1016039 - "TypeError: candidate is undefined" when switching tab group (panorama) by keyboard shortcut

Status: VERIFIED FIXED

(Firefox :: Tabbed Browser, defect)

Description

[YUKI "Piro" Hiroshi]

The shortcut "Ctrl-Shift-`" switches the panorama. However, if the mouse cursor is on any tab, it fails to update visibility of tabs. As the result, broken group appears.

Steps to reproduce:
 1. Open a new browser window.
 2. Open the browser console by Ctrl-Shift-J.
 3. Open three tabs: "about:blank?1", "about:blank?2", and "about:blank?3".
 4. Enter to the Panorama view by Ctrl-Shift-E.
 5. Create two groups:
     A - "about:blank?1"
     B - "about:blank?2" and "about:blank?3"
 6. Click "about:blank?1" thumbnail to enter the group A.
 7. Now there is only one visible tab.
    Then, move your mouse cursor on the tab.
 8. Switch group by Ctrl-Shift-`.

Actual result:
  I'm in the group B, but there is only one visible tab "about:blank?2".
  The secondary tab in the group "about:blank?3" is still hidden.
  And, the error "TypeError: candidate is undefined tabbrowser.xml:4725"
  appears in the browser console.

Expected result:
  I'm in the group B and there are two visible tabs "about:blank?2" and
  "about:blank?3". There is no error in the browser console.

Tested environment:
 * Windows 7 Home Premium
 * Firefox 29.0.1 and Nightly 32.0a1 (2014-05-26)
 * With no addon

The error is always reported from the section in tabbrowser.xml:

>      <method name="_mouseenter">
>        <body><![CDATA[
>          if (this.closing)
>            return;
>
>          let tabContainer = this.parentNode;
>          let visibleTabs = tabContainer.tabbrowser.visibleTabs;
>          let tabIndex = visibleTabs.indexOf(this);
>          if (tabIndex == 0) {
>            tabContainer._beforeHoveredTab = null;
>          } else {
>            let candidate = visibleTabs[tabIndex - 1];
>            if (!candidate.selected) {  // <= this line.

Comment 1

[Dão Gottwald [:dao]]

Seems like _mouseenter should return early if the tab is hidden (this.hidden) just like it does for this.closing.

Comment 2

[Michael Pruett]

Attachment: Patch

Updating _mouseenter to return early for hidden as well as closed tabs seems to fix this problem.

Comment 3

[Dão Gottwald [:dao]]

Comment on attachment 8432113 [details] [diff] [review]
Patch

Thanks!

Comment 4

[Michael Pruett]

Comment on attachment 8432113 [details] [diff] [review]
Patch

Here are the try server results:

https://tbpl.mozilla.org/?tree=Try&rev=4d5bc721cf23

Comment 5

[Dão Gottwald [:dao]]

https://hg.mozilla.org/integration/fx-team/rev/773efcc4ed6b

Comment 6

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/773efcc4ed6b

Comment 7

[Alice0775 White]

I think this should be fixed in Aurora31.0a2 which will be next ESR.

Comment 8

[Dão Gottwald [:dao]]

Comment on attachment 8432113 [details] [diff] [review]
Patch

[Approval Request Comment]
Bug caused by (feature/regressing bug #): bug 879597

User impact if declined: see "Steps to reproduce" and "Actual result" in comment 0 (there's not just the error, but tabs erroneously remain hidden)

Testing completed (on m-c, etc.): on m-c

Risk to taking this patch (and alternatives if risky): very low

String or IDL/UUID changes made by this patch: none

Comment 9

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-aurora/rev/ef5c82db859e

Comment 10

[Paul Silaghi, QA [:pauly]]

Reproduced in Nightly 2014-06-01.
Verified fixed 32.0a1 (2014-06-09), win 7 x64.

Comment 11

[Ada [:adalucinet]]

Reproduced with Nightly 2014-05-26 on Mac OS X 10.9.2.
Verified as fixed with latest Aurora 31.0a2 (Build ID: 20140609004001) on Windows 7 x64, Mac OS X 10.9.2 and Ubuntu 14.04 x32.