Further simplification.

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

 package SkijaInjectSample
 
-import org.jetbrains.skiko.OpenGLApi
-import org.jetbrains.skiko.Engine
 import org.jetbrains.skiko.SkiaWindow
 
 import java.awt.event.MouseEvent
@@ -18,7 +16,6 @@ fun main(args: Array<String>) {
 }
 
 fun createWindow(title: String) {
-    val engine: Engine = Engine.get()
 
     var mouseX = 0
     var mouseY = 0
@@ -37,7 +34,7 @@ fun createWindow(title: String) {
         override fun mouseMoved(event: MouseEvent) {
             mouseX = event.x
             mouseY = event.y
-            engine.render(window.layer)
+            window.display()
         }
     })
 

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

-package org.jetbrains.skiko
-
-class Engine private constructor() {
-    private var api = GraphicsApi.UNKNOWN
-    fun currentApi(): GraphicsApi {
-        return api
-    }
-
-    /**
-     * GAG - At the moment always initializes OpenGL.
-     * @param osType The current OS type of the device.
-     */
-    private fun initSuitableGraphicsApi(osType: OSType) {
-        when {
-            osType === OSType.MAC_OS -> {
-                OpenGLApi.get() // for Metal
-                instance.api = GraphicsApi.OPENGL
-            }
-            osType === OSType.LINUX -> {
-                OpenGLApi.get() // for Vulkan and OpenGL
-                instance.api = GraphicsApi.OPENGL
-            }
-            osType === OSType.WINDOWS -> {
-                OpenGLApi.get() // for Vulkan and OpenGL
-                instance.api = GraphicsApi.OPENGL
-            }
-            else -> {
-                OpenGLApi.get() // default
-                instance.api = GraphicsApi.OPENGL
-            }
-        }
-    }
-
-    fun render(drawable: Drawable) {
-        drawable.updateLayer()
-        drawable.redrawLayer()
-    }
-
-    companion object {
-        private lateinit var instance: Engine
-        fun get(): Engine {
-            if (!this::instance.isInitialized) {
-                instance = Engine()
-                instance.initSuitableGraphicsApi(OSType.getCurrent())
-            }
-            return instance
-        }
-    }
-}

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

@@ -5,9 +5,12 @@ import java.awt.Canvas
 
 open class HardwareLayer : Canvas(), Drawable {
     override fun paint(g: Graphics) {
-        Engine.get().render(this)
+        display()
+    }
+    open fun display() {
+        this.updateLayer()
+        this.redrawLayer()
     }
-
     open fun draw() {}
     external override fun redrawLayer()
     external override fun updateLayer()

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

@@ -14,7 +14,7 @@ object Library {
     fun load(resourcePath: String, name: String) {
         if (loaded) return
 
-        val libFileName = "$libPrefix$name$libExtension"
+        val libFileName = System.mapLibraryName(name)
         val url = Library::class.java.getResource(resourcePath + libFileName)
         val libFile = when {
             url == null -> error("Library $libFileName is not found in $resourcePath")
@@ -28,33 +28,7 @@ object Library {
                 }
             }
         }
-        //println("Loading $url from ${libFile.absolutePath}")
         System.load(libFile.absolutePath)
         loaded = true
     }
-
-    private val libPrefix: String
-        get() = if (currentOS == OS.Windows) "" else "lib"
-
-    private val libExtension: String
-        get() = when (currentOS) {
-            OS.Mac -> ".dylib"
-            OS.Linux -> ".so"
-            OS.Windows -> ".dll"
-        }
-
-    private val currentOS by lazy {
-        val osName = System.getProperty("os.name") ?: error("Unknown OS: 'os.name' is null")
-        val os = osName.toLowerCase(Locale.ROOT)
-        when {
-            os.contains("mac") || os.contains("darwin") -> OS.Mac
-            os.contains("win") -> OS.Windows
-            os.contains("nux") -> OS.Linux
-            else -> error("Unknown OS: $osName")
-        }
-    }
-
-    private enum class OS {
-        Linux, Mac, Windows
-    }
 }
\ No newline at end of file

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

@@ -4,25 +4,16 @@ enum class OSType {
     MAC_OS, LINUX, WINDOWS, UNKNOWN;
 
     companion object {
-        private lateinit var currentOSType: OSType
-        fun getCurrent(): OSType {
-                if (!this::currentOSType.isInitialized) {
-                    currentOSType = defineOsType()
-                }
-                return currentOSType
-        }
+        val currentOs = defineOsType()
 
         private fun defineOsType(): OSType {
             val osName = System.getProperty("os.name").toLowerCase()
-            if (isWindows(osName)) {
-                return WINDOWS
-            }
-            if (isMac(osName)) {
-                return MAC_OS
+            return when {
+                isWindows(osName) -> WINDOWS
+                isMac(osName) -> MAC_OS
+                isUnix(osName) -> LINUX
+                else -> UNKNOWN
             }
-            return if (isUnix(osName)) {
-                LINUX
-            } else UNKNOWN
         }
 
         private fun isWindows(name: String): Boolean {

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

@@ -22,12 +22,6 @@ class OpenGLApi private constructor() {
     external fun glGetIntegerv(pname: Int): Int
 
     companion object {
-        private lateinit var instance: OpenGLApi
-        fun get(): OpenGLApi {
-            if (!this::instance.isInitialized) {
-                instance = OpenGLApi()
-            }
-            return instance
-        }
+        val instance = OpenGLApi()
     }
 }
\ No newline at end of file

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

@@ -57,7 +57,7 @@ open class SkiaLayer : HardwareLayer() {
         }
 
         skijaState.apply {
-            val gl = OpenGLApi.get()
+            val gl = OpenGLApi.instance
             gl.glClearColor(1.0f, 1.0f, 1.0f, 1.0f)
             gl.glClear(gl.GL_COLOR_BUFFER_BIT)
 
@@ -72,7 +72,7 @@ open class SkiaLayer : HardwareLayer() {
     private fun initSkija() {
         val dpi = contentScale
         skijaState.clear()
-        val gl: OpenGLApi = OpenGLApi.get()
+        val gl: OpenGLApi = OpenGLApi.instance
         val fbId = gl.glGetIntegerv(gl.GL_DRAW_FRAMEBUFFER_BINDING)
         skijaState.renderTarget = BackendRenderTarget.makeGL(
             (width * dpi).toInt(),
@@ -111,8 +111,12 @@ open class SkiaWindow : JFrame() {
             override fun componentResized(e: ComponentEvent) {
                 layer.reinit()
                 layer.setSize(width, height)
-                Engine.get().render(layer)
+                display()
             }
         })
     }
+
+    fun display() {
+        layer.display()
+        }
 }

skiko/src/jvmMain/objectiveC/macos/drawlayer.m

@@ -46,11 +46,14 @@ JavaVM *jvm;
     CGLSetCurrentContext(ctx);
 
     if (self.jvm != NULL) {
+        // TODO: cache wndClass and drawMethod.
         JNIEnv *env;
         (*self.jvm)->AttachCurrentThread(self.jvm, (void **)&env, NULL);
 
-        jclass wndClass = (*env)->GetObjectClass(env, self.windowRef);
-        jmethodID drawMethod = (*env)->GetMethodID(env, wndClass, "draw", "()V");
+        static jclass wndClass = NULL;
+        if (!wndClass) wndClass = (*env)->GetObjectClass(env, self.windowRef);
+        static jmethodID drawMethod = NULL;
+        if (!drawMethod) drawMethod = (*env)->GetMethodID(env, wndClass, "draw", "()V");
         if (NULL == drawMethod) {
             NSLog(@"The method Window.draw() not found!");
             return;