compare-versions: Safari support

[robinwhittleton]

This works in as much as it loads a browser (not headless of course), screenshots full pages, and diffs them. Safaridriver doesn’t have full page support of course, but the Firefox fallback function works.

Having said that, we have some problems. I had some unexpected hangs on Goriot where it did nothing for minutes on end. But worse, the diffs seem unreliable. E.g. here’s a diff of Goriot’s dedication page where I made no change:

For the main file I added a single letter at the end. Safaridriver produced a 76MB PNG for that that appears to be corrupt, or at any rate none of the image editing software I have can edit it.

So I’d say that we specifically don’t want to merge this. But putting it up for consideration anyway.

[robinwhittleton]

Looking again at the “new” image, it looks like rather than safaridriver capturing the contents of the Safari window pre-composition, it just screenshotted a rect from the composited desktop. The diffed blobs are drop-shadows from other windows I had open. So I’d suggest that that is definitely not acceptable.

[acabal]

OK, thanks. It sounds like it's a no go. So I'll close this and comment out the Safari code in browser.py with a note. Thanks for investigating!