Does anyone know if the iPad has any limitations on the canvas tag?
Currently I'm working on a creative that uses a flipbook and audio tag combination to simulate inline video content. The animations are drawn to the canvas element and synced with the audio content being played. There are 4 short video clips that get played when someone clicks on the four buttons below.
http://cs.sandbox.millennialmedia.com/~tkirchner/rich/K/kungfupanda2_test/
The problem I'm having though is in iPad. After playing a few animations, mobile safari just suddenly crashes. It never happens when I play it on my iPhone but it happens every time on the iPad. Its not one particular animation either because if I click a different combination of buttons, the previous clip that it crashed on plays fine, and then it decides to crash on another clip.
I think the problem might have to do with the amount of memory Safari gives individual page views. I found a blog post that explains that problem pretty well.
http://roblaplaca.com/blog/2010/05/05/ipad-safari-image-limit-workaround/
According to that post, once mobile Safari reaches a particular threshold of memory, images begin to return blank. This is consistant with my finds so far. The iPad that I'm testing this all on is running iOS 3.2.1 (and before anyone tells me that I should just explain to my boss that nobody uses 3.X anymore, I tried... they still want me to investigate this). I borrowed a co-workers iPad running iOS 4.2.1 and that device didn't crash, but some of the images weren't being drawn to the canvas.
I'm pretty sure its a problem with the canvas tag too, because I tried experimenting with running the animation without drawing anything to the canvas element, and the page never crashed.
Thats why I think maybe its a limitation with Safari's support of the canvas tag. Of course, I'm open to anybody else's suggestions.
Feels kinda weird answering my own question again, buuuut I figured if anyone did a search on this kind of question, an answer would be helpful.
I believe my original hypothesis was correct. The total amount of images that the aniamtions were using was around 600+. I think the older iPad loaded as many as it could and then when it ran out of cache and the canvas tag was trying to draw images that weren't really there anymore, it crashed.
Eventually we ended up serving the ad to devices with iOS 4.2 and higher, since the problem didn't seem to occur on those newer devices. Plus, we compressed the image sizes further, so that helped reduce the amount of images we were storing into memory.
If anybody knows approximately what the cache threshold in iOS 4.2 or higher browsers are, I'd appreciate it if you commented. Just want to get an idea of how many KB of image data I can safely load.
Related
There is a problem with the sprite animation on the homepage of one of my clients, but it only appears when the site is viewed on an iOS device, namely an iPhone or iPad. I can't replicate the problem on any other device or emulator, so I'm having an issue troubleshooting it (don't own an iPhone or iPad). The problem is: what looks to be a 1px line is appearing on the right edge of the animation frame pretty much all the time, and a similar line flickers occasionally at the top of the frame as the animation runs. The animation itself is a simple javascript sprite sheet animation. I'm operating under the assumption that I have the sprite animation programmed correctly since it appears correctly on every other device, platform and browser I've checked. It even works in IE.
Two questions:
What would cause a simple sprite animation to display differently when rendered by iOS?
As a small business consultant, I don't have the time and my clients don't have the budget for me to physically test on every single device, so I have to rely on emulators. What other options do I have if the emulators don't properly demonstrate what the device will display?
I'm not entirely sure of the protocol regarding posting a link to my client's production website, but happy to send a link to anyone willing to help that responds and/or messages me.
welcome to SO.
I spend a lot of time working specifically with iOS on the web and have run into similar situations. Without tweaking an example you post I won't be able to prove it exactly, but this should at least give you direction.
Flickering or semi opaque lines are often caused by the scaling set to the asset. In the world of high DPI displays and fluid layouts, there are differences in rounding that result in fine lines, shimmers, et al. Is there any scaling set on the assets, e.g. background-size, downsampling?
The emulators are displaying the software correctly - these issues are a result of hardware. Best thing you can do is buy a flagship for all of the platforms you test on, or look into local resources like Clearleft's Device Testing Lab
Working on an AIR iOS app and noticed a strange thing.
In my app I have a navigation panel that displays over the main content-holding Sprite. Having this panel display was causing the app to crash on iPad1 (guessing too much memory). So I added a function to basically draw the content-holder Sprite (via BitmapData draw function) into a Sprite above it, and turn the content-holder visibility off. Basically, taking a screenshot.
However, I'm seeing on 2 different iPads now that any dynamically added text in the content-holder isn't being drawn. Sometimes, the first time it does, but not after.
One thing noticed is that turning off the cacheAsBitmap property of the text fields fixes the problem. Unfortunately, that is not an option as the app is very text heavy and the performance is noticeably slower if the dynamically generated text isn't bitmapped.
Any ideas on what may be going on?
Thanks in advance for any help.
-Mark
Looks like cacheAsBitmap on the dynamic text fields was the problem. By turning that off temporarily, taking the screenshot and then turning back on when done with screenshot, I was able to work around the issue.
Not sure if it's an AIR/iOS issue or maybe a lack of memory?
FYI, in case somebody sees similar problem. Hope that helps.
I am developping a swipe gallery for mobile devices. Users can change images by sliding the screen, as any normal images gallery in most iPhone app.
Here is a demo:
http://daviddarx.com/stuffs/work/custom/swip/
To debug the iOS orientation bug (which let the content zoomed when you change the orientation), I used the only library that correct that:
http://scottjehl.github.com/iOS-Orientationchange-Fix/
Unfortunately, this library is working perfectly most of the time, but it happens to fail and not work correctly. This happen around 1 time on 10 times, and the result is then the same as if the library wasn't here.
This is not a huge problem on most of the mobile and responsive website, as the user can manually dezoom and then get back to the normal display.
But the problem here is that I had to disable the zoom function, to make my system work correctly. So, when the bug happen, once on 10 times, the gallery is then just bugged and stay like that....
So, here are my questions:
-do you know any other library that manage that bug fix, and is 100% completely reliable?
-if not, do you know a way to correct the used library to get a 100% support rate?
-if not, do you have any idea or solution for me?
Thank you in advance for your help!
David
There's an outstanding pull request on Scott Jehl's repo that uses slope detection instead of absolute values which seems to not suffer from the intermittent-ness of the original solution.
https://github.com/PeterWooster/iOS-Orientationchange-Fix/
I am developing a small web application optimized for iPad (using mainly javascript & CSS quirks and hacks). However, there is an issue that I just can not find or come up how to resolve.
The thing is that if I change the orientation of the iPad, during the rotation animation a transparent ("checkered") background is shown in the places that were not rendered in previous orientation. One guy on forums.macrumors.com posted an excellent screenshot illustrating this behavior. The thing is, since my application has a rather dark look and & feel, this checkered background showing during the rotation seems to be awkwardly out of place.
However, this guy's screenshot was for the iPhone - that said, and considering that stackoverflow.com is more programming-focused, I thought I'd ask if anyone struggled with and, hopefully, successfully resolved this issue.
Safari displays the checkered background when the rendering can't keep up (try scrolling really fast). As far as I know there is no way of changing the pattern.
I've been working on an iPad-specific site that uses HTML5 video and though I've got video playback working, I can't for the life of me get the poster image to appear. It looks fine on Desktop Safari. Here's the code:
<video src="video/about_the_man.mp4" controls height=360 width=480 poster="video/posters/about_the_man.jpg"></video>
I've using this link as a reference (listing 1.2): https://developer.apple.com/library/archive/documentation/AudioVideo/Conceptual/Using_HTML5_Audio_Video/AudioandVideoTagBasics/AudioandVideoTagBasics.html#//apple_ref/doc/uid/TP40009523-CH2-SW6
It says that on iOS the poster image will be shown until the user initiates playback, but right now all I'm getting is a black video-sized screen with a big play button in the center. I've looked at other postings on this top (here and here) but neither solution has worked for me. The only thing that's a little bit unconventional about the site is that the video element is in an inline lightbox, so initially on pageload it's not visible, but I don't know why that would make a difference.
I had the exact same problem. I decided to try my code on other iPad's, and it worked fine. The poster image showed up.
After scratching my head for a bit, the solution was to hard reset the iPad and try again. After a reboot, my iPad displayed the poster image as it should.
Maybe it will work for you?
I found there is a limit to the amount of images you can load on an iPad
Here is what it says:
I hit a mobile Safari limitation recently when building an AJAX-y site
on the iPad. If you load a ton of images eventually mobile Safari cuts
you off and will display a [?] instead of the image. After doing some
tests it appears that this limit is around 6.5 MB. Here’s a test page
I made that attempts to load 20 500kb images. When opening this page
on an iPad, 7 of the images don’t appear, even though in Charles they
are returning 200 – success. I’m assuming this is similar to the way
autoplay is disabled for the video tag on iPad/iPhone. Apple probably
wants to make sure users don’t get overloaded with downloads when
browsing on 3G.
Anyhow, 6.5 MB is a hefty load and wouldn’t fare well on 3G, but for one reason or another you may want to work around this limitation. I found the easiest way to patch my code was to load the image into a canvas tag using drawImage(). The canvas tag appears to be immune to the limitation.
Here’s another test page using the canvas tag, all the images should load.