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.
Related
Hello StackOverflow 😀​
I'm having a strange problem with a react app when switching tabs in chrome (the app is already loaded). example : (Link to video if the gif is too low quality)
You can see there is a small white flash before it shows the site itself (something like 0.2 sec), the thing is my app is a little heavier I guess and it's sometimes 0.5-0.75 sec of white screen flash like that which is annoying customers.
Some of them describe it: 'the web page being blank for a 0.5 sec every time we go to another tab in the web browser and we get back to your app.'
I have seen some sites that have the same issue, for example, instacart.com, some of them have 0.1-sec white flash, and some of them have longer flash.
My question is how can I improve this? and what is related to this?
Most of the questions here are related to some stuff that is in react-native, but my app is react web.
I have read about FOUC but I'm not really sure if it's the issue.
btw I don't think it's related to the power of the computer (I'm getting this on a ryzen9 PC and M1 pro mac with 32 GB ram).
Thanks for help.
Also, this problem seems to only exist in chrome, in firefox it doesn't have any white flash. I guess it's related to this (see the first answer). How can I improve it?
The reason may vary. There are several ways to assess and solve performance issue(or flickering issue) with your web app.
Here's what comes to my mind:
Environment check before troubleshooting an web app
I'm getting this on a ryzen9 PC and M1 pro mac with 32 GB ram
The machine spec only holds some portion of performance assessment. It may or may not matter. because,
OS can slow down the performance due to its update issue. what OS are you using?
Web browser can cause the slowness as well. what internet browser are you using? and what version of browser is it? are you using any specific plugin or extension that may cause trouble?
So when assessing or QAing an web app, it is necessary to describe every little detail. When I was developing a Vue web app back in 2019 in a startup, there actually have been some real performance issues in production deployed environment that are bound to specific version of browser; not just that, one time I had a chrome extension causing a crash for my web app as well. Always make the reproducible environment clear unless it is exact which code section is causing the problem.
Once made the details clear, try to reproduce the problem. Does it reproduce in different browser, different machine, different OS? if not, environment is clearly not an issue.
Finding Problem with (any) Web App
If these little details are not causing the problem, it's time to get metrics inside browser.
I had no choice but to skip the environment assessment because the setting isn't clear in the question. But please do not skip that part; it is crucial. The problem might be fixable in current environment but it can remain in different environment.
Somebody already mentioned React devtool profiling in comment but I also recommend these tools:
Chrome Performance Tab
Chrome Lighthouse(previously Chrome Audit Tab)
Please try run a performance check with these tools first.
I've run a performance recording from Chrome Performance Tab and limited the scope to the flashing moment - and a slight moment afterwards.
(screenshots inside red lines are indicating white screen flashing moment)
Most Probable Reasons at the Moment
according to Chrome Performance Tab + Lighthouse audit, these problems are existing in that flashing moment.
treeshaking/code splitting is not used properly: whopping 40000 lines of code in a one file!(content.js) it should served in smaller chunks, so that the codes not important at first rendering must be loaded only when needed. check your code splitting setting first.
lighthouse also highlighted unused codes in a big chunk of single file are the biggest reason for performance dragging in your site before FCP(First Contentful Paint).
too many third party scripts: every third party code is casually lying around in the page with <script /> tag, without any performance tweaks. there are far too many third party libs running. they are not blocking the main thread as they are in async mode, but loading too many of them in parallel is definitely slowing the app. try load third party libs only when needed by inserting them dynamically.
this is most probable reason to my eyes but we need to dive deeper before drawing any conclusions.
Is it possible that this is related to Hardware Acceleration? I usually turn this off in my browsers, and I do not experience what you're explaining on the site you provided (I'm running Chrome on a Macbook Pro 2020 13" intel).
Perhaps turning Hardware Acceleration off will fix the issue?
You said that the issue only appears in Chrome, do you have any extensions that could affect the page when switching tabs? I'm thinking any extensions that reads or edits the page in any form or way.
I guess you have already tried this, but if not: could re-installing chrome and testing the sites with a fresh install (no extensions, no profile logged in...) work?
So in the end the solution was pretty crazy, we had a picture with the logo of our company in the navbar (which is appearing on each page of the app).
The problem with the picture was - whopping 35,000 px width and 5,000 px height.
You couldn't see it because it was inside a div with a fixed height and width.
The way I found that - opened dev tools, and started to delete the divs.
for example, we have:
<div id="root">
<div>1</div>
<div>2</div>
</div>
So I delete div 1, then check if the problem is still there. if the problem is still there I go delete div 2. And continue like that till you find something crazy like a 32,000px picture.
Very 'old school' but it is what it is (:
Another odd timeline event where it doesn't even make network request for more than 5 seconds
I have a performance issue on iPad Air 2 using Safari when reloading this page
http://demo.phppointofsalestaging.com/slow.html
The first time it is pretty fast; but refreshes after the 1st load are slow. (5-10 seconds) AND it doesn't happen every time. It is not a network issue because I have tried on local network with same results.
It is also not a server side performance issue as the url above is just a static html file.
It also doesn't appear to be a CSS issue as if I remove all CSS it is still slow.
What I have tried so far is to remove js files 1 by 1 to see if that helps. It has been really hard to narrow it down due to the random nature of the problem and that it only occurs on iPad.
Also I know that my CSS and js are not contacted or minified; as we are still doing active development.
If I remove all js it is fast.
We use third party scripts; but since the issue doesn't happen on desktop it is hard to use profiling tools.
I am looking for any methods to profile on iPad Air 2
I am running iOS 9.1; but this happens on 8 too.
Interesting note: it is slow when hitting refresh icon; but not tapping url and then go.
Chris you can't use the #import rule in other places different than the beginning of the document, that was the issue.
MDN about the #import rule:
The #import CSS at-rule allows to import style rules from other style sheets. These rules must precede all other types of rules, except #charset rules; as it is not a nested statement, it cannot be used inside conditional group at-rules.
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 am developing a reasonably large application on PhoneGap version 2.8 for Android. The issue that I can't seem to fix or even understand why it is happening is described as follows. When I start the application, initially a white screen is shown, which is completely fine since I undestand that it takes a moment or two to launch cordova. I have added a plugin to the project that puts the application to the background when user clicks "back" button in the "home" view. I can see that my app is still running in the task manager which is all fine and dandy. If I click on the app to bring it to foreground, app returns to foreground but views blank white screen for ~3 seconds, after which my view is rendered. I am wondering if there is any way I could speed up whatever the process is going on. I have noticed that it doesn't happen if my app isn't installed with APK but is run by IDE in debug mode (in which case it runs instantly just like any other normal app), but it still persists, if I click on the app icon in the apps menu.
I know that onDeviceReady event is fired way before the blank screen is gone. I know that some html is added into DOM tree. By the time white screen disappears even my ajax request is back with more data to be displayed on the screen. I know that whatever is, that effect is not because of my scripts being loaded in.
I suspect that this is effect is due to Phonegap taking a moment to restore it's Activity, or WebView to restore (if that makes sense).
I have tested that on different physical devices (Galaxy S2 and S3, HTC One X).
There is alot of optimization still to be done (memory is leaking somewhere, and there seems to be alot of performance issues with older phones eg. HTC One V).
I have tried to show Splashscreen while the white screen is up, but it is hard to estimate, when i should hide it (javascript seems to be running asynchroniously in relation to white screen).
Perhaps anyone would be kind enough to explain what is causing the white screen to be present and what could be done to resolve that issue.
Much obliged,
Erich
I'm making an html interface to upload images on a server with Drag & Drop and multiple selection files. I want to display the pictures before sending them to the server. So I first try to use FileReader but I have had some problems like in this post. so I change my way and I decided to use blob:url like ebidel recommends in the post, with window.URL.createObjectURL() and window.URL.revokeObjectURL() to release memory.
But now, I've got another problem, which is similar to this one. I want that a client could upload 200 images at time if he wants. But the browser crashed and the ram used was very high! So I thought that maybe too much images were displayed at the same time, and I set up a system with a waiting queue of files using an array, in order to treat only 10 files at time. But the problem still occurs.
On Google Chrome, if I check chrome://blob-internals/ the files (which are normally already released by window.URL.revokeObjectURL()) are released approximately after a 8 seconds delay. On Firefox I'm not sure but it seems like if the files were not released (I check on about:memory -> images for that)
Is my code which is bad, or is it a problem independent of me? Is there a solution to force the navigators to release immediately the memory? If it can help, this is the part of JavaScripton which the problems occurs: link expired because code was not included in question.
EDIT
This is a kind of own answer + an answer to bennlich (too long text for a comment)
I understood from the answer of user1835582 that I could indeed remove the Blob/File but while the browser needs images it keeps them somewhere in memory (which is logical). So it's the fact to display images (many & heavy) that gave me crashes & slow downs, not the revokeObjectURL method. Moreover, each browser manages the memory by its own way, leading to different behaviors. Here is how I came to this conclusion.
First, let's try that revokeObjectURL works well, with a simple example using the source code of https://developer.mozilla.org/en-US/docs/Using_files_from_web_applications#Example.3A_Using_object_URLs_to_display_images.
Using Chrome you can verify that Blob are well revoked, by checking chrome://blob-internals/ or trying to open displayed images into a new tab that will be blank. Note : to fully release Blob references, add document.getElementById("fileElem").value = "". When I posted my question some years ago, it was about 8 seconds to release blob, now it's almost immediate (probably due to improvements in Chrome & / or to a better computer)
Then, time for a charge test. I did it with a hundred of jpg of ~2.5 Mo each. After that images have been displayed, I scrolled the page. Chrome crashed and Firefox was slow (not tested on others browsers). However, when I commented li.appendChild(img) all went well, even with a huge bunch of images. This shows that problems are not coming from revokeObjectURL method which in fact works properly, but from displaying lot of heavy images. You can also test to create a simple html page with hundreds of heavy images and scroll it => same result (crash / slow down).
Finally to look deeper about images memory management, it's interesting on Firefox to look into about:memory. For example I saw that when the window is active, Firefox uncompresses the images (images -> uncompressed-heap goes up), while raw (images -> raw) is always stable (relative to the the quantity of images loaded). There is a good discussion about memory management here : http://jeff.ecchi.ca/blog/2010/09/19/free-my-memory.
With window.URL.revokeObjectURL() you can only get [Blob] or [File] object. You can not force remove from memory.
Note.
Browsers are not finalized and they can leak from these facilities. If you implement the animation, you have to understand that at your own risk.
This isn't an answer, but I just want to say that, as far as I can tell, this is still an issue in the latest version of Chrome (35). I made a test page that exposes the problem:
http://ecobyte.com/tmp/chromecrash-1a.html
If you select a large number (say, 600) of high resolution photos on your computer and drop them into the box on that page, it will crash Chrome (tried on Windows 7 and Mac OS X 10.8.5).
If you look at the source you can see that sequence of ops is:
createObjectURL
load the img (don't add to DOM!)
revokeObjectURL to free the ref
Lose the img ref
Repeat all steps for next dropped image
Seems like only a single image should be in memory/referenced at any given moment, but eventually this crashes Chrome.