[win] Generic TextEditor: Some unicode characters cause text to be rendered incorrectly

[nlisker]

Describe the bug
Redirected from Eclipse JDT: eclipse-jdt/eclipse.jdt.ui#1403

Adding some unicode characters to a text editor can cause either a change in the font of the line in which the character is added, or the character to not be displayed correctly.

To Reproduce
Open any text file in a text editor. My demonstration is with a .java file, but in the link above a .txt file is also used. Type text into that file, for example: (" abc ").

Copy the character ⭳ (\u2B73).

1. Paste it at the start of the string, the character is shown correctly, but the string changes its font:
2. Paste it at the end of the string, the character is shown incorrectly, but the string does not change font:
3. Copy a non-problematic character, like ← (\u2190).
   a. Paste it between ⭳ and abc, the characters are shown correctly and the font does not change: ,
   b. Paste it at the edge, and the problem resurfaces:

The same issue occurs with the character ⮠ (\u2BA0).

Expected behavior
The characters will show correctly and the string will not change its font regardless of the positions those characters appear at.

Environment:

1. Select the platform(s) on which the behavior is seen:
   Only tested on Windows.

• • All OS
• • Windows
• • Linux
• • macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc)
   Windows 10

3. JRE/JDK version
   21 and 22

Version since
Eclipse 2024-03, haven't tested older versions.
Text file encoding doesn't seem to matter. Tested UTF-8, UTF-16, UTF-16BE, UTF-16LE and ISO-8859-1.

[fedejeanne]

@nlisker thank you for reporting this issue!

Is this something you would like to work on or were you just reporting it? :-)

[nlisker]

Just reporting. I don't know SWT and the Eclipse inner workings well enough to be able to work on this in a meaningful amount of time.

[jukzi]

not reproducible with a plain org.eclipse.swt.custom.StyledText