I know that this is not a 'good question' to pose—but I'm desperate by now and need to find some inspiration.
I have a questionnaire page/web-app that uses CSS transitions to slide to the next page of questions/options. It is well-tested and the transitions in question aren't complex.
But the transition to one special page went out of control recently. And although I consider myself well versed in CSS and JavaScript I'm totally lost with this problem.
The construct in question works like this:
I have a 'window' that is positioned absolutely and has its overflow hidden. Inside that is a page container positioned relative to no left or top values or transforms given. The pages inside this container are positioned absolutely according to their status classes positioned on the left: 0 (active), left 100% (not yet shown), and left: -100% (already done)
What happens now is that when I switch classes to show a certain page, the page container 'jumps to the left'. In Chrome nearly -100% in Firefox about -70% same in Safari.
Those values are my guess because when I open the dev-tools, nothing is to be found in the styles, in the computed values anywhere.
When I move back to the previous page the container jumps back to its original position, and if I move again to the critical page it stays.
I do no positioning whatsoever with JavaScript anywhere, I only switch classes on HTML elements.
After hours of experimenting back and forth, I found out that the problem is in some way JavaScript-related anyhow.
Using the exact same CSS and HTML with a slightly older version of JavaScript does not show the strange behavior. The changes in the Script are mostly ES2020-module related, and the new version does nothing even remotely related to DOM manipulation different from the older working version.
When not using transitions, the shift of the container does not occur.
Has anyone come across something similar? Does anyone know of other tools to deeper analyze the current layout state of a page more than the respective developer tools of the browsers? Any other ideas?
Today I found a solution and at least some kind of explanation, but I still have to investigate some more to truly understand the why and how. I'll post an update if I find a better explanation.
The problem has to do with a text field and focus.
The page in question has a text (search) as its main component.
[I am aware and always was that browsers try to move focused elements into view, regardless of what the author's CSS says.
Therefore, when I decided to give focus to the text field which it does not have on its own, as every page movement required a button to be clicked, I did so on transitionend. This has never changed. When the issue first occurred, one of the things I tried first was to disable that (auto) focus behavior. It did not solve the problem.
I cannot say what made that change in behavior happen. I change the construction of the page to include a grid some time before the issue occurred. That in itself was not the reason, however (it worked for quite some time with that system, and removing it did not sole the behavior).]
What solved the issue was to initially fully disable the text field and only enable it on transitionend (then focusing it).
The reason browsers moved the page to different positions likely has to do with this situation, as the text fields width is ch based.
The important takeaway (for now) for me is, that there is no hint to be found in the developer tools when the browsers moves - elements in the (in my case unsuccessful) attempt to keep inputs in the viewport. I think that this should be changed/fixed.
I will as soon as I have the time try to better understand the things that made the problem occur, If someone has information or experience with similar situations pleas add useful hints and background info.