Add some pictures

README.md

@@ -27,10 +27,20 @@ Main features:
 
 Common visualisation objects such as VisualObject and VisualGroup.
 
+Class diagram: 
+
+![](doc/resources/class-diag-common.png)
+
+This module also includes configuration editors for JS (in jsMain) and JVM (in jvmMain).
+
+Note: this module is not 3D-specific.
 
 ### dataforge-vis-spatial
 
-Includes common description and serializers for 3D visualisation, JavaFX and Three.js implementations.
+Includes common classes and serializers for 3D visualisation, Three.js and JavaFX implementations.
+
+Class diagram:
+![](doc/resources/class-diag-3d.png)
 
 
 ### dataforge-vis-spatial-gdml
@@ -58,6 +68,8 @@ To see the demo: run `demo/spatial-showcase/distribution/installJsDist` Gradle t
 
 Other demos can be built similarly.  
 
+![](doc/resources/spatial-showcase.png)
+
 ##### muon-monitor
 
 A full-stack application example, showing the 
@@ -68,8 +80,12 @@ Includes server back-end generating events, as well as visualization front-end.
 To run full-stack app (both server and browser front-end), run 
 `demo/muon-monitor/application/run` task.
 
+![](doc/resources/muon-monitor.png)
+
 ##### gdml
 
 Visualization example for geometry defined as GDML file. Once you open Web application,
 drag-and-drop GDML file to the window to see visualization. For example file, use 
 `demo\gdml\src\jsMain\resources\cubes.gdml`.
+
+![](doc/resources/gdml-demo.png)

dataforge-vis-common/src/commonMain/kotlin/hep/dataforge/vis/common/VisualGroup.kt

@@ -16,6 +16,10 @@ interface VisualGroup : Provider, Iterable<VisualObject>, VisualObject {
 
     val styleSheet: StyleSheet?
 
+    /**
+     * A map of direct children for specific target
+     * (currently "visual" or "style")
+     */
     override fun provideTop(target: String): Map<Name, Any> =
         when (target) {
             VisualObject.TYPE -> children.flatMap { (key, value) ->