Added SkiaPanel. Added Swing integration support.

samples/SkijaInjectSample/src/main/kotlin/SkijaInjectSample/SwingSkia.kt

 package SkijaInjectSample
 
+import java.awt.Color
 import java.awt.Dimension
 import java.awt.BorderLayout
 import java.awt.event.KeyEvent
@@ -7,9 +8,11 @@ import java.awt.event.MouseEvent
 import java.awt.event.MouseMotionAdapter
 import javax.swing.JFrame
 import javax.swing.JButton
+import javax.swing.JLayeredPane
+import javax.swing.JPanel
 import javax.swing.event.MouseInputAdapter
 import javax.swing.WindowConstants
-import org.jetbrains.skiko.SkiaLayer
+import org.jetbrains.skiko.SkiaPanel
 
 fun Button(text: String): JButton {
     val btn = JButton(text)
@@ -23,13 +26,25 @@ fun SwingSkia() {
     window.defaultCloseOperation = WindowConstants.EXIT_ON_CLOSE
     window.title = "SwingSkiaWindow"
 
-    val layer = SkiaLayer()
+    val panel = SkiaPanel()
 
     window.contentPane.add(Button("North"), BorderLayout.NORTH)
     window.contentPane.add(Button("West"), BorderLayout.WEST)
     window.contentPane.add(Button("East"), BorderLayout.EAST)
     window.contentPane.add(Button("South"), BorderLayout.SOUTH)
-    window.contentPane.add(layer, BorderLayout.CENTER)
+    window.contentPane.add(panel, BorderLayout.CENTER)
+
+    val btnPanelOK = JPanel()
+    btnPanelOK.setLayout(BorderLayout(0, 0))
+    btnPanelOK.setBounds(50, 50, 200, 40)
+    btnPanelOK.setBackground(Color.white)
+    btnPanelOK.add(JButton("OK"))
+
+    val btnCancel = JButton("Cancel")
+    btnCancel.setBounds(300, 50, 200, 40)
+
+    panel.add(btnPanelOK)
+    panel.add(btnCancel)
 
     val state = State()
     state.text = window.title
@@ -37,13 +52,13 @@ fun SwingSkia() {
     var mouseX = 0
     var mouseY = 0
 
-    layer.renderer = Renderer { renderer, w, h -> displayScene(renderer, w, h, mouseX, mouseY, state) }
+    panel.layer.renderer = Renderer { renderer, w, h -> displayScene(renderer, w, h, mouseX, mouseY, state) }
 
-    layer.addMouseMotionListener(object : MouseMotionAdapter() {
+    panel.layer.addMouseMotionListener(object : MouseMotionAdapter() {
         override fun mouseMoved(event: MouseEvent) {
             mouseX = event.x
             mouseY = event.y
-            layer.display()
+            panel.layer.display()
         }
     })
 

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/SkiaLayer.kt

 package org.jetbrains.skiko
 
+import java.awt.Component
 import org.jetbrains.skija.BackendRenderTarget
 import org.jetbrains.skija.Canvas
 import org.jetbrains.skija.ColorSpace
 import org.jetbrains.skija.DirectContext
 import org.jetbrains.skija.FramebufferFormat
+import org.jetbrains.skija.Rect
 import org.jetbrains.skija.Surface
 import org.jetbrains.skija.SurfaceColorFormat
 import org.jetbrains.skija.SurfaceOrigin
+import org.jetbrains.skija.ClipMode
 
 private class SkijaState {
+    val canvasBleach: () -> Unit
+    init {
+        when (hostOs) {
+            OS.MacOS -> canvasBleach = { canvas?.clear(0) }
+            else -> canvasBleach = { canvas?.clear(-1) }
+        }
+    }
     var context: DirectContext? = null
     var renderTarget: BackendRenderTarget? = null
     var surface: Surface? = null
@@ -32,6 +42,7 @@ open class SkiaLayer() : HardwareLayer() {
     open val api: GraphicsApi = GraphicsApi.OPENGL
 
     var renderer: SkiaRenderer? = null
+    val clipComponets = mutableListOf<Component>()
 
     private val skijaState = SkijaState()
     protected var inited: Boolean = false
@@ -60,12 +71,33 @@ open class SkiaLayer() : HardwareLayer() {
         }
         initSkija()
         skijaState.apply {
-            canvas!!.clear(-1)
+            canvasBleach.invoke()
+            
+            // cliping
+            for (component in clipComponets) {
+                clipRectBy(component)
+            }
+
             renderer?.onRender(canvas!!, width, height)
             context!!.flush()
         }
     }
 
+    private fun clipRectBy(component: Component) {
+        skijaState.apply {
+            canvas!!.clipRect(
+                Rect.makeLTRB(
+                    component.x.toFloat(),
+                    component.y.toFloat(),
+                    component.x.toFloat() + component.width.toFloat(),
+                    component.y.toFloat() + component.height.toFloat()
+                ),
+                ClipMode.DIFFERENCE,
+                true
+            )
+        }
+    }
+
     private fun initSkija() {
         val dpi = contentScale
         initRenderTarget(dpi)

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/SkiaPanel.kt

+package org.jetbrains.skiko
+
+import java.awt.Color
+import java.awt.Component
+import java.awt.event.ComponentAdapter
+import java.awt.event.ComponentEvent
+import javax.swing.JLayeredPane
+import org.jetbrains.skija.Rect
+
+open class SkiaPanel: JLayeredPane {
+    val layer = SkiaLayer()
+
+    constructor() : super() {
+        setLayout(null)
+        setBackground(Color.white)
+    }
+
+    override fun add(component: Component): Component {
+        layer.clipComponets.add(component)
+        return super.add(component, Integer.valueOf(0))
+    }
+
+    override fun addNotify() {
+        super.addNotify()
+        super.add(layer, Integer.valueOf(10))
+
+        addComponentListener(object : ComponentAdapter() {
+            override fun componentResized(e: ComponentEvent) {
+                layer.reinit()
+                layer.setSize(width, height)
+            }
+        })
+    }
+
+     override fun removeNotify() {
+        super.removeNotify()
+     }
+}

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/SkiaWindow.kt

@@ -5,7 +5,7 @@ import java.awt.event.ComponentEvent
 import javax.swing.JFrame
 
 open class SkiaWindow : JFrame() {
-    val layer: SkiaLayer = SkiaLayer()
+    val layer = SkiaLayer()
 
     init {
         contentPane.add(layer)