Create automated background memory manager. (#141)

skiko/build.gradle.kts

@@ -13,7 +13,7 @@ plugins {
     id("de.undercouch.download") version "4.1.1"
 }
 
-val coroutinesVersion = "1.4.1"
+val coroutinesVersion = "1.5.0"
 
 buildscript {
     dependencies {
@@ -556,6 +556,7 @@ val createChecksums by project.tasks.registering(org.gradle.crypto.checksum.Chec
 }
 
 val skikoJvmRuntimeJar by project.tasks.registering(Jar::class) {
+    dependsOn(createChecksums)
     archiveBaseName.set("skiko-$target")
     from(skikoJvmJar.map { zipTree(it.archiveFile) })
     from(maybeSign.get().outputs.files)

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

+package org.jetbrains.skiko
+
+import kotlinx.coroutines.*
+import java.util.concurrent.atomic.AtomicInteger
+
+/**
+ * This class is intended to mitigate issues coming from the situation that we have
+ * pretty large native peers (Skia objects) for rather tiny Java wrappers.
+ * It is especially visible for situation with paragraph classes.
+ * As a result, memory consumption grows dramatically.
+ * To solve this issue, we force periodic GC if certain amount of frames was rendered,
+ * making sure that we'll have memory consumption under control.
+ */
+internal object FrameWatcher {
+    var gcDelayMillis = 30_000L
+    var minFramesToRenderer = 1_000
+
+    fun start() {
+        // We initiate GC on IO threads, so that rendering is not blocked in
+        // cases of concurrent collectors.
+        @OptIn(DelicateCoroutinesApi::class)
+        GlobalScope.launch(Dispatchers.IO) {
+            while (true) {
+                // Wait some time between collection attempts.
+                delay(gcDelayMillis)
+                // Ensure that certain number of frames were rendered, as we allocate Skia
+                // garbage when rendering.
+                if (frameCounter.get() > minFramesToRenderer) {
+                    System.gc()
+                    frameCounter.set(0)
+                }
+            }
+        }
+    }
+
+    fun nextFrame() {
+        frameCounter.addAndGet(1)
+    }
+
+    private val frameCounter = AtomicInteger(0)
+}

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

@@ -2,12 +2,13 @@ package org.jetbrains.skiko
 
 import javax.swing.UIManager
 
-object Setup {
+internal object Setup {
     fun init(
         noEraseBackground: Boolean = System.getProperty("skiko.rendering.noerasebackground") != "false",
         globalLAF: Boolean = System.getProperty("skiko.rendering.laf.global") == "true",
         useScreenMenuBar: Boolean = System.getProperty("skiko.rendering.useScreenMenuBar") != "false",
-        autoLinuxDpi: Boolean = System.getProperty("skiko.linux.autodpi") == "true"
+        autoLinuxDpi: Boolean = System.getProperty("skiko.linux.autodpi") == "true",
+        automateGC: Boolean = System.getProperty("skiko.gc.auto") != "false"
     ) {
         if (hostOs == OS.Linux && autoLinuxDpi) {
             val scale = linuxGetSystemDpiScale()
@@ -29,6 +30,10 @@ object Setup {
         } catch (e: UnsupportedOperationException) {
             // Not all platforms allow this.
         }
+
+        if (automateGC) {
+           FrameWatcher.start()
+        }
     }
 }
 

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

@@ -350,6 +350,7 @@ open class SkiaLayer(
             }
             flush()
         }
+        FrameWatcher.nextFrame()
     }
 
     // Captures current layer as bitmap.

skiko/src/jvmTest/kotlin/org/jetbrains/skiko/SeveralClassloaders.kt

@@ -101,7 +101,9 @@ class SeveralClassloaders {
         val jar = System.getProperty("skiko.jar.path")
         val stdlibClass = Class.forName("kotlin.jvm.internal.Intrinsics")
         val stdLibJar = stdlibClass.protectionDomain.codeSource.location
-        val urls = listOf(Paths.get(jar).toUri().toURL(), stdLibJar)
+        val coroutinesClass = Class.forName("kotlinx.coroutines.CoroutineDispatcher")
+        val coroutinesJar = coroutinesClass.protectionDomain.codeSource.location
+        val urls = listOf(Paths.get(jar).toUri().toURL(), stdLibJar, coroutinesJar)
         val loaders = mutableListOf<ClassLoader>()
         repeat(4) {
             loaders += PlatformAndURLClassLoader(urls)