From 25538451009af2391b4988a281c40f1f152ae736 Mon Sep 17 00:00:00 2001
From: Love Billenius <lovebillenius@disroot.org>
Date: Fri, 10 Apr 2026 10:05:57 +0200
Subject: [PATCH] fix Android swipe gesture edge cases

---
 PLAN.md                                       |  1 +
 .../app/core/gestures/HermesGestures.kt       | 35 +++++++++++++++++-
 .../gestures/HermesSwipeDownDetectorTest.kt   | 37 +++++++++++++++++++
 3 files changed, 71 insertions(+), 2 deletions(-)
 create mode 100644 mobile/android-app/app/src/test/java/com/hermes/app/core/gestures/HermesSwipeDownDetectorTest.kt

diff --git a/PLAN.md b/PLAN.md
index abd26b2..22889e9 100644
--- a/PLAN.md
+++ b/PLAN.md
@@ -24,6 +24,7 @@ This is the canonical working plan and progress log for the project. Use this fi
 - iOS project scaffolding now exists as `mobile/ios-app/HermesApp.xcodeproj` with a shared scheme and XCTest target.
 - iOS sources and tests build and pass in Xcode on an iPhone simulator, and a standalone localization/error-mapping harness passes.
 - Android local unit tests now cover localization, error mapping, and analytics batch conversion, and `./gradlew testDebugUnitTest` passes with the Android SDK installed.
+- Android swipe-down gesture handling now uses cumulative drag distance, and edge-case tests cover upward drags, slow swipes, and per-gesture single-trigger behavior.
 
 ### Still Open
 
diff --git a/mobile/android-app/app/src/main/java/com/hermes/app/core/gestures/HermesGestures.kt b/mobile/android-app/app/src/main/java/com/hermes/app/core/gestures/HermesGestures.kt
index 6fa7784..23fcb7f 100644
--- a/mobile/android-app/app/src/main/java/com/hermes/app/core/gestures/HermesGestures.kt
+++ b/mobile/android-app/app/src/main/java/com/hermes/app/core/gestures/HermesGestures.kt
@@ -4,9 +4,40 @@ import androidx.compose.foundation.gestures.detectVerticalDragGestures
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.input.pointer.pointerInput
 
+internal class HermesSwipeDownDetector(
+    private val threshold: Float = 32f,
+) {
+    private var totalDrag = 0f
+    private var triggered = false
+
+    fun onDrag(dragAmount: Float): Boolean {
+        if (triggered) {
+            return false
+        }
+
+        totalDrag = (totalDrag + dragAmount).coerceAtLeast(0f)
+        if (totalDrag >= threshold) {
+            triggered = true
+            return true
+        }
+
+        return false
+    }
+
+    fun reset() {
+        totalDrag = 0f
+        triggered = false
+    }
+}
+
 fun Modifier.hermesSwipeDown(onSwipeDown: () -> Unit): Modifier = pointerInput(onSwipeDown) {
-    detectVerticalDragGestures { _, dragAmount ->
-        if (dragAmount > 32f) {
+    val detector = HermesSwipeDownDetector()
+    detectVerticalDragGestures(
+        onDragStart = { detector.reset() },
+        onDragEnd = { detector.reset() },
+        onDragCancel = { detector.reset() },
+    ) { _, dragAmount ->
+        if (detector.onDrag(dragAmount)) {
             onSwipeDown()
         }
     }
diff --git a/mobile/android-app/app/src/test/java/com/hermes/app/core/gestures/HermesSwipeDownDetectorTest.kt b/mobile/android-app/app/src/test/java/com/hermes/app/core/gestures/HermesSwipeDownDetectorTest.kt
new file mode 100644
index 0000000..5affa51
--- /dev/null
+++ b/mobile/android-app/app/src/test/java/com/hermes/app/core/gestures/HermesSwipeDownDetectorTest.kt
@@ -0,0 +1,37 @@
+package com.hermes.app.core.gestures
+
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class HermesSwipeDownDetectorTest {
+    @Test
+    fun triggersAfterCumulativeDownwardDrag() {
+        val detector = HermesSwipeDownDetector(threshold = 32f)
+
+        assertFalse(detector.onDrag(10f))
+        assertFalse(detector.onDrag(10f))
+        assertTrue(detector.onDrag(12f))
+    }
+
+    @Test
+    fun doesNotTriggerForSmallOrUpwardDrags() {
+        val detector = HermesSwipeDownDetector(threshold = 32f)
+
+        assertFalse(detector.onDrag(20f))
+        assertFalse(detector.onDrag(-15f))
+        assertFalse(detector.onDrag(20f))
+    }
+
+    @Test
+    fun onlyTriggersOncePerGestureUntilReset() {
+        val detector = HermesSwipeDownDetector(threshold = 32f)
+
+        assertTrue(detector.onDrag(40f))
+        assertFalse(detector.onDrag(40f))
+
+        detector.reset()
+
+        assertTrue(detector.onDrag(40f))
+    }
+}