SwiftUI Truncation Detection

A SwiftUI demo exploring how to detect text truncation without any private APIs. Two invisible "ghost" copies of a Text view are measured under different constraints, and their sizes are compared against the visible text to determine whether it has wrapped, been truncated, or both.

The Problem

SwiftUI's Text view does not expose whether its content was truncated. There is no built-in API to ask "did this text get cut off?"

The Technique

Two invisible copies ("ghosts") of the same string are rendered alongside the visible text, each with a different layout constraint removed:

┌───────────────────────────────────────────────────────────────────────┐
│  Copy                 Constraint removed    What it tells us          │
│  ──────────────       ──────────────────    ──────────────────        │
│  visible              (none — fully          The actual rendered      │
│                        constrained)          size in the container    │
│                                                                       │
│  horizontalGhost      width is unlocked     "How wide would I be      │
│                       (height stays locked)  with no width limit?"    │
│                                              → single-line width      │
│                                                                       │
│  verticalGhost        height is unlocked    "How tall would I be      │
│                       (width stays locked)   with no height limit?"   │
│                                              → fully-wrapped height   │
└───────────────────────────────────────────────────────────────────────┘

By comparing those three sizes at runtime you can determine exactly what happened to the text:

Condition	Meaning
visibleSize.height > horizontalGhostSize.height	Text has wrapped onto multiple lines
visibleSize.height < verticalGhostSize.height	Wrapped text is still truncated (lines cut off)
visibleSize.width < horizontalGhostSize.width	Single-line text is truncated (characters cut off)

This approach is based on the technique described by Fatbobman in this article and presented at iOS Conference Singapore.

Project Structure

File	Purpose
AdaptiveAmountList.swift	AdaptiveAmountRow and its three layout implementations (CompactAmountRowLayout, StandardAmountRowLayout, ExtendedAmountRowLayout), plus TruncationDetectingText, SizeHolder, LayoutMode, and LayoutTruncationStatus.
TruncationDetectionView.swift	Standalone demo of the raw truncation detection measurements with labelled diagnostic output.
RootView.swift	Navigation root linking to both demos.