Merge pull request #50 from PureSwift/feature/gestures

Add DragGesture and onLongPressGesture

Author: colemancda

AndroidSwiftUICore/Sources/AndroidSwiftUICore/Gesture.swift

@@ -0,0 +1,109 @@
+//
+//  Gesture.swift
+//  AndroidSwiftUICore
+//
+//  Continuous gestures. A drag reports through the fixed string callback rather
+//  than growing the bridge with a two-number entry point: the interpreter sends
+//  "<phase>;<startX>,<startY>;<x>,<y>" in points, which rebuilds a Value here.
+//
+
+import Foundation
+
+/// A gesture recognized on a view. `.gesture(_:)` currently accepts `DragGesture`.
+public protocol Gesture {}
+
+public struct DragGesture: Gesture {
+
+    /// The state of a drag as it is recognized.
+    public struct Value {
+        public var startLocation: CGPoint
+        public var location: CGPoint
+        public var translation: CGSize
+    }
+
+    /// How far the touch must move before the drag is recognized.
+    public var minimumDistance: Double
+
+    internal var changedAction: ((Value) -> Void)?
+    internal var endedAction: ((Value) -> Void)?
+
+    public init(minimumDistance: Double = 10) {
+        self.minimumDistance = minimumDistance
+    }
+
+    public func onChanged(_ action: @escaping (Value) -> Void) -> DragGesture {
+        var copy = self
+        copy.changedAction = action
+        return copy
+    }
+
+    public func onEnded(_ action: @escaping (Value) -> Void) -> DragGesture {
+        var copy = self
+        copy.endedAction = action
+        return copy
+    }
+}
+
+internal extension DragGesture.Value {
+
+    /// Rebuilds a value from the interpreter's `"<phase>;<sx>,<sy>;<x>,<y>"`.
+    init?(payload: String) {
+        let fields = payload.split(separator: ";")
+        guard fields.count == 3 else { return nil }
+        let start = fields[1].split(separator: ",").compactMap { Double($0) }
+        let current = fields[2].split(separator: ",").compactMap { Double($0) }
+        guard start.count == 2, current.count == 2 else { return nil }
+        self.startLocation = CGPoint(x: start[0], y: start[1])
+        self.location = CGPoint(x: current[0], y: current[1])
+        self.translation = CGSize(width: current[0] - start[0], height: current[1] - start[1])
+    }
+}
+
+// MARK: - Modifiers
+
+public struct _GestureModifier: RenderModifier, _CallbackModifier {
+
+    let gesture: DragGesture
+
+    public var _modifierNode: ModifierNode { ModifierNode(kind: "drag") }
+
+    public func _callbackNode(in context: ResolveContext) -> ModifierNode {
+        let changed = gesture.changedAction
+        let ended = gesture.endedAction
+        let id = context.callbacks.register(.string { payload in
+            guard let value = DragGesture.Value(payload: payload) else { return }
+            if payload.hasPrefix("ended") {
+                ended?(value)
+            } else {
+                changed?(value)
+            }
+        })
+        return ModifierNode(kind: "drag", args: [
+            "action": .int(Int(id)),
+            "minimumDistance": .double(gesture.minimumDistance),
+        ])
+    }
+}
+
+public struct _LongPressModifier: RenderModifier, _CallbackModifier {
+
+    let action: () -> Void
+
+    public var _modifierNode: ModifierNode { ModifierNode(kind: "longPress") }
+
+    public func _callbackNode(in context: ResolveContext) -> ModifierNode {
+        let id = context.callbacks.register(.void(action))
+        return ModifierNode(kind: "longPress", args: ["action": .int(Int(id))])
+    }
+}
+
+public extension View {
+
+    func gesture(_ gesture: DragGesture) -> ModifiedContent<Self, _GestureModifier> {
+        modifier(_GestureModifier(gesture: gesture))
+    }
+
+    func onLongPressGesture(perform action: @escaping () -> Void) -> ModifiedContent<Self, _LongPressModifier> {
+        modifier(_LongPressModifier(action: action))
+    }
+}

AndroidSwiftUICore/Tests/AndroidSwiftUICoreTests/EvaluatorTests.swift

@@ -187,6 +187,68 @@ struct ModifierTests {
         #expect(tapped)
     }
 
+    @Test("onLongPressGesture registers its own callback distinct from a tap")
+    func longPress() {
+        var tapped = false
+        var pressed = false
+        let host = ViewHost(
+            Text("x")
+                .onTapGesture { tapped = true }
+                .onLongPressGesture { pressed = true }
+        )
+        let node = host.evaluate()
+        guard case .int(let tapID)? = node.modifiers.first(where: { $0.kind == "onTapGesture" })?.args["action"],
+              case .int(let pressID)? = node.modifiers.first(where: { $0.kind == "longPress" })?.args["action"] else {
+            Issue.record("missing gesture callbacks"); return
+        }
+        #expect(tapID != pressID)
+        host.callbacks.invokeVoid(Int64(pressID))
+        #expect(pressed)
+        #expect(!tapped)
+    }
+
+    @Test("A drag reports translation to onChanged, then a final value to onEnded")
+    func dragGesture() {
+        var changes: [CGSize] = []
+        var ended: CGSize?
+        let host = ViewHost(
+            Text("x").gesture(
+                DragGesture()
+                    .onChanged { changes.append($0.translation) }
+                    .onEnded { ended = $0.translation }
+            )
+        )
+        let node = host.evaluate()
+        let drag = node.modifiers.first { $0.kind == "drag" }
+        #expect(drag?.args["minimumDistance"] == .double(10))
+        guard case .int(let id)? = drag?.args["action"] else {
+            Issue.record("missing drag callback"); return
+        }
+        // the interpreter's payload: phase, start point, current point (in points)
+        host.callbacks.invokeString(Int64(id), "changed;10.0,20.0;40.0,25.0")
+        host.callbacks.invokeString(Int64(id), "ended;10.0,20.0;60.0,20.0")
+        #expect(changes.count == 1)
+        #expect(changes.first?.width == 30)    // 40 − 10
+        #expect(changes.first?.height == 5)    // 25 − 20
+        #expect(ended?.width == 50)
+        #expect(ended?.height == 0)
+    }
+
+    @Test("A malformed drag payload is ignored rather than crashing")
+    func dragGestureMalformed() {
+        var changes = 0
+        let host = ViewHost(
+            Text("x").gesture(DragGesture().onChanged { _ in changes += 1 })
+        )
+        let node = host.evaluate()
+        guard case .int(let id)? = node.modifiers.first(where: { $0.kind == "drag" })?.args["action"] else {
+            Issue.record("missing drag callback"); return
+        }
+        host.callbacks.invokeString(Int64(id), "changed;garbage")
+        host.callbacks.invokeString(Int64(id), "")
+        #expect(changes == 0)
+    }
+
     @Test("onAppear and onDisappear emit distinct callback kinds")
     func appearDisappear() {
         let node = ViewHost(Text("x").onAppear {}.onDisappear {}).evaluate()

Demo/App.swiftpm/Sources/Catalog.swift

@@ -50,6 +50,7 @@ struct CatalogEntry: Identifiable {
         CatalogEntry(id: "appearance", title: "Appearance", screen: AnyCatalogScreen(AppearancePlayground())),
         CatalogEntry(id: "animation", title: "Animation", screen: AnyCatalogScreen(AnimationPlayground())),
         CatalogEntry(id: "interaction", title: "Interaction", screen: AnyCatalogScreen(InteractionPlayground())),
+        CatalogEntry(id: "gesture", title: "Gestures", screen: AnyCatalogScreen(GesturePlayground())),
         CatalogEntry(id: "navigation", title: "Navigation", screen: AnyCatalogScreen(NavigationPlayground())),
         CatalogEntry(id: "searchable", title: "Searchable", screen: AnyCatalogScreen(SearchablePlayground())),
         CatalogEntry(id: "tab", title: "TabView", screen: AnyCatalogScreen(TabViewPlayground())),

Demo/App.swiftpm/Sources/GesturePlaygrounds.swift

@@ -0,0 +1,57 @@
+#if canImport(AndroidSwiftUI)
+import AndroidSwiftUI
+#else
+import SwiftUI
+#endif
+
+struct GesturePlayground: View {
+
+    @State private var dragX = 0.0
+    @State private var dragY = 0.0
+    @State private var dropped = "not yet"
+    @State private var presses = 0
+    @State private var taps = 0
+
+    var body: some View {
+        ScrollView {
+            VStack(alignment: .leading, spacing: 0) {
+                Example("DragGesture") {
+                    VStack(alignment: .leading, spacing: 8) {
+                        Text("Offset: \(Int(dragX)), \(Int(dragY))")
+                        Text("Last drop: \(dropped)")
+                        RoundedRectangle(cornerRadius: 12)
+                            .fill(.blue)
+                            .frame(width: 90, height: 90)
+                            .offset(x: dragX, y: dragY)
+                            .gesture(
+                                DragGesture()
+                                    .onChanged { value in
+                                        dragX = value.translation.width
+                                        dragY = value.translation.height
+                                    }
+                                    .onEnded { value in
+                                        dropped = "\(Int(value.translation.width)), \(Int(value.translation.height))"
+                                    }
+                            )
+                        Button("Reset") {
+                            dragX = 0
+                            dragY = 0
+                        }
+                    }
+                }
+                Example("onLongPressGesture") {
+                    VStack(alignment: .leading, spacing: 8) {
+                        Text("Taps: \(taps)   Long presses: \(presses)")
+                        Text("Tap or press and hold")
+                            .foregroundColor(.white)
+                            .padding()
+                            .background(Color.purple)
+                            .cornerRadius(8)
+                            .onTapGesture { taps += 1 }
+                            .onLongPressGesture { presses += 1 }
+                    }
+                }
+            }
+        }
+    }
+}

Demo/swiftui/src/commonMain/kotlin/com/pureswift/swiftui/Render.kt

@@ -3,6 +3,11 @@ package com.pureswift.swiftui
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
+import androidx.compose.foundation.ExperimentalFoundationApi
+import androidx.compose.foundation.combinedClickable
+import androidx.compose.foundation.gestures.detectDragGestures
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.horizontalScroll
 import androidx.compose.foundation.verticalScroll
@@ -1062,6 +1067,7 @@ private fun fontWeightFor(name: String): FontWeight = when (name) {
 /// animation (explicit `withAnimation` tree, or this node's `.animation`
 /// modifier) applies, and `snap` otherwise.
 @Composable
+@OptIn(ExperimentalFoundationApi::class)
 internal fun ViewNode.composeModifiers(): Modifier {
     val implicit = modifiers.firstOrNull { it.kind == "animation" && it.args["curve"] != null }
         ?.let { AnimSpec(it.args.string("curve") ?: "easeInOut", (it.args.double("durationMs") ?: 350.0).toInt()) }
@@ -1124,9 +1130,66 @@ internal fun ViewNode.composeModifiers(): Modifier {
                 modifier.clip(shape)
             }
 
+            // Tap and long press share one detector: two competing pointer
+            // handlers on the same view would fight over the gesture.
             "onTapGesture" -> {
                 val id = entry.args.long("action")
-                if (id != null) modifier.clickable { SwiftBridge.sink.invokeVoid(id) } else modifier
+                val longID = modifiers.firstOrNull { it.kind == "longPress" }?.args?.long("action")
+                when {
+                    id == null -> modifier
+                    longID == null -> modifier.clickable { SwiftBridge.sink.invokeVoid(id) }
+                    else -> modifier.combinedClickable(
+                        onClick = { SwiftBridge.sink.invokeVoid(id) },
+                        onLongClick = { SwiftBridge.sink.invokeVoid(longID) },
+                    )
+                }
+            }
+
+            "longPress" -> {
+                val id = entry.args.long("action")
+                // already wired above when this view also has a tap handler
+                val hasTap = modifiers.any { it.kind == "onTapGesture" }
+                if (id == null || hasTap) modifier
+                else modifier.combinedClickable(onClick = {}, onLongClick = { SwiftBridge.sink.invokeVoid(id) })
+            }
+
+            // Continuous drag: positions are reported in points, converted from
+            // the pointer's pixels, as "<phase>;<startX>,<startY>;<x>,<y>".
+            "drag" -> {
+                val id = entry.args.long("action")
+                if (id == null) modifier else {
+                // The detector is a long-running coroutine, so it must be keyed
+                // by the node's STABLE id: keying by the callback id would tear
+                // the gesture down mid-drag, since every onChanged re-evaluates
+                // the tree and mints a fresh id. The lambda then reads the id
+                // from a holder so it never dispatches to a reclaimed callback.
+                val latest = remember(this@composeModifiers.id) { longArrayOf(id) }
+                latest[0] = id
+                modifier.pointerInput(this@composeModifiers.id) {
+                    var start = Offset.Zero
+                    // Accumulate per-event deltas rather than reading absolute
+                    // positions: a view that offsets itself by the translation
+                    // moves under the finger, and absolute readings would
+                    // compensate for that motion and collapse toward zero.
+                    var total = Offset.Zero
+                    fun payload(phase: String): String {
+                        val end = start + total
+                        return "$phase;${start.x.toDp().value},${start.y.toDp().value};" +
+                            "${end.x.toDp().value},${end.y.toDp().value}"
+                    }
+                    detectDragGestures(
+                        onDragStart = { start = it; total = Offset.Zero },
+                        onDrag = { change, dragAmount ->
+                            change.consume()
+                            total += dragAmount
+                            SwiftBridge.sink.invokeString(latest[0], payload("changed"))
+                        },
+                        // ends carrying the final translation, as SwiftUI does
+                        onDragEnd = { SwiftBridge.sink.invokeString(latest[0], payload("ended")) },
+                        onDragCancel = { SwiftBridge.sink.invokeString(latest[0], payload("ended")) },
+                    )
+                }
+                }
             }
 
             // Dim disabled content; controls also drop interactivity via their
@@ -1155,7 +1218,7 @@ private val KNOWN_MODIFIER_KINDS = setOf(
     "scale", "opacity", "border", "shadow", "clipShape", "onTapGesture", "disabled",
     "font", "fontWeight", "italic", "foregroundColor", "lineLimit", "multilineTextAlignment",
     "tint", "onAppear", "onDisappear", "task", "onChange", "animation", "tag", "tabItem",
-    "transition", "focused",
+    "transition", "focused", "longPress", "drag",
 )
 
 // Folds a frame entry: fixed size, fill (maxWidth/Height .infinity), bounded