feat: replace theme-based text color with WCAG luminance contrast (Closes #7) (#69)

2026-03-13 14:08:05 +01:00
parent b819217ff4
commit a9cf04de0e
4 changed files with 148 additions and 12 deletions
--- a/sharedUI/src/commonTest/kotlin/org/shahondin1624/ContrastUtilsTest.kt
+++ b/sharedUI/src/commonTest/kotlin/org/shahondin1624/ContrastUtilsTest.kt
@@ -0,0 +1,90 @@
+package org.shahondin1624
+
+import androidx.compose.ui.graphics.Color
+import org.shahondin1624.model.attributes.AttributeType
+import org.shahondin1624.theme.contrastRatio
+import org.shahondin1624.theme.contrastTextColor
+import org.shahondin1624.theme.relativeLuminance
+import kotlin.math.abs
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class ContrastUtilsTest {
+
+    @Test
+    fun whiteLuminanceIsOne() {
+        val luminance = relativeLuminance(Color.White)
+        assertTrue(luminance > 0.99, "White luminance should be ~1.0, was $luminance")
+    }
+
+    @Test
+    fun blackLuminanceIsZero() {
+        val luminance = relativeLuminance(Color.Black)
+        assertTrue(luminance < 0.01, "Black luminance should be ~0.0, was $luminance")
+    }
+
+    @Test
+    fun contrastRatioBlackOnWhiteIs21() {
+        val ratio = contrastRatio(Color.White, Color.Black)
+        assertTrue(ratio > 20.9, "Contrast ratio of white/black should be ~21:1, was $ratio")
+    }
+
+    @Test
+    fun contrastRatioIsSymmetric() {
+        val ratio1 = contrastRatio(Color.Red, Color.Blue)
+        val ratio2 = contrastRatio(Color.Blue, Color.Red)
+        assertTrue(
+            abs(ratio1 - ratio2) < 0.001,
+            "Contrast ratio should be symmetric: $ratio1 vs $ratio2"
+        )
+    }
+
+    @Test
+    fun contrastTextColorForWhiteIsBlack() {
+        assertEquals(Color.Black, contrastTextColor(Color.White))
+    }
+
+    @Test
+    fun contrastTextColorForBlackIsWhite() {
+        assertEquals(Color.White, contrastTextColor(Color.Black))
+    }
+
+    @Test
+    fun allAttributeColorsMeetWcagContrast() {
+        for (type in AttributeType.entries) {
+            val textColor = contrastTextColor(type.color)
+            val ratio = contrastRatio(type.color, textColor)
+            assertTrue(
+                ratio >= 4.5,
+                "Attribute ${type.name} (color=${type.color}) with text $textColor " +
+                    "has contrast ratio $ratio, which is below WCAG 4.5:1"
+            )
+        }
+    }
+
+    @Test
+    fun midGrayGetsAppropriateContrast() {
+        // Mid-gray (0.5, 0.5, 0.5) should get either black or white with sufficient contrast
+        val midGray = Color(0.5f, 0.5f, 0.5f)
+        val textColor = contrastTextColor(midGray)
+        val ratio = contrastRatio(midGray, textColor)
+        assertTrue(
+            ratio >= 4.5,
+            "Mid-gray with text $textColor has contrast ratio $ratio, below WCAG 4.5:1"
+        )
+    }
+
+    @Test
+    fun darkBlueGetsWhiteText() {
+        // Dark blue like Willpower (Color.Blue) should get white text
+        assertEquals(Color.White, contrastTextColor(Color.Blue))
+    }
+
+    @Test
+    fun brightYellowGetsBlackText() {
+        // Bright yellow like Agility Color(239, 229, 138) should get black text
+        val agility = Color(239 / 255f, 229 / 255f, 138 / 255f)
+        assertEquals(Color.Black, contrastTextColor(agility))
+    }
+}