3.5.1 Garbled non-Latin text while copying and pasting within Game Mode

[dkaknbk]

Your system information

• Steam client version: 1697843490
• SteamOS version: 3.5.1 Preview channel
• Opted into Steam client beta?: [Yes]
• Opted into SteamOS beta?: [Yes]
• Have you checked for updates in Settings > System?: [Yes]

Please describe your issue in as much detail as possible:

Describe what you expected should happen and what did happen.

Expected behavior: Within Game Mode, when I copy text and paste it into any location, the resulting text is reproduced identically.

Actual behavior: Within Game Mode, when I copy non-Latin text (e.g. Japanese, Cyrillic) and paste it, the resulting text is garbled under certain conditions depending on the application it is pasted in.

Example 1:
While in Game mode, copy text from inside the Steam game Final Fantasy XIV and attempt to paste it back into the in-game chat window, the SteamOS "Note" feature, the search bar in the Game Mode Library or Store pages or the non-Steam applications Kate text editor (preinstalled) or Anki flashcard (Flatpak installed via Discover). The non-Latin text is garbled.

Source Text:
Welcome to Phantom! レストエリアに入った！
チグサ : ヤンサの地はね、深い霧が雑音を消してしまうから、 昔から静かで穏やかなのよ。 そこに生きる私たちも、そんな日々が送れるといいわね。

Result when pasted in any of the above locations:
Welcome to Phantom! レストエリア�入���
�グサ : ヤンサ�地���深�霧�雑音を消������ら� 昔�ら����や���よ。 ���生�る���も��ん�日々��れる�����。

Result in-game:

Example 2:
While in Game Mode, open any website using non-Latin characters (e.g. https://el.wikipedia.org/wiki/%CE%A3%CE%BA%CF%8D%CE%BB%CE%BF%CF%82) in Google Chrome and copy any text. When pasting this text into any of the locations described in Example 1, the text is garbled. However, if I paste copied text anywhere WITHIN Google Chrome (e.g. the Google search bar or any text boxes on any website) or INTO Google Chrome from another source (e.g. the above text directly from Final Fantasy XIV), the text pastes as expected.

Source Text:
Ο σκύλος είναι θηλαστικό ζώο του γένους Κύων (επιστ. Canis lupus familiaris - Κύων ο λύκος ο οικείος). Η καταγωγή του προέρχεται από τον κοινό λύκο. Ο σκύλος αποτελεί ένα από τα κοινότερα κατοικίδια ζώα.

Result when pasted outside Chrome:
Ο σκ�λος είναι θηλαστικό ζώο του γένους Κ�ων (επιστ. Canis lupus familiaris - Κ�ων ο λ�κος ο οικείος). Η καταγωγή του π�οέ�χεται από τον κοινό λ�κο. Ο σκ�λος αποτελεί ένα από τα κοινότε�α κατοικίδια ζώα.

Result when pasted into Chrome:
Ο σκύλος είναι θηλαστικό ζώο του γένους Κύων (επιστ. Canis lupus familiaris - Κύων ο λύκος ο οικείος). Η καταγωγή του προέρχεται από τον κοινό λύκο. Ο σκύλος αποτελεί ένα από τα κοινότερα κατοικίδια ζώα.

Example 3:
While in Game Mode, open the Kate text editor as a non-Steam game and open a simple text file which already contains non-Latin text (e.g. any of the examples above). The existing non-Latin text is properly displayed when opening the file. Within the same file, copy a part of the existing non-Latin text and paste it into the same file. The pasted text is garbled. When typing new non-Latin text via the keyboard rather than pasting previously copied text, the issue does not occur and the text is normal. The exact same issue also occurs in the Anki flashcard application.

Steps for reproducing this issue:

1. While in Game Mode, copy any non-Latin characters from any source (e.g. the examples provided above)
2. Paste the text into various locations (e.g. SteamOS "Note" feature, the search bar in the Steam OS interface or the Kate text editor)
3. The text will become garbled. The only exception I have found so far is Google Chrome, where the text will paste as expected.

[dkaknbk]

This issue still persists in 3.5.5 in the stable channel, I had to downgrade back to 3.4 as this makes some of my main use cases for the deck impossible.