Fatbobman's SwiftUI tips distilled via Codex

swift_guidelines.md

SwiftUI best practise

This doc distills layout and scrolling guidance from Fatbobman SwiftUI articles. It focuses on layout, sizing, alignment, stacks/grids, safe areas, overlays/backgrounds, and scrolling/lazy containers.

Layout fundamentals

• Learn the size pipeline (proposed size, required size, layout size, view size) so you know why frame and measuring can behave unexpectedly. Source: https://fatbobman.com/en/posts/layout-dimensions-1/
• Similar-looking layouts can have different layout semantics. Use frame and fixedSize with intent, and prefer the container that matches the layout contract you want. Source: https://fatbobman.com/en/posts/layout-dimensions-2/
• Use the simplest layout tool that meets the requirement: offset, alignmentGuide, layoutPriority, and ScrollView can all solve the same UI, but they affect layout differently. Source: https://fatbobman.com/en/posts/layout-in-swiftui-way/
• Centering can be done via Spacer, frame(alignment:), overlay, or GeometryReader. Prefer alignment and spacers before geometry reading. Source: https://fatbobman.com/en/posts/centering_the_view_in_swiftui/
• layoutPriority changes size allocation in HStack/VStack, and in ZStack it can also affect the container size. Keep that in mind when layering. Source: https://fatbobman.com/en/posts/exploring-the-secrets-of-layoutpriority-in-zstack/

Alignment and spacing

• Alignment is guide-based. Use alignmentGuide for precise alignment, and define custom guides when default guides do not express the layout you need. Source: https://fatbobman.com/en/posts/layout-alignment/
• Default spacing: nil is dynamic based on adjacent view types; if you want consistent gaps, set spacing explicitly. Sources: https://fatbobman.com/en/posts/spacing-of-swiftui/ and https://fatbobman.com/en/snippet/resolving-inconsistent-spacing-in-swiftui-vstackhstack-layouts/
• Spacing can be negative or used for layout behavior (not just gaps). Be explicit when you need pixel-accurate control. Source: https://fatbobman.com/en/posts/spacing-of-swiftui/

Overlay, background, and layering

• overlay and background are not just ZStack. The main view owns the size, and the overlay/background aligns to it. Use them when you want stable sizing. Source: https://fatbobman.com/en/posts/in-depth-exploration-of-overlay-and-background-modifiers-in-swiftui/
• overlay can be a cleaner partner for measurement than wrapping everything in a ZStack or extra container. Source: https://fatbobman.com/en/posts/in-depth-exploration-of-overlay-and-background-modifiers-in-swiftui/

Geometry and measurement

• GeometryReader is a layout container and can change layout. Use it when you need container-proposed size, not for simple alignment tasks. Source: https://fatbobman.com/en/posts/geometryreader-blessing-or-curse/
• Prefer newer geometry hooks (onGeometryChange, visualEffect) to read size without re-parenting layout when possible. Source: https://fatbobman.com/en/posts/geometryreader-blessing-or-curse/
• Use ignoredByLayout when you need a transform that should not influence layout calculations (e.g., avoid safe-area expansion or anchor distortion). Source: https://fatbobman.com/en/posts/demystifying-swiftuis-ignoredbylayout/
• For adaptive text layouts, use ViewThatFits or a priority-based layout selection to avoid truncation. Source: https://fatbobman.com/en/posts/how-to-detect-text-truncation-in-swiftui/

Text layout

• For complex rich text and mixed text+views, AttributedString can be limiting. Consider specialized rendering approaches that handle mixed layout and selection tradeoffs. Source: https://fatbobman.com/en/posts/a-deep-dive-into-swiftui-rich-text-layout/
• When detecting truncation, combine fixedSize, geometry checks, and adaptive layout selection instead of hardcoding sizes. Source: https://fatbobman.com/en/posts/how-to-detect-text-truncation-in-swiftui/

Grids and stacks

• Prefer LazyVGrid/LazyHGrid for large collections; be cautious with nested grids, and simplify if you hit layout anomalies. Source: https://fatbobman.com/en/posts/analysis-approach-and-resolution-strategies-for-swiftui-layout-issues/ and https://fatbobman.com/en/posts/howto-swiftui-grid/
• Use LazyVStack/LazyHStack for large lists inside a ScrollView to avoid rendering offscreen items. Source: https://fatbobman.com/en/posts/howto-swiftui-lazystack/

Lists and lazy containers

• List and LazyVStack are not equivalent: List is a system-backed container with built-in behaviors, while LazyVStack is pure SwiftUI. Choose based on styling, control needs, and performance tradeoffs. Source: https://fatbobman.com/en/posts/list-or-lazyvstack/
• Using ForEach inside List gives layout flexibility but can affect performance; prefer List's dynamic initializer when possible. Source: https://fatbobman.com/en/posts/swiftui-list-foreach/
• For lazy containers, ensure data sources support random access, watch id changes, and avoid top-level conditional content that breaks laziness. Source: https://fatbobman.com/en/posts/tips-and-considerations-for-using-lazy-containers-in-swiftui/

ScrollView and scroll control

• SwiftUI 5 ScrollView adds contentMargins, safeAreaPadding, scrollIndicatorsFlash, scrollClipDisabled, scrollTargetLayout, scrollPosition, and scrollTargetBehavior. Use these before custom hacks. Source: https://fatbobman.com/en/posts/new-features-of-scrollview-in-swiftui5/
• Scroll control APIs evolved rapidly; prefer modern hooks like scrollPosition, onScrollPhaseChange, onScrollGeometryChange, and onScrollVisibilityChange where available. Source: https://fatbobman.com/en/posts/the-evolution-of-swiftui-scroll-control-apis/
• Use ScrollViewReader with ID-based anchors for scroll-to-position, but note it does not expose current position. Source: https://fatbobman.com/en/posts/howto-swiftui-scrollviewreader/
• Default paging may misalign in landscape; implement a custom ScrollTargetBehavior when precision matters. Source: https://fatbobman.com/en/posts/mastering-swiftui-scrolling-implementing-custom-paging/
• Disable bounce/scroll when content fits with scrollBounceBehavior(.basedOnSize) or a ViewThatFits switch. Source: https://fatbobman.com/en/snippet/disabling-scroll-in-swiftui-scrollview-when-content-is-smaller-than-container/
• If shadows or overflow get clipped, use scrollClipDisabled() (iOS 17+) or adjust the underlying scroll view for legacy targets. Source: https://fatbobman.com/en/snippet/preventing-scrollview-content-clipping-in-swiftui/
• Detect active scrolling via runloop or PreferenceKey approaches when you need to react to scroll state. Source: https://fatbobman.com/en/posts/how_to_judge_scrollview_is_scrolling/