1277894 - Support surrogate pair when cropping XUL label.

Status: RESOLVED DUPLICATE of bug 1164759

(Core :: XUL, defect)

Description

[Tooru Fujisawa [:arai]]

Attachment: long title with emoji

Currently surrogate pair is totally ignored when cropping text in XUL element.
This results in broken title in Tab, when it crops title text at the middle of surrogate pair.

We should support it, as webpages could use emoji in their title, and in most case Tab cannot show entire title.

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Testcase A (Tab title)

1. open attached HTML
2. add and remove other tabs

Actual result:

sometimes emoji is shown and sometimes box with code is shown

Expected result:

always emoji is shown

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Testcase B (all crop variants):

1. evaluate the following code in Scratchpad, with Browser environment.
   it adds 3 labels at the bottom of the browser window

  var w =  Services.wm.getMostRecentWindow("navigator:browser");

  var l = w.document.createElement("label");
  l.setAttribute("value",  ("\uD83D\uDC38\uD83C\uDF40\uD83D\uDC9A").repeat(20));
  l.setAttribute("crop", "start");
  w.document.documentElement.appendChild(l);

  l = l.cloneNode(false);
  l.setAttribute("crop", "end");
  w.document.documentElement.appendChild(l);

  l = l.cloneNode(false);
  l.setAttribute("crop", "center");
  w.document.documentElement.appendChild(l);

2. resize the browser window gradually to make those labels cropped


Actual result:

sometimes emoji is shown and sometimes box with code is shown


Expected result:

always emoji is shown

Comment 1

[Tooru Fujisawa [:arai]]

testing a patch.
https://treeherder.mozilla.org/#/jobs?repo=try&revision=89758d73d634

Comment 2

[Neil Deakin]

There's already a patch for this in bug 1164759. It works but the test doesn't.