Fix "open windows stress test"

There were NullPointerException.

Also rename dispose to disposeCanvas.

And add method "dispose" for full dispose

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

 package org.jetbrains.skiko
 
-import org.jetbrains.skija.*
+import org.jetbrains.skija.Canvas
+import org.jetbrains.skija.ClipMode
+import org.jetbrains.skija.Picture
+import org.jetbrains.skija.PictureRecorder
+import org.jetbrains.skija.Rect
 import org.jetbrains.skiko.context.ContextHandler
 import org.jetbrains.skiko.context.createContextHandler
 import org.jetbrains.skiko.redrawer.Redrawer
 import java.awt.Graphics
-import java.awt.event.*
+import java.awt.event.HierarchyEvent
+import java.awt.event.InputMethodListener
+import java.awt.event.KeyListener
+import java.awt.event.MouseListener
+import java.awt.event.MouseMotionListener
+import java.awt.event.MouseWheelListener
 import javax.swing.JPanel
 import javax.swing.SwingUtilities.isEventDispatchThread
 
@@ -99,7 +108,6 @@ open class SkiaLayer(
         if (isInited) {
             redrawer?.dispose()  // we should dispose redrawer first (to cancel `draw` in rendering thread)
             contextHandler?.dispose()
-            contextHandler?.destroyContext()
             picture?.instance?.close()
             pictureRecorder.close()
             backedLayer.dispose()

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/context/ContextHandler.kt

@@ -6,11 +6,9 @@ import org.jetbrains.skija.DirectContext
 import org.jetbrains.skija.Picture
 import org.jetbrains.skija.Surface
 import org.jetbrains.skiko.GraphicsApi
-import org.jetbrains.skiko.SkiaLayer
 import org.jetbrains.skiko.OS
-import org.jetbrains.skiko.SkikoProperties
+import org.jetbrains.skiko.SkiaLayer
 import org.jetbrains.skiko.hostOs
-import org.jetbrains.skiko.redrawer.Redrawer
 
 internal fun createContextHandler(layer: SkiaLayer, renderApi: GraphicsApi): ContextHandler {
     return when (renderApi) {
@@ -45,9 +43,14 @@ internal abstract class ContextHandler(val layer: SkiaLayer) {
     }
 
     fun dispose() {
+        disposeCanvas()
+        destroyContext()
+    }
+
+    fun disposeCanvas() {
         surface?.close()
         renderTarget?.close()
     }
 
-    open fun destroyContext() = Unit
+    protected open fun destroyContext() = Unit
 }

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/context/Direct3DContextHandler.kt

 package org.jetbrains.skiko.context
 
-import java.lang.ref.Reference
 import org.jetbrains.skija.ColorSpace
-import org.jetbrains.skija.FramebufferFormat
-import org.jetbrains.skija.Picture
 import org.jetbrains.skija.Surface
 import org.jetbrains.skija.SurfaceColorFormat
 import org.jetbrains.skija.SurfaceOrigin
 import org.jetbrains.skija.impl.Native
 import org.jetbrains.skiko.SkiaLayer
-import org.jetbrains.skiko.redrawer.Direct3DRedrawer
-import org.jetbrains.skiko.redrawer.Redrawer
 import org.jetbrains.skiko.destroyContext
+import org.jetbrains.skiko.redrawer.Direct3DRedrawer
+import java.lang.ref.Reference
 
 internal class Direct3DContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
     val directXRedrawer: Direct3DRedrawer
@@ -35,7 +32,7 @@ internal class Direct3DContextHandler(layer: SkiaLayer) : ContextHandler(layer)
     }
 
     override fun initCanvas() {
-        dispose()
+        disposeCanvas()
 
         val scale = layer.contentScale
         val w = (layer.width * scale).toInt().coerceAtLeast(0)
@@ -69,6 +66,8 @@ internal class Direct3DContextHandler(layer: SkiaLayer) : ContextHandler(layer)
     }
 
     override fun destroyContext() {
-        destroyContext(Native.getPtr(context!!))
+        if (context != null) {
+            destroyContext(Native.getPtr(context!!))
+        }
     }
 }

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/context/MetalContextHandler.kt

@@ -4,10 +4,10 @@ import org.jetbrains.skija.ColorSpace
 import org.jetbrains.skija.Surface
 import org.jetbrains.skija.SurfaceColorFormat
 import org.jetbrains.skija.SurfaceOrigin
-import org.jetbrains.skiko.SkiaLayer
-import org.jetbrains.skiko.redrawer.MetalRedrawer
 import org.jetbrains.skija.impl.Native
+import org.jetbrains.skiko.SkiaLayer
 import org.jetbrains.skiko.destroyContext
+import org.jetbrains.skiko.redrawer.MetalRedrawer
 
 internal class MetalContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
     val metalRedrawer: MetalRedrawer
@@ -26,7 +26,7 @@ internal class MetalContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
     }
 
     override fun initCanvas() {
-        dispose()
+        disposeCanvas()
 
         val scale = layer.contentScale
         val w = (layer.width * scale).toInt().coerceAtLeast(0)
@@ -52,6 +52,8 @@ internal class MetalContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
     }
 
     override fun destroyContext() {
-        destroyContext(Native.getPtr(context!!))
+        if (context != null) {
+            destroyContext(Native.getPtr(context!!))
+        }
     }
 }

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/context/OpenGLContextHandler.kt

@@ -2,15 +2,13 @@ package org.jetbrains.skiko.context
 
 import org.jetbrains.skija.ColorSpace
 import org.jetbrains.skija.FramebufferFormat
-import org.jetbrains.skija.Picture
 import org.jetbrains.skija.Surface
 import org.jetbrains.skija.SurfaceColorFormat
 import org.jetbrains.skija.SurfaceOrigin
+import org.jetbrains.skiko.OpenGLApi
 import org.jetbrains.skiko.SkiaLayer
 import org.jetbrains.skiko.makeGLContext
 import org.jetbrains.skiko.makeGLRenderTarget
-import org.jetbrains.skiko.OpenGLApi
-import org.jetbrains.skiko.redrawer.Redrawer
 
 internal class OpenGLContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
     override fun initContext(): Boolean {
@@ -26,7 +24,7 @@ internal class OpenGLContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
     }
 
     override fun initCanvas() {
-        dispose()
+        disposeCanvas()
 
         val scale = layer.contentScale
         val w = (layer.width * scale).toInt().coerceAtLeast(0)

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/context/SoftwareContextHandler.kt

 package org.jetbrains.skiko.context
 
-import java.awt.AlphaComposite
-import java.awt.color.ColorSpace
-import java.awt.Color
-import java.awt.Graphics2D
+import org.jetbrains.skija.Bitmap
+import org.jetbrains.skija.Canvas
+import org.jetbrains.skija.ColorAlphaType
+import org.jetbrains.skija.ImageInfo
+import org.jetbrains.skija.Picture
+import org.jetbrains.skiko.SkiaLayer
 import java.awt.Transparency
-import java.awt.image.ComponentColorModel
+import java.awt.color.ColorSpace
 import java.awt.image.BufferedImage
+import java.awt.image.ComponentColorModel
 import java.awt.image.DataBuffer
 import java.awt.image.DataBufferByte
-import java.awt.image.WritableRaster
 import java.awt.image.Raster
-import org.jetbrains.skija.Bitmap
-import org.jetbrains.skija.ColorAlphaType
-import org.jetbrains.skija.Canvas
-import org.jetbrains.skiko.SkiaLayer
-import org.jetbrains.skija.ImageInfo
-import org.jetbrains.skija.Picture
-import org.jetbrains.skiko.redrawer.Redrawer
+import java.awt.image.WritableRaster
 
 internal class SoftwareContextHandler(layer: SkiaLayer) : ContextHandler(layer) {
     override val bleachConstant = -1 // it looks like java.awt.Canvas doesn't support transparency
@@ -40,7 +36,7 @@ internal class SoftwareContextHandler(layer: SkiaLayer) : ContextHandler(layer)
     }
 
     override fun initCanvas() {
-        dispose()
+        disposeCanvas()
         
         val scale = layer.contentScale
         val w = (layer.width * scale).toInt().coerceAtLeast(0)