Recently I've been testing my website using screen readers and ran into a page that lags like crazy when using NVDA. More specifically:
All browser actions are substantially delayed, but NVDA itself runs perfectly fine
For example, the page normally loads in its entirety in less than a second, but with NVDA active, the first image can take several minutes to render
Refreshing the page takes several minutes to execute
Even switching or closing the tab takes several seconds
After some extensive debugging, I isolated the issue into a rather specific set of criteria causing the slowdown:
This only happens on Firefox (I'm currently on Firefox 90); Chrome and Edge are fine
This only happens with NVDA; VoiceOver on Mac is fine even on Firefox. I do not have JAWS.
The action causing a slow down is setting an element's textContent on every requestAnimationFrame, so it's happening dozens of times per second
I am uncertain if this is experimentally significant, but I'm running on Windows 10 Home
I managed to scrape together a minimal CodePen example. I used CodePen here because the simplest way I could replicate the issue was by refreshing the page. In the example is a refresh button that activates a spinner, so if the page is fast the spinner will show up for only a brief moment; if it's slow then you'll get to observe the spinner in all its glory.
What I see when I try to refresh:
So while I isolated what is causing the issue, I have no idea why this is happening and hence how to solve my original page's problem without deactivating the widget outright.
What might be the underlying cause(s) of Firefox/NVDA slowing down on a page setting textContent?
Is there an alternative to setting textContent that I can or perhaps should consider?
Is this perhaps an issue that should be filed directly with either Firefox, NVDA, or both?
Thank you!
Addendum:
NVDA Github Issue: This open issue indicates long pages are slow to load, which may be related to my problem
My Website's Page: The page on my website I'm talking about
Related
One page on a client's site causes Chrome to hang unresponsively for 15 seconds or so. On macOS, the browser locks up completely and the spinning wheel appears.
There are no issues whatsoever in Safari or Firefox. I have no idea why this is happening, and DevTools doesn't seem to give any clues as to what's causing it.
Here's a screenshot of the timeline — note the flurry of activity in the final second, when the browser becomes responsive after seemingly doing "nothing" in the latter half:
Some comments on the timeline above:
At ~12,500ms the page looks ready. In any other browser, it is ready for interaction at this point. You can see the final green chunk in the timeline finishes around here.
Chrome completely locks up between 12,500ms and 28,500ms.
I initially assumed the problem was with one of the 3rd-party/analytics scripts, as you can see the timeline shows activity from these right in the final second (> 28,000ms). I tried switching every one of these off, but exactly the same thing happens.
This is a particularly large page, as it lists several thousand records in a JS datatable. I appreciate performance can be improved, but I don't believe that's the root cause. The page/plugin has been working absolutely fine for several years.
What can I try next? Thanks! 🙏
This turned out to be a bug in Google Chrome v107. Updating to v108 fixed the issue immediately.
My Angular 2 Application is slow to respond (1-5 seconds) to key input, button clicks, tabbing across inputs, etc. only when Chrome Developer Tools is open. Material 2 animations also become slow and choppy.
I've been developing this application for three months, and use Chrome DevTools every day. This issue cropped up seemingly overnight.
What I know:
I stashed all pending application changes to revert my application to a time when this was not a problem. The issue persisted.
Chrome DevTools doesn't seem to slow down any other application (ie. google inbox, google maps) in the same browser session.
Maddeningly, when I run the DevTools' Timeline "Record" to try to gain visibility into the issue, the issue disappears and the page reacts at normal speed again! I assume this is the best clue that I have, but I don't know the internal workings of DevTools well enough to know how "Timeline Record" changes things.
I've restarted Chrome and deleted all cached data.
Nothing of the sort happens in Firefox or IE when I open the Developer tools in those.
Any recommendations on where to look next would be greatly appreciated!
Final answer:
Remove all breakpoints
Even if they're not getting hit this fixed it for me and got performance back to normal.
May be a bigger issue if you have logging breakpoints - so try deleting those first if you're attached to your breakpoints.
Previous answers:
I came up with a workaround - although still not really figured out what is actually wrong.
I also discovered a bunch of tools I didn't even know existed that I'd skipped over before - they're under More tools.
Start by opening the Performance Monitor. This shows a nice CPU graph isolated for your Chrome tab - the Windows task manager is as useless as it ever was.
This is the behavior I got when choosing a date from mat-calendar. No other logic running - just selecting a date. I removed everything from app-component and just put a mat-calendar and it took ten seconds to change the date!
Other controls are generally fine. I could open dialogs, use combo boxes etc. and nice and fast. But selecting a date gave me this nonsense:
I tried emptying local storage, clearing cache, etc. and then I changed port number for my website. I simply changed dev.example.com:44300 to dev.example.com:44301 - in other words Chrome now thought it was a different website.
This is what it looked like after I switched port number.
I also got the same effect using a reverse proxy server - which put my local machine on the internet - so I could try to duplicate the issue from other machines. I could not.
So hope that helps someone - still no clue what's in the cache for this server that is having such a massive impact on performance. But for sure it's not just my code.
Here's a few other things to try:
Test with --aot flag
This didn't make a difference to me, but good to narrow things down.
Add some controls that don't do anything (as a control)
This way you can find if some specific action or control is causing the slow down. You should of course be able to toggle these instantly.
Just toggle them on and off, hide something.
<mat-radio-group>
<mat-radio-button [value]="false">
bloop
</mat-radio-button>
<mat-radio-button [value]="false">
bloop bloop
</mat-radio-button>
</mat-radio-group>
Enable Rendering debugging options
Make sure you aren't re-rendering the whole page constantly
The rendering option above will show this to some extent, but one thing I like to do is just add a random text box - type in it and if the text subsequently disappears you know that control has been rerendered.
<!-- yes, just a standard text box -->
<input type="text"/>
Just hide things with *ngIf="false"
Hide controls (yours and third party) and see if anything is causing problems.
For me I'm currently suspecting mat-calendar is causing issues - but I'm still thoroughly confused as to why enabling 'Record' makes the problem non existent.
I've fixed the issue, but I'll never know what was causing it. Likely a setting that I had accidentally changed.
I deleted the Chrome App and reinstalled, everything is back to normal. I'm going to leave this question open in case anyone else has this problem or wants to contribute.
It is normal for every web app to run slowly with Chrome dev tools opened.
Especially if you have inspect tab open, that it's like a new page opened in the same time + has animations on any block render.
We had this issue today at a colleagues workstation. Turned out that it was a chrome-extension (don't remember, something with "ghost" in its name). So maybe try out using guest-mode and check whether the issue still occurs. If it doesn't, successively reactivate the extensions to see which one is causing the problems. If it still occurs, follow the other proposed approaches.
I’m experiencing this odd issue where the web inspector in both Safari and Chrome don’t refresh after a full page reload until about 10–20 seconds later, and only with the web app I’m building. Anyone ever seen anything like this?
Here is a video showing the issue.
The video starts with a page refresh. When you see the blue screen that means the page is fully refreshed. A full 13 seconds later you’ll see the content of the inspector on the right refresh.
This is a relatively heavy React app I’m building, but actual browser performance has been great. I see no lag times or chuggy responses in the actual UI. Only this strange inspector issue. Safari fares slightly better, but still a weird lag.
I’ve no idea if this is a React issue, an OSX issue, a browser issue, or something else entirely. Happy to move this to the appropriate place once I find out (fingers crossed).
Good day,
I have a problem with IE and iframes.
So I have a huge application with legacy code, designed in early 2000. iFrames are used everywhere.
When something big is loaded inside the iframe, there is no display in browser throbber. So the loading icon starts spinning only when the main page is loaded, not iframes, so its impossible to say if anything is happening at all.
The users complain, that IE10+ gives them this problem, earlier versions worked. For me IE9 also has this issue.
Unfortunately, it is impossible to use JS on every page and manually add the 'loading please wait' icon or message, there are more than 100 pages with more then one iframe on each.
Chrome works fine, but nothing except IE can be used.
Could you please recommend solution for this trouble?
I've built a Javascript-heavy web app and recently tweaked it to work on iPad (it needed tweaks because it allows drawing by moving the mouse around, and onmousedown/onmousemove would not get triggered until finger release).
Now, with the tweaks, the app runs fine on Mobile Safari. I'm seeing a problem, however, where the first time I try to load the app on the iPad, it often crashes Mobile Safari. However, reopening the browser and refreshing the page loads the app perfectly and it's fully usable. After doing some research I found out that the most common cause for Mobile Safari crash is over 6MB of pictures or multiple pictures loaded through Javascript. My app only uses images for icons, so the total image size is actually very small (probably under 100KB total), my JS code, however, is 2.5MB uncompressed and 350KB compressed using gz (which is how I'm sending it to the client).
I've also read that loading images through CSS can avoid crashes due to the image size limit. I figured it was worth a try since it's also possible the crash is due to large number of images, not just total image size. After changing some of my icons to be rendered using CSS background-image property, the crash seemed to have gone. I decided to go a step further and tweak all other icons to render using CSS backgrounds as well. After changing all of my images to be rendered using CSS, all of a sudden the crash seems to be back.
Which leads me to several possible conclusions:
A.) Even the partial CSS fix I made did not actually help but somehow I got extremely lucky and saw no crash while reloading my app and restarting the iPad multiple times (then the crash is likely somewhere with my JS code or other parts of the page)
B.) I introduced some other issue when changing the rest of my icons to load through css (if that's the case, I wouldn't expect reloading the page to fix the issue, but it does)
C.) The crash is due to something in my Javascript unrelated to images (but then why does it load and work correctly after reload)
D.) iPad chokes when trying to render/uncompress that much Javascript at once (I haven't heard of this being an issue, but it's also rare to see a chunk of Javascript this big)
Does anyone know what other issues aside from 6MB image limit can cause Mobile Safari to crash the first time a page is loaded, but not the second?
If it helps, here is the link to my web app (this is the old version that loads images through JS): http://www.grafpad.com/grafpad/canvas/demo (it's written in Pyjamas, which is why there is so much generated Javascript).
Thanks
You need to remember that compared to your desktop the iPad is seriously underpowered. Its particularly limited in memory. I noticed right away that there were many, many script blocks on the page. Without tearing your app apart completely to try and find the culprit you might start by combining, just to see if its just dealing with that many nodes that is causing the crash.