Add FontMetricsTests

Tests/SwiftUIMathTests/Internal/Font/FontMetricsTests.swift

@@ -0,0 +1,79 @@
+import CoreGraphics
+import CoreText
+import Foundation
+import Testing
+
+@testable import SwiftUIMath
+
+@Suite
+struct FontMetricsTests {
+  private let fontName: Math.Font.Name = .latinModern
+
+  private func makePlatformFont(size: CGFloat = 20) throws -> Math.PlatformFont {
+    try #require(Math.PlatformFont(font: Math.Font(name: fontName, size: size)))
+  }
+
+  @Test
+  func loadsGraphicsFont() throws {
+    let font = try #require(Math.FontRegistry.shared.graphicsFont(named: fontName))
+    #expect(font.fullName != nil)
+  }
+
+  @Test
+  func createsPlatformFontsAtDifferentSizes() throws {
+    let font12 = try makePlatformFont(size: 12)
+    let font24 = try makePlatformFont(size: 24)
+    #expect(CTFontGetSize(font12.ctFont) == 12)
+    #expect(CTFontGetSize(font24.ctFont) == 24)
+  }
+
+  @Test
+  func metricsHavePositiveMathUnit() throws {
+    let platformFont = try makePlatformFont()
+    #expect(platformFont.metrics.mathUnit > 0)
+  }
+
+  @Test
+  func verticalVariantsUseTableEntries() throws {
+    let platformFont = try makePlatformFont()
+    let table = try #require(Math.FontRegistry.shared.table(named: fontName))
+    let entry = try #require(table.vVariants.first { !$0.value.isEmpty })
+    let glyph = platformFont.cgFont.getGlyphWithGlyphName(name: entry.key as CFString)
+    #expect(glyph != 0)
+    let variants = platformFont.metrics.verticalVariants(forGlyph: glyph)
+    #expect(!variants.isEmpty)
+  }
+
+  @Test
+  func horizontalVariantsUseTableEntries() throws {
+    let platformFont = try makePlatformFont()
+    let table = try #require(Math.FontRegistry.shared.table(named: fontName))
+    let entry = try #require(table.hVariants.first { !$0.value.isEmpty })
+    let glyph = platformFont.cgFont.getGlyphWithGlyphName(name: entry.key as CFString)
+    #expect(glyph != 0)
+    let variants = platformFont.metrics.horizontalVariants(forGlyph: glyph)
+    #expect(!variants.isEmpty)
+  }
+
+  @Test
+  func verticalAssemblyIsAvailableForExtensibleGlyphs() throws {
+    let platformFont = try makePlatformFont()
+    let table = try #require(Math.FontRegistry.shared.table(named: fontName))
+    let entry = try #require(table.vAssembly.first)
+    let glyph = platformFont.cgFont.getGlyphWithGlyphName(name: entry.key as CFString)
+    #expect(glyph != 0)
+    let assembly = platformFont.metrics.verticalAssembly(forGlyph: glyph)
+    #expect(!assembly.isEmpty)
+  }
+
+  @Test
+  func metricValuesAreFinite() throws {
+    let platformFont = try makePlatformFont()
+    let glyph = platformFont.cgFont.getGlyphWithGlyphName(name: "f" as CFString)
+    #expect(glyph != 0)
+    let italicCorrection = platformFont.metrics.italicCorrection(forGlyph: glyph)
+    let topAccent = platformFont.metrics.topAccentAdjustment(forGlyph: glyph)
+    #expect(italicCorrection.isFinite)
+    #expect(topAccent.isFinite)
+  }
+}