Handle property clearing in updates.

demo/sat-demo/src/main/kotlin/ru/mipt/npm/sat/satServer.kt

@@ -3,6 +3,7 @@ package ru.mipt.npm.sat
 
 import hep.dataforge.names.toName
 import hep.dataforge.vision.solid.Solid
+import hep.dataforge.vision.solid.clear
 import hep.dataforge.vision.solid.color
 import hep.dataforge.vision.solid.invoke
 import hep.dataforge.vision.three.server.*
@@ -42,7 +43,7 @@ fun main() {
             val targetVision = sat[target] as Solid
             targetVision.color("red")
             delay(300)
-            targetVision.color("darkgreen")
+            targetVision.color.clear()
             delay(10)
         }
     }

visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/Vision.kt

@@ -57,6 +57,9 @@ public interface Vision : Described {
      */
     public fun setProperty(name: Name, item: MetaItem<*>?, notify: Boolean = true)
 
+    /**
+     * Subscribe on property updates. The subscription is bound to the given [scope] and canceled when the scope is canceled
+     */
     public fun onPropertyChange(scope: CoroutineScope, callback: suspend (Name) -> Unit)
 
     /**
@@ -81,7 +84,7 @@ public interface Vision : Described {
     public suspend fun notifyPropertyChanged(propertyName: Name): Unit
 
     /**
-     * Update this vision using external meta. Children are not updated.
+     * Update this vision using a dif represented by [VisionChange].
      */
     public fun update(change: VisionChange)
 

visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionBase.kt

@@ -3,12 +3,14 @@ package hep.dataforge.vision
 import hep.dataforge.meta.Config
 import hep.dataforge.meta.MetaItem
 import hep.dataforge.meta.MutableMeta
+import hep.dataforge.meta.asMetaItem
 import hep.dataforge.meta.descriptors.NodeDescriptor
 import hep.dataforge.meta.descriptors.defaultItem
 import hep.dataforge.meta.descriptors.get
-import hep.dataforge.meta.update
 import hep.dataforge.names.Name
 import hep.dataforge.names.asName
+import hep.dataforge.names.plus
+import hep.dataforge.values.Null
 import hep.dataforge.values.ValueType
 import hep.dataforge.vision.Vision.Companion.STYLE_KEY
 import kotlinx.coroutines.CoroutineScope
@@ -27,6 +29,7 @@ internal data class PropertyListener(
     val action: (name: Name) -> Unit,
 )
 
+
 @Serializable
 @SerialName("vision")
 public open class VisionBase : Vision {
@@ -100,6 +103,8 @@ public open class VisionBase : Vision {
             }
     }
 
+
+    //TODO check memory consumption for the flow
     @Transient
     private val propertyInvalidationFlow: MutableSharedFlow<Name> = MutableSharedFlow()
 
@@ -116,13 +121,30 @@ public open class VisionBase : Vision {
         propertyInvalidationFlow.emit(propertyName)
     }
 
-    public fun configure(block: MutableMeta<*>.() -> Unit) {
+    public fun configure(block: suspend MutableMeta<*>.() -> Unit) {
+        scope.launch {
             getOrCreateConfig().block()
         }
+    }
 
     override fun update(change: VisionChange) {
+
+        fun updateProperties(at: Name, item: MetaItem<*>) {
+            when (item) {
+                is MetaItem.ValueItem -> {
+                    if (item.value == Null) {
+                        setProperty(at, null)
+                    } else
+                        setProperty(at, item)
+                }
+                is MetaItem.NodeItem -> item.node.items.forEach { (token, childItem) ->
+                    updateProperties(at + token, childItem)
+                }
+            }
+        }
+
         change.properties?.let {
-            getOrCreateConfig().update(it)
+            updateProperties(Name.EMPTY, it.asMetaItem())
         }
     }
 

visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionChange.kt

@@ -3,6 +3,7 @@ package hep.dataforge.vision
 import hep.dataforge.meta.*
 import hep.dataforge.names.Name
 import hep.dataforge.names.plus
+import hep.dataforge.values.Null
 import kotlinx.coroutines.*
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow
@@ -30,7 +31,8 @@ public class VisionChangeBuilder : VisionContainerBuilder<Vision> {
 
     public fun propertyChanged(visionName: Name, propertyName: Name, item: MetaItem<*>?) {
         if (visionName == Name.EMPTY) {
-            propertyChange[propertyName] = item
+            //Write property removal as [Null]
+            propertyChange[propertyName] = (item ?: Null.asMetaItem())
         } else {
             getOrPutChild(visionName).propertyChanged(Name.EMPTY, propertyName, item)
         }
@@ -112,6 +114,10 @@ public fun Vision.flowChanges(
     coroutineScope {
         collectChange(Name.EMPTY, this@flowChanges) { collector }
 
+        //Send initial vision state
+        val initialChange = VisionChange(vision = isolate(manager))
+        emit(initialChange)
+
         while (currentCoroutineContext().isActive) {
             //Wait for changes to accumulate
             delay(collectionDuration)

visionforge-server/src/main/kotlin/hep/dataforge/vision/three/server/VisionServer.kt

@@ -134,14 +134,6 @@ public class VisionServer internal constructor(
 
             try {
                 withContext(visionManager.context.coroutineContext) {
-
-                    val initialVision = VisionChange(vision = vision)
-                    val initialJson =  visionManager.jsonFormat.encodeToString(
-                        VisionChange.serializer(),
-                        initialVision
-                    )
-                    outgoing.send(Frame.Text(initialJson))
-
                     vision.flowChanges(visionManager, updateInterval.milliseconds).collect { update ->
                         val json = visionManager.jsonFormat.encodeToString(
                             VisionChange.serializer(),

visionforge-solid/src/commonMain/kotlin/hep/dataforge/vision/solid/ColorAccessor.kt

@@ -0,0 +1,51 @@
+package hep.dataforge.vision.solid
+
+import hep.dataforge.meta.MutableItemProvider
+import hep.dataforge.meta.set
+import hep.dataforge.meta.value
+import hep.dataforge.names.Name
+import hep.dataforge.values.Value
+import hep.dataforge.values.asValue
+import hep.dataforge.values.string
+import hep.dataforge.vision.Colors
+import hep.dataforge.vision.VisionBuilder
+
+@VisionBuilder
+public class ColorAccessor(private val parent: MutableItemProvider, private val colorKey: Name) {
+    public var value: Value?
+        get() = parent.getItem(colorKey).value
+        set(value) {
+            parent[colorKey] = value
+        }
+}
+
+public var ColorAccessor?.string: String?
+    get() = this?.value?.string
+    set(value) {
+        this?.value = value?.asValue()
+    }
+
+/**
+ * Set [webcolor](https://en.wikipedia.org/wiki/Web_colors) as string
+ */
+public operator fun ColorAccessor?.invoke(webColor: String) {
+    this?.value = webColor.asValue()
+}
+
+/**
+ * Set color as RGB integer
+ */
+public operator fun ColorAccessor?.invoke(rgb: Int) {
+    this?.value = Colors.rgbToString(rgb).asValue()
+}
+
+/**
+ * Set color as RGB
+ */
+public operator fun ColorAccessor?.invoke(r: UByte, g: UByte, b: UByte) {
+    this?.value = Colors.rgbToString(r, g, b).asValue()
+}
+
+public fun ColorAccessor?.clear(){
+    this?.value = null
+}

visionforge-solid/src/commonMain/kotlin/hep/dataforge/vision/solid/SolidMaterial.kt

@@ -6,51 +6,13 @@ import hep.dataforge.meta.descriptors.attributes
 import hep.dataforge.names.Name
 import hep.dataforge.names.asName
 import hep.dataforge.names.plus
-import hep.dataforge.values.Value
 import hep.dataforge.values.ValueType
 import hep.dataforge.values.asValue
-import hep.dataforge.values.string
 import hep.dataforge.vision.*
 import hep.dataforge.vision.solid.SolidMaterial.Companion.MATERIAL_COLOR_KEY
 import hep.dataforge.vision.solid.SolidMaterial.Companion.MATERIAL_KEY
 import hep.dataforge.vision.solid.SolidMaterial.Companion.MATERIAL_OPACITY_KEY
 
-@VisionBuilder
-public class ColorAccessor(private val parent: MutableItemProvider, private val colorKey: Name) {
-    public var value: Value?
-        get() = parent.getItem(colorKey).value
-        set(value) {
-            parent[colorKey] = value
-        }
-}
-
-public var ColorAccessor?.string: String?
-    get() = this?.value?.string
-    set(value) {
-        this?.value = value?.asValue()
-    }
-
-/**
- * Set [webcolor](https://en.wikipedia.org/wiki/Web_colors) as string
- */
-public operator fun ColorAccessor?.invoke(webColor: String) {
-    this?.value = webColor.asValue()
-}
-
-/**
- * Set color as RGB integer
- */
-public operator fun ColorAccessor?.invoke(rgb: Int) {
-    this?.value = Colors.rgbToString(rgb).asValue()
-}
-
-/**
- * Set color as RGB
- */
-public operator fun ColorAccessor?.invoke(r: UByte, g: UByte, b: UByte) {
-    this?.value = Colors.rgbToString(r, g, b).asValue()
-}
-
 @VisionBuilder
 public class SolidMaterial : Scheme() {