Develop Reference

Detect hover in overlaying element while allowing all pointer actions

I am building an audio player in a SPA and have a main player widget that shows the currently playing track along with controls at the bottom of the page. The desired UI is to hide all controls but the play/pause button until the user hovers near the play/pause button. At this point the extra information, seek bar, volume controls etc. will be animated onto the screen.
Excuse my shoddy drawing
I should add that the controls are positioned fixed to the bottom of the screen.
Initially, I tried adding an extra fixed positioned div on top of everything (high z-index) and using that to trigger the hover event. Obviously, this doesn't allow for clicking the buttons below it so I tried pointer-events: none on the element but then no hover event is registered.
I then tried putting the hover region underneath the control elements and adding the hover trigger to both the hover region and the controls. This causes strange behavior when moving the cursor between the hover region and any controls (i.e. to click pause/play).
My next thought is to scrap the hover region HTML element and use a pure JS solution. I could register a mousemove event to the document body and detect when the cursor is within the hover region, triggering control animations. However, I am worried this might cause performance issues as seems a bit heavy.
I hope someone has some input/improvements on the things I have tried or comes up with something I haven't thought of!
BTW: I am using angular2 for the animation if that sparks some bright ideas to use that.
Update 1
Here's a jsFiddle showing the first two attempts. Change the z-index of hover-region to see the effect of it being on top of the play button or below.

I've created a working version for you at http://jsfiddle.net/6wk69fvo/1/. You already did what I was going to suggest, which is to use onmouseenter and onmouseleave.
But rather than just checking the hover area, you also need to check the toolbar area, and then just OR the two values together.
Also note that I put the play / pause button as a child of the hover area. If you don't want to do that, you'd need to create a third check for mouseenter or mouseleave for that div.

You can alter the control's opacity make it visible/invisible. Here is a simple example done in pure html/js to avoid the overhead of setting up an ng2 app, yet, I'm sure you can quickly adapt it to your code.

Is it possible to have an image follow mouse cursor without blocking its click events?

I have an image follow my mouse cursor (image is set to be directly beneath the cursor). All is well except now I cant really click on anything, because when i click, im just selecting the image and not the elements under it. Is there anyway to ignore the image when it comes to mouse events like click or mousedown?
I dont want to use a custom cursor (cursor: url(...)). Just need the mouse events to propagate to the elements under the image.
Edit:
adding pointer-events: none; sorta works, but disables cursor: none.

Using CSS for the image, you can make clicks pass through it by adding pointer-events: none;.
See Click through a DIV to underlying elements

You can create a fixed html div that follows the mousecursor using javascript. This way you are not limited to only images but also content.

How to invoke an additional click and a drag when a button is clicked

Is it possible for a click or mouseup event to launch a function where an additional click and drag event is invoked on another part of the div or on another div?
In short when I click on something I want the mouseup event to create the equivalent of the user quickly selecting another div (or part of the same div) and dragging it. I am not looking for a css animation perse'. I know that sounds weird but read below for what I think I need this for
The problem I am trying to solve with this
The problem I am trying to solve with this is the following.
I am making this tool:
https://dl.dropboxusercontent.com/u/57427474/JsPlumb_troubleshooting/trace3.html
When the user types into the pad, clicks the green button and moves the editor all works fine. But if they then again click the green button and add additional content to the notepad (and then closes the editor) the JSplumb wire-nodes get out of wack and don't update as in the picture below.
https://dl.dropboxusercontent.com/u/57427474/JsPlumb_troubleshooting/img.png
However, when I drag the div the nodes fall back into place.
I was thinking if I could add an eventListener that slightly drags the div (using a mouse event) when the user clicks the green button I could subtly fix this.

You may be able to use trigger();
$("#myButton").trigger("click");
ymmv

Trigger onMouseOver when mouse pointer already is over after page load

I have several pages that are all very similar. They have some javascript rollover links (images are preloaded, then there is a onMouseOver event that calls an image swap function and finally, there is a onMouseOut event that restores the original image).
When the user clicks on a rollover link that points to another page that has a rollover link on the exact same position, the image on the new page would be expected to load on the "over" state. This is not the case in Chrome and Safari (IE and Firefox work as expected).
So... On page load, is there a way to check if the mouse is already hovering the image to swap it right away? Something like "OnMouseAlreadyOver"?
Thank you.

If you using jQuery, it works without any problems!
http://jsfiddle.net/beuae
(not only for buttons, for divs also)
Actually, jQuery is a very good framework which assures everything goes as you expect, and cross-browser. This example confirms it.

The W3C standard says
onmouseover = script [CT]
The onmouseover event occurs when the pointing device is moved onto an element. This attribute may be used with most elements.
onmousemove = script [CT]
The onmousemove event occurs when the pointing device is moved while it is over an element. This attribute may be used with most elements.
mouseover is fired on moving over the boundary of the object. mousemove happens when the mouse is already over the element.
You may need to use onmousemove (or even both).

You may need to actually do the calculation based on the element position and the mouse cursor position.
//Get Mouse Position
document.onmousemove=getMouseCoordinates;
function getMouseCoordinates(event){
ev = event || window.event;
mouseX = ev.pageX;
mouseY = ev.pageY;
}

You can't without passing a variable to the other page or using cookies to track which was hovered (and that will fail over if people do change their mouse position)
In theory you could check the mouse position and the button position however there is no way to get the mouse position unless an event is triggered, so the mouse has to move and if it move the CSS :hover should get triggered.
It's a minor issue tho, I doubt most people are going to click a link, wait for the next page and then expect that link to be hovered and ready to click again (why wouldn't anyone one to keep clicking the same button unless it does different things)
From a UX point of view I wonder if webkit doesn't have the best approach here, why port the action of one page to another.

You can use document.getElementFromPoint(mouseX, mouseY) to get the element, but the only way to get the cursor's position is via an event. The problem is, the only events are clicks and mouse movements, which require user input from the beginning, which is what you're trying to avoid.
In short, no, it's not possible to do with JavaScript. You're left with using CSS.

Clicking on an element sets focus but not cursor?

I have an html page where I set the focus on the first input element on load. I can see that the focus is set because I ask the background of the element to go orange and I can see the orange background. However, the cursor is not shown in the element.
Then when I click on the other input elements, I can see the focus move to them but still no cursor is shown. The cursor only appears when I use the tab key.
Please could someone explain to me why this happens and how I can make this cursor appear without having to use the tab key?
This is for IE8 only. (It's an intranet site)
Code as requested for how I'm setting focus:
$(document).ready(function(){
$('#rachel').focus();
});
EDIT
I didn't think to mention that the problem is happening on a popup window that looks to be implemented like a layer. Is it possible for layers to block the cursor?