- UI scale is not relative to the DPI scale. If the UI scale is not set to "automatic", then the game UI will be unusually small or large if the display DPI is changed (e.g. when a high-DPI laptop is plugged into a normal-DPI external display). Setting the UI scale to "automatic" partially fixes this, but prevents customization.
- Zoom values are not relative to display DPI. In particular, the zoom is always set to 1.0 when starting or loading a game, meaning that game content starts zoomed out on a high-DPI display.
- player.display_scale reflects the current value of the UI scale, not the DPI scale. As a result, it cannot be reliably used by mods to correct for DPI.
A more complete solution would be to multiply all values used for UI scale and map zoom (including in Lua APIs) by the DPI scale.