1253191 - Selected range jumps as I select text on the "Scroll of Lorem Ipsum" testcase

Status: NEW

(Core :: DOM: Selection, defect, P5)

Description

[arni2033]

>>>   My Info:   Win7_64, Nightly 47, 32bit, ID 20160229030448
Also happens on Firefox 44.
STR:
1. Open attachment 8710335 [details] (from bug 1241394)
2. Scroll the text block to the middle, so that the 1st <hr> on the page was visible
3. (not necessary step) Open Style editor, add stylesheet with rules
  #container{
    height:2000px!important;
    max-height:2000px!important;
    transform: translate(-50%, 50%) rotateY(20deg)!important;
  }
  body{
    height:10000px!important;
  }
4. Move mouse pointer between letters "o" and "n" in the last word "consectetur" before <hr>
5. Hold left mouse button to start selection
6. Move mouse pointer between the last text line before <hr> and <hr> itself
7. Slowly move mouse pointer horizontally to the left side of #container (~10px from the left border)
8. Slowly move mouse pointer horizontally to the right side of #container (~10px from the
   scrollbar at the right)

AR:
 There're 3 possible states of selection range:
 (1) text between the start point in Step 4 and a character in string "tincidunt velit at",
     that corresponds to the current vertical caret coordinate [not ok]
 (2) text between the start point in Step 4 and a character in string "Cras justo turpis, vulputate",
     that corresponds to the current vertical caret coordinate [OK]
 (3) text between the first character on the page and the point in Step 4 [not ok]

ER:  
 There should be no state 1, no state 3.

Comment 1

[arni2033]

Attachment: screencast 1 - Selected range jumps as I select text on the 'Scroll of Lorem Ipsum' testcase.webm

Comment 2

[Jens Stutte [:jstutte]]

Bulk-downgrade of unassigned, 4 years untouched DOM/Storage bugs' priority.

If you have reason to believe this is wrong (especially for the severity), please write a comment and ni :jstutte.