Refactoring pass for iOS counterpart of Skiko (#781)

* Refactor SkikoUIView and Metal interaction

* Move load logic to init

* Remove dead code

* Use contentScaleFactor for calculating drawable size

* Move UITouch.isPressed to filescope

* Add trace logs for anomaly situations

skiko/src/iosMain/kotlin/org/jetbrains/skiko/SkiaLayer.ios.kt

@@ -3,45 +3,30 @@ package org.jetbrains.skiko
 import kotlinx.cinterop.useContents
 import org.jetbrains.skia.Canvas
 import org.jetbrains.skia.PixelGeometry
-import org.jetbrains.skiko.context.MetalContextHandler
-import org.jetbrains.skiko.redrawer.MetalRedrawer
+import org.jetbrains.skia.Surface
 import platform.UIKit.*
 import kotlin.system.getTimeNanos
-import org.jetbrains.skia.*
 
 actual open class SkiaLayer {
-
-    fun isShowing(): Boolean {
-        return true
-    }
-
-    fun showScreenKeyboard() {
-        view?.becomeFirstResponder()
-    }
-
-    fun hideScreenKeyboard() { view?.resignFirstResponder() }
-
-    fun isScreenKeyboardOpen(): Boolean {
-        return if (view == null) false else view!!.isFirstResponder
-    }
+    internal var needRedrawCallback: () -> Unit = {}
 
     actual var renderApi: GraphicsApi
         get() = GraphicsApi.METAL
-        set(value) { throw UnsupportedOperationException() }
+        set(_) { throw UnsupportedOperationException() }
 
     actual val contentScale: Float
         get() = view!!.contentScaleFactor.toFloat()
 
     actual var fullscreen: Boolean
         get() = true
-        set(value) { throw UnsupportedOperationException() }
+        set(_) { throw UnsupportedOperationException() }
 
     actual var transparency: Boolean
         get() = false
-        set(value) { throw UnsupportedOperationException() }
+        set(_) { throw UnsupportedOperationException() }
 
     actual fun needRedraw() {
-        redrawer?.needRedraw()
+        needRedrawCallback.invoke()
     }
 
     actual val component: Any?
@@ -57,56 +42,24 @@ actual open class SkiaLayer {
             return@useContents size.height.toFloat()
         }
 
-    internal var view: UIView? = null
-    // We need to keep reference to gesturesDetector as Objective-C will only keep weak reference here.
-    internal var gesturesDetector = SkikoGesturesDetector(this)
-    var gesturesToListen: Array<SkikoGestureEventKind>? = null
-        set(value) {
-            field = value
-            initGestures()
-        }
-
-    internal fun initGestures() {
-        gesturesDetector.setGesturesToListen(gesturesToListen)
-    }
+    internal var view: SkikoUIView? = null
 
     actual fun attachTo(container: Any) {
-        attachTo(container as UIView)
+        view = container as SkikoUIView
     }
 
-    fun attachTo(view: UIView) {
-        this.view = view
-        contextHandler = MetalContextHandler(this)
-        // TODO: maybe add observer for view.viewDidDisappear() to detach us?
-        redrawer = MetalRedrawer(this).apply {
-            needRedraw()
-        }
-    }
-
-    private var isDisposed = false
     actual fun detach() {
-        if (!isDisposed) {
-            redrawer?.dispose()
-            redrawer = null
-            contextHandler?.dispose()
-            contextHandler = null
-            isDisposed = true
-        }
+        view?.detach()
     }
-    actual var skikoView: SkikoView? = null
 
-    internal var redrawer: MetalRedrawer? = null
-    private var contextHandler: MetalContextHandler? = null
+    actual var skikoView: SkikoView? = null
 
     internal actual fun draw(canvas: Canvas) {
-        check(!isDisposed) { "SkiaLayer is disposed" }
-        val (w, h) = view!!.frame.useContents {
-            size.width to size.height
-        }
-        val pictureWidth = (w.toFloat() * contentScale).coerceAtLeast(0.0F)
-        val pictureHeight = (h.toFloat() * contentScale).coerceAtLeast(0.0F)
+        throw UnsupportedOperationException("Don't call it, artifact of wrong abstraction")
+    }
 
-        skikoView?.onRender(canvas, pictureWidth.toInt(), pictureHeight.toInt(), getTimeNanos())
+    internal fun draw(surface: Surface) {
+        skikoView?.onRender(surface.canvas, surface.width, surface.height, getTimeNanos())
     }
 
     actual val pixelGeometry: PixelGeometry

skiko/src/iosMain/kotlin/org/jetbrains/skiko/SkikoGesturesDetector.ios.kt

-package org.jetbrains.skiko
-
-import kotlinx.cinterop.ObjCAction
-import kotlinx.cinterop.useContents
-import platform.darwin.NSObject
-import platform.Foundation.NSSelectorFromString
-import platform.UIKit.*
-
-// See https://developer.apple.com/documentation/uikit/touches_presses_and_gestures/using_responders_and_the_responder_chain_to_handle_events?language=objc
-internal class SkikoGesturesDetector(
-    private val layer: SkiaLayer
-) : NSObject() {
-
-    val view: UIView?
-        get() = layer.view
-
-    @ObjCAction
-    fun onTap(sender: UITapGestureRecognizer) {
-        val (x, y) = sender.locationInView(view).useContents { x to y }
-        layer.skikoView?.onGestureEvent(
-            SkikoGestureEvent(
-                x = x,
-                y = y,
-                kind = SkikoGestureEventKind.TAP,
-                state = toSkikoGestureState(sender.state)
-            )
-        )
-    }
-    @ObjCAction
-    fun onDoubleTap(sender: UITapGestureRecognizer) {
-        val (x, y) = sender.locationInView(view).useContents { x to y }
-        layer.skikoView?.onGestureEvent(
-            SkikoGestureEvent(
-                x = x,
-                y = y,
-                kind = SkikoGestureEventKind.DOUBLETAP,
-                state = toSkikoGestureState(sender.state)
-            )
-        )
-    }
-    @ObjCAction
-    fun onLongPress(sender: UILongPressGestureRecognizer) {
-        val (x, y) = sender.locationInView(view).useContents { x to y }
-        layer.skikoView?.onGestureEvent(
-            SkikoGestureEvent(
-                x = x,
-                y = y,
-                kind = SkikoGestureEventKind.LONGPRESS,
-                state = toSkikoGestureState(sender.state)
-            )
-        )
-    }
-    @ObjCAction
-    fun onPinch(sender: UIPinchGestureRecognizer) {
-        val (x, y) = sender.locationInView(view).useContents { x to y }
-        layer.skikoView?.onGestureEvent(
-            SkikoGestureEvent(
-                x = x,
-                y = y,
-                kind = SkikoGestureEventKind.PINCH,
-                scale = sender.scale,
-                velocity = sender.velocity,
-                state = toSkikoGestureState(sender.state)
-            )
-        )
-    }
-    @ObjCAction
-    fun onRotation(sender: UIRotationGestureRecognizer) {
-        val (x, y) = sender.locationInView(view).useContents { x to y }
-        layer.skikoView?.onGestureEvent(
-            SkikoGestureEvent(
-                x = x,
-                y = y,
-                kind = SkikoGestureEventKind.ROTATION,
-                rotation = sender.rotation,
-                velocity = sender.velocity,
-                state = toSkikoGestureState(sender.state)
-            )
-        )
-    }
-    @ObjCAction
-    fun onSwipe(sender: UISwipeGestureRecognizer) {
-        val (x, y) = sender.locationInView(view).useContents { x to y }
-        layer.skikoView?.onGestureEvent(
-            SkikoGestureEvent(
-                x = x,
-                y = y,
-                kind = SkikoGestureEventKind.SWIPE,
-                direction = toSkikoGestureDirection(sender.direction),
-                state = toSkikoGestureState(sender.state)
-            )
-        )
-    }
-    @ObjCAction
-    fun onPan(sender: UIPanGestureRecognizer) {
-        val (x, y) = sender.locationInView(view).useContents { x to y }
-        layer.skikoView?.onGestureEvent(
-            SkikoGestureEvent(
-                x = x,
-                y = y,
-                kind = SkikoGestureEventKind.PAN,
-                state = toSkikoGestureState(sender.state)
-            )
-        )
-    }
-
-    // We have ':' in selector to take care of function argument.
-    private val gestureRecognizers = hashMapOf(
-        SkikoGestureEventKind.TAP to UITapGestureRecognizer(this, NSSelectorFromString("onTap:")),
-        SkikoGestureEventKind.DOUBLETAP to UITapGestureRecognizer(this, NSSelectorFromString("onDoubleTap:")).apply {
-            numberOfTapsRequired = 2.toULong()
-        },
-        SkikoGestureEventKind.LONGPRESS to UILongPressGestureRecognizer(this, NSSelectorFromString("onLongPress:")),
-        SkikoGestureEventKind.PINCH to UIPinchGestureRecognizer(this, NSSelectorFromString("onPinch:")),
-        SkikoGestureEventKind.ROTATION to UIRotationGestureRecognizer(this, NSSelectorFromString("onRotation:")),
-        SkikoGestureEventKind.SWIPE to UISwipeGestureRecognizer(this, NSSelectorFromString("onSwipe:")),
-        SkikoGestureEventKind.PAN to UIPanGestureRecognizer(this, NSSelectorFromString("onPan:"))
-    )
-
-    fun setGesturesToListen(gestures: Array<SkikoGestureEventKind>?) {
-        clearGesturesToListen()
-        if (!gestures.isNullOrEmpty()) {
-            for (gesture in gestures) {
-                if (gestureRecognizers.containsKey(gesture)) {
-                    view?.addGestureRecognizer(gestureRecognizers.get(gesture)!!)
-                }
-            }
-        }
-    }
-
-    private fun clearGesturesToListen() {
-        for ((key, value) in gestureRecognizers) {
-            view?.removeGestureRecognizer(value)
-        }
-    }
-}

skiko/src/iosMain/kotlin/org/jetbrains/skiko/SkikoUIView.kt

@@ -4,8 +4,13 @@ import kotlinx.cinterop.*
 import org.jetbrains.skia.Point
 import org.jetbrains.skia.Rect
 import org.jetbrains.skiko.ios.SkikoUITextInputTraits
+import org.jetbrains.skiko.redrawer.MetalRedrawer
 import platform.CoreGraphics.*
 import platform.Foundation.*
+import platform.Metal.MTLCreateSystemDefaultDevice
+import platform.Metal.MTLDeviceProtocol
+import platform.Metal.MTLPixelFormatBGRA8Unorm
+import platform.QuartzCore.CAMetalLayer
 import platform.UIKit.*
 import platform.darwin.NSInteger
 import kotlin.math.max
@@ -18,40 +23,83 @@ import kotlin.math.min
 @Suppress("CONFLICTING_OVERLOADS")
 @ExportObjCClass
 class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
-    @OverrideInit
-    constructor(frame: CValue<CGRect>) : super(frame)
+    companion object : UIViewMeta() {
+        override fun layerClass() = CAMetalLayer
+    }
 
+    @Suppress("UNUSED") // required by Objective-C runtime
     @OverrideInit
-    constructor(coder: NSCoder) : super(coder)
-
-    init {
-        multipleTouchEnabled = true
+    constructor(coder: NSCoder) : super(coder) {
+        throw UnsupportedOperationException("init(coder: NSCoder) is not supported for SkikoUIView")
     }
 
-    private var skiaLayer: SkiaLayer? = null
+    private val _device: MTLDeviceProtocol =
+        MTLCreateSystemDefaultDevice() ?: throw IllegalStateException("Metal is not supported on this system")
+    private val _metalLayer: CAMetalLayer get() = layer as CAMetalLayer
+    private var _skiaLayer: SkiaLayer? = null
     private var _pointInside: (Point, UIEvent?) -> Boolean = { _, _ -> true }
     private var _skikoUITextInputTrains: SkikoUITextInputTraits = object : SkikoUITextInputTraits {}
     private var _inputDelegate: UITextInputDelegateProtocol? = null
     private var _currentTextMenuActions: TextActions? = null
+    private lateinit var _redrawer: MetalRedrawer
+
+    /*
+     * When there at least one tracked touch, we need notify redrawer about it. It should schedule CADisplayLink which
+     * affects frequency of polling UITouch events on high frequency display and forces it to match display refresh rate.
+     */
+    private var _touchesCount = 0
+        set(value) {
+            field = value
+
+            val needHighFrequencyPolling = value > 0
+
+            _redrawer.needsProactiveDisplayLink = needHighFrequencyPolling
+        }
+
+    init {
+        multipleTouchEnabled = true
+        opaque = false // For UIKit interop through a "Hole"
+
+        _metalLayer.also {
+            // Workaround for KN compiler bug
+            // Type mismatch: inferred type is platform.Metal.MTLDeviceProtocol but objcnames.protocols.MTLDeviceProtocol? was expected
+            @Suppress("USELESS_CAST")
+            it.device = _device as objcnames.protocols.MTLDeviceProtocol?
+
+            it.pixelFormat = MTLPixelFormatBGRA8Unorm
+            doubleArrayOf(0.0, 0.0, 0.0, 0.0).usePinned { pinned ->
+                it.backgroundColor = CGColorCreate(CGColorSpaceCreateDeviceRGB(), pinned.addressOf(0))
+            }
+            it.framebufferOnly = false
+        }
+    }
 
     // merging two constructors might cause a binary incompatibility, which will result in a unclear linking error,
     // if a project using newer compose depends on an older compose transitively
     // https://youtrack.jetbrains.com/issue/KT-60399
+    @Suppress("UNUSED") // public API
     constructor(
         skiaLayer: SkiaLayer,
         frame: CValue<CGRect> = CGRectNull.readValue(),
-        pointInside: (Point, UIEvent?) -> Boolean = {_,_-> true }
+        pointInside: (Point, UIEvent?) -> Boolean = { _, _ -> true }
     ) : this(skiaLayer, frame, pointInside, skikoUITextInputTrains = object : SkikoUITextInputTraits {})
 
     constructor(
         skiaLayer: SkiaLayer,
         frame: CValue<CGRect> = CGRectNull.readValue(),
-        pointInside: (Point, UIEvent?) -> Boolean = {_,_-> true },
+        pointInside: (Point, UIEvent?) -> Boolean = { _, _ -> true },
         skikoUITextInputTrains: SkikoUITextInputTraits
     ) : super(frame) {
-        this.skiaLayer = skiaLayer
+        _skiaLayer = skiaLayer
         _pointInside = pointInside
         _skikoUITextInputTrains = skikoUITextInputTrains
+
+        _redrawer = MetalRedrawer(_metalLayer) { surface ->
+            skiaLayer.draw(surface)
+        }
+
+        skiaLayer.needRedrawCallback = _redrawer::needRedraw
+        skiaLayer.view = this
     }
 
     /**
@@ -88,7 +136,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
         menu.hideMenu()
     }
 
-    fun isTextMenuShown():Boolean {
+    fun isTextMenuShown(): Boolean {
         return _currentTextMenuActions != null
     }
 
@@ -108,20 +156,32 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
         _currentTextMenuActions?.selectAll?.invoke()
     }
 
-    fun detach() = skiaLayer?.detach()
+    internal fun detach() {
+        _redrawer.dispose()
+    }
 
     fun load(): SkikoUIView {
-        val (width, height) = UIScreen.mainScreen.bounds.useContents {
-            this.size.width to this.size.height
+        // TODO: redundant, remove in next refactor pass
+        return this
+    }
+
+    override fun didMoveToWindow() {
+        super.didMoveToWindow()
+
+        window?.screen?.let {
+            contentScaleFactor = it.scale
+            _redrawer.maximumFramesPerSecond = it.maximumFramesPerSecond
         }
-        setFrame(CGRectMake(0.0, 0.0, width, height))
-        contentScaleFactor = UIScreen.mainScreen.scale
-        skiaLayer?.let { layer ->
-            layer.attachTo(this)
-            layer.initGestures()
+    }
+
+    override fun layoutSubviews() {
+        super.layoutSubviews()
+
+        val scaledSize = bounds.useContents {
+            CGSizeMake(size.width * contentScaleFactor, size.height * contentScaleFactor)
         }
 
-        return this
+        _metalLayer.drawableSize = scaledSize
     }
 
     fun showScreenKeyboard() = becomeFirstResponder()
@@ -133,7 +193,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * https://developer.apple.com/documentation/uikit/uikeyinput/1614457-hastext
      */
     override fun hasText(): Boolean {
-        return skiaLayer?.skikoView?.input?.hasText() ?: false
+        return _skiaLayer?.skikoView?.input?.hasText() ?: false
     }
 
     /**
@@ -143,7 +203,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * @param text A string object representing the character typed on the system keyboard.
      */
     override fun insertText(text: String) {
-        skiaLayer?.skikoView?.input?.insertText(text)
+        _skiaLayer?.skikoView?.input?.insertText(text)
     }
 
     /**
@@ -152,7 +212,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * https://developer.apple.com/documentation/uikit/uikeyinput/1614572-deletebackward
      */
     override fun deleteBackward() {
-        skiaLayer?.skikoView?.input?.deleteBackward()
+        _skiaLayer?.skikoView?.input?.deleteBackward()
     }
 
     override fun canBecomeFirstResponder() = true
@@ -162,7 +222,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
             for (press in withEvent.allPresses) {
                 val uiPress = press as? UIPress
                 if (uiPress != null) {
-                    skiaLayer?.skikoView?.onKeyboardEvent(
+                    _skiaLayer?.skikoView?.onKeyboardEvent(
                         toSkikoKeyboardEvent(press, SkikoKeyboardEventKind.DOWN)
                     )
                 }
@@ -176,7 +236,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
             for (press in withEvent.allPresses) {
                 val uiPress = press as? UIPress
                 if (uiPress != null) {
-                    skiaLayer?.skikoView?.onKeyboardEvent(
+                    _skiaLayer?.skikoView?.onKeyboardEvent(
                         toSkikoKeyboardEvent(press, SkikoKeyboardEventKind.UP)
                     )
                 }
@@ -193,23 +253,10 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
         return _pointInside(skiaPoint, withEvent)
     }
 
-    /*
-     * When there at least one tracked touch, we need notify redrawer about it. It should schedule CADisplayLink which
-     * affects frequency of polling UITouch events on high frequency display and forces it to match display refresh rate.
-     */
-    private var touchesCount = 0
-        set(value) {
-            field = value
-
-            val needHighFrequencyPolling = value > 0
-
-            skiaLayer?.redrawer?.needsProactiveDisplayLink = needHighFrequencyPolling
-        }
-
     override fun touchesBegan(touches: Set<*>, withEvent: UIEvent?) {
         super.touchesBegan(touches, withEvent)
 
-        touchesCount += touches.size
+        _touchesCount += touches.size
 
         sendTouchEventToSkikoView(withEvent!!, SkikoPointerEventKind.DOWN)
     }
@@ -217,7 +264,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
     override fun touchesEnded(touches: Set<*>, withEvent: UIEvent?) {
         super.touchesEnded(touches, withEvent)
 
-        touchesCount -= touches.size
+        _touchesCount -= touches.size
 
         sendTouchEventToSkikoView(withEvent!!, SkikoPointerEventKind.UP)
     }
@@ -230,7 +277,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
     override fun touchesCancelled(touches: Set<*>, withEvent: UIEvent?) {
         super.touchesCancelled(touches, withEvent)
 
-        touchesCount -= touches.size
+        _touchesCount -= touches.size
 
         sendTouchEventToSkikoView(withEvent!!, SkikoPointerEventKind.UP)
     }
@@ -249,7 +296,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
             )
         }
 
-        skiaLayer?.skikoView?.onPointerEvent(
+        _skiaLayer?.skikoView?.onPointerEvent(
             SkikoPointerEvent(
                 x = pointers.centroidX,
                 y = pointers.centroidY,
@@ -261,10 +308,6 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
         )
     }
 
-    private val UITouch.isPressed get() =
-        phase != UITouchPhase.UITouchPhaseEnded &&
-            phase != UITouchPhase.UITouchPhaseCancelled
-
     override fun inputDelegate(): UITextInputDelegateProtocol? {
         return _inputDelegate
     }
@@ -280,7 +323,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * @return A substring of a document that falls within the specified range.
      */
     override fun textInRange(range: UITextRange): String? {
-        return skiaLayer?.skikoView?.input?.textInRange(range.toIntRange())
+        return _skiaLayer?.skikoView?.input?.textInRange(range.toIntRange())
     }
 
     /**
@@ -290,11 +333,11 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * @param withText A string to replace the text in range.
      */
     override fun replaceRange(range: UITextRange, withText: String) {
-        skiaLayer?.skikoView?.input?.replaceRange(range.toIntRange(), withText)
+        _skiaLayer?.skikoView?.input?.replaceRange(range.toIntRange(), withText)
     }
 
     override fun setSelectedTextRange(selectedTextRange: UITextRange?) {
-        skiaLayer?.skikoView?.input?.setSelectedTextRange(selectedTextRange?.toIntRange())
+        _skiaLayer?.skikoView?.input?.setSelectedTextRange(selectedTextRange?.toIntRange())
     }
 
     /**
@@ -305,7 +348,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * https://developer.apple.com/documentation/uikit/uitextinput/1614541-selectedtextrange
      */
     override fun selectedTextRange(): UITextRange? {
-        return skiaLayer?.skikoView?.input?.getSelectedTextRange()?.toUITextRange()
+        return _skiaLayer?.skikoView?.input?.getSelectedTextRange()?.toUITextRange()
     }
 
     /**
@@ -317,7 +360,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * https://developer.apple.com/documentation/uikit/uitextinput/1614489-markedtextrange
      */
     override fun markedTextRange(): UITextRange? {
-        return skiaLayer?.skikoView?.input?.markedTextRange()?.toUITextRange()
+        return _skiaLayer?.skikoView?.input?.markedTextRange()?.toUITextRange()
     }
 
     override fun setMarkedTextStyle(markedTextStyle: Map<Any?, *>?) {
@@ -342,7 +385,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
             location.toInt() to length.toInt()
         }
         val relativeTextRange = locationRelative until locationRelative + lengthRelative
-        skiaLayer?.skikoView?.input?.setMarkedText(markedText, relativeTextRange)
+        _skiaLayer?.skikoView?.input?.setMarkedText(markedText, relativeTextRange)
     }
 
     /**
@@ -351,7 +394,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * https://developer.apple.com/documentation/uikit/uitextinput/1614512-unmarktext
      */
     override fun unmarkText() {
-        skiaLayer?.skikoView?.input?.unmarkText()
+        _skiaLayer?.skikoView?.input?.unmarkText()
     }
 
     override fun beginningOfDocument(): UITextPosition {
@@ -363,7 +406,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      * https://developer.apple.com/documentation/uikit/uitextinput/1614555-endofdocument
      */
     override fun endOfDocument(): UITextPosition {
-        return IntermediateTextPosition(skiaLayer?.skikoView?.input?.endOfDocument() ?: 0)
+        return IntermediateTextPosition(_skiaLayer?.skikoView?.input?.endOfDocument() ?: 0)
     }
 
     /**
@@ -383,7 +426,7 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
      */
     override fun positionFromPosition(position: UITextPosition, offset: NSInteger): UITextPosition? {
         val p = (position as? IntermediateTextPosition)?.position ?: return null
-        val endOfDocument = skiaLayer?.skikoView?.input?.endOfDocument()
+        val endOfDocument = _skiaLayer?.skikoView?.input?.endOfDocument()
         return if (endOfDocument != null) {
             IntermediateTextPosition(max(min(p + offset, endOfDocument), 0))
         } else {
@@ -485,12 +528,16 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
         when (action) {
             NSSelectorFromString(UIResponderStandardEditActionsProtocol::copy.name + ":") ->
                 _currentTextMenuActions?.copy != null
+
             NSSelectorFromString(UIResponderStandardEditActionsProtocol::cut.name + ":") ->
                 _currentTextMenuActions?.cut != null
+
             NSSelectorFromString(UIResponderStandardEditActionsProtocol::paste.name + ":") ->
                 _currentTextMenuActions?.paste != null
+
             NSSelectorFromString(UIResponderStandardEditActionsProtocol::selectAll.name + ":") ->
                 _currentTextMenuActions?.selectAll != null
+
             else -> false
         }
 
@@ -500,7 +547,9 @@ class SkikoUIView : UIView, UIKeyInputProtocol, UITextInputProtocol {
     override fun textContentType(): UITextContentType? = _skikoUITextInputTrains.textContentType()
     override fun isSecureTextEntry(): Boolean = _skikoUITextInputTrains.isSecureTextEntry()
     override fun enablesReturnKeyAutomatically(): Boolean = _skikoUITextInputTrains.enablesReturnKeyAutomatically()
-    override fun autocapitalizationType(): UITextAutocapitalizationType = _skikoUITextInputTrains.autocapitalizationType()
+    override fun autocapitalizationType(): UITextAutocapitalizationType =
+        _skikoUITextInputTrains.autocapitalizationType()
+
     override fun autocorrectionType(): UITextAutocorrectionType = _skikoUITextInputTrains.autocorrectionType()
 
     override fun dictationRecognitionFailed() {
@@ -574,3 +623,8 @@ private fun NSWritingDirection.directionToStr() =
         UITextLayoutDirectionDown -> "Down"
         else -> "unknown direction"
     }
+
+private val UITouch.isPressed
+    get() =
+        phase != UITouchPhase.UITouchPhaseEnded &&
+                phase != UITouchPhase.UITouchPhaseCancelled

skiko/src/iosMain/kotlin/org/jetbrains/skiko/SkikoViewController.kt

-package org.jetbrains.skiko
-
-import kotlinx.cinterop.*
-import platform.Foundation.*
-import platform.UIKit.*
-
-@ExportObjCClass
-class SkikoViewController : UIViewController {
-    @OverrideInit
-    constructor() : super(nibName = null, bundle = null)
-    @OverrideInit
-    constructor(coder: NSCoder) : super(coder)
-
-    constructor(skikoUIView: SkikoUIView) : this() {
-        this.skikoUIView = skikoUIView
-    }
-
-    private var skikoUIView: SkikoUIView? = null
-
-    override fun loadView() {
-        if (skikoUIView == null) {
-            super.loadView()
-        } else {
-            this.view = skikoUIView!!.load()
-        }
-    }
-
-    override fun viewDidLoad() {
-        super.viewDidLoad()
-        skikoUIView?.showScreenKeyboard()
-    }
-
-    // viewDidUnload() is deprecated and not called.
-    override fun viewDidDisappear(animated: Boolean) {
-        skikoUIView?.detach()
-    }
-}

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

-package org.jetbrains.skiko.context
-
-import kotlinx.cinterop.useContents
-import org.jetbrains.skia.*
-import org.jetbrains.skiko.RenderException
-import org.jetbrains.skiko.SkiaLayer
-import org.jetbrains.skiko.redrawer.MetalRedrawer
-
-internal class MetalContextHandler(layer: SkiaLayer) : ContextHandler(layer, layer::draw) {
-    val metalRedrawer: MetalRedrawer
-        get() = layer.redrawer!!
-
-    override fun initContext(): Boolean {
-        try {
-            if (context == null) {
-                context = metalRedrawer.makeContext()
-            }
-        } catch (e: Exception) {
-            println("${e.message}\nFailed to create Skia Metal context!")
-            return false
-        }
-        return true
-    }
-
-    private var currentWidth = 0
-    private var currentHeight = 0
-    private fun isSizeChanged(width: Int, height: Int): Boolean {
-        if (width != currentWidth || height != currentHeight) {
-            currentWidth = width
-            currentHeight = height
-            return true
-        }
-        return false
-    }
-
-    override fun initCanvas() {
-        disposeCanvas()
-        val scale = layer.contentScale
-        val (w, h) = layer.view!!.frame.useContents {
-            (size.width * scale).toInt().coerceAtLeast(0) to (size.height * scale).toInt().coerceAtLeast(0)
-        }
-
-        if (isSizeChanged(w, h)) {
-            metalRedrawer.syncSize()
-        }
-
-        if (w > 0 && h > 0) {
-            renderTarget = metalRedrawer.makeRenderTarget(w, h)
-
-            surface = Surface.makeFromBackendRenderTarget(
-                context!!,
-                renderTarget!!,
-                SurfaceOrigin.TOP_LEFT,
-                SurfaceColorFormat.BGRA_8888,
-                ColorSpace.sRGB,
-                SurfaceProps(pixelGeometry = layer.pixelGeometry)
-            ) ?: throw RenderException("Cannot create surface")
-
-            canvas = surface!!.canvas
-        } else {
-            renderTarget = null
-            surface = null
-            canvas = null
-        }
-    }
-
-    override fun flush() {
-        // TODO: maybe make flush async as in JVM version.
-        super.flush()
-        surface?.flushAndSubmit()
-        metalRedrawer.finishFrame()
-    }
-
-   override fun rendererInfo(): String {
-        return "Native Metal: device ${metalRedrawer.device.name}"
-    }
-}
-

skiko/src/iosMain/kotlin/org/jetbrains/skiko/redrawer/MetalRedrawer.ios.kt

 package org.jetbrains.skiko.redrawer
 
 import kotlinx.cinterop.*
-import org.jetbrains.skia.BackendRenderTarget
-import org.jetbrains.skia.DirectContext
-import org.jetbrains.skiko.SkiaLayer
-import org.jetbrains.skiko.context.ContextHandler
-import org.jetbrains.skiko.context.MetalContextHandler
-import platform.CoreGraphics.CGColorCreate
-import platform.CoreGraphics.CGColorSpaceCreateDeviceRGB
-import platform.CoreGraphics.CGContextRef
-import platform.CoreGraphics.CGSizeMake
+import org.jetbrains.skia.*
+import org.jetbrains.skiko.Logger
 import platform.Foundation.NSRunLoop
 import platform.Foundation.NSSelectorFromString
-import platform.Metal.MTLCreateSystemDefaultDevice
-import platform.Metal.MTLDeviceProtocol
-import platform.Metal.MTLPixelFormatBGRA8Unorm
 import platform.QuartzCore.*
 import platform.darwin.*
+import kotlin.math.roundToInt
 
 internal class MetalRedrawer(
-    private val layer: SkiaLayer
-) : Redrawer {
-    private val contextHandler = MetalContextHandler(layer)
-    override val renderInfo: String get() = contextHandler.rendererInfo()
-
+    private val metalLayer: CAMetalLayer,
+    private val drawIntoSurfaceCallback: (Surface) -> Unit
+) {
     private var isDisposed = false
-    internal val device = MTLCreateSystemDefaultDevice() ?: throw IllegalStateException("Metal is not supported on this system")
+
+    // Workaround for KN compiler bug
+    // Type mismatch: inferred type is objcnames.protocols.MTLDeviceProtocol but platform.Metal.MTLDeviceProtocol was expected
+    @Suppress("USELESS_CAST")
+    private val device = metalLayer.device as platform.Metal.MTLDeviceProtocol?
+        ?: throw IllegalStateException("CAMetalLayer.device can not be null")
     private val queue = device.newCommandQueue() ?: throw IllegalStateException("Couldn't create Metal command queue")
-    private var currentDrawable: CAMetalDrawableProtocol? = null
-    private val metalLayer = MetalLayer()
+    private val context = DirectContext.makeMetal(device.objcPtr(), queue.objcPtr())
 
     // Semaphore for preventing command buffers count more than swapchain size to be scheduled/executed at the same time
     private val inflightSemaphore = dispatch_semaphore_create(metalLayer.maximumDrawableCount.toLong())
 
+    var maximumFramesPerSecond: NSInteger
+        get() = caDisplayLink.preferredFramesPerSecond
+        set(value) {
+            caDisplayLink.preferredFramesPerSecond = value
+        }
+
     /*
      * Indicates that scene is invalidated and next display link callback will draw
      */
@@ -55,7 +54,7 @@ internal class MetalRedrawer(
         if (hasScheduledDrawOnNextVSync) {
             hasScheduledDrawOnNextVSync = false
 
-            drawIfLayerIsShowing()
+            draw()
         }
 
         if (!needsProactiveDisplayLink) {
@@ -67,47 +66,20 @@ internal class MetalRedrawer(
         target = frameListener,
         selector = NSSelectorFromString(FrameTickListener::onDisplayLinkTick.name)
     )
+
     init {
-        metalLayer.init(this.layer, contextHandler, device)
         caDisplayLink.setPaused(true)
         caDisplayLink.addToRunLoop(NSRunLoop.mainRunLoop, NSRunLoop.mainRunLoop.currentMode)
     }
 
-    fun makeContext() = DirectContext.makeMetal(device.objcPtr(), queue.objcPtr())
-
-    fun makeRenderTarget(width: Int, height: Int): BackendRenderTarget {
-        // If more than swapchain size count of command buffers are inflight
-        // wait until one finishes work
-        dispatch_semaphore_wait(inflightSemaphore, DISPATCH_TIME_FOREVER)
-        currentDrawable = metalLayer.nextDrawable()!!
-        return BackendRenderTarget.makeMetal(width, height, currentDrawable!!.texture.objcPtr())
-    }
-
-    override fun dispose() {
+    internal fun dispose() {
         if (!isDisposed) {
             caDisplayLink.invalidate()
-            contextHandler.dispose()
-            metalLayer.dispose()
             isDisposed = true
         }
     }
 
-    override fun syncSize() {
-        metalLayer.contentsScale = layer.contentScale.toDouble()
-        val osView = layer.view!!
-        val (w, h) = osView.frame.useContents {
-            size.width to size.height
-        }
-        metalLayer.frame = osView.frame
-        metalLayer.init(layer, contextHandler, device)
-        metalLayer.drawableSize = CGSizeMake(w * metalLayer.contentsScale, h * metalLayer.contentsScale)
-
-        osView.window?.screen?.maximumFramesPerSecond?.let {
-            caDisplayLink.preferredFramesPerSecond = it
-        }
-    }
-
-    override fun needRedraw() {
+    internal fun needRedraw() {
         check(!isDisposed) { "MetalRedrawer is disposed" }
 
         hasScheduledDrawOnNextVSync = true
@@ -116,86 +88,66 @@ internal class MetalRedrawer(
         caDisplayLink.setPaused(false)
     }
 
-    override fun redrawImmediately() {
-        // TODO: separate iOS MetalRedrawer from Redrawer, it's a false abstraction, iOS only uses MetalRedrawer explicitly
-        throw UnsupportedOperationException("This should never be called on iOS")
-    }
-
-    private fun drawIfLayerIsShowing() {
-        if (layer.isShowing()) {
-            draw()
-        }
-    }
-
     private fun draw() {
-        // TODO: maybe make flush async as in JVM version.
-        autoreleasepool { //todo measure performance without autoreleasepool
-            if (!isDisposed) {
-                contextHandler.draw()
-            }
+        if (isDisposed) {
+            return
         }
-    }
 
-    fun finishFrame() {
         autoreleasepool {
-            currentDrawable?.let {
-                val commandBuffer = queue.commandBuffer()!!
-                commandBuffer.label = "Present"
-                commandBuffer.presentDrawable(it)
-                commandBuffer.addCompletedHandler {
-                    // Signal work finish, allow a new command buffer to be scheduled
-                    dispatch_semaphore_signal(inflightSemaphore)
-                }
-                commandBuffer.commit()
-                currentDrawable = null
+            val (width, height) = metalLayer.drawableSize.useContents {
+                width.roundToInt() to height.roundToInt()
             }
-        }
-    }
-}
 
-internal class MetalLayer : CAMetalLayer {
-    private lateinit var skiaLayer: SkiaLayer
-    private lateinit var contextHandler: ContextHandler
-
-    @OverrideInit
-    constructor() : super()
-
-    @OverrideInit
-    constructor(layer: Any) : super(layer)
-
-    fun init(
-        skiaLayer: SkiaLayer,
-        contextHandler: ContextHandler,
-        theDevice: MTLDeviceProtocol
-    ) {
-        this.skiaLayer = skiaLayer
-        this.contextHandler = contextHandler
-        this.setNeedsDisplayOnBoundsChange(true)
-        this.removeAllAnimations()
-        // TODO: looks like a bug in K/N interop.
-        this.device = theDevice as objcnames.protocols.MTLDeviceProtocol?
-        this.pixelFormat = MTLPixelFormatBGRA8Unorm
-        this.contentsGravity = kCAGravityTopLeft
-        doubleArrayOf(0.0, 0.0, 0.0, 0.0).usePinned {
-            this.backgroundColor =
-                CGColorCreate(CGColorSpaceCreateDeviceRGB(), it.addressOf(0))
-        }
-        this.framebufferOnly = false
-        this.opaque = false // For UIKit interop through a "Hole"
-        skiaLayer.view?.let {
-            this.frame = it.frame
-            it.layer.addSublayer(this)
-        }
-    }
+            if (width <= 0 || height <= 0) {
+                return@autoreleasepool
+            }
 
-    fun dispose() {
-        this.removeFromSuperlayer()
-        // TODO: anything else to dispose the layer?
-    }
+            dispatch_semaphore_wait(inflightSemaphore, DISPATCH_TIME_FOREVER)
+
+            val metalDrawable = metalLayer.nextDrawable()
+
+            if (metalDrawable == null) {
+                Logger.warn { "'metalLayer.nextDrawable()' returned null. 'metalLayer.allowsNextDrawableTimeout' should be set to false. Skipping the frame." }
+                dispatch_semaphore_signal(inflightSemaphore)
+                return@autoreleasepool
+            }
+
+            val renderTarget = BackendRenderTarget.makeMetal(width, height, metalDrawable.texture.objcPtr())
+
+            val surface = Surface.makeFromBackendRenderTarget(
+                context,
+                renderTarget,
+                SurfaceOrigin.TOP_LEFT,
+                SurfaceColorFormat.BGRA_8888,
+                ColorSpace.sRGB,
+                SurfaceProps(pixelGeometry = PixelGeometry.UNKNOWN)
+            )
+
+            if (surface == null) {
+                Logger.warn { "'Surface.makeFromBackendRenderTarget' returned null. Skipping the frame." }
+                renderTarget.close()
+                // TODO: manually release metalDrawable when K/N API arrives
+                dispatch_semaphore_signal(inflightSemaphore)
+                return@autoreleasepool
+            }
+
+            surface.canvas.clear(Color.WHITE)
+            drawIntoSurfaceCallback(surface)
+            surface.flushAndSubmit()
 
-    override fun drawInContext(ctx: CGContextRef?) {
-        contextHandler.draw()
-        super.drawInContext(ctx)
+            val commandBuffer = queue.commandBuffer()!!
+            commandBuffer.label = "Present"
+            commandBuffer.presentDrawable(metalDrawable)
+            commandBuffer.addCompletedHandler {
+                // Signal work finish, allow a new command buffer to be scheduled
+                dispatch_semaphore_signal(inflightSemaphore)
+            }
+            commandBuffer.commit()
+
+            surface.close()
+            renderTarget.close()
+            // TODO manually release metalDrawable when K/N API arrives
+        }
     }
 }