ry);
ctx.quadraticCurveTo(x, y, x + rx, y);
} else {
ctx.rect(x, y, width, height);
}
},
drawPoint: function(ctx, style, radius, x, y) {
var type, edgeLength, xOffset, yOffset, height, size;
if (style && typeof style === 'object') {
type = style.toString();
if (type === '[object HTMLImageElement]' || type === '[object HTMLCanvasElement]') {
ctx.drawImage(style, x - style.width / 2, y - style.height / 2, style.width, style.height);
return;
}
}
if (isNaN(radius) || radius <= 0) {
return;
}
switch (style) {
// Default includes circle
default:
ctx.beginPath();
ctx.arc(x, y, radius, 0, Math.PI * 2);
ctx.closePath();
ctx.fill();
break;
case 'triangle':
ctx.beginPath();
edgeLength = 3 * radius / Math.sqrt(3);
height = edgeLength * Math.sqrt(3) / 2;
ctx.moveTo(x - edgeLength / 2, y + height / 3);
ctx.lineTo(x + edgeLength / 2, y + height / 3);
ctx.lineTo(x, y - 2 * height / 3);
ctx.closePath();
ctx.fill();
break;
case 'rect':
size = 1 / Math.SQRT2 * radius;
ctx.beginPath();
ctx.fillRect(x - size, y - size, 2 * size, 2 * size);
ctx.strokeRect(x - size, y - size, 2 * size, 2 * size);
break;
case 'rectRounded':
var offset = radius / Math.SQRT2;
var leftX = x - offset;
var topY = y - offset;
var sideSize = Math.SQRT2 * radius;
ctx.beginPath();
this.roundedRect(ctx, leftX, topY, sideSize, sideSize, radius / 2);
ctx.closePath();
ctx.fill();
break;
case 'rectRot':
size = 1 / Math.SQRT2 * radius;
ctx.beginPath();
ctx.moveTo(x - size, y);
ctx.lineTo(x, y + size);
ctx.lineTo(x + size, y);
ctx.lineTo(x, y - size);
ctx.closePath();
ctx.fill();
break;
case 'cross':
ctx.beginPath();
ctx.moveTo(x, y + radius);
ctx.lineTo(x, y - radius);
ctx.moveTo(x - radius, y);
ctx.lineTo(x + radius, y);
ctx.closePath();
break;
case 'crossRot':
ctx.beginPath();
xOffset = Math.cos(Math.PI / 4) * radius;
yOffset = Math.sin(Math.PI / 4) * radius;
ctx.moveTo(x - xOffset, y - yOffset);
ctx.lineTo(x + xOffset, y + yOffset);
ctx.moveTo(x - xOffset, y + yOffset);
ctx.lineTo(x + xOffset, y - yOffset);
ctx.closePath();
break;
case 'star':
ctx.beginPath();
ctx.moveTo(x, y + radius);
ctx.lineTo(x, y - radius);
ctx.moveTo(x - radius, y);
ctx.lineTo(x + radius, y);
xOffset = Math.cos(Math.PI / 4) * radius;
yOffset = Math.sin(Math.PI / 4) * radius;
ctx.moveTo(x - xOffset, y - yOffset);
ctx.lineTo(x + xOffset, y + yOffset);
ctx.moveTo(x - xOffset, y + yOffset);
ctx.lineTo(x + xOffset, y - yOffset);
ctx.closePath();
break;
case 'line':
ctx.beginPath();
ctx.moveTo(x - radius, y);
ctx.lineTo(x + radius, y);
ctx.closePath();
break;
case 'dash':
ctx.beginPath();
ctx.moveTo(x, y);
ctx.lineTo(x + radius, y);
ctx.closePath();
break;
}
ctx.stroke();
},
clipArea: function(ctx, area) {
ctx.save();
ctx.beginPath();
ctx.rect(area.left, area.top, area.right - area.left, area.bottom - area.top);
ctx.clip();
},
unclipArea: function(ctx) {
ctx.restore();
},
lineTo: function(ctx, previous, target, flip) {
if (target.steppedLine) {
if ((target.steppedLine === 'after' && !flip) || (target.steppedLine !== 'after' && flip)) {
ctx.lineTo(previous.x, target.y);
} else {
ctx.lineTo(target.x, previous.y);
}
ctx.lineTo(target.x, target.y);
return;
}
if (!target.tension) {
ctx.lineTo(target.x, target.y);
return;
}
ctx.bezierCurveTo(
flip ? previous.controlPointPreviousX : previous.controlPointNextX,
flip ? previous.controlPointPreviousY : previous.controlPointNextY,
flip ? target.controlPointNextX : target.controlPointPreviousX,
flip ? target.controlPointNextY : target.controlPointPreviousY,
target.x,
target.y);
}
};
// DEPRECATIONS
/**
* Provided for backward compatibility, use Chart.helpers.canvas.clear instead.
* @namespace Chart.helpers.clear
* @deprecated since version 2.7.0
* @todo remove at version 3
* @private
*/
helpers.clear = exports.clear;
/**
* Provided for backward compatibility, use Chart.helpers.canvas.roundedRect instead.
* @namespace Chart.helpers.drawRoundedRectangle
* @deprecated since version 2.7.0
* @todo remove at version 3
* @private
*/
helpers.drawRoundedRectangle = function(ctx) {
ctx.beginPath();
exports.roundedRect.apply(exports, arguments);
ctx.closePath();
};