Move canvas preparation from ContextHandler.draw to SkiaLayer.awt.update()

skiko/src/androidMain/kotlin/org/jetbrains/skiko/SkiaLayer.android.kt

@@ -20,21 +20,6 @@ actual open class SkiaLayer {
             if (value) throw IllegalArgumentException("changing fullscreen is unsupported")
         }
 
-    actual var transparency: Boolean
-        get() = false
-        set(value) {
-            if (value) throw IllegalArgumentException("transparency unsupported")
-        }
-
-    /**
-     * The background color of the layer.
-     */
-    actual internal var backgroundColor: Int = Color.WHITE
-        set(value) {
-            field = value
-            needRender()
-        }
-
     actual var renderDelegate: SkikoRenderDelegate? = null
 
     actual fun attachTo(container: Any) {
@@ -81,8 +66,5 @@ actual open class SkiaLayer {
     actual val component: Any?
         get() = this.container
 
-    actual internal val cutoutRectangles: List<ClipRectangle>
-        get() = emptyList()
-
     internal actual fun draw(canvas: Canvas): Unit = TODO()
 }

skiko/src/awtMain/kotlin/org/jetbrains/skiko/SkiaLayer.awt.kt

@@ -5,6 +5,7 @@ import kotlinx.coroutines.GlobalScope
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.launch
 import org.jetbrains.skia.*
+import org.jetbrains.skiko.context.cutoutFromClip
 import org.jetbrains.skiko.redrawer.Redrawer
 import org.jetbrains.skiko.redrawer.RedrawerManager
 import java.awt.Color
@@ -194,13 +195,20 @@ actual open class SkiaLayer internal constructor(
     }
 
     private var _transparency: Boolean = false
-    actual var transparency: Boolean
+
+    /**
+     * Whether transparency is enabled.
+     */
+    var transparency: Boolean
         get() = _transparency
         set(value) {
             configureBackground(value, _background)
         }
 
-    internal actual var backgroundColor: Int
+    /**
+     * The color, in ARGB format, with which the layer is cleared before rendering.
+     */
+    internal var backgroundColor: Int
         get() = background.rgb  // Will return an ancestor's non-null background after setBackground(null).
         set(value) {
             configureBackground(_transparency, Color(value, true))
@@ -333,11 +341,11 @@ actual open class SkiaLayer internal constructor(
         jComponent.add(this)
     }
 
+    /**
+     * A list of rectangles to cut out from the rendered content; No content will be drawn inside them.
+     */
     val clipComponents = mutableListOf<ClipRectangle>()
 
-    internal actual val cutoutRectangles: List<ClipRectangle>
-        get() = clipComponents
-
     @Volatile
     private var isDisposed = false
 
@@ -603,13 +611,27 @@ actual open class SkiaLayer internal constructor(
         // If this approach will be changed, create an issue in https://youtrack.jetbrains.com/issues/CMP for changing it in
         // https://github.com/JetBrains/compose-multiplatform/blob/e4e2d329709cded91a09cc612d4defbce37aad96/benchmarks/multiplatform/benchmarks/src/commonMain/kotlin/MeasureComposable.kt#L151 as well
 
+        val contentScale = this.contentScale
         val pictureWidth = (backedLayer.width * contentScale).coerceAtLeast(0f)
         val pictureHeight = (backedLayer.height * contentScale).coerceAtLeast(0f)
         val intWidth = pictureWidth.toInt()
         val intHeight = pictureHeight.toInt()
 
         val pictureRecorder = pictureRecorder!!
-        val canvas = pictureRecorder.beginRecording(0f, 0f, pictureWidth, pictureHeight)
+        val canvas = pictureRecorder.beginRecording(0f, 0f, pictureWidth, pictureHeight).apply {
+            for (clip in clipComponents) {
+                cutoutFromClip(clip, contentScale)
+            }
+
+            val layerBg = backgroundColor
+            clear(
+                if (transparency && (redrawer?.isTransparentBackgroundSupported() == true)) {
+                    layerBg
+                } else {
+                    layerBg or 0xFF000000.toInt()
+                }
+            )
+        }
 
         try {
             isRendering = true

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

@@ -10,11 +10,6 @@ import java.awt.color.ColorSpace
 import java.awt.image.*
 
 internal class SoftwareContextHandler(layer: SkiaLayer) : ContextFreeContextHandler(layer) {
-    override fun isTransparentBackgroundSupported(): Boolean {
-        // TODO: why Software rendering has another transparency logic from the beginning
-        return hostOs == OS.MacOS
-    }
-
     val colorModel = ComponentColorModel(
         ColorSpace.getInstance(ColorSpace.CS_sRGB),
         true,

skiko/src/awtMain/kotlin/org/jetbrains/skiko/redrawer/AWTRedrawer.kt

@@ -74,4 +74,6 @@ internal abstract class AWTRedrawer(
     protected fun checkDisposed() {
         check(!isDisposed) { "${this.javaClass.simpleName} is disposed" }
     }
+
+    override fun isTransparentBackgroundSupported() = defaultIsTransparentBackgroundSupported(layer)
 }

skiko/src/awtMain/kotlin/org/jetbrains/skiko/redrawer/SoftwareRedrawer.kt

@@ -55,4 +55,9 @@ internal class SoftwareRedrawer(
             }
         }
     }
+
+    override fun isTransparentBackgroundSupported(): Boolean {
+        // TODO: why Software rendering has another transparency logic from the beginning
+        return hostOs == OS.MacOS
+    }
 }

skiko/src/awtTest/kotlin/org/jetbrains/skiko/SkiaLayerTest.kt

@@ -15,6 +15,7 @@ import org.jetbrains.skiko.context.JvmContextHandler
 import org.jetbrains.skiko.redrawer.MetalRedrawer
 import org.jetbrains.skiko.redrawer.MetalVSyncer
 import org.jetbrains.skiko.redrawer.Redrawer
+import org.jetbrains.skiko.redrawer.defaultIsTransparentBackgroundSupported
 import org.jetbrains.skiko.swing.SkiaSwingLayer
 import org.jetbrains.skiko.util.ScreenshotTestRule
 import org.jetbrains.skiko.util.UiTestScope
@@ -565,6 +566,7 @@ class SkiaLayerTest {
         override fun needRender(throttledToVsync: Boolean) = frameDispatcher.scheduleFrame()
         override fun renderImmediately() = Unit
         override fun update(nanoTime: Long) = layer.update(nanoTime)
+        override fun isTransparentBackgroundSupported() = defaultIsTransparentBackgroundSupported(layer)
 
         override val renderInfo: String
             get() = ""

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

@@ -28,26 +28,11 @@ expect open class SkiaLayer {
      */
     var fullscreen: Boolean
 
-    /**
-     * If transparency is enabled.
-     */
-    var transparency: Boolean
-
-    /**
-     * The color, in ARGB format, with which the layer is cleared before rendering.
-     */
-    internal var backgroundColor: Int
-
     /**
      * Underlying platform component.
      */
     val component: Any?
 
-    /**
-     * A list of rectangles to cut out from the rendered content; No content will be drawn inside them.
-     */
-    internal val cutoutRectangles: List<ClipRectangle>
-
     /**
      * Current view used for rendering.
      */

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

@@ -42,35 +42,10 @@ internal abstract class ContextHandler(
         initCanvas()
         canvas?.runRestoringState {
             clear(Color.TRANSPARENT)
-
-            val scale = layer.contentScale
-            for (clip in layer.cutoutRectangles) {
-                cutoutFromClip(clip, scale)
-            }
-
-            val layerBg = layer.backgroundColor
-            clear(
-                if (layer.transparency && isTransparentBackgroundSupported()) {
-                    layerBg
-                } else {
-                    layerBg or 0xFF000000.toInt()
-                }
-            )
-
             drawContent()
         }
         flush()
     }
-
-    protected open fun isTransparentBackgroundSupported(): Boolean {
-        if (hostOs == OS.MacOS) {
-            // macOS transparency is always supported
-            return true
-        }
-
-        // for non-macOS in fullscreen transparency is not supported
-        return !layer.fullscreen
-    }
 }
 
 @Suppress("NOTHING_TO_INLINE")
@@ -85,7 +60,7 @@ internal inline fun Canvas.cutoutFromClip(rectangle: ClipRectangle, scale: Float
     )
 }
 
-private inline fun Canvas.runRestoringState(block: Canvas.() -> Unit) {
+internal inline fun Canvas.runRestoringState(block: Canvas.() -> Unit) {
     val restoreCount = save()
     try {
         block()

skiko/src/commonMain/kotlin/org/jetbrains/skiko/redrawer/Redrawer.kt

@@ -1,5 +1,8 @@
 package org.jetbrains.skiko.redrawer
 
+import org.jetbrains.skiko.OS
+import org.jetbrains.skiko.SkiaLayer
+import org.jetbrains.skiko.hostOs
 import kotlin.time.TimeSource
 
 private val initialTime = TimeSource.Monotonic.markNow()
@@ -12,4 +15,15 @@ internal interface Redrawer {
     fun update(nanoTime: Long = initialTime.elapsedNow().inWholeNanoseconds)
     fun setVisible(isVisible: Boolean) = Unit
     val renderInfo: String
+    fun isTransparentBackgroundSupported(): Boolean
+}
+
+internal fun defaultIsTransparentBackgroundSupported(layer: SkiaLayer): Boolean {
+    if (hostOs == OS.MacOS) {
+        // macOS transparency is always supported
+        return true
+    }
+
+    // for non-macOS in fullscreen transparency is not supported
+    return !layer.fullscreen
 }

skiko/src/linuxMain/kotlin/org/jetbrains/skiko/SkiaLayer.linux.kt

@@ -12,16 +12,8 @@ actual open class SkiaLayer  {
     actual var fullscreen: Boolean
         get() = TODO("Not yet implemented")
         set(value) {}
-    actual var transparency: Boolean
-        get() = TODO("Not yet implemented")
-        set(value) {}
-    internal actual var backgroundColor: Int
-        get() = TODO("Not yet implemented")
-        set(value) {}
     actual val component: Any?
         get() = TODO("Not yet implemented")
-    internal actual val cutoutRectangles: List<ClipRectangle>
-        get() = emptyList()
     actual fun needRender(throttledToVsync: Boolean) {
         TODO("unimplemented")
     }

skiko/src/macosMain/kotlin/org/jetbrains/skiko/SkiaLayer.macos.kt

@@ -49,24 +49,6 @@ actual open class SkiaLayer {
             if (value) throw IllegalArgumentException("fullscreen unsupported")
         }
 
-    /**
-     * Transparency is not supported on macOS native.
-     */
-    actual var transparency: Boolean
-        get() = false
-        set(value) {
-            if (value) throw IllegalArgumentException("transparency unsupported")
-        }
-
-    /**
-     * The background color of the layer.
-     */
-    internal actual var backgroundColor: Int = Color.WHITE
-        set(value) {
-            field = value
-            needRender()
-        }
-
     /**
      * Underlying [NSView]
      */
@@ -76,9 +58,6 @@ actual open class SkiaLayer {
     actual val component: Any?
         get() = this.nsView
 
-    internal actual val cutoutRectangles: List<ClipRectangle>
-        get() = emptyList()
-
     /**
      * Implements rendering logic and events processing.
      */
@@ -172,7 +151,9 @@ actual open class SkiaLayer {
         val pictureWidth = (width * contentScale).coerceAtLeast(0.0)
         val pictureHeight = (height * contentScale).coerceAtLeast(0.0)
 
-        val canvas = pictureRecorder.beginRecording(0f, 0f, pictureWidth.toFloat(), pictureHeight.toFloat())
+        val canvas = pictureRecorder.beginRecording(0f, 0f, pictureWidth.toFloat(), pictureHeight.toFloat()).apply {
+            clear(Color.WHITE)
+        }
         renderDelegate?.onRender(canvas, pictureWidth.toInt(), pictureHeight.toInt(), nanoTime)
 
         val picture = pictureRecorder.finishRecordingAsPicture()

skiko/src/macosMain/kotlin/org/jetbrains/skiko/redrawer/MetalRedrawer.macos.kt

@@ -191,6 +191,8 @@ internal class MacOsMetalRedrawer(
             }
         }
     }
+
+    override fun isTransparentBackgroundSupported() = defaultIsTransparentBackgroundSupported(skiaLayer)
 }
 
 internal class MetalLayer : CAMetalLayer {

skiko/src/macosMain/kotlin/org/jetbrains/skiko/redrawer/OpenGLRedrawer.macos.kt

@@ -78,6 +78,8 @@ internal class MacOsOpenGLRedrawer(
         glLayer.setNeedsDisplay()
         skiaLayer.nsView.setNeedsDisplay(true)
     }
+
+    override fun isTransparentBackgroundSupported() = defaultIsTransparentBackgroundSupported(skiaLayer)
 }
 
 internal class MacosGLLayer : CAOpenGLLayer {

skiko/src/uikitMain/kotlin/org/jetbrains/skiko/SkiaLayer.uikit.kt

@@ -20,19 +20,6 @@ actual open class SkiaLayer {
         get() = true
         set(_) { throw UnsupportedOperationException() }
 
-    actual var transparency: Boolean
-        get() = false
-        set(_) { throw UnsupportedOperationException() }
-
-    /**
-     * The background color of the layer, as transparency is not supported.
-     */
-    internal actual var backgroundColor: Int = Color.WHITE
-        set(value) {
-            field = value
-            needRender()
-        }
-
     actual fun needRender(throttledToVsync: Boolean) {
         needRedrawCallback.invoke()
     }
@@ -46,9 +33,6 @@ actual open class SkiaLayer {
     actual val component: Any?
         get() = this.view
 
-    internal actual val cutoutRectangles: List<ClipRectangle>
-        get() = emptyList()
-
     val width: Float
        get() = view!!.frame.useContents {
            return@useContents size.width.toFloat()
@@ -80,7 +64,9 @@ actual open class SkiaLayer {
     }
 
     internal fun draw(surface: Surface) {
-        renderDelegate?.onRender(surface.canvas, surface.width, surface.height, currentNanoTime())
+        val canvas = surface.canvas
+        canvas.clear(Color.WHITE)
+        renderDelegate?.onRender(canvas, surface.width, surface.height, currentNanoTime())
     }
 
     actual val pixelGeometry: PixelGeometry