Develop Reference

Getting mouse coordinates in SDK first-time right-click

For an SDK add-on, I am trying to detect, on right-click, the closest page anchor (as described here).
Since JavaScript apparently has no way to query the mouse coordinates without first creating a mouse event listener, and since I don't want an expensive mouseover listener running all of the time on every single page! (and polling to rebuild a mouse listener is ugly and not fully accurate anyways), I was hoping I could get the mouse coordinates from a click event. Unfortunately, although self.on('click' does fire:
This event is without an event object from which mouse coordinates could be obtained
Adding a normal window.addEventListener('click',... listener doesn't actually get fired in the SDK content script with the first menu selection for some reason (it does fire subsequently, however).
Here is my workaround, but I want to fire on the current exact coordinates, not the coordinates of the node:
var x, y;
window.addEventListener('click', function (e) {
if (e.button === 2) {
x = e.clientX;
y = e.clientY;
}
}, true);
self.on('click', function (node) {
if (!x) { // Since this is not showing the first time, we fire on the node (which is specifically an element, not a text node), though we really want the real clientX and clientY where the mouse is, not this simulation based on where the element is
node.dispatchEvent(new MouseEvent('click', {
button: 2
}));
}
// Use document.caretPositionFromPoint with x and y to determine location of text
Is there any other way to get the actual mouse coordinates?

You can actually query the mouse coordinates without a mouse listener.
This page has a bunch of examples: https://developer.mozilla.org/en-US/docs/Mozilla/js-ctypes/Standard_OS_Libraries
It has to be done on per OS basis though as it uses JS-Ctypes. If you're worried about performance don't fear at all. You can use the code asynchronously via ChromeWorkers

Getting the coordinates of an element relative to page

I was testing out an approach to a solution and found that the methods or functions available for a programmatically triggered JavaScript event is different from ones that are available when the user clicks on the element. For instance, I wasn't able to get the mouse positions of the click event. If the user had clicked, I would have been able to get the mouse positions and a lot more. I am adding the events and triggering it via jQuery. Any reason for this? Any one know how I can get the mouse position after programmatically triggering it using jQuery?

you can use the offset jquery function:
var clickedPostion = $(this).offset();
alert(e.clientX - clickedPostion.left);
alert(e.clientY - clickedPostion.top);
I know the sample it is on click, but you can change it to mousemove()
Here is a working sample:
http://jsfiddle.net/6wccZ/

Triggering mousemove on the mouse's current position

Suppose we have a <div> with a mousemove handler bound to it. If the mouse pointer enters and moves around this div, the event is triggered.
However, I am dealing with a rich web application where <div>s move around the screen, appear and disappear... So it may happen that a <div> appears under the mouse pointer. In this case, mousemove is not triggered. However, I need it to be. (Note that replacing mousemove with mouseover does not change this behavior.)
Specifically, the <div> has to be highlighted and I deem it as a UI flaw to require the user to do a slight mouse move in order to trigger the highlighting.
Is it possible to trigger the mousemove event programatically? And I do not mean
document.getElementById('mydiv').onmousemove();
because onmousemove is parametrised by the event object, which I do not have.
Is it possible to make browser behave as if onmousemove was triggered on the current mouse's position (although in fact the mouse didn't move)?

You could modify your mousemove to keep a state variable with the current mouse coordinates, and use that information to perform a collision detection that you call both on mouse move, and on moving a div.
A little example of what that might look like

You actually can create a mousemove event object to pass in, using something like this:
window.onload = function () {
document.getElementById("test").onmousemove = function(e) { console.log(e); };
document.getElementById("test").onclick = function(e) {
var e = document.createEvent('MouseEvents');
e.initMouseEvent('mousemove',true,true,document.defaultView,<detail>,<screenX>,<screenY>,<mouseX>,<mouseY>,false,false,false,false,<button>,null);
this.onmousemove(e);
};
};
Of course, here I'm firing it on a click, but you can do it on whatever event you want, such as when your div becomes visible, check to see if the mouse is within it. You just need to make sure your parameters are right, and you need to track the mouse position on your own. Also, there's some differences in IE, I think. Here's my source: http://chamnapchhorn.blogspot.com/2008/06/artificial-mouse-events-in-javascript.html. He added a little extra code to account for it.
Here's a fiddle to play around with. http://jsfiddle.net/grimertop90/LxT7V/1/

Duplicate events in prototype

I have a setup where I have a grid of elements and when I rollover each element a popup appears like an advanced tooltip. I first check if the popup needs to follow the moused over elements mouse position, if so I use a mousemove event. I first stopObserving in case there was one set before, then I start observing. Do I really need to do this or is prototype smart enough to not to add duplicate events on the same element.
show:function(param){
if(this.isFollow){
$(param.target).stopObserving('mousemove', this.onMouseMove);
$(param.target).observe('mousemove', this.onMouseMove);
}
},
//param.target is the element that is being rolled over. I pass this in to my show method to then find its x and y position.
onMouseMove:function(event){
var xPos = Event.pointerX(event);
var yPos = Event.pointerY(event);
_self._popup.setStyle({left: xPos + 10 + "px", top:yPos + 10 + "px"});
}
Second question. When I move my mouse across the elements really fast my popup that is following the mouse sometimes lags and the mouse goes over the popup obstructing the mouseover event on the element below it.
I presume this is the nature of the mousemove as its not rendering fast enough. Should I be using setTimeout or something like that instead of mousemove, to prevent this lag.

1) No, Prototype won't set the same event handler twice. It'll only happen if you declare your handler function in-line (i.e. element.observe('click', function(){…})) since the handler will be sent a newly created function each time, and never the exact same instance of a function.
But in your case, where you're referring to the onMouseMove function, Prototype will check whether that particular function is already registered for that particular event, on that particular element. And if it is, it won't be registered again.
2) You can't avoid the lag on fast mouse movements, no. The browser won't send the mousemove events fast enough. You could use a timer, but I'd probably try registering a single mousemove handler for the parent element of all the grid-elements (or maybe even document itself), and use the X/Y coordinates to figure out which grid-element to show the tooltip for. Then you don't have to bother with setting event handlers for each element. I.e. if the grid was a standard table, I'd listen for events on the <table> element itself, rather than on each and every <td>. Especially if you still want to implement a timer, I should think, it'd be easier to deal with everything in one place (otherwise, a timer might accidentally execute on some element you've already moused out of, and your tooltip will flicker back and forth or something. If you only want 1 tooltip at a time, it's easier to manage it in 1 place.)

Detect if mouse is over an element when page loads with Javascript

I have an image that I want to have trigger certain behaviors when the mouse is over, I have a mouseover and mouseout method, but if you happen to have your mouse over the image when the page loads, the mouseover method never fires until you leave the image and come back over it.
Is there a way to detect if the mouse is over an element on the fly without the mouse having to be off of the element and then come over the element to trigger the JS mouseover event? Like is there a document.getElementById("blah").mouseIsOver() type function in Javascript?

I believe this is possible without any action from the user. When your page loads, bind the mouseover event to your image and hide your image (i.e. using CSS display:none). Use setTimeout() to show it again in a few milliseconds (10 should be enough). The even should be fired.
If you don't want to cause the 'flick' effect on your image, you may try using some temporary element instead, attaching event to it, and delegating the event onto your image.
I have no idea if this is cross-browser solution, but it worked from my Firefox 3.0 console ;)

You could use the mousemove event. That would trigger anytime the user moves a mouse; so the only instance of the trigger not firing would be if the user does not move the mouse at all, which should be rare.
The only problem with this is that the event would fire anytime the mouse would move over your image, so you would get a LOT of those events while over the component. What you would probably need to do is implement some sort of flag within your method when the event fires. You turn on the flag when the event first fires, and you turn it off when you leave the component.
This is less than ideal, but I think this will probably satisfy your problem scenario. The following is some quick pseudo code on what that solution might look like, I think it should work.
<img src="blah.png" onmousemove="JavaScript:triggerOn(event)" onmouseout="JavaScript:triggerOff(event)"/>
...
<script type='text/javascript'>
var TriggerActive = false;
function triggerOn(e){
e = e||window.e;
if( !TriggerActive){
TriggerActive = true;
// Do something
} else {
// Trigger already fired, ignore this event.
}
}
function triggerOff(e){
e = e||window.e;
if(TriggerActive)
TriggerActive = false;
}
</script>
You can find some great mouse event information including browser compatibility notes here.

Use document.querySelectpor and onload/onready events.
var a = document.querySelector('#a:hover');
if (a) {
// Mouse cursor is above a
}
else {
// Mouse cursor is outside a
}

There is no way to get the mouse coordinates aside from listening for mouse events, namely mousemove, mouseover etc. However, these events are very sensitive in the sense that moving the cursor by just one pixel is enough to trigger them, so having the cursor hover over your image while perfectly still should be somewhat unusual.