refactor: Preparing core module for Compose support

build.gradle.kts

@@ -4,6 +4,7 @@ plugins {
     id("kool.androidlib-conventions") apply false
     id("kool.lib-conventions") apply false
     id("kool.publish-conventions") apply false
+    alias(libs.plugins.compose.compiler) apply false
 }
 
 allprojects {

buildSrc/src/main/kotlin/kool.lib-conventions.gradle.kts

@@ -38,6 +38,7 @@ kotlin {
             optIn("kotlin.contracts.ExperimentalContracts")
             optIn("kotlin.io.encoding.ExperimentalEncodingApi")
             optIn("kotlin.ExperimentalStdlibApi")
+            optIn("de.fabmax.kool.InternalKoolAPI")
         }
     }
     sourceSets {

gradle/libs.versions.toml

@@ -1,5 +1,7 @@
 [versions]
 agp = "8.12.3"
+compose = "1.9.3"
+compose-mini = "0.0.1"
 kotlin = "2.3.0"
 kotlin-coroutines = "1.10.2"
 kotlin-serialization = "1.9.0"
@@ -51,8 +53,11 @@ physx-wasm = { group = "npm", name = "physx-js-webidl", version.ref = "physx-was
 box2d-jni = { group = "de.fabmax.box2d-jni", name = "box2d-jni", version.ref = "box2d-jni" }
 box2d-android = { group = "de.fabmax.box2d-jni", name = "box2d-jni-android", version.ref = "box2d-jni" }
 box2d-wasm = { group = "npm", name = "kool-box2d-wasm", version.ref = "box2d-wasm" }
-
-# wgpu backend
+compose-runtime = { module = "org.jetbrains.compose.runtime:runtime", version.ref = "compose" }
+compose-mini-runtime = { group = "me.dvyy.compose.mini", name = "runtime", version.ref = "compose-mini"}
+compose-mini-modifier = { group = "me.dvyy.compose.mini", name = "modifier", version.ref = "compose-mini" }
+compose-mini-modifier-composed = { group = "me.dvyy.compose.mini", name = "modifier-composed", version.ref = "compose-mini"}
+# wgpu backcend
 wgpu4k = { module = "io.ygdrasil:wgpu4k", version.ref = "wgpu4k" }
 webgpu-descriptors = { module = "io.ygdrasil:webgpu-ktypes-descriptors", version.ref = "webgpu-ktypes" }
 rococoa = { module = "io.ygdrasil:rococoa", version.ref = "rococoa" }
@@ -71,6 +76,9 @@ plugindep-maven-publish = { group = "com.vanniktech", name = "gradle-maven-publi
 
 [plugins]
 webidl = { id = "de.fabmax.webidl-util", version = "0.10.5" }
+compose-compiler = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }
+jetbrainsCompose = { id = "org.jetbrains.compose", version.ref = "compose" }
+
 
 [bundles]
 lwjgl = ["lwjgl-core", "lwjgl-glfw", "lwjgl-jemalloc", "lwjgl-opengl", "lwjgl-vulkan", "lwjgl-vma", "lwjgl-shaderc", "lwjgl-nfd", "lwjgl-stb", "lwjgl-jawt", "lwjgl-msdfgen"]

kool-core/build.gradle.kts

@@ -13,6 +13,7 @@ kotlin {
             api(libs.kotlin.coroutines)
             implementation(libs.kotlin.serialization.json)
             implementation(libs.kotlin.atomicfu)
+            implementation(libs.compose.runtime)
         }
         commonTest.dependencies {
             implementation(libs.kotlin.test)

kool-core/src/commonMain/kotlin/de/fabmax/kool/Annotations.kt

@@ -0,0 +1,15 @@
+package de.fabmax.kool
+
+@RequiresOptIn(
+    level = RequiresOptIn.Level.ERROR,
+    message = "This is internal Kool API that may lead to unexpected behavior or change without warning."
+)
+@Target(
+    AnnotationTarget.CLASS,
+    AnnotationTarget.FUNCTION,
+    AnnotationTarget.PROPERTY,
+    AnnotationTarget.PROPERTY_GETTER,
+    AnnotationTarget.PROPERTY_SETTER,
+)
+@Retention(AnnotationRetention.BINARY)
+annotation class InternalKoolAPI

kool-core/src/commonMain/kotlin/de/fabmax/kool/KoolContext.kt

@@ -1,5 +1,6 @@
 package de.fabmax.kool
 
+import androidx.compose.runtime.snapshots.Snapshot
 import de.fabmax.kool.input.Input
 import de.fabmax.kool.pipeline.ComputePass
 import de.fabmax.kool.pipeline.GpuPass
@@ -11,6 +12,7 @@ import de.fabmax.kool.scene.Scene
 import de.fabmax.kool.util.BufferedList
 import de.fabmax.kool.util.KoolDispatchers
 import de.fabmax.kool.util.Time
+import kotlinx.atomicfu.atomic
 
 /**
  * @author fabmax
@@ -25,6 +27,11 @@ abstract class KoolContext {
 
     private var prevFrameTime = Time.precisionTime
 
+    private val applyScheduled = atomic(false)
+    private val snapshotHandle = Snapshot.registerGlobalWriteObserver {
+        applyScheduled.compareAndSet(expect = false, update = true)
+    }
+
     val onRender = BufferedList<(KoolContext) -> Unit>()
     val onShutdown = BufferedList<(KoolContext) -> Unit>()
 
@@ -40,6 +47,10 @@ abstract class KoolContext {
             .also { brdf -> onShutdown += { brdf.release() } }
     }
 
+    init {
+        onShutdown += { snapshotHandle.dispose() }
+    }
+
     abstract fun openUrl(url: String, sameWindow: Boolean = true)
 
     abstract fun run()
@@ -73,7 +84,14 @@ abstract class KoolContext {
 
         Input.poll(this)
 
+        // Apply any mutable state changes from user input
+        if (applyScheduled.compareAndSet(expect = true, update = false)) {
+            Snapshot.sendApplyNotifications()
+        }
+
         KoolDispatchers.Frontend.executeDispatchedTasks()
+        Time.composeFrameClock.sendFrame(Time.nanoTime) // Let recomposer update UI nodes
+
         onRender.update()
         for (i in onRender.indices) {
             onRender[i](this)

kool-core/src/commonMain/kotlin/de/fabmax/kool/modules/ui2/Dimension.kt

@@ -48,4 +48,6 @@ value class Dp(val value: Float): Dimension, Comparable<Dp> {
             return fromPx(round(pxf))
         }
     }
-}
+}
+
+val Number.dp: Dp get() = Dp(this.toFloat())

kool-core/src/commonMain/kotlin/de/fabmax/kool/modules/ui2/ScrollPane.kt

@@ -181,7 +181,7 @@ open class ScrollPaneNode(parent: UiNode?, surface: UiSurface) : UiNode(parent,
         var currentScrollY = state.yScrollDp.use()
         var desiredScrollX = state.xScrollDpDesired.use()
         var desiredScrollY = state.yScrollDpDesired.use()
-
+        val parent = parent
         if (parent != null) {
             state.viewWidthDp.set(parent.widthPx / UiScale.measuredScale)
             state.viewHeightDp.set(parent.heightPx / UiScale.measuredScale)
@@ -221,4 +221,4 @@ open class ScrollPaneNode(parent: UiNode?, surface: UiSurface) : UiNode(parent,
     companion object {
         val factory: (UiNode, UiSurface) -> ScrollPaneNode = { parent, surface -> ScrollPaneNode(parent, surface) }
     }
-}
+}

kool-core/src/commonMain/kotlin/de/fabmax/kool/modules/ui2/UiModifier.kt

@@ -46,6 +46,7 @@ open class UiModifier(val surface: UiSurface) {
     val onDragStart: MutableList<(PointerEvent) -> Unit> by listProperty()
     val onDrag: MutableList<(PointerEvent) -> Unit> by listProperty()
     val onDragEnd: MutableList<(PointerEvent) -> Unit> by listProperty()
+    val onRender: MutableList<UiNode.() -> Unit> by listProperty()
 
     protected fun <T> property(defaultVal: T): PropertyHolder<T> {
         val holder = PropertyHolder { defaultVal }
@@ -309,4 +310,4 @@ fun <T: UiModifier> T.dragListener(draggable: Draggable): T {
     onDrag(draggable::onDrag)
     onDragEnd(draggable::onDragEnd)
     return this
-}
+}

kool-core/src/commonMain/kotlin/de/fabmax/kool/modules/ui2/UiNode.kt

@@ -1,5 +1,6 @@
 package de.fabmax.kool.modules.ui2
 
+import de.fabmax.kool.InternalKoolAPI
 import de.fabmax.kool.KoolContext
 import de.fabmax.kool.math.MutableVec2f
 import de.fabmax.kool.math.MutableVec4f
@@ -12,15 +13,23 @@ import kotlin.math.max
 import kotlin.math.min
 import kotlin.reflect.KClass
 
-abstract class UiNode(val parent: UiNode?, override val surface: UiSurface) : UiScope {
+abstract class UiNode(parent: UiNode?, override val surface: UiSurface) : UiScope {
+    @set:InternalKoolAPI
+    var parent: UiNode? = parent
+
     override val uiNode: UiNode get() = this
 
     var nodeIndex = 0
         private set
 
     protected val oldChildren = mutableListOf<UiNode>()
-    protected val mutChildren = mutableListOf<UiNode>()
+
+    @InternalKoolAPI
+    val mutChildren = mutableListOf<UiNode>()
+
+    @OptIn(InternalKoolAPI::class)
     val children: List<UiNode> get() = mutChildren
+
     val weakMemory = WeakMemory()
 
     private var scopeName: String? = null
@@ -131,7 +140,7 @@ abstract class UiNode(val parent: UiNode?, override val surface: UiSurface) : Ui
         this.topPx = minY
         this.rightPx = maxX
         this.bottomPx = maxY
-
+        val parent = parent
         if (parent != null) {
             clipBoundsPx.x = max(parent.clipLeftPx, minX)
             clipBoundsPx.y = max(parent.clipTopPx, minY)
@@ -205,6 +214,7 @@ abstract class UiNode(val parent: UiNode?, override val surface: UiSurface) : Ui
     open fun render(ctx: KoolContext) {
         modifier.background?.renderUi(this)
         modifier.border?.renderUi(this)
+        modifier.onRender.forEach { render -> render(this) }
     }
 
     open fun measureContentSize(ctx: KoolContext) {
@@ -412,4 +422,4 @@ abstract class UiNode(val parent: UiNode?, override val surface: UiSurface) : Ui
     companion object {
         val NO_CLIP = Vec4f(-1e9f, -1e9f, 1e9f, 1e9f)
     }
-}
+}

kool-core/src/commonMain/kotlin/de/fabmax/kool/modules/ui2/UiSurface.kt

@@ -16,11 +16,17 @@ import de.fabmax.kool.scene.geometry.MeshBuilder
 import de.fabmax.kool.scene.geometry.Usage
 import de.fabmax.kool.util.*
 
+/**
+ * @property clearViewportOnUpdateUi
+ * Whether the viewport node should have defaults applied when updating UI.
+ * Set to false if managing UI nodes externally (ex. via Compose.)
+ */
 open class UiSurface(
     val parentScene: Scene,
     colors: Colors = Colors.darkColors(),
     sizes: Sizes = Sizes.medium,
-    name: String = "uiSurface"
+    name: String = "uiSurface",
+    val clearViewportOnUpdateUi: Boolean = true,
 ) : Node(name) {
 
     constructor(
@@ -155,7 +161,7 @@ open class UiSurface(
         perfPrep = pt.takeMs().also { pt.reset() }
 
         viewport.setBounds(0f, 0f, viewportWidth.use(this), viewportHeight.use(this))
-        viewport.applyDefaults()
+        if (clearViewportOnUpdateUi) viewport.applyDefaults()
         composeContent()
         perfCompose = pt.takeMs().also { pt.reset() }
 
@@ -758,4 +764,4 @@ open class UiSurface(
             }
         }
     }
-}
+}

kool-core/src/commonMain/kotlin/de/fabmax/kool/util/Time.kt

@@ -1,13 +1,15 @@
 package de.fabmax.kool.util
 
+import androidx.compose.runtime.BroadcastFrameClock
+import de.fabmax.kool.InternalKoolAPI
 import de.fabmax.kool.util.Time.frameCount
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.update
+import kotlin.time.Clock
 
 object Time {
-    private val systemClock = SystemClock()
     /**
      * Time since previous frame in seconds.
      */
@@ -44,7 +46,25 @@ object Time {
      * measure time intervals. Precision depends on platform, on JVM it should be around nanoseconds, on JS it should
      * be around 0.1 milliseconds.
      */
-    val precisionTime: Double get() = systemClock.now()
+    val precisionTime: Double get() = nanoTime / 1_000_000_000.0
+
+    /**
+     * Current system clock time in nanoseconds.
+     */
+    val nanoTime: Long get() {
+        val now = Clock.System.now()
+        return now.epochSeconds * 1_000_000_000L + now.nanosecondsOfSecond
+    }
+
+    /**
+     * Frame clock from Jetpack compose runtime.
+     * Frames are emitted after polling user input and dispatching any queued frontend scope tasks.
+     *
+     * Any blocks waiting for a new frame will run immediately when the frame is emitted, then switch
+     * to their parent context to return the result.
+     */
+    @InternalKoolAPI
+    val composeFrameClock = BroadcastFrameClock()
 
     internal fun update(dt: Double) {
         gameTime += dt
@@ -54,10 +74,4 @@ object Time {
         for (i in frameTimes.indices) { sum += frameTimes[i] }
         fps = (frameTimes.size / sum) * 0.1 + fps * 0.9
     }
-}
-
-internal expect fun SystemClock(): SystemClock
-
-internal interface SystemClock {
-    fun now(): Double
 }