feat(wasm): Add MemoryManager support

Author: jeromelaban

src/Uno.UI/WasmScripts/Uno.UI.d.ts

@@ -1104,6 +1104,11 @@ declare namespace Uno.Storage.Streams {
         static truncateAsync(streamId: string, length: number): Promise<string>;
     }
 }
+declare namespace Windows.System {
+    class MemoryManager {
+        static getAppMemoryUsage(): any;
+    }
+}
 interface Navigator {
     wakeLock: WakeLock;
 }

src/Uno.UI/WasmScripts/Uno.UI.js

@@ -4038,6 +4038,24 @@ var Uno;
         })(Streams = Storage.Streams || (Storage.Streams = {}));
     })(Storage = Uno.Storage || (Uno.Storage = {}));
 })(Uno || (Uno = {}));
+var Windows;
+(function (Windows) {
+    var System;
+    (function (System) {
+        class MemoryManager {
+            static getAppMemoryUsage() {
+                if (typeof Module === "object") {
+                    // Returns an approximate memory usage for the current wasm module.
+                    // Initial buffer size is determine by the initial wasm memory defined in
+                    // emscripten.
+                    return Module.HEAPU8.length;
+                }
+                return 0;
+            }
+        }
+        System.MemoryManager = MemoryManager;
+    })(System = Windows.System || (Windows.System = {}));
+})(Windows || (Windows = {}));
 var WakeLockType;
 (function (WakeLockType) {
     WakeLockType["screen"] = "screen";

src/Uno.UI/ts/Windows/System/MemoryManager.ts

@@ -0,0 +1,16 @@
+namespace Windows.System {
+
+	export class MemoryManager {
+
+		static getAppMemoryUsage() {
+			if (typeof Module === "object") {
+
+				// Returns an approximate memory usage for the current wasm module.
+				// Initial buffer size is determine by the initial wasm memory defined in
+				// emscripten.
+				return (<any>Module).HEAPU8.length;
+			}
+			return 0;
+		}
+	}
+}

src/Uno.UWP/Generated/3.0.0.0/Windows.System/MemoryManager.cs

@@ -7,7 +7,7 @@ namespace Windows.System
 	#endif
 	public static partial class MemoryManager 
 	{
-		#if false || __IOS__ || NET461 || __WASM__ || __SKIA__ || __NETSTD_REFERENCE__ || __MACOS__
+		#if false || __IOS__ || NET461 || false || __SKIA__ || __NETSTD_REFERENCE__ || __MACOS__
 		[global::Uno.NotImplemented("__IOS__", "NET461", "__WASM__", "__SKIA__", "__NETSTD_REFERENCE__", "__MACOS__")]
 		public static ulong AppMemoryUsage
 		{
@@ -27,7 +27,7 @@ public static ulong AppMemoryUsage
 			}
 		}
 		#endif
-		#if false || __IOS__ || NET461 || __WASM__ || __SKIA__ || __NETSTD_REFERENCE__ || __MACOS__
+		#if false || __IOS__ || NET461 || false || __SKIA__ || __NETSTD_REFERENCE__ || __MACOS__
 		[global::Uno.NotImplemented("__IOS__", "NET461", "__WASM__", "__SKIA__", "__NETSTD_REFERENCE__", "__MACOS__")]
 		public static ulong AppMemoryUsageLimit
 		{

src/Uno.UWP/System/MemoryManager.Wasm.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Globalization;
+using Uno.Foundation;
+
+namespace Windows.System
+{
+	public partial class MemoryManager
+	{
+		private const string JsType = "Windows.System.MemoryManager";
+
+		public static ulong AppMemoryUsage
+		{
+			get
+			{
+				if(ulong.TryParse(WebAssemblyRuntime.InvokeJS(
+					$"{JsType}.getAppMemoryUsage()"),
+					NumberStyles.Any,
+					CultureInfo.InvariantCulture, out var value))
+				{
+					return value;
+				}
+
+				throw new Exception($"getAppMemoryUsage returned an unsupported value");
+			}
+		}
+
+		public static ulong AppMemoryUsageLimit
+		{
+			get
+			{
+				if (Environment.GetEnvironmentVariable("UNO_BOOTSTRAP_EMSCRIPTEN_MAXIMUM_MEMORY") == "4GB")
+				{
+					return 4ul * 1024 * 1024 * 1024;
+				}
+
+				return 2ul * 1024 * 1024 * 1024;
+			}
+		}
+	}
+}