Capture Scroll Event on Element with overflow: hidden Using Javascript - javascript

EDIT: Thanks for the comments so far! Here's a JS fiddle with (hopefully all of) the relevant code:
https://jsfiddle.net/3y1cw6nt/
I have an image slider set up where the images' classes are toggled between .above, .active and .below, and their top: attribute changes accordingly.
At the moment the toggle is activated by an event listener for up and down arrow key presses, and I have html, body { height: 100vh, overflow: hidden } so that the user can't scroll to the the images which are .below or .above.
Is there a way to still capture scroll up and down events and trigger the class changes using Javascript?
I've tried this solution, but it isn't working - var st is undefined no matter what I do to the page, which I guess is because no scroll event is being captured and therefore var st is never declared.
Thanks a lot!

The body doesn't scroll, so there is no scroll event.
Have a look at a different set of events: mousemove, touch. Support for touch events can be rather varied across devices, so perhaps a library like Hammer would also come in handy.

Related

Javascript: Child should not be inheriting mouse state from Parent

I'm trying to create a small image that follows the mouse around but only exists inside a specific area. I'm using javascript/jquery to create the image when the mouse enters the area and remove it when the mouse leaves.
The problem is, if I create the "follower" inside the area div, the image seems to be considered part of it's parent for determining mouse state, and thus it continues to exist even after the mouse is outside the area.
(If I move the mouse fast enough the cursor will escape and the follower disapears.)
Here is the code I'm using:
$("#area").mouseenter(function() {
$("#area").append("<img id='follower' src='follower.png'/>");
});
$("#area").mousemove(function(event){
$("#follower").css("top",event.pageY-35);
$("#follower").css("left",event.pageX-35);
});
$("#area").mouseleave(function() {
$("#follower").remove();
});
JSFiddle: http://jsfiddle.net/cgWdF/186/
I have also attempted creating the "follower" inside a separate div, which works but results in a weird flickering of the image, as seen here: http://jsfiddle.net/cgWdF/187/
Any help, with this, would be appreciated. It doesn't matter whether the follower is created inside the area div, or not, as long as the flickering affect isn't seen. Also, I'd like to keep the code as compact as possible, but I'll take what I can get.
This occurs because the element on which you mouseleave is not the one on which you think it happens. In fact, your sprite is triggering the event instead because your pointer is over it at that time.
To prevent that from happening, you can force the page to cancel all pointer events on your sprite. By doing that, #area will trigger your pointer events as intended. The css rule pointer-events might be helpful for this.
CSS
#follower {
position: absolute;
height: 80px;
pointer-events: none;
}
There are probably better ways to deal with that but it's the most simple I can come up with for now.
Hope this helps!
See FIDDLE.

How do I use pointer-events to react only to scroll event?

Is it possible to set pointer-events to only react to scrolling or drag on a touch-pad? I have a div 'in the way' for scrolling a complex html arrangement* and I would like to know if I can limit the pointer events to only react to scroll / mouse wheel actions.
I am interested in knowing whether I understand this correctly. If pointer-events:none; means that all events are void, how can I kill all events but leave one active?
I have set up an HTML area that is bigger than the box it fits in, but if I were to show the scroll bar, it would seem higher than it should be because of a pop-up (position:top) element. This area still needs to be scrolled so to achieve this I have used jQuery to make my 'box to scroll' follow an invisible div within a div:
<div id="scrollcontrol"style="overflow-y:auto;overflow-x:hidden;position:absolute;
top:12px;left:180px;width:40px;height:1300px;">
<div id="catscrollpos"style="position:absolute;
top:0px;width:200px;height:2250px;">
</div>
</div>
Script
$('#scrollcontrol').scroll(function({
$('#rangetable').css({
'top':$('#catscrollpos').position().top+'px'
});
});
As for specification in the docs:
When an element has applied pointer-events: none;
The element is never the target of any mouse events and any events are void;
Please look at this demonstration:
http://jsbin.com/wewosumehi/1/
Events are not being fired, you cannot even scroll the container.

Apply gradient over page without hindering user interaction [duplicate]

I have a div that has background:transparent, along with border. Underneath this div, I have more elements.
Currently, I'm able to click the underlying elements when I click outside of the overlay div. However, I'm unable to click the underlying elements when clicking directly on the overlay div.
I want to be able to click through this div so that I can click on the underlying elements.
Yes, you CAN do this.
Using pointer-events: none along with CSS conditional statements for IE11 (does not work in IE10 or below), you can get a cross browser compatible solution for this problem.
Using AlphaImageLoader, you can even put transparent .PNG/.GIFs in the overlay div and have clicks flow through to elements underneath.
CSS:
pointer-events: none;
background: url('your_transparent.png');
IE11 conditional:
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src='your_transparent.png', sizingMethod='scale');
background: none !important;
Here is a basic example page with all the code.
Yes, you CAN force overlapping layers to pass through (ignore) click events.
PLUS you CAN have specific children excluded from this behavior...
You can do this, using pointer-events
pointer-events influences the reaction to click-, tap-, scroll- und hover events.
In a layer that should ignore / pass-through mentioned events you set
pointer-events: none;
Children of that unresponsive layer that need to react mouse / tap events again need:
pointer-events: auto;
That second part is very helpful if you work with multiple overlapping div layers (probably some parents being transparent), where you need to be able to click on child elements and only that child elements.
Example usage:
.parent {
pointer-events:none;
}
.child {
pointer-events:auto;
}
<div class="parent">
I'm unresponsive
I'm clickable again, wohoo !
</div>
Allowing the user to click through a div to the underlying element depends on the browser. All modern browsers, including Firefox, Chrome, Safari, and Opera, understand pointer-events:none.
For IE, it depends on the background. If the background is transparent, clickthrough works without you needing to do anything. On the other hand, for something like background:white; opacity:0; filter:Alpha(opacity=0);, IE needs manual event forwarding.
See a JSFiddle test and CanIUse pointer events.
I'm adding this answer because I didn’t see it here in full. I was able to do this using elementFromPoint. So basically:
attach a click to the div you want to be clicked through
hide it
determine what element the pointer is on
fire the click on the element there.
var range-selector= $("")
.css("position", "absolute").addClass("range-selector")
.appendTo("")
.click(function(e) {
_range-selector.hide();
$(document.elementFromPoint(e.clientX,e.clientY)).trigger("click");
});
In my case the overlaying div is absolutely positioned—I am not sure if this makes a difference. This works on IE8/9, Safari Chrome and Firefox at least.
Hide overlaying the element
Determine cursor coordinates
Get element on those coordinates
Trigger click on element
Show overlaying element again
$('#elementontop').click(e => {
$('#elementontop').hide();
$(document.elementFromPoint(e.clientX, e.clientY)).trigger("click");
$('#elementontop').show();
});
I needed to do this and decided to take this route:
$('.overlay').click(function(e){
var left = $(window).scrollLeft();
var top = $(window).scrollTop();
//hide the overlay for now so the document can find the underlying elements
$(this).css('display','none');
//use the current scroll position to deduct from the click position
$(document.elementFromPoint(e.pageX-left, e.pageY-top)).click();
//show the overlay again
$(this).css('display','block');
});
I currently work with canvas speech balloons. But because the balloon with the pointer is wrapped in a div, some links under it aren't click able anymore. I cant use extjs in this case.
See basic example for my speech balloon tutorial requires HTML5
So I decided to collect all link coordinates from inside the balloons in an array.
var clickarray=[];
function getcoo(thatdiv){
thatdiv.find(".link").each(function(){
var offset=$(this).offset();
clickarray.unshift([(offset.left),
(offset.top),
(offset.left+$(this).width()),
(offset.top+$(this).height()),
($(this).attr('name')),
1]);
});
}
I call this function on each (new) balloon. It grabs the coordinates of the left/top and right/down corners of a link.class - additionally the name attribute for what to do if someone clicks in that coordinates and I loved to set a 1 which means that it wasn't clicked jet. And unshift this array to the clickarray. You could use push too.
To work with that array:
$("body").click(function(event){
event.preventDefault();//if it is a a-tag
var x=event.pageX;
var y=event.pageY;
var job="";
for(var i in clickarray){
if(x>=clickarray[i][0] && x<=clickarray[i][2] && y>=clickarray[i][1] && y<=clickarray[i][3] && clickarray[i][5]==1){
job=clickarray[i][4];
clickarray[i][5]=0;//set to allready clicked
break;
}
}
if(job.length>0){
// --do some thing with the job --
}
});
This function proofs the coordinates of a body click event or whether it was already clicked and returns the name attribute. I think it is not necessary to go deeper, but you see it is not that complicate.
Hope in was enlish...
Another idea to try (situationally) would be to:
Put the content you want in a div;
Put the non-clicking overlay over the entire page with a z-index higher,
make another cropped copy of the original div
overlay and abs position the copy div in the same place as the original content you want to be clickable with an even higher z-index?
Any thoughts?
I think the event.stopPropagation(); should be mentioned here as well. Add this to the Click function of your button.
Prevents the event from bubbling up the DOM tree, preventing any parent handlers from being notified of the event.
Just wrap a tag around all the HTML extract, for example
<a href="/categories/1">
<img alt="test1" class="img-responsive" src="/assets/photo.jpg" />
<div class="caption bg-orange">
<h2>
test1
</h2>
</div>
</a>
in my example my caption class has hover effects, that with pointer-events:none; you just will lose
wrapping the content will keep your hover effects and you can click in all the picture, div included, regards!
An easier way would be to inline the transparent background image using Data URIs as follows:
.click-through {
pointer-events: none;
background: url(data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7);
}
I think that you can consider changing your markup. If I am not wrong, you'd like to put an invisible layer above the document and your invisible markup may be preceding your document image (is this correct?).
Instead, I propose that you put the invisible right after the document image but changing the position to absolute.
Notice that you need a parent element to have position: relative and then you will be able to use this idea. Otherwise your absolute layer will be placed just in the top left corner.
An absolute position element is positioned relative to the first parent
element that has a position other than static.
If no such element is found, the containing block is html
Hope this helps. See here for more information about CSS positioning.
You can place an AP overlay like...
#overlay {
position: absolute;
top: -79px;
left: -60px;
height: 80px;
width: 380px;
z-index: 2;
background: url(fake.gif);
}
<div id="overlay"></div>
just put it over where you dont want ie cliked. Works in all.
This is not a precise answer for the question but may help in finding a workaround for it.
I had an image I was hiding on page load and displaying when waiting on an AJAX call then hiding again however...
I found the only way to display my image when loading the page then make it disappear and be able to click things where the image was located before hiding it was to put the image into a DIV, make the size of the DIV 10x10 pixels or small enough to prevent it causing an issue then hiding the containing div. This allowed the image to overflow the div while visible and when the div was hidden, only the divs area was affected by inability to click objects beneath and not the whole size of the image the DIV contained and was displaying.
I tried all the methods to hide the image including CSS display=none/block, opacity=0, hiding the image with hidden=true. All of them resulted in my image being hidden but the area where it was displayed to act like there was a cover over the stuff underneath so clicks and so on wouldn't act on the underlying objects. Once the image was inside a tiny DIV and I hid the tiny DIV, the entire area occupied by the image was clear and only the tiny area under the DIV I hid was affected but as I made it small enough (10x10 pixels), the issue was fixed (sort of).
I found this to be a dirty workaround for what should be a simple issue but I was not able to find any way to hide the object in its native format without a container. My object was in the form of etc. If anyone has a better way, please let me know.
I couldn't always use pointer-events: none in my scenario, because I wanted both the overlay and the underlying element(s) to be clickable / selectable.
The DOM structure looked like this:
<div id="outerElement">
<div id="canvas-wrapper">
<canvas id="overlay"></canvas>
</div>
<!-- Omitted: element(s) behind canvas that should still be selectable -->
</div>
(The outerElement, canvas-wrapper and canvas elements have the same size.)
To make the elements behind the canvas act normally (e.g. selectable, editable), I used the following code:
canvasWrapper.style.pointerEvents = 'none';
outerElement.addEventListener('mousedown', event => {
const clickedOnElementInCanvas = yourCheck // TODO: check if the event *would* click a canvas element.
if (!clickedOnElementInCanvas) {
// if necessary, add logic to deselect your canvas elements ...
wrapper.style.pointerEvents = 'none';
return true;
}
// Check if we emitted the event ourselves (avoid endless loop)
if (event.isTrusted) {
// Manually forward element to the canvas
const mouseEvent = new MouseEvent(event.type, event);
canvas.dispatchEvent(mouseEvent);
mouseEvent.stopPropagation();
}
return true;
});
Some canvas objects also came with input fields, so I had to allow keyboard events, too.
To do this, I had to update the pointerEvents property based on whether a canvas input field was currently focused or not:
onCanvasModified(canvas, () => {
const inputFieldInCanvasActive = // TODO: Check if an input field of the canvas is active.
wrapper.style.pointerEvents = inputFieldInCanvasActive ? 'auto' : 'none';
});
it doesn't work that way. the work around is to manually check the coordinates of the mouse click against the area occupied by each element.
area occupied by an element can found found by 1. getting the location of the element with respect to the top left of the page, and 2. the width and the height. a library like jQuery makes this pretty simple, although it can be done in plain js. adding an event handler for mousemove on the document object will provide continuous updates of the mouse position from the top and left of the page. deciding if the mouse is over any given object consists of checking if the mouse position is between the left, right, top and bottom edges of an element.
Nope, you can't click ‘through’ an element. You can get the co-ordinates of the click and try to work out what element was underneath the clicked element, but this is really tedious for browsers that don't have document.elementFromPoint. Then you still have to emulate the default action of clicking, which isn't necessarily trivial depending on what elements you have under there.
Since you've got a fully-transparent window area, you'll probably be better off implementing it as separate border elements around the outside, leaving the centre area free of obstruction so you can really just click straight through.

How does one move html elements with scroll?

I want to create scroll behavior like what can be found here. If you scroll down the page you will notice the crabs, sharks, waves etc are animated whenever the page moves. How can this be achieved? Is this a script or CSS animation?
Edit: text bubbles also appear and disappear at different scroll points.
If you would like a more robust jQuery script to help you out: Per the answer at Loading a long page with multiple backgrounds based on vertical scroll value in jQuery?:
A slightly more full fat solution to the already great one suggested
by Justin is to use jQuery Waypoints to manage the in viewport events.
...
(the answer by Nicholas Evens)
It is a script, just bind a function to the window 'scroll' event with a callback function to do whatever you want. You can tell how far you've scrolled with window.scrollY.
$(window).bind('scroll', function () {
console.log(window.scrollY);
});
You need to subscribe scroll event using jQuery and move your element basing on the scrolling offset whitch can be reached using .scrollTop() property
$(window).scroll(function () {
var scrollOffset = $(this).scrollTop();
// move element to the offcet
});
I didn't look at the site's source code, but I believe it depends on JS. Javascript is necessary to listen to the scroll event of the page, and act according to the current value of document.scrollTop. Then the elements can be positioned with JS, and images can be switched either directly in JS, or by using CSS to change some element's CSS class.
That is definitly a script, you can attach an onscroll event and get the percentage of the current scroll and just position your "crabs" depending on that.
There was already a lot of scripts of how to get the percentage here

Safari iphone/ipad "mouse hover" on new link after prior one is replaced with javascript

After you click a link on the iphone or ipad, it leaves a simulated mouse hover that triggers the a:hover css styling on that link. If the link has a javascript handler that keeps you on same page, the hover state will not change until you click on another link.
This gets weird if you have an ajax widget that asks questions and each answer is link. When you touch one of the answers, it highlights with the hover state, and then when the question and answers are replaced (using javascript) by a new question and answers, the new answer that appears in the same position as the prior answer has its hover state automatically triggered. I want to prevent that from happening to the new answer link.
Is there any way (maybe some something in javascript) that can give me the same result as the "hover" no longer being above this element?
Notes:
I know I could just have a:hover use the same css styling as a, but a:active styling is hardly noticeable since the active state of a touch click is so brief, so I'm hoping for something that can show the hover state on a link until I replace it with new html
I have tried a variety of approaches in javascript, like calling "blur()" on the dom element and some other stuff, but no luck—I'm starting to think that the best solution is to apply classes to the links on javascript events to manage the hover state myself (or just leave it as it is)
The problem is that when you replace the content in place, Mobile Safari treats the new elements as if they were the old ones, because they occupy the same position in the DOM. One workaround is to remove the old elements first, then add the new elements asynchronously. The simplest way to do this is using setTimeout().
http://jsfiddle.net/chad/JNZvu/10/
// When we click on an answer
$('body').on('click', '.answer', function(){
// don't follow it's link
event.preventDefault();
// fade out the container
$('.container').fadeOut(function(){
// remove old elements (happens after fadeOut because we are in the callback)
$('.container').html('');
// add new elements asynchronously and fade container back in.
setTimeout( '$(\'.container\').html(\'<a class="answer" href="#c">link 3</a><a class="answer" href="#d">link 4</a>\');$(\'.container\').fadeIn();', 0);
});
});
When doing this for real, the fadeOut would be called at the same time as the AJAX function, and then the removal/addition would happen in the AJAX callback.
You can try writing another :hover rule that activates when the parent has a particular class, in effect negating the existing hover rule. The class on the parent would need to be added on touchend and removed on touchstart, so that the default rule could take effect on the next link clicked or touched.
I just solved a similar problem where I want hover styling for list items, but since the parent can scroll with one finger using iscroll, I need to cancel that hover effect as soon as the scroll list moves. It's using jQuery, but you get the idea:
$('ul.scroll').bind('touchmove', function(e) {
$(this).addClass('moving');
});
$('ul.scroll').bind('touchstart', function(e) {
$(this).removeClass('moving');
});
here are my style rules:
ul.scroll li:hover {
background-color: #D1E8DA;
}
ul.scroll.moving li:hover {
background-color: #EFEFEF;
}

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