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REOPEN-F7 follow-up: empty-label test counts layouts through the measure seam, no test-only read in source (#32616 review P2) #32799

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Merged
lawrencecchen merged 1 commit into from
Nov 3, 2026
Merged

REOPEN-F7 follow-up: empty-label test counts layouts through the measure seam, no test-only read in source (#32616 review P2) #32799

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24 changes: 15 additions & 9 deletions Packages/macOS/CmuxNext/Sources/CmuxNextDesign/Text/LabelText.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -105,29 +105,36 @@ enum LabelText {

private static func isWrapping(_ mode: NSLineBreakMode) -> Bool { mode == .byWordWrapping || mode == .byCharWrapping }

/// The text the shared stack laid out last (tests: whether a measure used TextKit).
static var lastLaidOutString: String { storage.string }
/// A text layout: what ``measure(_:font:shape:width:scale:layOut:)`` asks for a text that
/// needs TextKit (by default ``laidOutMetrics(_:font:shape:width:scale:)``).
typealias Layout = @MainActor (NSAttributedString, NSFont?, Shape, CGFloat?, CGFloat) -> Metrics

/// The layout of `text` (font set, no paragraph settings yet) with `width` points for the
/// text (nil: unbounded), at `scale` pixels per point.
static func measure(_ text: NSAttributedString, font: NSFont?, shape: Shape, width: CGFloat?, scale: CGFloat) -> Metrics {
/// text (nil: unbounded), at `scale` pixels per point. `layOut` lays out a text that needs it.
static func measure(_ text: NSAttributedString, font: NSFont?, shape: Shape, width: CGFloat?, scale: CGFloat,
layOut: Layout = LabelText.laidOutMetrics) -> Metrics {
// An empty label at an unbounded width is one empty line of its font: as tall as
// ``WholePointLines`` sets that line, its baseline at the rounded ascender, no width. It
// needs no layout (REOPEN-F7: a window's sidebar makes about 100 empty labels before its
// first frame, and laying each out cost 22 to 25 ms profiled).
if text.length == 0, width == nil {
let line = NSAttributedString(string: " ", attributes: [.font: font ?? .systemFont(ofSize: NSFont.systemFontSize)])
let line = emptyLine(font: font)
if let metrics = WholePointLines.metrics(of: line, in: NSRange(location: 0, length: line.length)) {
let scale = max(scale, 1)
let height = (metrics.height * scale).rounded(.up) / scale
return Metrics(size: NSSize(width: 0, height: height), firstBaseline: metrics.ascent,
lastBaselineFromBottom: height - metrics.ascent)
}
}
return laidOutMetrics(text, font: font, shape: shape, width: width, scale: scale)
return layOut(text, font, shape, width, scale)
}

/// ``measure(_:font:shape:width:scale:)`` laid out in the shared TextKit stack.
/// The one empty line an empty label is: a space in `font` (nil: the system font).
private static func emptyLine(font: NSFont?) -> NSAttributedString {
NSAttributedString(string: " ", attributes: [.font: font ?? .systemFont(ofSize: NSFont.systemFontSize)])
}

/// ``measure(_:font:shape:width:scale:layOut:)`` laid out in the shared TextKit stack.
static func laidOutMetrics(_ text: NSAttributedString, font: NSFont?, shape: Shape, width: CGFloat?, scale: CGFloat) -> Metrics {
// Alignment moves lines, not their breaks or heights: measure left-aligned, so an
// unbounded width keeps the lines at the left edge.
Expand All @@ -136,8 +143,7 @@ enum LabelText {
// A field measures its lines whole; only its drawing truncates the last visible one.
measuring.truncatesLastVisibleLine = false
// An empty label is one empty line of its font.
let shown = text.length > 0 ? text
: NSAttributedString(string: " ", attributes: [.font: font ?? .systemFont(ofSize: NSFont.systemFontSize)])
let shown = text.length > 0 ? text : emptyLine(font: font)
// A field measures the lines it shows: its first `lines` lines, laid out as if unlimited
// (a limited container sets the rest of the text on its last line).
let shownLines = measuring.wraps && measuring.lines > 0 ? measuring.lines : Int.max
Expand Down
56 changes: 29 additions & 27 deletions Packages/macOS/CmuxNext/Tests/CmuxNextDesignTests/EmptyLabelMeasureTests.swift
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Expand Up @@ -8,46 +8,48 @@ import Testing
/// That was 22 to 25 ms of the profiled window build. An empty line's size is its font's line
/// height (``LabelText/WholePointLines``): it needs no layout.
@MainActor @Suite(.serialized) struct EmptyLabelMeasureTests {
private static let sentinel = "sentinel, laid out before the label"
private static let fonts: [NSFont?] = [.systemFont(ofSize: 13), .systemFont(ofSize: 11), .systemFont(ofSize: 10.5),
.monospacedSystemFont(ofSize: 12, weight: .regular), .boldSystemFont(ofSize: 17),
.systemFont(ofSize: 9.5), NSFont(name: "Times New Roman", size: 14), nil]

private static func layOutSentinel() {
_ = LabelText.measure(NSAttributedString(string: sentinel), font: .systemFont(ofSize: 13),
shape: ChromeLabel(frame: .zero).shape, width: nil, scale: 2)
#expect(LabelText.lastLaidOutString == sentinel)
}

@Test func anEmptyLabelLaysNoTextOut() {
Self.layOutSentinel()
let label = ChromeLabel(font: .systemFont(ofSize: 11))
_ = label.intrinsicContentSize
_ = label.firstBaselineOffsetFromTop
#expect(LabelText.lastLaidOutString == Self.sentinel, "an empty label laid its line out in TextKit")
#expect(label.frame.height > 0)
}

@Test func anEmptyLabelLaysOutAsTextKitWould() {
let fonts: [NSFont] = [.systemFont(ofSize: 13), .systemFont(ofSize: 11), .systemFont(ofSize: 10.5),
.monospacedSystemFont(ofSize: 12, weight: .regular), .boldSystemFont(ofSize: 17),
.systemFont(ofSize: 9.5)]
private static var shapes: [LabelText.Shape] {
var shapes = [ChromeLabel(frame: .zero).shape, ChromeLabel(font: .systemFont(ofSize: 13)).shape,
ChromeLabel(wrappingLabelWithString: "").shape]
var twoLines = shapes[2]
twoLines.lines = 2
twoLines.truncatesLastVisibleLine = true
shapes.append(twoLines)
return shapes
}

@Test func anEmptyLabelLaysNoTextOut() {
var layouts = 0
let counting: LabelText.Layout = { text, font, shape, width, scale in
layouts += 1
return LabelText.laidOutMetrics(text, font: font, shape: shape, width: width, scale: scale)
}
for font in Self.fonts {
for shape in Self.shapes {
_ = LabelText.measure(NSAttributedString(), font: font, shape: shape, width: nil, scale: 2, layOut: counting)
}
}
#expect(layouts == 0, "an empty label at an unbounded width laid its line out in TextKit")
// Text, and an empty text at a set width, still lay out.
_ = LabelText.measure(NSAttributedString(string: "Title"), font: nil, shape: Self.shapes[0], width: nil, scale: 2, layOut: counting)
_ = LabelText.measure(NSAttributedString(), font: nil, shape: Self.shapes[2], width: 120, scale: 2, layOut: counting)
#expect(layouts == 2)
}

@Test func anEmptyLabelLaysOutAsTextKitWould() {
let empty = NSAttributedString()
for font in fonts {
for shape in shapes {
for font in Self.fonts {
for shape in Self.shapes {
for scale: CGFloat in [1, 2, 3] {
let measured = LabelText.measure(empty, font: font, shape: shape, width: nil, scale: scale)
let laidOut = LabelText.laidOutMetrics(empty, font: font, shape: shape, width: nil, scale: scale)
#expect(measured == laidOut, "\(font.fontName) \(font.pointSize) pt, \(shape), scale \(scale)")
#expect(measured == laidOut, "\(font?.fontName ?? "no font") \(font?.pointSize ?? 0) pt, \(shape), scale \(scale)")
}
}
}
// No font: the system font, as TextKit lays it out.
let shape = shapes[0]
#expect(LabelText.measure(empty, font: nil, shape: shape, width: nil, scale: 2)
== LabelText.laidOutMetrics(empty, font: nil, shape: shape, width: nil, scale: 2))
}
}
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