Provides a base implementation of the Vulkan surface view (VkSurfaceView.kt) and its accompanying components.

The implementation is meant to be extended and updated in order to integrate it with the existing Godot java and native codebase.

7 files changed, 474 insertions, 2 deletions

diff --git a/platform/android/java/app/build.gradle b/platform/android/java/app/build.gradle
index 990fb35c46..632cedf34d 100644
--- a/platform/android/java/app/build.gradle
+++ b/platform/android/java/app/build.gradle
@@ -15,6 +15,7 @@ buildscript {
     }
     dependencies {
         classpath libraries.androidGradlePlugin
+        classpath libraries.kotlinGradlePlugin
 //CHUNK_BUILDSCRIPT_DEPENDENCIES_BEGIN
 //CHUNK_BUILDSCRIPT_DEPENDENCIES_END
     }
@@ -34,6 +35,7 @@ allprojects {
 
 dependencies {
     implementation libraries.supportCoreUtils
+    implementation libraries.kotlinStdLib
 
     if (rootProject.findProject(":lib")) {
         implementation project(":lib")
diff --git a/platform/android/java/app/config.gradle b/platform/android/java/app/config.gradle
index 7a983a1cc8..4fdb88314f 100644
--- a/platform/android/java/app/config.gradle
+++ b/platform/android/java/app/config.gradle
@@ -4,13 +4,16 @@ ext.versions = [
     minSdk             : 18,
     targetSdk          : 29,
     buildTools         : '29.0.1',
-    supportCoreUtils   : '28.0.0'
+    supportCoreUtils   : '28.0.0',
+    kotlinVersion      : '1.3.61'
 
 ]
 
 ext.libraries = [
     androidGradlePlugin: "com.android.tools.build:gradle:$versions.androidGradlePlugin",
-    supportCoreUtils   : "com.android.support:support-core-utils:$versions.supportCoreUtils"
+    supportCoreUtils   : "com.android.support:support-core-utils:$versions.supportCoreUtils",
+    kotlinGradlePlugin : "org.jetbrains.kotlin:kotlin-gradle-plugin:$versions.kotlinVersion",
+    kotlinStdLib       : "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$versions.kotlinVersion"
 ]
 
 ext.getExportPackageName = { ->
diff --git a/platform/android/java/build.gradle b/platform/android/java/build.gradle
index 01cb78653d..f0be6e18ce 100644
--- a/platform/android/java/build.gradle
+++ b/platform/android/java/build.gradle
@@ -9,6 +9,7 @@ buildscript {
     }
     dependencies {
         classpath libraries.androidGradlePlugin
+        classpath libraries.kotlinGradlePlugin
     }
 }
 
diff --git a/platform/android/java/lib/build.gradle b/platform/android/java/lib/build.gradle
index eb97484b9c..4b5873ce25 100644
--- a/platform/android/java/lib/build.gradle
+++ b/platform/android/java/lib/build.gradle
@@ -2,6 +2,7 @@ apply plugin: 'com.android.library'
 
 dependencies {
     implementation libraries.supportCoreUtils
+    implementation libraries.kotlinStdLib
 }
 
 def pathToRootDir = "../../../../"
diff --git a/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkRenderer.kt b/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkRenderer.kt
new file mode 100644
index 0000000000..67faad8ddd
--- /dev/null
+++ b/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkRenderer.kt
@@ -0,0 +1,99 @@
+/*************************************************************************/
+/*  VkRenderer.kt                                                        */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+@file:JvmName("VkRenderer")
+package org.godotengine.godot.vulkan
+
+import android.view.Surface
+
+/**
+ * Responsible to setting up and driving the Vulkan rendering logic.
+ *
+ * <h3>Threading</h3>
+ * The renderer will be called on a separate thread, so that rendering
+ * performance is decoupled from the UI thread. Clients typically need to
+ * communicate with the renderer from the UI thread, because that's where
+ * input events are received. Clients can communicate using any of the
+ * standard Java techniques for cross-thread communication, or they can
+ * use the  [VkSurfaceView.queueOnVkThread] convenience method.
+ *
+ * @see [VkSurfaceView.startRenderer]
+ */
+internal class VkRenderer {
+
+	/**
+	 * Called when the surface is created and signals the beginning of rendering.
+	 */
+	fun onVkSurfaceCreated(surface: Surface) {
+		nativeOnVkSurfaceCreated(surface)
+	}
+
+	/**
+	 * Called after the surface is created and whenever its size changes.
+	 */
+	fun onVkSurfaceChanged(surface: Surface, width: Int, height: Int) {
+		nativeOnVkSurfaceChanged(surface, width, height)
+	}
+
+	/**
+	 * Called to draw the current frame.
+	 */
+	fun onVkDrawFrame() {
+		nativeOnVkDrawFrame()
+	}
+
+	/**
+	 * Called when the rendering thread is resumed.
+	 */
+	fun onVkResume() {
+		nativeOnVkResume()
+	}
+
+	/**
+	 * Called when the rendering thread is paused.
+	 */
+	fun onVkPause() {
+		nativeOnVkPause()
+	}
+
+	/**
+	 * Called when the rendering thread is destroyed and used as signal to tear down the Vulkan logic.
+	 */
+	fun onVkDestroy() {
+		nativeOnVkDestroy()
+	}
+
+	private external fun nativeOnVkSurfaceCreated(surface: Surface)
+	private external fun nativeOnVkSurfaceChanged(surface: Surface, width: Int, height: Int)
+	private external fun nativeOnVkResume()
+	private external fun nativeOnVkDrawFrame()
+	private external fun nativeOnVkPause()
+	private external fun nativeOnVkDestroy()
+}
diff --git a/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkSurfaceView.kt b/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkSurfaceView.kt
new file mode 100644
index 0000000000..1c594f3201
--- /dev/null
+++ b/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkSurfaceView.kt
@@ -0,0 +1,136 @@
+/*************************************************************************/
+/*  VkSurfaceView.kt                                                     */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+@file:JvmName("VkSurfaceView")
+package org.godotengine.godot.vulkan
+
+import android.content.Context
+import android.view.SurfaceHolder
+import android.view.SurfaceView
+
+/**
+ * An implementation of SurfaceView that uses the dedicated surface for
+ * displaying Vulkan rendering.
+ * <p>
+ * A [VkSurfaceView] provides the following features:
+ * <p>
+ * <ul>
+ * <li>Manages a surface, which is a special piece of memory that can be
+ * composited into the Android view system.
+ * <li>Accepts a user-provided [VkRenderer] object that does the actual rendering.
+ * <li>Renders on a dedicated [VkThread] thread to decouple rendering performance from the
+ * UI thread.
+ * </ul>
+ */
+internal class VkSurfaceView(context: Context) : SurfaceView(context), SurfaceHolder.Callback {
+
+	companion object {
+		fun checkState(expression: Boolean, errorMessage: Any) {
+			check(expression) { errorMessage.toString() }
+		}
+	}
+
+	/**
+	 * Thread used to drive the vulkan logic.
+	 */
+	private val vkThread: VkThread by lazy {
+		VkThread(this, renderer)
+	}
+
+	/**
+	 * Performs the actual rendering.
+	 */
+	private lateinit var renderer: VkRenderer
+
+	init {
+		isClickable = true
+		holder.addCallback(this)
+	}
+
+	/**
+	 * Set the [VkRenderer] associated with the view, and starts the thread that will drive the vulkan
+	 * rendering.
+	 *
+	 * This method should be called once and only once in the life-cycle of [VkSurfaceView].
+	 */
+	fun startRenderer(renderer: VkRenderer) {
+		checkState(!this::renderer.isInitialized, "startRenderer must only be invoked once")
+		this.renderer = renderer
+		vkThread.start()
+	}
+
+	/**
+	 * Queues a runnable to be run on the Vulkan rendering thread.
+	 *
+	 * Must not be called before a [VkRenderer] has been set.
+	 */
+	fun queueOnVkThread(runnable: Runnable) {
+		vkThread.queueEvent(runnable)
+	}
+
+	/**
+	 * Resumes the rendering thread.
+	 *
+	 * Must not be called before a [VkRenderer] has been set.
+	 */
+	fun onResume() {
+		vkThread.onResume()
+	}
+
+	/**
+	 * Pauses the rendering thread.
+	 *
+	 * Must not be called before a [VkRenderer] has been set.
+	 */
+	fun onPause() {
+		vkThread.onPause()
+	}
+
+	/**
+	 * Tear down the rendering thread.
+	 *
+	 * Must not be called  before a [VkRenderer] has been set.
+	 */
+	fun onDestroy() {
+		vkThread.blockingExit()
+	}
+
+	override fun surfaceChanged(holder: SurfaceHolder, format: Int, width: Int, height: Int) {
+		vkThread.onSurfaceChanged(width, height)
+	}
+
+	override fun surfaceDestroyed(holder: SurfaceHolder) {
+		vkThread.onSurfaceDestroyed()
+	}
+
+	override fun surfaceCreated(holder: SurfaceHolder) {
+		vkThread.onSurfaceCreated()
+	}
+}
diff --git a/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkThread.kt b/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkThread.kt
new file mode 100644
index 0000000000..2e332840bf
--- /dev/null
+++ b/platform/android/java/lib/src/org/godotengine/godot/vulkan/VkThread.kt
@@ -0,0 +1,230 @@
+/*************************************************************************/
+/*  VkThread.kt                                                          */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+@file:JvmName("VkThread")
+package org.godotengine.godot.vulkan
+
+import android.util.Log
+import java.util.concurrent.locks.ReentrantLock
+import kotlin.concurrent.withLock
+
+/**
+ * Thread implementation for the [VkSurfaceView] onto which the vulkan logic is ran.
+ *
+ * The implementation is modeled after [android.opengl.GLSurfaceView]'s GLThread.
+ */
+internal class VkThread(private val vkSurfaceView: VkSurfaceView, private val vkRenderer: VkRenderer) : Thread(TAG) {
+
+	companion object {
+		private val TAG = VkThread::class.java.simpleName
+	}
+
+	/**
+	 * Used to run events scheduled on the thread.
+	 */
+	private val eventQueue = ArrayList<Runnable>()
+
+	/**
+	 * Used to synchronize interaction with other threads (e.g: main thread).
+	 */
+	private val lock = ReentrantLock()
+	private val lockCondition = lock.newCondition()
+
+	private var shouldExit = false
+	private var exited = false
+	private var rendererInitialized = false
+	private var rendererResumed = false
+	private var resumed = false
+	private var hasSurface = false
+	private var width = 0
+	private var height = 0
+
+	/**
+	 * Determine when drawing can occur on the thread. This usually occurs after the
+	 * [android.view.Surface] is available, the app is in a resumed state.
+	 */
+	private val readyToDraw
+		get() = hasSurface && resumed
+
+	private fun threadExiting() {
+		lock.withLock {
+			exited = true
+			lockCondition.signalAll()
+		}
+	}
+
+	/**
+	 * Queue an event on the [VkThread].
+	 */
+	fun queueEvent(event: Runnable) {
+		lock.withLock {
+			eventQueue.add(event)
+			lockCondition.signalAll()
+		}
+	}
+
+	/**
+	 * Request the thread to exit and block until it's done.
+	 */
+	fun blockingExit() {
+		lock.withLock {
+			shouldExit = true
+			lockCondition.signalAll()
+			while (!exited) {
+				try {
+					Log.i(TAG, "Waiting on exit for $name")
+					lockCondition.await()
+				} catch (ex: InterruptedException) {
+					currentThread().interrupt()
+				}
+			}
+		}
+	}
+
+	/**
+	 * Invoked when the app resumes.
+	 */
+	fun onResume() {
+		lock.withLock {
+			resumed = true
+			lockCondition.signalAll()
+		}
+	}
+
+	/**
+	 * Invoked when the app pauses.
+	 */
+	fun onPause() {
+		lock.withLock {
+			resumed = false
+			lockCondition.signalAll()
+		}
+	}
+
+	/**
+	 * Invoked when the [android.view.Surface] has been created.
+	 */
+	fun onSurfaceCreated() {
+		// This is a no op because surface creation will always be followed by surfaceChanged()
+		// which provide all the needed information.
+	}
+
+	/**
+	 * Invoked following structural updates to [android.view.Surface].
+	 */
+	fun onSurfaceChanged(width: Int, height: Int) {
+		lock.withLock {
+			hasSurface = true
+			this.width = width
+			this.height = height
+			lockCondition.signalAll()
+		}
+	}
+
+	/**
+	 * Invoked when the [android.view.Surface] is no longer available.
+	 */
+	fun onSurfaceDestroyed() {
+		lock.withLock {
+			hasSurface = false
+			lockCondition.signalAll()
+		}
+	}
+
+	/**
+	 * Thread loop modeled after [android.opengl.GLSurfaceView]'s GLThread.
+	 */
+	override fun run() {
+		try {
+			while (true) {
+				var event: Runnable? = null
+				lock.withLock {
+					while (true) {
+						// Code path for exiting the thread loop.
+						if (shouldExit) {
+							vkRenderer.onVkDestroy()
+							return
+						}
+
+						// Check for events and execute them outside of the loop if found to avoid
+						// blocking the thread lifecycle by holding onto the lock.
+						if (eventQueue.isNotEmpty()) {
+							event = eventQueue.removeAt(0)
+							break;
+						}
+
+						if (readyToDraw) {
+							if (!rendererResumed) {
+								rendererResumed = true
+								vkRenderer.onVkResume()
+
+								if (!rendererInitialized) {
+									rendererInitialized = true
+									vkRenderer.onVkSurfaceCreated(vkSurfaceView.holder.surface)
+								}
+
+								vkRenderer.onVkSurfaceChanged(vkSurfaceView.holder.surface, width, height)
+							}
+
+							// Break out of the loop so drawing can occur without holding onto the lock.
+							break;
+						} else if (rendererResumed) {
+							// If we aren't ready to draw but are resumed, that means we either lost a surface
+							// or the app was paused.
+							rendererResumed = false
+							vkRenderer.onVkPause()
+						}
+						// We only reach this state if we are not ready to draw and have no queued events, so
+						// we wait.
+						// On state change, the thread will be awoken using the [lock] and [lockCondition], and
+						// we will resume execution.
+						lockCondition.await()
+					}
+				}
+
+				// Run queued event.
+				if (event != null) {
+					event?.run()
+					continue
+				}
+
+				// Draw only when there no more queued events.
+				vkRenderer.onVkDrawFrame()
+			}
+		} catch (ex: InterruptedException) {
+			Log.i(TAG, ex.message)
+		} catch (ex: IllegalStateException) {
+			Log.i(TAG, ex.message)
+		} finally {
+			threadExiting()
+		}
+	}
+
+}