threadsafe MathFont, MTFontV2, MTFontMathTableV2 with concurrent testScripts.

Tests/SwiftMathTests/MTFontMathTableV2Tests.swift

@@ -1,6 +1,6 @@
 //
 //  MTFontMathTableV2Tests.swift
-//  
+//
 //
 //  Created by Peter Tang on 15/9/2023.
 //
@@ -25,4 +25,57 @@ final class MTFontMathTableV2Tests: XCTestCase {
             print("\($0.rawValue).plist: \(values)")
         }
     }
+    private let executionQueue = DispatchQueue(label: "com.swiftmath.mathbundle", attributes: .concurrent)
+    private let executionGroup = DispatchGroup()
+    let totalCases = 1000
+    var testCount = 0
+    func testConcurrentThreadsafeScript() throws {
+        testCount = 0
+        var mathFont: MathFont { .allCases.randomElement()! }
+        var size: CGFloat { CGFloat.random(in: 20 ... 40) }
+        let mtfonts = Array( 0 ..< 10 ).map { _ in mathFont.mtfont(size: size) }
+        for caseNumber in 0 ..< totalCases {
+            helperConcurrentMTFontMathTableV2(caseNumber, mtfont: mtfonts.randomElement()!, in: executionGroup, on: executionQueue)
+        }
+        executionGroup.notify(queue: .main) { [weak self] in
+            guard let self = self else { return }
+            XCTAssertEqual(self.testCount, totalCases)
+            print("\(self.testCount) completed =================")
+        }
+    }
+    func helperConcurrentMTFontMathTableV2(_ count: Int, mtfont: MTFontV2, in group: DispatchGroup, on queue: DispatchQueue) {
+        let workitem = DispatchWorkItem {
+            let mTable = mtfont.mathTable
+            let values = [
+                mTable?.fractionNumeratorDisplayStyleShiftUp,
+                mTable?.fractionNumeratorShiftUp,
+                mTable?.fractionDenominatorDisplayStyleShiftDown,
+                mTable?.fractionDenominatorShiftDown,
+                mTable?.fractionNumeratorDisplayStyleGapMin,
+                mTable?.fractionNumeratorGapMin,
+            ].compactMap{$0}
+            if count % 50 == 0 {
+                print(values) // accessed these values on global thread.
+            }
+            XCTAssertNotNil(mTable)
+        }
+        workitem.notify(queue: .main) { [weak self] in
+            // print("\(Thread.isMainThread ? "main" : "global") completed .....")
+            let mTable = mtfont.mathTable
+            if count % 70 == 0 {
+                let values = [
+                    mTable?.fractionNumeratorDisplayStyleShiftUp,
+                    mTable?.fractionNumeratorShiftUp,
+                    mTable?.fractionDenominatorDisplayStyleShiftDown,
+                    mTable?.fractionDenominatorShiftDown,
+                    mTable?.fractionNumeratorDisplayStyleGapMin,
+                    mTable?.fractionNumeratorGapMin,
+                ].compactMap{$0}
+                print(values) // accessed these values on main thread.
+            }
+            self?.testCount += 1
+        }
+        queue.async(group: group, execute: workitem)
+    }
+
 }