When C++APZ is enabled in Fennec, events that are generated by nsWindowUtil may result in off by one errors when received by the DOM. This is caused by the fact that the PresShell resolution must be applied to the event coordinates before being dispatched which introduces rounding errors. To work around the failure in test_bug388794.html it is necessary to convert the string compares to regex so that the off by one rounding errors may be accounted for.

Can we fix this by adding a meta-viewport tag to the test such that the resolution is always 1.0?

Comment on attachment 8686225 [details] [diff] [review] 0001-Bug-1223937-test_bug388794.html-fails-string-match-test-due-to-off-by-one-error-in-Fennec-with-C-APZ-15111112-201e8cf.patch roc, we'd like to land this to fix this test on Fennec with the C++ APZ. There's rounding errors caused by the resolution. The other alternative is to just disable the test on Fennec.

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #2) > Can we fix this by adding a meta-viewport tag to the test such that the > resolution is always 1.0? (For the record, the problem with this is that the test runs inside an iframe in the harness, and so meta-viewport tags don't make a difference. At least that's what we think.. haven't tried it)