1640272 - Clicking on a scroll bar of the javascript debugger blows up firefox

Status: RESOLVED WORKSFORME

(Core :: Graphics: WebRender, defect)

Description

[Joe Searle]

Attachment: mozconfig

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 Edge/18.18363

Steps to reproduce:

Built firefox on Windows 10 from mozilla-central with the mozconfig file as attahed below. Than ran it without a pre-existing C:\mozilla-source\mozilla-central\obj-x86_64-pc-mingw32\tmp\profile-default file. Killed the new features tab. entered about:debugging for the existing tab. Clicked on This Nightly. Loaded by temporary Add-on. Opened my .html file. Brought up the JavaScript debugger. Caused the debugger to load ExpTypeGreekNew.html. caused the debugger to load "cutCopyPasteTextarea.js". Set a breakpoint on line 1147 of "ExpTypeGreekNew.html". Set a breakpoint on line 4 of "cutCopyPasteTextarea.js". Entered some characters in the textarea element of the html. Used the mouse to select a portion to the characters just entered. FWIW, these will be Unicode characters in the Greek and Coptic block by default. Right click on the textarea elements portion of the page to bring up my context menu. Left click on "Copy" of the my context menu to force the JavaScript debugger to hit the breakpoint in "ExpTypeGreekNew.html". Left click on the debugger's stepover icon to force the evaluation of "choice". Left click on the right most scroll bar so that I can confirm the value of choice in the scope area. It has the correct value "Copy". "Step Over" until I got to line 1182 to confirm that the switch statement performed as expected. Left click on Continue to cause the debugger to hit the breakpoint set in "cutCopyPasteTextarea.js". Once there click on Step Over once to force the evaluation of "choice". Try to confirm the value choice by left clicking on the right most scroll bar of the debugger in the "open" area of that scroll bar (not on the incremental down arrow) to get to the Scope area and examine the value of "choice".

Actual results:

Instead of scrolling that sub window, firefox barfs on std out and terminates.
FWIW, just before this when I got this point, I was using the down arrow repeatedly to scroll to the Scope area to confirm the value "choice". I suppose if I'd give the debugger's window more vertical height I wouldn't be getting into these scrolling problems. Anyway, repeatedly using the Scroll bar's down arrow caused it to stop working. In standard out I saw something to the effect: too many micro scroll adjustments, the scroll bar is now locked!. Paraphrasing the military, debugging the debugger seems to be a target rich environment.

Expected results:

Should have scrolled that sub window.

Comment 1

[Joe Searle]

Attachment: ExpTypeGreekNew.html

Comment 2

[Joe Searle]

Attachment: manifest.json

Comment 3

[Joe Searle]

Attachment: cutCopyPasteTextarea.js

Comment 4

[Joe Searle]

Attachment: stdout/error of firefox

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Comment 6

[Logan Smyth [:loganfsmyth]]

This looks like a pretty WebRender-heavy stack trace, so gonna bump this over there for now.

Comment 7

[Dzmitry Malyshau [:kvark]]

Looks like OOM shmem in BuildWrMaskImage.
Nicola, perhaps you have an idea?
Marking as S2 in the meantime.

Comment 8

[Tim Spurway [:tspurway]]

S1 or S2 bugs need an assignee - could you find someone for this bug?

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

The bug has a release status flag that shows some version of Firefox is affected, thus it will be considered confirmed.

Comment 10

[Glenn Watson [:gw]]

Assuming this is resolved, please reopen if not.