I have 2 canvases. One, the main canvas. Upon which all is drawn, Second, the speech bubble canvas (balloon). Which displays information about specific regions on my main canvas upon client clicks.
I was playing around with my canvas after introducing the speech bubble and came across an issue.
This is a simple code that shows how the speech bubble is introduced:-
http://jsfiddle.net/m1erickson/AJvkN/
My canvas is a timeline, and is scrollable; has historical events plotted on it. Once a user clicks on an event a speech bubble appears.
Now what I don't want to happen is, when a client clicks on the canvas, a speech bubble appears and then scrolls, the speech bubble moves to a new position on the scrolled image, however still showing information about the previous location.
For this we have the hideballoon () which assigns css property left : -200. However this still causes inconsistencies. For example if I drag the canvas from left to right, the balloon doesn't disappear with the scroll, but reappears in a new position.
there is a .remove() function $("#balloon").remove()
This successfully removes the balloon however, the issue with this is:- it removes the balloon completely, and no future clicks will pop up any more speech bubbles. This is not what I want. I want something dynamic.
Click on event >> speech bubble appears >> scroll canvas >> speech bubble disappears >> click on canvas >> speech bubble pertaining to new click appears back >> and so on and so forth.
[Edited]
Use .show() and .hide() to keep the balloon out of your way when its not needed
When the user scrolls the window then just hide the balloon.
I assume you're scrolling the window instead of the canvas. If you're scrolling the canvas, just use $("#canvas").scroll( ... ) instead.
So when you need the balloon:
// move the balloon canvas to the target
$("#balloon").css({left:offsetX+X, top:offsetY+Y});
// and show it
$("#balloon").show();
And hide the balloon when the user clicks on it or when the window scrolls:
// listen for clicks on the balloon and then hide the balloon
$("#balloon").click(function(e){ $("#balloon").hide(); });
// listen for scrolls and then hide the balloon
$(window).scroll(function(e){
$("#balloon").hide();
});
Here’s working sample code and a Fiddle: http://jsfiddle.net/m1erickson/uWHkv/
<!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{ width:2000px; background-color: ivory; padding:10px;padding-top:100px; }
#canvas{border:1px solid red;}
#balloon{ position:absolute; left:-200px; }
</style>
<script>
$(function(){
// get reference to our drawing canvas
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
// get reference to our balloon canvas
var balloon=document.getElementById("balloon");
var popCtx=balloon.getContext("2d");
// get the position of canvas relative to window
var canvasOffset=$("#canvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
// define some targets and their basic info
var count=1;
var circles=[];
for(var x=50;x<1900;x+=50){
circles.push({
x:x, y:120, radius:20,
color:"blue",
info:"I'm #"+(count++)});
}
// draw the target circles on the canvas
ctx.fillStyle="yellow";
ctx.font="16px verdana";
for(var i=0;i<circles.length;i++){
drawCircle(circles[i]);
ctx.beginPath();
ctx.fillText(i+1,circles[i].x-8,circles[i].y+5);
}
// listen for clicks on the canvas and show the balloon
$("#canvas").click(function(e){
// get the mouseclick position
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// account for the window scrolling
var scrollX=$(window).scrollLeft();
var scrollY=$(window).scrollTop();
// see if we clicked on any targets
for(var i=0;i<circles.length;i++){
var circle=circles[i];
var dx=(circle.x-scrollX)-mouseX;
var dy=(circle.y-scrollY)-mouseY;
var radius=circle.radius;
// true if we clicked in the target circle
if(dx*dx+dy*dy<=radius*radius){
drawBalloon(circles[i].x+radius,circles[i].y-100,circles[i].info);
}
}
});
// listen for clicks on the balloon and then hide the balloon
$("#balloon").click(function(e){ $("#balloon").hide(); });
// listen for scrolls and then hide the balloon
$(window).scroll(function(e){
$("#balloon").hide();
});
function drawCircle(circle){
ctx.save();
ctx.beginPath();
ctx.fillStyle=circle.color;
ctx.strokeStyle="black";
ctx.lineWidth=3;
ctx.arc(circle.x,circle.y,circle.radius,0,Math.PI*2,false);
ctx.closePath();
ctx.fill();
ctx.stroke();
ctx.restore();
}
function drawBalloon(X,Y,theInfo){
popCtx.save();
popCtx.fillStyle="#FD0";
popCtx.strokeStyle="#000";
// draw the balloon
popCtx.beginPath();
popCtx.moveTo(52,02);
popCtx.quadraticCurveTo(02,02,02,42);
popCtx.quadraticCurveTo(02,77,27,77);
popCtx.quadraticCurveTo(27,102,07,102);
popCtx.quadraticCurveTo(37,102,42,77);
popCtx.quadraticCurveTo(102,77,102,42);
popCtx.quadraticCurveTo(102,02,52,02);
popCtx.lineWidth=3;
popCtx.stroke();
popCtx.fill();
// draw theInfo
popCtx.font="10pt arial";
popCtx.fillStyle="black";
popCtx.fillText(theInfo,10,50);
popCtx.restore();
// move the balloon canvas to the target
$("#balloon").css({left:offsetX+X, top:offsetY+Y});
$("#balloon").show();
}
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="canvas" width=1950 height=300></canvas>
<canvas id="balloon" width=105 height=105></canvas>
</body>
</html>