I have a situation when a fixed-size and overflow:hidden element in a browser window contains a very long image, which is basically a vertical sequence of animation frames.
The animation has to occur when a user is scrolling the window. Specifically, advance in $(window).scrollTop() implies corresponding shift in animation frames.
Simple linear dependency between scroll offset and frame number gives me excellent smooth animation on Mac OS, but Windows has a "jumpy" scroll and we instead see an immediate 'jump' from one frame to another.
Now, as though I do feel I'm going to need to detect offset delta between scroll events, and animate the frame advance accordingly using time-based iterations, the question stands: is there a way to make Windows generate a smoother change in scroll offset somewhat like Mac OS does?
Thank you.
Related
I am trying out this new implementation where I am updating some div's bottom/top value to emulate fixed position using javascript with scroll event. The problem is while scrolling the div's are getting a fixed position but moving little bit up/down depending on scroll direction. Had to do it this way as I used transform scale. So CSS position fixed doesn't work. Any optimization advice will be very helpful.
the code is here --> Alternative of position fixed using JavaScript shows weird behavior on window resize
If you check my page on desktop/laptop you can experience that. It depends on a lot of variables like how powerful the device is, browser to browser. I am hoping that if anyone has access to MAC OS on safari and chrome or Windows chrome or any desktop/laptop with a decent browser on it may check the user experience and leave a comment about how laggy jittery is it? Is it like okay or bad?
the webpage link --> https://elomymelo.com/soundcore-motion-boom-plus.html
All you need to do is, scroll down half of my page clicking the link above on desktop/laptop. The right side content should get fixed. But may have jittery behavior on scroll. And please leave a comment about how bad is the experience?
Thanks for your time. This will help me a lot to figure out if I should implement it on the other pages or not. Any optimization advice will be very helpful.
In the following fiddle, there is significant jitter while scrolling. The jitter is noticed only in Safari on Mac, while Chrome and Firefox scrolls the page smoothly.
https://jsfiddle.net/saptarshi17/akxuLL9x/
The jitter is a result of applying parallax effect on the first paragraph. The parallax is implemented by dynamically calculating the top css property triggered by scroll events. I am noticing this on Mac OSX El Capitan, not sure about Windows.
So far, I tried:
Added a mousewheel event-listener in addition to scroll as per this accepted answer on SO.
Tried wrapping the css("top", ...) function call within requestAnimationFrame()
Changed div from relative to absolute to avoid costly reflows.
Added preserve3d property to "hardware accelerate" position calculation as per some comments somewhere on SO.
Since 2 and 3 haven't helped, I assume the core issue has much to do with Safari's scroll implementation and less about frame-rate optimizations. There is a delay Safari's predictive rendering and the subsequent handler call which offsets the position. This results in 2 renders causing the jitter. While I understand Safari's intention behind the first render which works in most cases, this seems to be wrong in cases when the developer wants to override positioning. Maybe there is a way to tell Safari to disable the predictive rendering.
I am trying to get a div to go from 100% opacity to 0% opacity on scroll.
I made this Fiddle and it works great in a web browser, just as I'd hope. It works in mobile browsers too, but with one horrible downside.
var divs = $('.cover_image');
$(window).on('scroll', function() {
var st = $(this).scrollTop();
divs.css({
'opacity': (1 - st / 40)
});
});
(What is happening in the fiddle is the top div is going to opacity:0 as you scroll, revealing another div below it with the same background-image, but blurred. Creating the impression the same image is blurring the more you scroll)
In a web browser as you scroll the div drops in opacity progressively with a fade like affect which is great.
However in a mobile browser the change of opacity doesn't take effect until you release your finger from the the screen. So there is no progressive change of opacity. It only makes the changes visually as you release your finger from the screen, not as you scroll.
Is there a solution for this? I have tried adding in scrolling touch to my css, but it doesn't make a difference.
-webkit-overflow-scrolling: touch
Scrolling distance on mobile works very different from desktop. Even if you detect each step in the touch event, this is only half the truth. When the user releases, the site will continue to scroll for a bit while deaccelerating. This is called momentum scroll and will in most cases not be picked up by the touch event.
There are to my knowledge no perfect solution to this, since different devices handle scroll and touch very differently. There are however a few options you could look into.
Scrolling libraries
There are libraries to help you solve this problem. For instance one called scrollability that emulates scrolling to work more consistently.
Scrollability adds a good imitation of iOS native scrolling to your
mobile web apps.
Scrollability is a single script, it's small, and it has no external
dependencies. Drop it into your page, add a few CSS classes to
scrollable elements, and scroll away.
Ignore the scroll completely
Don't look at the touch or scroll events. Instead use setInterval or requestAnimationFrame with desired frequency that reports the pages current position (document.documentElement.scrollTop) at all time. Base your animation on this value instead of scroll or touch events. You might want to limit this to touch devices since it's not needed for desktop.
Write your own scroll functionality
Disable scrolling and make your own, without for instance momentum scroll, that is suited for your needs. Note that the scroll event is usually disabled on desktop if you disable scroll, but mousewheel works. I have been down this path and I would not recommend it. Instead you should probably go with the library approach at the top.
I've created a website with a parallax street scene. See here for an archived version.
It works just fine on all major desktop browsers, and Safari Mobile. It works fine in Mobile Firefox and Chrome for Android Beta also. However the default Android browser has issues with the scroll event. Let me be clear. Scrolling is not the issue. The div scrolls as required. The scroll event doesn't fire. This issue I experience on Honeycomb as well as ICS.
I'm not concerned about other mobile browsers because for mobile screen sizes one usually does not see the parallax scene; mediaqueries and conditional JavaScript loading take care of that. Responsive design and all that jazz.
Basically, I've written a parallise() jQuery plugin that positions each image based on its position and 'depth'. This function is bound to the scroll event.
On Android Browser, this event only fires at the start of the next touch, instead of continuously.
OK, so I thought that perhaps if I bound the function to touchstart, touchmove, and touchend events I would solve my issue. No cigar. Other touch events are also bugged. Applying the suggested workaround causes the events to fire, but as I have to e.preventDefault(), scrolling (the whole point of the exercise) is disabled.
What if I just poll the position of the stage div relative to the window div? Turns out that the position information is only updated at the start of the next touch.
I am at the end of my tether. Any help would be much appreciated.
Even if the touch events worked correctly on the bugged versions of Android, and you were then effectively able to track the native scroll position during a drag, this would be prone to error. For example, it wouldn't account for the momentum animation which happens after the touching has finished.
iOS and Android make sacrifices to improve the performance of scrolling. On both platforms, it's not possible to get the accurate scroll position until the scroll has completed. The scroll event (on the <body>) doesn't fire until the momentum animation is finished. So while your original question is about scroll events on an overflowing <div>, fixing this might not be totally helpful for you anyway.
If you want an animation to update in time with the scroll, then you need to perform the scroll programatically rather than using the browser's native scroll. The best library to do this is iScroll. You can achieve parallax effects very easily as seen in this demo.
If you need more complex effects (the walking character, in your example), you can opt for the "probe" version of iScroll which allows pixel-perfect polling of scroll position in return for reduced performance.
However, there are many downsides to using iScroll:
You may need to change your markup and styling
It is unnecessary overhead for desktop browsers, but due to markup changes may be difficult to use only as a fallback
The scrolling will not feel perfect - on iOS, with its usually excellent scrolling performance - the slight difference in momentum calculation can feel jarring. On Android, the scrolling can become more laggy than usual.
Swipe shim that doesn't need preventdefault on touchstart: https://github.com/TNT-RoX/android-swipe-shim
I need to smoothly scroll a large amount of text up the screen. Using webkitTransform does this very well, but I would also like to enable the user to change the speed of the scrolling or pause the scrolling based on how fast they're reading. From what I've found, there isn't a way to change the duration of a webkit transition once it has started. Using setInterval and moving the text works, but it gets jumpy and hard to read as the speed increases.
Can anyone recommend a good way to do this that would allow for the user to adjust speed and still give readable text at higher speeds?
I don't know much about modifying currently running CSS3 transformations, but as an alternative solution, I would scroll a large amount of text with JavaScript by using the browser's native scrolling with scrollTop (.scrollTop() if you are using jQuery).
This allows the user to have a familiar interface even without JavaScript, and can be simply implemented with setTimeout() or setInterval(). If the final result is too jumpy, try modifying scrollTop in smaller intervals, but faster. (i.e., instead of adding +100 every 500ms, try adding +10 every 50ms)