Add next / prev animations

demo/src/main/kotlin/eu/wewox/pagecurl/MainActivity.kt

@@ -48,14 +48,12 @@ class MainActivity : ComponentActivity() {
                         modifier = Modifier.overlayControls(
                             next = {
                                 scope.launch {
-                                    val next = (state.current + 1).coerceAtMost(state.max - 1)
-                                    state.snapTo(next)
+                                    state.next()
                                 }
                             },
                             prev = {
                                 scope.launch {
-                                    val prev = (state.current - 1).coerceAtLeast(0)
-                                    state.snapTo(prev)
+                                    state.prev()
                                 }
                             },
                             center = {

pagecurl/src/main/kotlin/eu/wewox/pagecurl/config/CurlConfig.kt

@@ -11,22 +11,20 @@ import eu.wewox.pagecurl.ExperimentalPageCurlApi
 @ExperimentalPageCurlApi
 public data class PageCurlConfig(
     val curl: CurlConfig = CurlConfig(),
-    val interaction: InteractionConfig = InteractionConfig()
+    val direction: PageCurlDirection = PageCurlDirection.StartToEnd,
+    val interaction: InteractionConfig = InteractionConfig(forward = direction.forward()),
 )
 
 @ExperimentalPageCurlApi
 public data class InteractionConfig(
-    val forward: CurlDirection = CurlDirection(
-        Rect(Offset(0.5f, 0.0f), Offset(1.0f, 1.0f)),
-        Rect(Offset(0.0f, 0.0f), Offset(0.5f, 1.0f)),
-    ),
-    val backward: CurlDirection = CurlDirection(forward.end, forward.start),
+    val forward: DragDirection,
+    val backward: DragDirection = DragDirection(forward.end, forward.start),
 )
 
 @ExperimentalPageCurlApi
-public data class CurlDirection(
+public data class DragDirection(
     val start: Rect,
-    val end: Rect
+    val end: Rect,
 )
 
 @ExperimentalPageCurlApi
@@ -48,3 +46,20 @@ public data class ShadowConfig(
     val radius: Dp = 15.dp,
     val offset: DpOffset = DpOffset((-5).dp, 0.dp),
 )
+
+@ExperimentalPageCurlApi
+public enum class PageCurlDirection {
+    StartToEnd,
+    // TODO (Alex) Add support for reversed end-to-start direction
+    //  EndToStart,
+}
+
+private fun left(): Rect = Rect(Offset(0.0f, 0.0f), Offset(0.5f, 1.0f))
+
+private fun right(): Rect = Rect(Offset(0.5f, 0.0f), Offset(1.0f, 1.0f))
+
+@ExperimentalPageCurlApi
+private fun PageCurlDirection.forward(): DragDirection =
+    when (this) {
+        PageCurlDirection.StartToEnd -> DragDirection(right(), left())
+    }

pagecurl/src/main/kotlin/eu/wewox/pagecurl/page/CurlGesture.kt

@@ -1,5 +1,7 @@
 package eu.wewox.pagecurl.page
 
+import androidx.compose.animation.core.Animatable
+import androidx.compose.animation.core.AnimationVector4D
 import androidx.compose.animation.core.VectorConverter
 import androidx.compose.animation.core.calculateTargetValue
 import androidx.compose.animation.splineBasedDecay
@@ -13,15 +15,60 @@ import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.input.pointer.util.VelocityTracker
 import androidx.compose.ui.unit.IntSize
 import eu.wewox.pagecurl.ExperimentalPageCurlApi
-import eu.wewox.pagecurl.config.CurlDirection
+import eu.wewox.pagecurl.config.DragDirection
 import eu.wewox.pagecurl.utils.rotate
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.launch
 import kotlin.math.PI
 
+@ExperimentalPageCurlApi
+internal fun Modifier.curlGesture(
+    state: PageCurlState.InternalState,
+    enabled: Boolean,
+    scope: CoroutineScope,
+    direction: DragDirection,
+    start: Edge,
+    end: Edge,
+    edge: Animatable<Edge, AnimationVector4D>,
+    onChange: () -> Unit,
+): Modifier =
+    curlGesture(
+        key = state,
+        enabled = enabled,
+        direction = direction,
+        onStart = {
+            scope.launch {
+                state.animateJob?.cancel()
+                edge.snapTo(start)
+            }
+        },
+        onCurl = { a, b ->
+            scope.launch {
+                edge.animateTo(Edge(a, b))
+            }
+        },
+        onEnd = {
+            scope.launch {
+                try {
+                    edge.animateTo(end)
+                } finally {
+                    onChange()
+                    edge.snapTo(start)
+                }
+            }
+        },
+        onCancel = {
+            scope.launch {
+                edge.animateTo(start)
+            }
+        },
+    )
+
 @ExperimentalPageCurlApi
 internal fun Modifier.curlGesture(
     key: Any?,
     enabled: Boolean,
-    direction: CurlDirection,
+    direction: DragDirection,
     onStart: () -> Unit,
     onCurl: (Offset, Offset) -> Unit,
     onEnd: () -> Unit,

pagecurl/src/main/kotlin/eu/wewox/pagecurl/page/PageCurl.kt

@@ -1,27 +1,14 @@
 package eu.wewox.pagecurl.page
 
-import androidx.compose.animation.core.Animatable
-import androidx.compose.animation.core.AnimationVector4D
-import androidx.compose.animation.core.TwoWayConverter
-import androidx.compose.animation.core.VisibilityThreshold
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.BoxWithConstraints
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.rememberUpdatedState
-import androidx.compose.runtime.saveable.Saver
-import androidx.compose.runtime.saveable.rememberSaveable
-import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.geometry.Offset
-import androidx.compose.ui.unit.Constraints
 import eu.wewox.pagecurl.ExperimentalPageCurlApi
-import eu.wewox.pagecurl.config.CurlDirection
 import eu.wewox.pagecurl.config.PageCurlConfig
-import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.launch
 
 @ExperimentalPageCurlApi
 @Composable
@@ -42,23 +29,23 @@ public fun PageCurl(
         Box(
             Modifier
                 .curlGesture(
-                    key = internalState,
+                    state = internalState,
                     enabled = updatedCurrent < state.max - 1,
                     scope = scope,
                     direction = config.interaction.forward,
-                    start = internalState.rightCurl,
-                    end = internalState.leftCurl,
-                    animatable = internalState.forward,
+                    start = internalState.rightEdge,
+                    end = internalState.leftEdge,
+                    edge = internalState.forward,
                     onChange = { state.current = updatedCurrent + 1 }
                 )
                 .curlGesture(
-                    key = internalState,
+                    state = internalState,
                     enabled = updatedCurrent > 0,
                     scope = scope,
                     direction = config.interaction.backward,
-                    start = internalState.leftCurl,
-                    end = internalState.rightCurl,
-                    animatable = internalState.backward,
+                    start = internalState.leftEdge,
+                    end = internalState.rightEdge,
+                    edge = internalState.backward,
                     onChange = { state.current = updatedCurrent - 1 }
                 )
         ) {
@@ -67,141 +54,16 @@ public fun PageCurl(
             }
 
             if (updatedCurrent < state.max) {
-                Box(Modifier.drawCurl(config.curl, internalState.forward.value.a, internalState.forward.value.b)) {
+                Box(Modifier.drawCurl(config.curl, internalState.forward.value.top, internalState.forward.value.bottom)) {
                     content(updatedCurrent)
                 }
             }
 
             if (updatedCurrent > 0) {
-                Box(Modifier.drawCurl(config.curl, internalState.backward.value.a, internalState.backward.value.b)) {
+                Box(Modifier.drawCurl(config.curl, internalState.backward.value.top, internalState.backward.value.bottom)) {
                     content(updatedCurrent - 1)
                 }
             }
         }
     }
 }
-
-@ExperimentalPageCurlApi
-@Composable
-public fun rememberPageCurlState(
-    max: Int,
-    initialCurrent: Int = 0,
-): PageCurlState =
-    rememberSaveable(
-        max, initialCurrent,
-        saver = Saver(
-            save = { it.current },
-            restore = {
-                PageCurlState(
-                    max = it,
-                    initialCurrent = initialCurrent
-                )
-            }
-        )
-    ) {
-        PageCurlState(
-            max = max,
-            initialCurrent = initialCurrent
-        )
-    }
-
-@ExperimentalPageCurlApi
-public class PageCurlState(
-    public val max: Int,
-    initialCurrent: Int = 0,
-) {
-    public var current: Int by mutableStateOf(initialCurrent)
-        internal set
-
-    internal var internalState: InternalState? by mutableStateOf(null)
-
-    internal fun setup(constraints: Constraints) {
-        if (internalState?.constraints == constraints) {
-            return
-        }
-
-        val maxWidthPx = constraints.maxWidth.toFloat()
-        val maxHeightPx = constraints.maxHeight.toFloat()
-
-        val left = Curl(Offset(0f, 0f), Offset(0f, maxHeightPx))
-        val right = Curl(Offset(maxWidthPx, 0f), Offset(maxWidthPx, maxHeightPx))
-
-        val forward = Animatable(right, Curl.VectorConverter, Curl.VisibilityThreshold)
-        val backward = Animatable(left, Curl.VectorConverter, Curl.VisibilityThreshold)
-
-        internalState = InternalState(constraints, left, right, forward, backward)
-    }
-
-    public suspend fun snapTo(value: Int) {
-        internalState?.reset()
-        current = value
-    }
-
-    internal data class InternalState(
-        val constraints: Constraints,
-        val leftCurl: Curl,
-        val rightCurl: Curl,
-        val forward: Animatable<Curl, AnimationVector4D>,
-        val backward: Animatable<Curl, AnimationVector4D>,
-    ) {
-        internal suspend fun reset() {
-            forward.snapTo(rightCurl)
-            backward.snapTo(leftCurl)
-        }
-    }
-}
-
-@ExperimentalPageCurlApi
-private fun Modifier.curlGesture(
-    key: Any?,
-    enabled: Boolean,
-    scope: CoroutineScope,
-    direction: CurlDirection,
-    start: Curl,
-    end: Curl,
-    animatable: Animatable<Curl, AnimationVector4D>,
-    onChange: () -> Unit,
-): Modifier =
-    curlGesture(
-        key = key,
-        enabled = enabled,
-        direction = direction,
-        onStart = {
-            scope.launch {
-                animatable.snapTo(start)
-            }
-        },
-        onCurl = { a, b ->
-            scope.launch {
-                animatable.animateTo(Curl(a, b))
-            }
-        },
-        onEnd = {
-            scope.launch {
-                try {
-                    animatable.animateTo(end)
-                } finally {
-                    onChange()
-                    animatable.snapTo(start)
-                }
-            }
-        },
-        onCancel = {
-            scope.launch {
-                animatable.animateTo(start)
-            }
-        },
-    )
-
-internal data class Curl(val a: Offset, val b: Offset) {
-    companion object {
-        val VectorConverter: TwoWayConverter<Curl, AnimationVector4D> =
-            TwoWayConverter(
-                convertToVector = { AnimationVector4D(it.a.x, it.a.y, it.b.x, it.b.y) },
-                convertFromVector = { Curl(Offset(it.v1, it.v2), Offset(it.v3, it.v4)) }
-            )
-
-        val VisibilityThreshold: Curl =
-            Curl(Offset.VisibilityThreshold, Offset.VisibilityThreshold)
-    }
-}

pagecurl/src/main/kotlin/eu/wewox/pagecurl/page/PageCurlState.kt

@@ -0,0 +1,181 @@
+package eu.wewox.pagecurl.page
+
+import androidx.compose.animation.core.Animatable
+import androidx.compose.animation.core.AnimationVector4D
+import androidx.compose.animation.core.TwoWayConverter
+import androidx.compose.animation.core.VisibilityThreshold
+import androidx.compose.animation.core.keyframes
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.Saver
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.geometry.Size
+import androidx.compose.ui.unit.Constraints
+import eu.wewox.pagecurl.ExperimentalPageCurlApi
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.NonCancellable
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+
+@ExperimentalPageCurlApi
+@Composable
+public fun rememberPageCurlState(
+    max: Int,
+    initialCurrent: Int = 0,
+): PageCurlState =
+    rememberSaveable(
+        max, initialCurrent,
+        saver = Saver(
+            save = { it.current },
+            restore = {
+                PageCurlState(
+                    max = it,
+                    initialCurrent = initialCurrent
+                )
+            }
+        )
+    ) {
+        PageCurlState(
+            max = max,
+            initialCurrent = initialCurrent
+        )
+    }
+
+@ExperimentalPageCurlApi
+public class PageCurlState(
+    public val max: Int,
+    initialCurrent: Int = 0,
+) {
+    public var current: Int by mutableStateOf(initialCurrent)
+        internal set
+
+    internal var internalState: InternalState? by mutableStateOf(null)
+
+    internal fun setup(constraints: Constraints) {
+        if (internalState?.constraints == constraints) {
+            return
+        }
+
+        val maxWidthPx = constraints.maxWidth.toFloat()
+        val maxHeightPx = constraints.maxHeight.toFloat()
+
+        val left = Edge(Offset(0f, 0f), Offset(0f, maxHeightPx))
+        val right = Edge(Offset(maxWidthPx, 0f), Offset(maxWidthPx, maxHeightPx))
+
+        val forward = Animatable(right, Edge.VectorConverter, Edge.VisibilityThreshold)
+        val backward = Animatable(left, Edge.VectorConverter, Edge.VisibilityThreshold)
+
+        internalState = InternalState(constraints, left, right, forward, backward)
+    }
+
+    public suspend fun snapTo(value: Int) {
+        current = value.coerceIn(0, max - 1)
+        internalState?.reset()
+    }
+
+    public suspend fun next(block: suspend Animatable<Edge, AnimationVector4D>.(Size) -> Unit = DefaultNext) {
+        internalState?.animateTo(
+            target = { current + 1 },
+            animate = { forward.block(it) }
+        )
+    }
+
+    public suspend fun prev(block: suspend Animatable<Edge, AnimationVector4D>.(Size) -> Unit = DefaultPrev) {
+        internalState?.animateTo(
+            target = { current - 1 },
+            animate = { backward.block(it) }
+        )
+    }
+
+    internal inner class InternalState(
+        val constraints: Constraints,
+        val leftEdge: Edge,
+        val rightEdge: Edge,
+        val forward: Animatable<Edge, AnimationVector4D>,
+        val backward: Animatable<Edge, AnimationVector4D>,
+    ) {
+
+        var animateJob: Job? = null
+
+        suspend fun reset() {
+            forward.snapTo(rightEdge)
+            backward.snapTo(leftEdge)
+        }
+
+        suspend fun animateTo(
+            target: () -> Int,
+            animate: suspend InternalState.(Size) -> Unit
+        ) {
+            animateJob?.cancel()
+
+            val targetIndex = target()
+            if (targetIndex < 0 || targetIndex >= max) {
+                return
+            }
+
+            coroutineScope {
+                animateJob = launch {
+                    try {
+                        reset()
+                        animate(Size(constraints.maxWidth.toFloat(), constraints.maxHeight.toFloat()))
+                    } finally {
+                        withContext(NonCancellable) {
+                            snapTo(target())
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+public data class Edge(val top: Offset, val bottom: Offset) {
+    internal companion object {
+        val VectorConverter: TwoWayConverter<Edge, AnimationVector4D> =
+            TwoWayConverter(
+                convertToVector = { AnimationVector4D(it.top.x, it.top.y, it.bottom.x, it.bottom.y) },
+                convertFromVector = { Edge(Offset(it.v1, it.v2), Offset(it.v3, it.v4)) }
+            )
+
+        val VisibilityThreshold: Edge =
+            Edge(Offset.VisibilityThreshold, Offset.VisibilityThreshold)
+    }
+}
+
+private val DefaultNext: suspend Animatable<Edge, AnimationVector4D>.(Size) -> Unit = { size ->
+    animateTo(
+        targetValue = size.start,
+        animationSpec = keyframes {
+            durationMillis = DefaultAnimDuration
+            size.end at 0
+            size.middle at DefaultMidPointDuration
+        }
+    )
+}
+
+private val DefaultPrev: suspend Animatable<Edge, AnimationVector4D>.(Size) -> Unit = { size ->
+    animateTo(
+        targetValue = size.end,
+        animationSpec = keyframes {
+            durationMillis = DefaultAnimDuration
+            size.start at 0
+            size.middle at DefaultAnimDuration - DefaultMidPointDuration
+        }
+    )
+}
+
+private const val DefaultAnimDuration: Int = 450
+private const val DefaultMidPointDuration: Int = 150
+
+private val Size.start: Edge
+    get() = Edge(Offset(0f, 0f), Offset(0f, height))
+
+private val Size.middle: Edge
+    get() = Edge(Offset(width, height / 2f), Offset(width / 2f, height))
+
+private val Size.end: Edge
+    get() = Edge(Offset(width, height), Offset(width, height))