Display tooltip in canvas graph
You can display tooltips when your user moves over your chart's data-dot
This tooltip is simply a second canvas which draws the text from the linked textbox and is positions itself above the data-dot.
First you create an array to hold the tooltip info for each of your data-dots.
var dots = [];
For each tooltip, you will need:
- The x/y coordinate of the data-dot,
- The radius of the data-dot,
- The id of the textbox you want to get the tip from.
- You also need rXr which always == radius squared (needed during hit testing)
Here is the code for creating tooltip info to be stored in dots[]
// define tooltips for each data point
for(var i = 0; i < data.values.length; i ++) {
dots.push({
x: getXPixel(data.values[i].X),
y: getYPixel(data.values[i].Y),
r: 4,
rXr: 16,
tip: "#text"+(i+1)
});
}
Then you set up a mousemove handler that looks through the dots array. The tooltip is displayed if the user moves inside any data=dot:
// request mousemove events
$("#graph").mousemove(function(e){handleMouseMove(e);});
// show tooltip when mouse hovers over dot
function handleMouseMove(e){
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// Put your mousemove stuff here
var hit = false;
for (var i = 0; i < dots.length; i++) {
var dot = dots[i];
var dx = mouseX - dot.x;
var dy = mouseY - dot.y;
if (dx * dx + dy * dy < dot.rXr) {
tipCanvas.style.left = (dot.x) + "px";
tipCanvas.style.top = (dot.y - 40) + "px";
tipCtx.clearRect(0, 0, tipCanvas.width, tipCanvas.height);
tipCtx.fillText($(dot.tip).val(), 5, 15);
hit = true;
}
}
if (!hit) { tipCanvas.style.left = "-200px"; }
}
[ Edited to fit into your code ]
Here is code and a Fiddle: http://jsfiddle.net/m1erickson/yLBjM/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: ivory; margin-top:35px; }
#wrapper{position:relative; width:300px; height:150px;}
canvas{border:1px solid red;}
#tip{background-color:white; border:1px solid blue; position:absolute; left:-200px; top:100px;}
</style>
<script>
$(function(){
var graph = document.getElementById("graph");
var ctx = graph.getContext("2d");
var tipCanvas = document.getElementById("tip");
var tipCtx = tipCanvas.getContext("2d");
var canvasOffset = $("#graph").offset();
var offsetX = canvasOffset.left;
var offsetY = canvasOffset.top;
var graph;
var xPadding = 30;
var yPadding = 30;
// Notice I changed The X values
var data = { values:[
{ X: 0, Y: 12 },
{ X: 2, Y: 28 },
{ X: 3, Y: 18 },
{ X: 4, Y: 34 },
{ X: 5, Y: 40 },
{ X: 6, Y: 80 },
{ X: 7, Y: 80 }
]};
// define tooltips for each data point
var dots = [];
for(var i = 0; i < data.values.length; i ++) {
dots.push({
x: getXPixel(data.values[i].X),
y: getYPixel(data.values[i].Y),
r: 4,
rXr: 16,
color: "red",
tip: "#text"+(i+1)
});
}
// request mousemove events
$("#graph").mousemove(function(e){handleMouseMove(e);});
// show tooltip when mouse hovers over dot
function handleMouseMove(e){
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// Put your mousemove stuff here
var hit = false;
for (var i = 0; i < dots.length; i++) {
var dot = dots[i];
var dx = mouseX - dot.x;
var dy = mouseY - dot.y;
if (dx * dx + dy * dy < dot.rXr) {
tipCanvas.style.left = (dot.x) + "px";
tipCanvas.style.top = (dot.y - 40) + "px";
tipCtx.clearRect(0, 0, tipCanvas.width, tipCanvas.height);
tipCtx.fillText($(dot.tip).val(), 5, 15);
hit = true;
}
}
if (!hit) { tipCanvas.style.left = "-200px"; }
}
// unchanged code follows
// Returns the max Y value in our data list
function getMaxY() {
var max = 0;
for(var i = 0; i < data.values.length; i ++) {
if(data.values[i].Y > max) {
max = data.values[i].Y;
}
}
max += 10 - max % 10;
return max;
}
// Returns the max X value in our data list
function getMaxX() {
var max = 0;
for(var i = 0; i < data.values.length; i ++) {
if(data.values[i].X > max) {
max = data.values[i].X;
}
}
// omited
//max += 10 - max % 10;
return max;
}
// Return the x pixel for a graph point
function getXPixel(val) {
// uses the getMaxX() function
return ((graph.width - xPadding) / (getMaxX() + 1)) * val + (xPadding * 1.5);
// was
//return ((graph.width - xPadding) / getMaxX()) * val + (xPadding * 1.5);
}
// Return the y pixel for a graph point
function getYPixel(val) {
return graph.height - (((graph.height - yPadding) / getMaxY()) * val) - yPadding;
}
graph = document.getElementById("graph");
var c = graph.getContext('2d');
c.lineWidth = 2;
c.strokeStyle = '#333';
c.font = 'italic 8pt sans-serif';
c.textAlign = "center";
// Draw the axises
c.beginPath();
c.moveTo(xPadding, 0);
c.lineTo(xPadding, graph.height - yPadding);
c.lineTo(graph.width, graph.height - yPadding);
c.stroke();
// Draw the X value texts
var myMaxX = getMaxX();
for(var i = 0; i <= myMaxX; i ++) {
// uses data.values[i].X
c.fillText(i, getXPixel(i), graph.height - yPadding + 20);
}
/* was
for(var i = 0; i < data.values.length; i ++) {
// uses data.values[i].X
c.fillText(data.values[i].X, getXPixel(data.values[i].X), graph.height - yPadding + 20);
}
*/
// Draw the Y value texts
c.textAlign = "right"
c.textBaseline = "middle";
for(var i = 0; i < getMaxY(); i += 10) {
c.fillText(i, xPadding - 10, getYPixel(i));
}
c.strokeStyle = '#f00';
// Draw the line graph
c.beginPath();
c.moveTo(getXPixel(data.values[0].X), getYPixel(data.values[0].Y));
for(var i = 1; i < data.values.length; i ++) {
c.lineTo(getXPixel(data.values[i].X), getYPixel(data.values[i].Y));
}
c.stroke();
// Draw the dots
c.fillStyle = '#333';
for(var i = 0; i < data.values.length; i ++) {
c.beginPath();
c.arc(getXPixel(data.values[i].X), getYPixel(data.values[i].Y), 4, 0, Math.PI * 2, true);
c.fill();
}
}); // end $(function(){});
</script>
</head>
<body>
<div id="wrapper">
<canvas id="graph" width=300 height=150></canvas>
<canvas id="tip" width=100 height=25></canvas>
</div>
<br><br>
<input type="text" id="text1" value="text 1"/><br><br>
<input type="text" id="text2" value="text 2"/><br><br>
<input type="text" id="text3" value="text 3"/><br><br>
<input type="text" id="text4" value="text 4"/><br><br>
<input type="text" id="text5" value="text 5"/><br><br>
<input type="text" id="text6" value="text 6"/><br><br>
<input type="text" id="text7" value="text 7"/><br><br>
</body>
</html>
I tried markE's solution and it worked flawlessly, EXCEPT that when you scroll down just a little bit (e.g. when you have your canvas a little down the site).
Then the positions where your mouseover is recognized will shift to the bottom the same length and it could happen that they end up outside of the canvas and will not be recognized at all...
When you use mouseEvent.pageX and mouseEvent.pageY instead of .clientX and .clientY, you should be fine. For more context, here is my code:
// Filling the dots
var dots = [];
// [...]
dots.push({
x: xCoord,
y: yCoord,
v: value,
r: 5,
tooltipRadius2: 7*7 // a little increased radius for making it easier to hit
});
// [...]
var tooltipCanvas = $('#tooltipCanvas')[0];
var tooltipCtx = tooltipCanvas.getContext('2d');
var canvasOffset = canvas.offset();
canvas.mousemove(function (e) {
// getting the mouse position relative to the page - not the client
var mouseX = parseInt(e.pageX - canvasOffset.left);
var mouseY = parseInt(e.pageY - canvasOffset.top);
var hit = false;
for (var i = 0; i < dots.length; i++) {
var dot = dots[i];
var dx = mouseX - dot.x;
var dy = mouseY - dot.y;
if (dx * dx + dy * dy < dot.tooltipRadius2) {
// show tooltip to the right and below the cursor
// and moving with it
tooltipCanvas.style.left = (e.pageX + 10) + "px";
tooltipCanvas.style.top = (e.pageY + 10) + "px";
tooltipCtx.clearRect(0, 0, tooltipCanvas.width, tooltipCanvas.height);
tooltipCtx.textAlign = "center";
tooltipCtx.fillText(dot.v, 20, 15);
hit = true;
// when a dot is found, don't keep on searching
break;
}
}
if (!hit) {
tooltipCanvas.style.left = "-200px";
}
});