Editor uses a proportional font with the default Linux font configuration

Reproduce the fresh-install behavior by opening /app/share/vscode/flatpak-warning.txt in the Flatpak application and run the supplied fc-match commands inside the sandbox. Review fix-flatpak-vscode-fonts.sh and the packaged default font configuration, then verify that the editor uses a monospace font without user settings while preserving the reported environment.

Description

On a fresh installation of the Flatpak version of Visual Studio Code, plain text in the editor appears to use a proportional font instead of a monospace font.

There was no settings.json in the default user profile when the problem occurred.

Environment

• Application ID: com.visualstudio.code
• VS Code version reported by Flatpak: 1.130.0
• Flatpak branch: stable
• Installation: system-wide

Steps to reproduce

1. Launch the Flatpak application with the default user settings.
2. Open the bundled /app/share/vscode/flatpak-warning.txt.
3. Observe the font used in the editor.

Expected behavior

The editor should use a monospace font with the default settings.

Actual behavior

The editor text appears proportional, including the bundled warning file.

Font diagnostics

The installed VS Code build specifies the following default Linux editor font family:

'Droid Sans Mono', monospace

Running these commands inside the Flatpak sandbox produced:

flatpak run --command=fc-match com.visualstudio.code "Droid Sans Mono"
# DejaVuSans.ttf: "DejaVu Sans" "Book"

flatpak run --command=fc-match com.visualstudio.code monospace
# DejaVuSansMono.ttf: "DejaVu Sans Mono" "Book"

flatpak run --command=fc-match com.visualstudio.code "Source Code Pro" \
  -f '%{family} spacing=%{spacing}\n'
# Source Code Pro spacing=100

Monospace fonts are therefore available inside the sandbox. However, the unavailable Droid Sans Mono family resolves to proportional DejaVu Sans when queried directly.

This suggests a font fallback or substitution issue, although the fc-match results alone do not establish exactly how Electron resolves the complete font-family list.

Workaround

Explicitly selecting an available monospace font resolves the editor display issue:

{
    "editor.fontFamily": "'Source Code Pro', 'DejaVu Sans Mono', monospace",
    "terminal.integrated.fontFamily": "'Source Code Pro', 'DejaVu Sans Mono', monospace"
}

The terminal setting was added as a precaution; the original issue was observed in the editor.

Possible investigation

Could you check whether the packaged default font configuration reliably falls back to a monospace font when Droid Sans Mono is absent?

Using an available monospace default or providing an appropriate font substitution may help avoid this on fresh installations.

fix-flatpak-vscode-fonts.sh