KVO instead of displayLink to fix perfomance problem

Author: Alex009

widgets/src/iosMain/def/objcAddtition.def

@@ -36,3 +36,7 @@ NSURLSessionDataTask* dataTask(NSURLSession* session, NSURL* url, void (^complet
     }
   ];
 }
+
+@protocol KeyValueObserver
+- (void)observeValueForKeyPath:(nullable NSString *)keyPath ofObject:(nullable id)object change:(nullable NSDictionary<NSKeyValueChangeKey, id> *)change context:(nullable void *)context;
+@end

widgets/src/iosMain/kotlin/dev/icerock/moko/widgets/core/factory/ButtonWithIconViewFactory.kt

@@ -20,7 +20,7 @@ import dev.icerock.moko.widgets.core.style.view.WidgetSize
 import dev.icerock.moko.widgets.core.utils.applyStateBackgroundIfNeeded
 import dev.icerock.moko.widgets.core.utils.applyTextStyleIfNeeded
 import dev.icerock.moko.widgets.core.utils.bind
-import dev.icerock.moko.widgets.core.utils.displayLink
+import dev.icerock.moko.widgets.core.utils.onBoundsChanged
 import dev.icerock.moko.widgets.core.utils.setEventHandler
 import dev.icerock.moko.widgets.core.widget.ButtonWidget
 import kotlinx.cinterop.useContents
@@ -141,9 +141,8 @@ actual class ButtonWithIconViewFactory actual constructor(
     }
 
     private fun setupLayoutUpdate(button: UIButton, viewFactory: ButtonWithIconViewFactory) {
-        button.displayLink(
+        button.onBoundsChanged(
             context = viewFactory,
-            objectForSkipCheck = { it.bounds }
         ) { button, viewFactory ->
             val icPadding: Double = viewFactory.iconPadding?.toDouble() ?: 0.0
 

widgets/src/iosMain/kotlin/dev/icerock/moko/widgets/core/utils/BackgroundExt.kt

@@ -98,9 +98,8 @@ fun UIButton.applyStateBackgroundIfNeeded(background: PressableState<Background<
 
     stateLayers.update(this)
 
-    this.displayLink(
+    this.onBoundsChanged(
         context = stateLayers,
-        objectForSkipCheck = { it.layer.bounds }
     ) { button, stateLayers ->
         val (width: CGFloat, height: CGFloat) = button.layer.bounds.useContents {
             this.size.width to this.size.height
@@ -165,9 +164,8 @@ fun UIView.applyBackgroundIfNeeded(background: Background<out Fill>?) {
     val bgLayer: CALayer = background.caLayer()
     layer.insertSublayer(bgLayer, 0U)
 
-    this.displayLink(
+    this.onBoundsChanged(
         context = bgLayer,
-        objectForSkipCheck = { it.layer.bounds }
     ) { view, bgLayer ->
         val (width: CGFloat, height: CGFloat) = view.layer.bounds.useContents {
             this.size.width to this.size.height

widgets/src/iosMain/kotlin/dev/icerock/moko/widgets/core/utils/UIControlExt.kt

@@ -4,12 +4,13 @@
 
 package dev.icerock.moko.widgets.core.utils
 
+import dev.icerock.moko.widgets.objc.KeyValueObserverProtocol
+import kotlinx.cinterop.COpaquePointer
 import kotlinx.cinterop.ObjCAction
 import kotlinx.cinterop.cstr
-import platform.Foundation.NSRunLoop
-import platform.Foundation.NSRunLoopCommonModes
+import platform.Foundation.NSKeyValueObservingOptionNew
 import platform.Foundation.NSSelectorFromString
-import platform.QuartzCore.CADisplayLink
+import platform.Foundation.addObserver
 import platform.UIKit.UIControl
 import platform.UIKit.UIControlEvents
 import platform.UIKit.UIGestureRecognizer
@@ -52,49 +53,51 @@ fun UIGestureRecognizer.setHandler(action: () -> Unit) {
     )
 }
 
-fun <T : Any, CTX> T.displayLink(
+fun <V : UIView, CTX> V.onBoundsChanged(
     context: CTX,
-    objectForSkipCheck: (T) -> Any,
-    action: (T, CTX) -> Unit
+    action: (V, CTX) -> Unit
 ) {
-    val ref: WeakReference<T> = WeakReference(this)
+    val ref: WeakReference<V> = WeakReference(this)
 
-    var displayLink: CADisplayLink? = null
-
-    var oldState: Any = objectForSkipCheck(this)
-    val target = LambdaTarget {
-        val strongRef: T? = ref.get()
-        if (strongRef == null) {
-            displayLink?.removeFromRunLoop(NSRunLoop.currentRunLoop, NSRunLoopCommonModes)
-            displayLink = null
-            return@LambdaTarget
-        }
-
-        val newState: Any = objectForSkipCheck(strongRef)
-        if (newState == oldState) return@LambdaTarget
+    val target = ObserverObject {
+        val strongRef: V = ref.get() ?: return@ObserverObject
 
         action(strongRef, context)
     }
 
-    CADisplayLink.displayLinkWithTarget(
-        target = target,
-        selector = NSSelectorFromString("displayLink:")
-    ).apply {
-        frameInterval = 1
-        addToRunLoop(NSRunLoop.currentRunLoop, NSRunLoopCommonModes)
-    }
+    objc_setAssociatedObject(
+        `object` = this,
+        key = "onBoundsChanged".cstr,
+        value = target,
+        policy = OBJC_ASSOCIATION_RETAIN
+    )
+
+    this.addObserver(
+        observer = target,
+        forKeyPath = "bounds",
+        options = NSKeyValueObservingOptionNew,
+        context = null
+    )
 }
 
-class LambdaTarget(val lambda: () -> Unit) : NSObject() {
+private class ObserverObject(
+    private val lambda: () -> Unit
+) : NSObject(), KeyValueObserverProtocol {
 
-    @ObjCAction
-    fun action() {
+    override fun observeValueForKeyPath(
+        keyPath: String?,
+        ofObject: Any?,
+        change: Map<Any?, *>?,
+        context: COpaquePointer?
+    ) {
         lambda()
     }
+}
+
+class LambdaTarget(val lambda: () -> Unit) : NSObject() {
 
     @ObjCAction
-    @Suppress("UnusedPrivateMember")
-    fun displayLink(link: CADisplayLink) {
+    fun action() {
         lambda()
     }
 }