Foundations / Style

Layout

Expand crates/theme/src/lib.rs

Law 4: numbers drive layout, colors are paint. The layout constants are f32 associated consts on Theme, so they resolve without reading the global at all:

div()
    .gap(px(Theme::SPACE_SM))
    .rounded(px(Theme::BUTTON_RADIUS))
    .h(px(Theme::HEADER_HEIGHT))

Spacing is SPACE_XS 4, SPACE_SM 8, SPACE_MD 12, SPACE_LG 16. Radii run CONTROL_RADIUS 6 for things that sit inside a control, BUTTON_RADIUS 8 for controls themselves, PANEL_RADIUS 10 for cards, SURFACE_RADIUS 12 for floating surfaces, BUBBLE_RADIUS 16 for message bubbles. Chrome heights — TITLEBAR_HEIGHT, HEADER_HEIGHT, STATUS_STRIP_HEIGHT — are named for the same reason: a status strip that is reserved rather than conditional keeps the composer from shifting when it fills.

SURFACE_RADIUS is read at both ends of a glass surface: the border paints it, and ui::material cuts the backdrop blur to it. A blur cut to a different radius frosts square corners outside a round border, visible only on glass and only at the corners — which is why the number is named once instead of written twice.

Nested corners come out of arithmetic rather than a second constant:

Theme::inset_radius(Theme::SURFACE_RADIUS, 4.0) // 8.0

That is SwiftUI's ContainerRelativeShape rule. gpui has no container shape to inherit at paint time, so the relationship is stated where the child is defined — a container that changes its padding carries its rows with it, and the derived value never hardens into a constant of its own.