Module ux_scale 

Global user-experience scale factor.

Distinct from [crate::device_scale], which tracks the physical device-pixel ratio so glyphs stay crisp on HiDPI displays. The UX scale exists because the same logical pixel feels very different to a user on a desktop monitor at desk distance vs. a phone held at arm’s length.

The cleanest mental model:

• device_scale: pixels per logical unit on the physical display surface. Always set by the platform shell to whatever window.devicePixelRatio / winit::Window::scale_factor reports. Driven by the hardware.
• ux_scale: how much bigger the user wants every logical unit to be on top of that. Driven by ergonomic / accessibility needs — small on a 27“ monitor read at arm’s length, bigger on a 6“ phone read at arm’s length, bigger still for users with reduced vision.

The framework multiplies the two when it computes the effective viewport / paint transform inside crate::App. Widgets always see “logical” units (already divided by the effective scale), so no per-widget changes are needed — only platform shells need to call set_ux_scale.

Suggested values

• 1.0 — desktop / laptop / cursor-driven UI. The default.
• 1.6 – 1.8 — mobile touch (phone / tablet) where the user reads at arm’s length and needs ~44 px touch targets. Auto-set when crate::input_profile::set_input_profile is called with any mobile variant.
• User-controlled accessibility setting on top of that — 1.0 to 2.0+ for users who explicitly want bigger UI.

Functions

effective_scale

Combined “physical pixels per logical unit” the framework uses for layout / paint scaling. device_scale * ux_scale.

set_ux_scale

Set the UX scale factor. Panics on non-positive values in debug.

ux_scale

Current UX scale factor. Multiplied with [crate::device_scale] in crate::App::layout / crate::App::paint to give the effective “physical pixels per logical unit” the framework actually uses.