Add a flag to control number of buffers used by Metal. Add a flag to control...

Add a flag to control number of buffers used by Metal. Add a flag to control Vsync on window resize (#968)

#### Number of buffers
MacOS
[doc](https://developer.apple.com/documentation/quartzcore/cametallayer/2938720-maximumdrawablecount?language=objc).
As far as I know AWT uses double buffering by default. So we would like
to experiment with this setting in Fleet. Also I expect that double
buffering should reduce user interaction latency.

#### Control VSync on window resize

I've noticed that on Linux and Windows we don't wait for VSync when
repainting synchronously, but only on macOS we do.
I suspect that locking EDT when we are waiting for VSync might lead to
problems with app responsivenes. So it would be nice to experiment with
this setting.

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

@@ -56,6 +56,7 @@ actual open class SkiaLayer internal constructor(
         externalAccessibleFactory: ((Component) -> Accessible)? = null,
         isVsyncEnabled: Boolean = SkikoProperties.vsyncEnabled,
         isVsyncFramelimitFallbackEnabled: Boolean = SkikoProperties.vsyncFramelimitFallbackEnabled,
+        frameBuffering: FrameBuffering = SkikoProperties.frameBuffering,
         renderApi: GraphicsApi = SkikoProperties.renderApi,
         analytics: SkiaLayerAnalytics = SkiaLayerAnalytics.Empty,
         pixelGeometry: PixelGeometry = PixelGeometry.UNKNOWN,
@@ -64,6 +65,7 @@ actual open class SkiaLayer internal constructor(
         SkiaLayerProperties(
             isVsyncEnabled,
             isVsyncFramelimitFallbackEnabled,
+            frameBuffering,
             renderApi
         ),
         RenderFactory.Default,

skiko/src/awtMain/kotlin/org/jetbrains/skiko/redrawer/Direct3DRedrawer.kt

@@ -72,7 +72,7 @@ internal class Direct3DRedrawer(
         check(!isDisposed) { "Direct3DRedrawer is disposed" }
         inDrawScope {
             update(System.nanoTime())
-            drawAndSwap(withVsync = false)
+            drawAndSwap(withVsync = SkikoProperties.windowsWaitForVsyncOnRedrawImmediately)
         }
     }
 

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

@@ -84,12 +84,17 @@ internal class LinuxOpenGLRedrawer(
         inDrawScope {
             it.makeCurrent(context)
             contextHandler.draw()
+            val turnOfVsync = properties.isVsyncEnabled && !SkikoProperties.linuxWaitForVsyncOnRedrawImmediately
+            if (turnOfVsync) {
                 it.setSwapInterval(0)
+            }
             it.swapBuffers()
             OpenGLApi.instance.glFinish()
+            if (turnOfVsync) {
                 it.setSwapInterval(swapInterval)
             }
         }
+    }
 
     private fun draw() {
         inDrawScope(contextHandler::draw)

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

@@ -67,8 +67,9 @@ internal class MetalRedrawer(
 
     init {
         onDeviceChosen(adapter.name)
+        val numberOfBuffers = properties.frameBuffering.numberOfBuffers() ?: 0 // zero means default for system
         val initDevice = layer.backedLayer.useDrawingSurfacePlatformInfo {
-            MetalDevice(createMetalDevice(layer.windowHandle, layer.transparency, adapter.ptr, it))
+            MetalDevice(createMetalDevice(layer.windowHandle, layer.transparency, numberOfBuffers, adapter.ptr, it))
         }
         _device = initDevice
         contextHandler = MetalContextHandler(layer, initDevice, adapter)
@@ -113,7 +114,7 @@ internal class MetalRedrawer(
         inDrawScope {
             update(System.nanoTime())
             if (!isDisposed) { // Redrawer may be disposed in user code, during `update`
-                performDraw()
+                performDraw(waitVsync = SkikoProperties.macOSWaitForPreviousFrameVsyncOnRedrawImmediately)
             }
         }
     }
@@ -154,13 +155,14 @@ internal class MetalRedrawer(
         windowOcclusionStateChannel.trySend(isOccluded)
     }
 
-    private fun performDraw() = synchronized(drawLock) {
+    private fun performDraw(waitVsync: Boolean = true) = synchronized(drawLock) {
         if (!isDisposed) {
+            if (waitVsync) {
                 // Wait for vsync because:
                 // - macOS drops the second/next drawables if they are sent in the same vsync
                 // - it makes frames consistent and limits FPS
                 displayLinkThrottler.waitVSync()
-
+            }
             autoreleasepool {
                 contextHandler.draw()
             }
@@ -185,7 +187,7 @@ internal class MetalRedrawer(
         setLayerVisible(device.ptr, isVisible)
     }
 
-    private external fun createMetalDevice(window: Long, transparency: Boolean, adapter: Long, platformInfo: Long): Long
+    private external fun createMetalDevice(window: Long, transparency: Boolean, frameBuffering: Int, adapter: Long, platformInfo: Long): Long
     private external fun disposeDevice(device: Long)
     private external fun resizeLayers(device: Long, x: Int, y: Int, width: Int, height: Int)
     private external fun setLayerVisible(device: Long, isVisible: Boolean)

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

@@ -69,6 +69,9 @@ internal class WindowsOpenGLRedrawer(
             contextHandler.draw()
             swapBuffers()
             OpenGLApi.instance.glFinish()
+            if (SkikoProperties.windowsWaitForVsyncOnRedrawImmediately) {
+                dwmFlush()
+            }
         }
     }
 

skiko/src/awtMain/objectiveC/macos/MetalRedrawer.mm

@@ -118,7 +118,7 @@ extern "C"
 {
 
 JNIEXPORT jlong JNICALL Java_org_jetbrains_skiko_redrawer_MetalRedrawer_createMetalDevice(
-    JNIEnv *env, jobject redrawer, jlong windowPtr, jboolean transparency, jlong adapterPtr, jlong platformInfoPtr)
+    JNIEnv *env, jobject redrawer, jlong windowPtr, jboolean transparency, jint frameBuffering, jlong adapterPtr, jlong platformInfoPtr)
 {
     @autoreleasepool {
         id<MTLDevice> adapter = (__bridge id<MTLDevice>) (void *) adapterPtr;
@@ -133,6 +133,10 @@ JNIEXPORT jlong JNICALL Java_org_jetbrains_skiko_redrawer_MetalRedrawer_createMe
         [container setNeedsDisplayOnBoundsChange: YES];
 
         AWTMetalLayer *layer = [AWTMetalLayer new];
+        if (frameBuffering == 2 || frameBuffering == 3) {
+            layer.maximumDrawableCount = frameBuffering;
+        }
+
         [container addSublayer: layer];
         layer.javaRef = env->NewGlobalRef(redrawer);
 

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

@@ -29,3 +29,17 @@ enum class GpuPriority(val value: String) {
         fun parseOrNull(value: String): GpuPriority? = GpuPriority.values().find { it.value == value }
     }
 }
+
+enum class FrameBuffering {
+    DEFAULT,
+    DOUBLE,
+    TRIPLE
+}
+
+fun FrameBuffering.numberOfBuffers(): Int? {
+    return when (this) {
+        FrameBuffering.DEFAULT -> null
+        FrameBuffering.DOUBLE -> 2
+        FrameBuffering.TRIPLE -> 3
+    }
+}
\ No newline at end of file

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

@@ -18,6 +18,7 @@ package org.jetbrains.skiko
 class SkiaLayerProperties(
     val isVsyncEnabled: Boolean = SkikoProperties.vsyncEnabled,
     val isVsyncFramelimitFallbackEnabled: Boolean = SkikoProperties.vsyncFramelimitFallbackEnabled,
+    val frameBuffering: FrameBuffering = SkikoProperties.frameBuffering,
     val renderApi: GraphicsApi = SkikoProperties.renderApi,
     val adapterPriority: GpuPriority = SkikoProperties.gpuPriority,
 ) {

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

@@ -34,6 +34,26 @@ object SkikoProperties {
 
     val vsyncEnabled: Boolean get() = getProperty("skiko.vsync.enabled")?.toBoolean() ?: true
 
+    val frameBuffering: FrameBuffering get() {
+        return when (getProperty("skiko.buffering")) {
+            "DOUBLE" -> FrameBuffering.DOUBLE
+            "TRIPLE" -> FrameBuffering.TRIPLE
+            else -> FrameBuffering.DEFAULT
+        }
+    }
+
+    val macOSWaitForPreviousFrameVsyncOnRedrawImmediately: Boolean get() {
+        return getProperty("skiko.rendering.macos.waitForPreviousFrameVsyncOnRedrawImmediately")?.toBoolean() ?: true
+    }
+
+    val windowsWaitForVsyncOnRedrawImmediately: Boolean get() {
+        return getProperty("skiko.rendering.windows.waitForFrameVsyncOnRedrawImmediately")?.toBoolean() ?: false
+    }
+
+    val linuxWaitForVsyncOnRedrawImmediately: Boolean get() {
+        return getProperty("skiko.rendering.linux.waitForFrameVsyncOnRedrawImmediately")?.toBoolean() ?: false
+    }
+
     /**
      * If vsync is enabled, but platform can't support it (Software renderer, Linux with uninstalled drivers),
      * we enable frame limit by the display refresh rate.