Bug 6350

Created attachment 5446 [details] test case

Here's why this happens: Positions passed to Selection::setBaseAndExtent are used to construct VisiblePositions. VisiblePositions take the input position and find its canonical position: the position that is visually equivalent but "deep" and at a rendered offset (this canonical position is referred to internally as a "deep equivalent" and is returned by VisiblePosition::deepEquivalent()) For example: <div><b>hello world</b></div> A VisiblePosition created with the Position (div, 0), would have a "deep equivalent" of (textnode, 0). A VisiblePosition created with the Positions (textnode, 6), (textnode, 7), and (textnode, 8) would all have deep equivalents of (textnode, 8). The behavior you see is caused because SelectionController takes the Positions passed to setBaseAndExxtent, creates VisiblePositions, then sets the base and the extent to the deep equivalents of those VisiblePositions. SelectionController does even more fiddling with its positions. When it creates start/end (from base/ extent), it upstream()s the end and downstream()s the start. Comments in SelectionController claim that this is necessary to "constrain" the selection to the fewest possible nodes, in order to make it canonical for purposes of comparison with other selections. I'm not sure why this is necessary, since VisiblePosition's are already canonical. Both of these things need to be addressed to fix this kind of bug (when ranges change when they are used to make selections).

See also: bug 15256.

I am able to reproduce this bug using attached test case in Safari 15.6 on macOS 12.5 and it shows offSet of 1 & 7 rather than 0 and 8. *** Safari 15.6 on macOS 12.5 *** body.firstChild.nodeValue: \n123456\n anchor: [object Text], offset: 1 focus: [object Text], offset: 7 *** Chrome Canary 106 *** body.firstChild.nodeValue: \n123456\n anchor: [object Text], offset: 0 focus: [object Text], offset: 8 *** Firefox Nightly 105 *** body.firstChild.nodeValue: \n123456\n anchor: [object Text], offset: 0 focus: [object Text], offset: 8 ________ I am not sure on web-spec but just wanted to share latest test results. Thanks!

<rdar://problem/97840483>

Fixed by Live Range Selection API. Confirmed on Safari Technology Preview 164. Marking this as "RESOLVED CONFIGURATION CHANGED". Thanks!