While working on this crate I noticed that if a font wasn't using the dynamic font component, it was still able to successfully render characters from the fonts that I had used in other text components, even though the component in question was only using the default font included with Bevy. After putting together the minimal reproduction repo and taking a closer look at the debug logs, it seems that cosmic_text is caching fonts to use as a fallback when the given font does not have support for the necessary characters.
Expectation
Texts should (?) render with the font that is (or isn't) provided,
What Happened
Texts are automatically selecting previously used fonts as fallbacks.
Additional information
These logs are taken from the minimal reproduction repo linked above:
Logs from first render (when the font was not cached)
2024-11-11T17:18:24.216542Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI'
2024-11-11T17:18:24.216621Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI Emoji'
2024-11-11T17:18:24.218546Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI'
2024-11-11T17:18:24.218683Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI Emoji'
2024-11-11T17:18:24.218804Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI Symbol'
2024-11-11T17:18:24.218902Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI Historic'
2024-11-11T17:18:24.219010Z DEBUG cosmic_text::font::fallback: Failed to find any fallback for [Han] locale 'en-US': '界'
Logs from the second render
2024-11-11T17:18:25.221886Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI'
2024-11-11T17:18:25.221966Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI Emoji'
2024-11-11T17:18:25.222059Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI Symbol'
2024-11-11T17:18:25.222179Z DEBUG cosmic_text::font::fallback: failed to find family 'Segoe UI Historic'
2024-11-11T17:18:25.222333Z DEBUG cosmic_text::font::fallback: Failed to find preset fallback for [Han] locale 'en-US', used 'Noto Sans JP': '界'
Thoughts
I like the idea of having font fallbacks, especially for i18n purposes, but I think the undocumented behavior may just lead to confusion more than anything else. And as the logs mentioned, it says "Failed to find preset fallback", so I assume we can customize this in some way, which could be a desirable public API that could be added.
Couple of thoughts on this:
Consider either disabling the fallback or expose the ability to customize it so users can set it
If the latter, it should definitely be documented
Less related but perhaps it would be beneficial if Bevy transitioned to using NotoSans and loads more variations of the fonts when the default_font feature is enabled - this way Bevy has international font support out of the box!
Bevy version
Bevy: Latest
mainCargo:cargo 1.82.0 (8f40fc59f 2024-08-21)OS: Windows 11What you did
I discovered this issue while working on an i18n crate for Bevy that loads dynamic fonts based on the selected locale.
I put together a minimal reproduction repo here: https://github.com/TurtIeSocks/bevy_font_bug
What went wrong
While working on this crate I noticed that if a font wasn't using the dynamic font component, it was still able to successfully render characters from the fonts that I had used in other text components, even though the component in question was only using the default font included with Bevy. After putting together the minimal reproduction repo and taking a closer look at the debug logs, it seems that
cosmic_textis caching fonts to use as a fallback when the given font does not have support for the necessary characters.Expectation
Texts should (?) render with the font that is (or isn't) provided,
What Happened
Texts are automatically selecting previously used fonts as fallbacks.
Additional information
These logs are taken from the minimal reproduction repo linked above:
Logs from first render (when the font was not cached)
Logs from the second render
Thoughts
I like the idea of having font fallbacks, especially for i18n purposes, but I think the undocumented behavior may just lead to confusion more than anything else. And as the logs mentioned, it says "Failed to find preset fallback", so I assume we can customize this in some way, which could be a desirable public API that could be added.
Couple of thoughts on this:
default_fontfeature is enabled - this way Bevy has international font support out of the box!