I use jQuery Mousewheel plugin and - for tests - I put the exact same code as the author of the plugin did:
$('body').on('mousewheel', function(event) {
console.log(event.deltaX, event.deltaY, event.deltaFactor);
});
Problem is - I'm always getting 100 for deltaFactor, and citing the author, it shouldn't behave like that:
In some use-cases we prefer to have the normalized delta but in others
we want to know how far the browser should scroll based on the users
input. This can be done by multiplying the deltaFactor by the deltaX
or deltaY event property to find the scroll distance the browser
reported.
What can I do?
It's fine. It simply means you have mouse wheel acceleration turned off. Simply use event.deltaX * event.deltaFactor and it will work everywhere.
Related
I have integrated a javascript audioplayer in a website, and it worked without problems. But ever since i limited the width of the webpage with a container div ('max-width'), the clickable timeline is not working correctly.
I narrowed down the problem, i think. This code calculates the mouseclick on the timeline:
function clickPercent(e) {
return (e.pageX - timeline.offsetLeft) / timelineWidth;
}
The problem is that pageX counts from the left browser edge, offsetLeft on the other hand counts from the parent element's edge. So when i click on the timeline, the player-dot jumps to the wrong position.
I made a JSfiddle demo: http://jsfiddle.net/2zkj25ss/35/
I suppose that i need something different than offsetLeft, something that can give me the absolute offset instead of the relative offset.
Can anyone help me with this? Please keep in mind that i'm not a programmer, and my JavaScript skills range from poor to non-existent.
If you don't need to support IE<9 (as in, windows XP and earlier which I doubt anyone needs to support), you can use Benjamin's solution instead.
Just replace timeline.offsetLeft in the function:
function clickPercent(e) {
return (e.pageX - (timeline.getBoundingClientRect().left + window.pageXOffset)) / timelineWidth;
}
I'm trying to prevent default scrolling behavior while still determining the number of pixels a user has attempted to scroll.
My objective is (at some vertical position on my page) to fix a navigation element to the top of the screen and hijack the scroll/swipe event to pull down a mobile menu when the user scrolls back up (so moving said element up and down by n pixels depending on how many pixels the user tries to scroll).
I am aware of the UX/accessibility concerns insofar as blocking native behavior, but the suits want what the suits want.
So far I have:
$('body').on({
'mousewheel' : function(e) {
e.preventDefault();
e.stopPropagation();
}
});
but am stumped as to how to access the number of pixels scrolled (since element/scroll offsets are no longer a guide).
Edit: Please note that this question is specifically asking for information regarding mouse/scroll actions while scrolling is blocked. Don't think this has been appropriately marked as duplicate.
This is browser-depended because of the mousewheel event you are using. This is because it is non-standard. Don't use it!
In Chrome (43.0) you get different properties with different values:
e.originalEvent.wheelDelta: -120
e.originalEvent.wheelDeltaY: -120
e.originalEvent.deltaY: 100
In IE (11.0), you can get only one property:
e.originalEvent.wheelDelta: -120
In Firefox (38.0.5), the capturing of the mousewheel event doesn't work at all.
Solution:
Use the wheel event (MDN reference). This event has the e.originalEvent.deltaY property in all browsers.
Before cancelling event propagation take the deltaY out of the original event like this
$('body').on({
'wheel' : function(e) {
console.log(e.originalEvent.deltaY);
e.preventDefault();
e.stopPropagation();
}
});
This question is more of an advice research, I do hope that it will be helpful for others and it won't closed, as I'm not quite sure where to ask for advice on this matter.
I've been developing for mobile for the past 6 months and I had the occasion to deal with all kinds of situations and bugs on various devices.
The most troubling was the scrolling issue, when it comes to scrolling in multiple areas of the website. On three projects that I have been working on I've been building a navigation that behaves the same way that the native iOS Facebook app has, or the Google website on mobile, etc. And for each one I came up with different solutions.
But a few days ago I have just released a new JavaScript library, drawerjs, that can be used to generate such navigation (so called off canvas concept). The difference between the other libs and this one is that is library agnostic, and it acts on touch behavior (the same way that the Facebook app behaves) not just open / close on click.
One of the things that I have left to implement is a solution for scrolling inside the menu and the navigation without affecting one another (most of the time when you scroll in such way, the content tends to scroll together with you menu or after you have reached the end of the menu scrolling).
I have two solutions in mind:
One approach would be to use the same principle I'm using for dragging the content and showing the navigation, on touchmove I prevent the default scrolling on document / content and I start translating the contents with the same amount you scroll. And with the same resistant behavior as a touch slider would have (when you exceed the boundaries and let go, the contents would translate back so it doesn't exceed the boundary anymore, or on swipe with the same behavior).
A second approach would be using the native overflow-scrolling that iOS has and would offer the same feel as described in the first approach. The downside of this would be that only iOS devices would have the nice resistant feature, but it would be, supposedly, less of a hassle the the first approach.
So I'm not quite sure which approach I should take, or if there any better solutions for that. I'm also trying to keep in mind that some users would like to hide the url bar, so scrolling on the body / html would have to be kept (on the y axis).
You could do touchmove . But as far as I understand, you want something like this?
http://jsfiddle.net/2DwyH/
using
var menu = $('#menu')
menu.on('mousewheel', function(e, d) {
if((this.scrollTop === (menu[0].scrollHeight - menu.height()) && d < 0) || (this.scrollTop === 0 && d > 0)) {
e.preventDefault();
}
});
Using this plugin from Brandon Aaron - github : https://github.com/brandonaaron/jquery-mousewheel
And it should work with Android: What DOM events are available to WebKit on Android?
Some more info here: Prevent scrolling of parent element?
Also without using the plugin above , using only jQuery you could do this like it says on the link above - answer from Troy Alford
$('.Scrollable').on('DOMMouseScroll mousewheel', function(ev) {
var $this = $(this),
scrollTop = this.scrollTop,
scrollHeight = this.scrollHeight,
height = $this.height(),
delta = (ev.type == 'DOMMouseScroll' ?
ev.originalEvent.detail * -40 :
ev.originalEvent.wheelDelta),
up = delta > 0;
var prevent = function() {
ev.stopPropagation();
ev.preventDefault();
ev.returnValue = false;
return false;
}
if (!up && -delta > scrollHeight - height - scrollTop) {
// Scrolling down, but this will take us past the bottom.
$this.scrollTop(scrollHeight);
return prevent();
} else if (up && delta > scrollTop) {
// Scrolling up, but this will take us past the top.
$this.scrollTop(0);
return prevent();
}
});
The JS Fiddle he mentions: http://jsfiddle.net/TroyAlford/4wrxq/1/
Why not just provide a fixed height to your widget (min and max will also do). Then define like these -
height: x px;
overflow-y: auto;
This way till the focus is inside the widget, it'll only overflow the widget, once outside the page will scroll without affecting widget content at all.
I am looking for help / a point in the right direction / or a solution for a flicker/jump, when scrolling on a looping/infinite website, which can be seen in this fiddle.
What seems to be causing the jump is:
"$(window).scrollTop(half_way - child_height);", and what could also be a Chrome windows scrollTop bug, but it is happening in all browsers at the moment.
If I remove "- child_height" there is no longer a flicker but the page no longer scrolls correctly, which can be seen in this fiddle.
Also, on the very first scroll the right hand column jumps up by three boxes - also because of 'half_way', which I can fix by giving it a "bottom: -600px;"
The full code:
http://jsfiddle.net/djsbaker/j3d8r/1/
var num_children = $('#up-left').children().length;
var child_height = $('#up-left').height() / num_children;
var half_way = num_children * child_height / 2;
$(window).scrollTop(half_way);
function crisscross() {
$('#up-left').css('bottom', '-' + window.scrollY + 'px');
$('#down-right').css('bottom', '-' + window.scrollY + 'px');
var firstLeft = $('#up-left').children().first();
var lastLeft = $('#up-left').children().last();
var lastRight = $('#down-right').children().last();
var firstRight = $('#down-right').children().first();
if (window.scrollY > half_way ) {
$(window).scrollTop(half_way - child_height);
lastRight.appendTo('#up-left');
firstLeft.prependTo('#down-right');
} else if (window.scrollY < half_way - child_height) {
$(window).scrollTop(half_way);
lastLeft.appendTo('#down-right');
firstRight.prependTo('#up-left');
}
}
$(window).scroll(crisscross);
Okay - here is a 'working' version - and by works I mean it less flickery than before. I thought it was flicker free, and it was when I was on battery power, but plugged into the mains and the CPU is fast enough to get flicker.
As I mentioned, to get rid of the flicker you need to clone the objects, manipulate them and then replace them into the DOM, rather than just manipulating the DOM directly.
I did this by getting the contents of <div id="content"> manipulating them and then replacing them into that <div>.
Also, it's a good idea to only find things in the DOM once, and from then on use a reference to that object rather than searching repeatedly. e.g.
var leftSide = $(clone).find('.up-left');
....
lastRight.appendTo(leftSide);
....
$(leftSide).css('bottom', '-' + window.scrollY + 'px');
rather than:
lastRight.appendTo('#up-left');
$('#up-left').css('bottom', '-' + window.scrollY + 'px');
Searching the DOM is relatively slow, and so storing references can improve performance/reduce flicker.
Storing the object also makes the code easier to understand (imho) as you can easily see that you're referencing the same thing, rather than possibly different things.
I still get flickering in chrome on windows with Danack solution. For this site I would control all the scrolling (you already scroll manually one of the sides), and give elements absolute positions.
Or if you insist on using the browser scrolling, may be use animations: animate the height of the last elements till 0px then use appendTo, and then animato from 0px to the normal height...
This might be a long shot, but I had the same flickering when working with infinitescroll,
and ended up using imagesLoaded.I ended up appending the additional images (now loaded) with a fade in, and that prevented them from flickering because of the fact they were loaded.
So maybe by using the imagesloaded - or a callback on the images, you can solve the flickering. It does decrease the speed though. I can image that if you want to scroll through everything as fast as possible, this might not be the solution. Good luck!
A solution would be to not use the native scrolling functionality but to simulate scrolling. This would be done by setting the overflow of your content to "hidden" in addition with capturing the "mousewheel" event on it and triggering some action when it is called. I started to try this out here (using MooTools instead of jQuery since I'm more fimilar with it). It's currently just "working" on the left side by altering the margin-top of the first element.
My next steps would be:
Check if the negative margin-top of the first element is bigger than the height of it and move it to the right side if so.
Same logic for the last box on the right side with a negative margin-bottom.
This has some downsides, though. Simulating scrolling doesn't feel as natural as the native scrolling functionality and clicking the mousewheel doesn't work. These might be solveable but it would require some more coding to get it to work smoothly. Anyway, in the end you would have a solution without any flickering and with no sticky scrollbar at the side (An idea for a replacement could be a small area on the side that triggers the scrolling on mouseover).
I thought it was related to line-height CSS property, but it doesn't work. How to adjust the scroll amount when clicking the scroll up/down buttons?
As far as I know, this isn't something you have control over. However, you could listen for the Javascript onScroll event and then use the Javascript scrollBy method to scroll the page more or less depending on what you wanted. I'm not sure how this would look though, things could be a bit jerky and confusing to the user. You'd also have to take into account whether or not the user has zoomed the page in or out.
Assuming you want to scroll an arbitrary area (rather than an object, such as a tree, that already supports scrolling), then you could set overflow: hidden and use explicit scrollbar elements. Unfortunately there's no easy way for script to detect user interaction with scrollbar elements, other than watching the curpos attribute.
You can't control, directly, the scroll increment in Firefox when clicking the scrollbar buttons but you can use this code:
//element may be window or a HTML element
//amount of incrementation should be an integer representing the number of pixels to be scrolled
//works in all last versions of major browsers
element.addEventListener(/firefox/i.test(navigator.userAgent) ? 'DOMMouseScroll' : 'mousewheel', function (event) {
element.scrollTop -= (event.detail ? (event.detail % 2 ? event.detail / -3 : event.detail / -2) : event.wheelDelta / 120) * amount;
event.preventDefault();
}