[sceMsgDialog] implemented sceMsgDialogInitialize (#22)

src/SharpEmu.Libs/CommonDialog/MsgDialogExports.cs

@@ -0,0 +1,27 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.HLE;
+using System.Threading;
+
+namespace SharpEmu.Libs.CommonDialog;
+
+public static class MsgDialogExports
+{
+    private const int AlreadyInitialized = unchecked((int)0x80B80002);
+    private static int _initialized;
+
+    [SysAbiExport(
+        Nid = "lDqxaY1UbEo",
+        ExportName = "sceMsgDialogInitialize",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceMsgDialog")]
+    public static int MsgDialogInitialize(CpuContext ctx)
+    {
+        var result = Interlocked.Exchange(ref _initialized, 1) == 0
+            ? 0
+            : AlreadyInitialized;
+        ctx[CpuRegister.Rax] = unchecked((ulong)result);
+        return result;
+    }
+}