Comments on: WebKit on the iPhone (Part 1)

By: Alexander

Alexander — Thu, 12 May 2011 22:33:24 +0000

@Marzzz
No, iCab doesn’t show a checkered pattern. Or what exactly do you mean?

By: Marzzz

Marzzz — Thu, 12 May 2011 20:42:27 +0000

Hmm, I don’t understand – iCab mobile does this…

By: Alexander

Alexander — Wed, 11 May 2011 23:29:05 +0000

@Marzzz
If another browser shows a checkered pattern while scrolling, it uses a private (and therefore forbidden) API. Apple might remove the Apps if they find out.

By: Marzzz

Marzzz — Wed, 11 May 2011 23:19:29 +0000

Hey you said that smooth checkerboarded scrolling is Not possible outside safari but it seems it’s no longer True as many browsers implement this now – could you Please explain me how this works eg why smooth scrolling is Not possible without the side effect of annoying checkerboarding??? Is the whole page converted to bitmap or smth like this so browser is cheating to get smoother scrolling? Checkerboards are highly annoying on IPad 1 (especially the ones that occur during page loading) but jerky scrolling on image intensive sites with browsers that doesnt use this technique is annoying as Well… Is IPad’s Cpu that weak it Cant scroll simple image gallery without choking? And one more thing which I don’t understand – In checkerboarding browsers while page is still loading and you scroll down to checkerboard it won’t dissapear until you stop scrolling and lift your finger – If you don’t checkerboard will remain visible… And it’s Not enough to lift your finger you have stop page from scrolling (“moving”) completly. Why is that? If browser has Scrollbar like icab’s scrollpad and you scroll page using it loading will continue regardless of scroling…

By: Nilesh

Nilesh — Sun, 04 Jul 2010 18:13:29 +0000

Great work man, Thank you very much….

By: ashish

ashish — Wed, 19 May 2010 09:37:37 +0000

also forgot to ask how stanza and other readers are doing it? Are they not using webview?

By: ashish

ashish — Wed, 19 May 2010 09:36:14 +0000

thanks Alexander, as you are saying that “always scroll less than a full page height”.
while loading a file to webview, the line space and paragraph spaces we can not determine where they will occur. How would be possible to calculate page height?

By: Alexander

Alexander — Tue, 18 May 2010 13:09:56 +0000

@ashish
There’s no simple solution here. You would have to manually measure the line heights of the text to be able to correct the scrolling offset. But please note that it is possible that you can’t find any offset at all which would not cut off a line of text. This can happen when a web page uses multiple columns and the text of these columns is offset by a half line.

Maybe a better pragmatic solution would be to always scroll less than a full page height. So the last line that is shown before scrolling (fully or only partially) will be shown as the first line after scrolling. This way you don’t need to be really exact.

By: ashish

ashish — Tue, 18 May 2010 10:58:20 +0000

@Alexander
I have the same question in this thread but its not answered properly. Any help from your point of view, how to deal with this?
http://stackoverflow.com/questions/2707210/uiwebview-paging-line-cut-off

By: Alexander

Alexander — Tue, 04 May 2010 21:30:56 +0000

@Sam
You won’t get notified when the page changes due to JavaScript. The only chance would be to do some checks yourself. You could do this on touch events or also every x seconds or so.

By: Sam

Sam — Tue, 04 May 2010 19:24:13 +0000

Thank you for this blog. I’m learning a lot.
I have a question about using Javascript like you do in some of your other posts. Can you detect when the web page changes due to Javascript? I’m trying to use your method for links with target=”_blank”, but it’s not working on the Google Reader site. Those links are created by javascript after the page has loaded and the user has clicked on an entry. Before that, they don’t have the target attribute. How do you detect links where the target attribute is added by javascript? Thank you.

By: Saving an Image from UIWebView | Steili.com

Saving an Image from UIWebView | Steili.com — Sat, 01 May 2010 03:07:57 +0000

[...] iCab Blog for the elementFromPoint idea – see Alexander’s comment on 9/1 11:55am, and the support [...]

By: Alexander

Alexander — Thu, 29 Apr 2010 10:21:50 +0000

@JC
There seems to be no public API to get the smooth “checkerboard scrolling” from in Safari.
In case you find a way to implement this using public APIs only, please let me know.

By: JC

JC — Wed, 28 Apr 2010 16:10:06 +0000

Hello Alexander.

Is there a simple way to make the UIWebView scroll more “smoothly” similar to Safari, where it offloads the offscreen portions with the “gray area”? Could this be done with CATileLayer?

By: Alexander

Alexander — Sun, 21 Mar 2010 21:55:21 +0000

@akp
There’s only one way to scroll a web view programmatically, and this is by using the JavaScript function “scrollTo”:

window.scrollTo(x, y);

The coordinates are document coordinates, not device coordinates.