You may be interested by this post :

https://community.notepad-plus-plus.org/topic/19990/regexp-fails-to-match-utf-8-characters/14

and by this site :

https://emojipedia.org/

Particularly, the points :

https://emojipedia.org/man-superhero/

https://emojipedia.org/emoji-11.0/

On the other hand, from this site    https://www.fontyukle.net/ara.php?ara=Segoe+UI   you could download a fairly new versions of all fonts of the Segoe UI family, listed below, with their main characteristics :

•----------------------------------------•------------------•--------------------------------------•---------•------------•----------•------------•
|        Segoe UI font variations        |  Microsoft Name  |  Font Names in "Fontyukle" archives  | Version | Characters |  Glyphs  | Kern pairs |
•----------------------------------------•------------------•--------------------------------------•---------•------------•----------•------------•
|  Segoe UI Black (TrueType)             |  seguibl.ttf     |  Segoe UI Black.TTF                  |   2.02  |    2,191   |   2,443  |    2,638   |
|  Segoe UI Black Italic (TrueType)      |  seguibli.ttf    |  Segoe UI Black Italic.TTF           |   2.02  |    2,191   |   2,544  |    8,467   |
|                                        |                  |                                      |         |            |          |            |
|  Segoe UI (TrueType)                   |  segoeui.ttf     |  Segoe UI.TTF                        |   5.62  |    3,952   |   5,344  |    8,292   |
|  Segoe UI Bold (TrueType)              |  segoeuib.ttf    |  Segoe UI Gras.ttf                   |   5.60  |    3,900   |   5,219  |    8,319   |
|  Segoe UI Bold Italic (TrueType)       |  segoeuiz.ttf    |  Segoe UI Gras Italique.ttf          |   5.30  |    2,826   |   3,377  |    8,613   |
|  Segoe UI Italic (TrueType)            |  segoeuii.ttf    |  Segoe UI Italique.ttf               |   5.30  |    2,826   |   3,377  |    5,739   |
|                                        |                  |                                      |         |            |          |            |
|  Segoe UI Emoji (TrueType)             |  seguiemj.ttf    |  Segoe UI Emoji.TTF                  |   1.29  |    1,962   |  12,189  |    1,394   |
|                                        |                  |                                      |         |            |          |            |
|  Segoe UI Historic (TrueType)          |  seguihis.ttf    |  Segoe UI Historic.TTF               |   1.03  |    3,658   |   4,737  |    1,352   |
|                                        |                  |                                      |         |            |          |            |
|  Segoe UI Light (TrueType)             |  segoeuil.ttf    |  Segoe UI Light.ttf                  |   5.60  |    3,902   |   5,231  |    5,503   |
|  Segoe UI Light Italic (TrueType)      |  seguili.ttf     |  Segoe UI Light Italic.ttf           |   5.30  |    2,826   |   3,389  |    8,388   |
|                                        |                  |                                      |         |            |          |            |
|  Segoe UI Semibold (TrueType)          |  seguisb.ttf     |  Segoe UI Semibold.TTF               |   5.62  |    3,948   |   5,271  |    8,291   |
|  Segoe UI Semibold Italic (TrueType)   |  seguisbi.ttf    |  Segoe UI Semibold Italic.TTF        |   5.32  |    2,874   |   3,437  |    5,209   |
|                                        |                  |                                      |         |            |          |            |
|  Segoe UI Semilight (TrueType)         |  segoeuisl.ttf   |  Segoe UI Semilight.TTF              |   5.62  |    3,950   |   5,219  |    8,293   |
|  Segoe UI Semilight Italic (TrueType)  |  seguisli.ttf    |  Segoe UI Semilight Italic.ttf       |   5,30  |    2,826   |   3,389  |    8,338   |
|                                        |                  |                                      |         |            |          |            |
|  Segoe UI Symbol (TrueType)            |  seguisym.ttf    |  Segoe UI Symbol.ttf                 |   6.23  |    7,362   |   9,209  |    1,361   |
•----------------------------------------•------------------•--------------------------------------•---------•------------•----------•------------•

Best Regards,

guy038

As far as I know, Notepad++ does not use an internal lookup table for unknown glyphs.

When I look at those characters (including superman) in Courier New, I see:

But if I use my normal Deja Vu Sans Mono font, I get:

Note that the female medical worker splits back to the component woman + medical-symbol, since Deja Vu Sans Mono does not have that glyph.

If Notepad++ were using a lookup table to find missing characters, then it would have used the same lookup on woman+medical under Deja Vu Sans Mono as it does with Courier New, but it obviously doesn’t.

Given the number of times in this forum that people have complained about Notepad++ displaying their character as an □, and we suggest that they use a font that knows that character, and then the character displays correctly for them, I am usually pretty confident in asserting that Notepad++ does not use alternate fonts for characters that don’t have a glyph in the chosen font.

On the other hand, some of the emoji you showed use codepoints above U+FFFF, and others use the ZWJ to do the emoji-combo-trick, and I don’t know how the Windows OS and the font system handle such circumstances under the hood. It may be some OS and/or font magic, rather than Notepad++ itself, “helping” you.

And as to your question: how to determine what’s happening behind the scenes and replicate that in generated PDFs: sorry, I don’t think the behind-the-scenes stuff is in Notepad++, so I don’t know how you’d replicate it in your generated PDF.