Module gradients 

Gradient colour-ramp (LUT) cache.

A gradient is drawn by sampling a pre-baked colour ramp. Baking a ramp is expensive relative to a frame, and the same gradient typically recurs across frames (a themed button, a scrim), so ramps are cached by the colour-affecting properties of the gradient — its stops, interpolation colour space and hue direction — which is exactly what GradientCacheKey captures. Geometry (start/end points, radii, angles) does not affect the ramp and is therefore deliberately absent from the key: two gradients that differ only in placement share one ramp.

Every cached ramp lives in one packed Rgba8Unorm byte buffer that is uploaded to a single texture as a flat texel stream. A cached ramp is addressed by a texel offset plus a width, so the buffer must stay contiguous: eviction therefore compacts the buffer and rewrites the offsets of the survivors.

Residency is bounded by GradientCache::capacity and reclaimed LRU by frame epoch. The epoch advances on every lookup, so each live entry carries a distinct last-used value and the eviction threshold is unambiguous.

Structs

CachedRamp

Where one cached gradient ramp lives in the packed LUT buffer.

GradientCache

An LRU cache of baked gradient colour ramps packed into one upload buffer.

GradientTextureLayout

Geometry of the single texture the packed gradient LUTs are uploaded into.

LutUpload

The packed LUT bytes padded to a texture’s footprint for one upload.

Constants

BYTES_PER_TEXEL

Bytes per texel of the gradient LUT texture (Rgba8Unorm).