1606083 - Message list column truncation results in broken characters

Status: RESOLVED DUPLICATE of bug 404856

(Thunderbird :: Folder and Message Lists, defect)

Description

[lasdka88+mozbugs]

Attachment: Example of the invalid character displayed when the clock symbol is truncated

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:71.0) Gecko/20100101 Firefox/71.0

Steps to reproduce:

I received an email with a U+1F550 CLOCK FACE ONE OCLOCK symbol (🕐) in the subject, with plain/alphanumeric text on either side. I noticed that in the message list the clock character was being displayed as a broken symbol instead - a square box with DB 3D inside - followed by an ellipsis (...) indicating that the text was being truncated due to the width of the Subject column.

Actual results:

I note that DB 3D are the first two bytes of the UTF-16BE representation of the U+1F550 character. It appears that the text truncation algorithm used for abbreviating the text in message list columns is truncating Unicode characters part-way through the byte sequence for a valid character, resulting in an invalid Unicode byte sequence.

If the message pane column is widened slightly such that the symbol is not truncated, it is displayed correctly.

Expected results:

The text abbreviation/truncation algorithm used in the message pane should never truncate a byte sequence mid-way through a valid Unicode character. Thus, the clock symbol should appear correctly, or not appear at all, but never appear as a broken character symbol.

Comment 1

[lasdka88+mozbugs]

Attachment: Shows the Subject widened to correctly display the clock character

Comment 2

[lasdka88+mozbugs]

Attachment: The example email used for the screenshots