Traditional Chinese (zh-TW) text not rendered in PPTX preview

For all's convenience, this issue is filed in English.

Describe the bug

When previewing a PowerPoint file (.pptx) that contains Traditional Chinese (zh-TW) text, QuickLook fails to render the CJK characters — slide titles, body paragraphs and table cells appear blank wherever Chinese should be. Latin characters, digits, punctuation, the table grid, and the slide background all render normally. The QuickLook window title bar shows the Chinese filename correctly, so the problem seems limited to the in-slide text renderer of the PPTX previewer.

To Reproduce

Steps to reproduce the behavior:

1. On a Windows system with Traditional Chinese installed, prepare a .pptx that contains Traditional Chinese text (titles, paragraphs, and table cells).
2. In File Explorer, select the file and press Space to invoke QuickLook.
3. Observe the preview: every region that should contain Chinese characters is blank, while ASCII content (e.g. 115, EMRD, SEMI-EMRD, IB-101, time ranges like 9:30-9:35, +, /) is shown as expected.
4. Open the same file in PowerPoint / ONLYOFFICE on the same machine for comparison — all Chinese characters render correctly.

Expected behavior

All Traditional Chinese characters in the slide should be displayed, matching how the file is rendered by the source application (PowerPoint / ONLYOFFICE). The renderer should fall back to a system CJK font when the requested font does not cover the glyphs.

Desktop (please complete the following information):

• OS Version: Windows 10 IoT Enterprise LTSC 2021 (10.0.19044)
• System display language / locale: Traditional Chinese (zh-TW)
• QuickLook Version: 4.5.0 (from MSI installer at %LOCALAPPDATA%\Programs\QuickLook\QuickLook.exe)
• File type tested: .pptx (PowerPoint)

Screenshots and Exception Log

Screenshots will be attached in a follow-up comment / by editing this issue in the browser (the GitHub CLI cannot upload images directly):

1. QuickLook preview — Chinese text missing (only ASCII characters and layout visible). Filename in title bar 115_RD_SD畢業典禮流程及走位.pptx renders correctly.

3. Reference — the same file opened in ONLYOFFICE, showing the full Traditional Chinese content (e.g. 115年EMRD暨SEMI-EMRD畢業典禮, table headers 時間 / 主題 / 人物 / 備註, row contents such as 典禮開始, 請大家就座, 長官致詞, 院長/執行長/副執行長, etc.).
   Additional notes

The file opens correctly in PowerPoint and ONLYOFFICE on the same machine, so the necessary CJK fonts are installed system-wide. This strongly suggests the QuickLook PPTX plugin is not falling back to a CJK-capable font when the embedded/requested font does not cover the glyphs, rather than a font-availability issue.

No source file or test is named. Start by locating the PPTX preview renderer and reproducing the issue with a file containing Traditional Chinese in slide titles, paragraphs, and table cells; trace how missing glyphs and font fallback are handled. Done means the Chinese text renders while the existing ASCII content, layout, and background remain intact.