flypig.co.uk

We didn't make much progress yesterday despite capturing all of the data flowing through the browser while visiting DuckDuckGo. While using ESR 91 the page just comes up completely blank, with no obvious error messages in the console output to indicate why.

I left things overnight to settle in my mind and by the morning I'd come up with a plan. So I suppose letting it settle was the right move.

But before getting in to that let me first thank PeperJohnny for sympathising with my testing plight. While of course I'm not happy to PeperJohnny suffers these frustrations as well, I am reassured by the knowledge that I'm not the only one! I share — and am encouraged by — PeperJohnny's belief that the reason can't hide itself forever!

Thanks also to hschmitt and lkraav for the useful comments about similar experiences rendering the Amazon Germany Web pages using the ESR 78 engine.

As it happens I also get this with Amazon UK using ESR 78. It's mighty unhelpful because pages appear briefly before blanking out, making the site next-to-useless. I wasn't aware of the portrait-to-landscape fix, which from the useful comments, I now find works very well. So thank you both for this nice input.

Unfortunately the problem with DuckDuckGo on ESR 91 seems to be different. Unlike the Amazon case the rendering doesn't even start, so the symptoms appear to be slightly different. Following the advice I did of course also try the portrait-to-landscape trick, but sadly this doesn't have any obvious effect.

One positive I can report is that Amazon no longer exhibits this annoying behaviour when using ESR 91. It does display other problematic behaviour, but fixing that will have to wait for a future investigation.

Thanks for all of the input, I always appreciate it, and am always pleased to follow up useful tips like these. When attempting to fix this kind of thing, ideas can be the scarcest of resources, so all suggestions are valuable.

So it looks like I still need a plan of attack. Continuing with the plan I cooked up overnight, unfortunately I don't have much time to execute it today, but maybe I can make a start on it. The approach I'm going to try is a "divide and conquer" approach. I've actually used it before when trying to fix other sites broken with earlier versions of the browser. Given this I'm not sure why it didn't occur to me last night; sometimes these things just take a little while to work their way out.

So my plan is to take a complete static copy of the DuckDuckGo HTML and store it on a server I have control over and can access from my development phones. I can then visit the site and, hopefully, the page will be similarly broken.

Having got to that point I can then start removing parts of the site to figure out which particular aspect of it is causing the rendering to fail. I call it "divide and conquer" because each time I'll take away a chunk of the code and see whether that solves the problem. If not, I'll remove a different chunk. Eventually something will have to render.

The tricky part here is getting an adequate copy of the site. If it's not close enough the issue won't manifest itself.

I've started off by exporting a full copy of the site using desktop Firefox. I started by taking a copy of the page while using the Responsive Design developer option to make the site believe it's running on a phone. But taking this site, posting it on a server and accessing it using ESR 91, I find this new copy of the site now loads perfectly.

So I tried a second time, this time capturing the full desktop site. Again, when I load this using ESR 91 on my phone it looks just fine, automatically displaying the mobile version.

This is all rather unhelpful.

Unfortunately it's now super-late here and I've still not got to the bottom of this. Maybe another night's sleep will help.

If you'd like to read any of my other gecko diary entries, they're all available on my Gecko-dev Diary page.