Slint 1.18 adds a flexbox layout, runtime z-order and an experimental Vello renderer

Sources: primary, discussion
Summary: The release adds FlexboxLayout with wrapping, runtime changes to item z-order, and spring animation curves, and gives arrays in .slint the push, remove and insert operations with matching Model APIs in every language binding. The Vello renderer sits behind the renderer-vello Cargo feature and CMake option and is selected through BackendSelector or the SLINT_BACKEND variable. The authors describe the release as quality-of-life work rather than a breaking change.
Why it matters: Layout work that previously had to be written in the host language now stays in the declarative markup.