fix(devtools-ios): Ensure UI modifications run on main thread

Modifications to the UI can only be made from the main thread.
Since {N} 5.3.0 all debugger protocol messages are processed
by the worker thread that receives them in iOS.

refs #7219, https://github.com/NativeScript/ios-runtime/pull/1101

tns-core-modules/utils/utils-common.ts

@@ -1,4 +1,5 @@
 import * as types from "./types";
+import { executeOnMainThread } from "./utils"
 
 export const RESOURCE_PREFIX = "res://";
 export const FILE_PREFIX = "file:///";
@@ -154,3 +155,10 @@ export function hasDuplicates(arr: Array<any>): boolean {
 export function eliminateDuplicates(arr: Array<any>): Array<any> {
     return Array.from(new Set(arr));
 }
+
+export function mainThreadify(func: Function): (...args: any[]) => void {
+    return function () {
+        const argsToPass = arguments;
+        executeOnMainThread(() => func.apply(this, argsToPass));
+    }
+}

tns-core-modules/utils/utils.android.ts

@@ -372,3 +372,14 @@ Please ensure you have your manifest correctly configured with the FileProvider.
         return false;
     }
 }
+
+export function executeOnMainThread(func: () => void) {
+    new android.os.Handler(android.os.Looper.getMainLooper())
+        .post(new java.lang.Runnable({
+            run: func
+        }));
+}
+
+export function isMainThread(): Boolean {
+    return android.os.Looper.myLooper() === android.os.Looper.getMainLooper();
+}

tns-core-modules/utils/utils.d.ts

@@ -269,6 +269,26 @@ export function GC();
  */
 export function releaseNativeObject(object: any /*java.lang.Object | NSObject*/);
 
+/**
+ * Dispatches the passed function for execution on the main thread
+ * @param func The function to execute on the main thread.
+ */
+export function executeOnMainThread(func: Function);
+
+/**
+ * Returns a function wrapper which executes the supplied function on the main thread.
+ * The wrapper behaves like the original function and passes all of its arguments BUT
+ * discards its return value.
+ * @param func The function to execute on the main thread
+ * @returns The wrapper function which schedules execution to the main thread
+ */
+export function mainThreadify(func: Function): (...args: any[]) => void
+
+/**
+ * @returns Boolean value indicating whether the current thread is the main thread
+ */
+export function isMainThread(): boolean
+
 /**
  * Returns true if the specified path points to a resource or local file.
  * @param path The path.

tns-core-modules/utils/utils.ios.ts

@@ -159,6 +159,14 @@ export function openUrl(location: string): boolean {
     return false;
 }
 
+export function executeOnMainThread(func: () => void) {
+    NSOperationQueue.mainQueue.addOperationWithBlock(func);
+}
+
+export function isMainThread(): Boolean {
+    return NSThread.isMainThread;
+}
+
 class UIDocumentInteractionControllerDelegateImpl extends NSObject implements UIDocumentInteractionControllerDelegate {
     public static ObjCProtocols = [UIDocumentInteractionControllerDelegate];