Performance

Design

• Calculation hot paths are @inlinable and O(1).
• Configuration is an immutable Hashable, Sendable value.
• There are no process-wide mutable caches, locks, notification observers, or dictionaries.
• SwiftUI reads one environment value shared by the scene.
• DimensFactors precomputes ratios for repeated render-loop use.
• Strategy dispatch computes only the operands selected by its branch; plain and physical values do no geometry work.
• Metal uniforms occupy four aligned SIMD4<Float> lanes (64 bytes).
• Metal buffers are created once and updated in place after configuration changes.
• Resize uses O(log n) binary search after building its bounded step table.

Avoiding unnecessary SwiftUI work

Place .appDimens() once at the scene root. Do not nest providers. @ScaledDimension depends only on the configuration environment and recalculates when that value changes.

DimensConfiguration is Hashable, so writing the same metrics does not invalidate environment consumers. Keep the provider above stable screen content, and never attach one provider to every row. A real window resize or Dynamic Type change must invalidate dependent views; that is necessary work rather than an avoidable recomposition.

Hot loops

Precompute factors whenever the configuration changes instead of repeating diagonal, perimeter, fit or fill calculations for every element:

let factors = DimensFactors(configuration)
let widths = source.map { factors.resolve(\$0, strategy: .fit) }

The fast path is immutable, Sendable, allocation-free per resolution and falls back to the complete strategy engine for option-dependent curves. Measure the consuming application in Instruments—absolute nanosecond claims are intentionally avoided because CPU, compiler optimization, thermal state and workload change the result.

Metal

let buffer = AppDimensMetal.makeBuffer(device: device, configuration: config)!
if config != previousConfig {
    AppDimensMetal.update(buffer, configuration: config)
    previousConfig = config
}

Never allocate a new buffer per frame. Keep layout values in points and use displayScale only for explicit pixel conversion.

Validation

CI runs debug tests, Thread Sanitizer, release compilation, and aggregate module builds against iOS, tvOS, watchOS, visionOS, and macOS SDKs. The watch build proves that unavailable UI, SIMD-uniform, and Metal APIs are removed at compilation while the aggregate module remains importable. Every SDK job uploads its complete xcodebuild log and prints extracted compiler diagnostics in the job summary on failure.