Initial save file implementation

Author: ds5678

AssetRipper.NativeDialogs.Example/Program.cs

@@ -37,7 +37,7 @@ static async Task Main(string[] args)
 		}
 		else if (arguments.SaveFile)
 		{
-			string? file = null;
+			string? file = await SaveFileDialog.SaveFileAsync();
 			Print(file);
 		}
 		else if (arguments.Message)

AssetRipper.NativeDialogs/SaveFileDialog.cs

@@ -0,0 +1,113 @@
+using System.Buffers;
+using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
+using TerraFX.Interop.Windows;
+
+namespace AssetRipper.NativeDialogs;
+
+public static class SaveFileDialog
+{
+	public static bool Supported =>
+		OperatingSystem.IsWindows() ||
+		OperatingSystem.IsMacOS() ||
+		(OperatingSystem.IsLinux() && Gtk.Global.IsSupported);
+
+	public static Task<string?> SaveFileAsync()
+	{
+		if (OperatingSystem.IsWindows())
+		{
+			return SaveFileAsyncWindows();
+		}
+		else if (OperatingSystem.IsMacOS())
+		{
+			return SaveFileAsyncMacOS();
+		}
+		else if (OperatingSystem.IsLinux())
+		{
+			return SaveFileAsyncLinux();
+		}
+		else
+		{
+			return Task.FromResult<string?>(null);
+		}
+	}
+
+	[SupportedOSPlatform("windows")]
+	private unsafe static Task<string?> SaveFileAsyncWindows()
+	{
+		// https://learn.microsoft.com/en-us/windows/win32/api/commdlg/ns-commdlg-openfilenamew
+
+		char[] buffer = ArrayPool<char>.Shared.Rent(ushort.MaxValue + 1); // Should be enough for the overwhelming majority of cases.
+		new Span<char>(buffer).Clear();
+
+		string filter = "All Files\0*.*\0\0";
+
+		fixed (char* bufferPtr = buffer)
+		fixed (char* filterPtr = filter)
+		{
+			OPENFILENAMEW ofn = default;
+			ofn.lStructSize = (uint)Unsafe.SizeOf<OPENFILENAMEW>();
+			ofn.hwndOwner = default; // No owner window.
+			ofn.lpstrFile = bufferPtr;
+			ofn.nMaxFile = (uint)buffer.Length;
+			ofn.lpstrFilter = filterPtr;
+			ofn.nFilterIndex = 1; // The first pair of strings has an index value of 1.
+			ofn.Flags = default;
+			if (Windows.GetSaveFileNameW(&ofn))
+			{
+				int length = Array.IndexOf(buffer, '\0');
+				if (length > 0)
+				{
+					string result = new(buffer, 0, length);
+					ArrayPool<char>.Shared.Return(buffer);
+					return Task.FromResult<string?>(result);
+				}
+			}
+		}
+
+		ArrayPool<char>.Shared.Return(buffer);
+		return Task.FromResult<string?>(null);
+	}
+
+	[SupportedOSPlatform("macos")]
+	private static Task<string?> SaveFileAsyncMacOS()
+	{
+		return ProcessExecutor.TryRun("osascript", "-e", "POSIX path of (choose file)");
+	}
+
+	[SupportedOSPlatform("linux")]
+	private static Task<string?> SaveFileAsyncLinux()
+	{
+		if (Gtk.Global.IsSupported)
+		{
+			string? result;
+			Gtk.Application.Init(); // spins a main loop
+			try
+			{
+				using Gtk.FileChooserNative dlg = new(
+					"Save a file", null,
+					Gtk.FileChooserAction.Save, "Save", "Cancel");
+
+				if (dlg.Run() == (int)Gtk.ResponseType.Accept)
+				{
+					result = dlg.File?.Path;
+				}
+				else
+				{
+					result = null; // User canceled the dialog
+				}
+			}
+			finally
+			{
+				Gtk.Application.Quit(); // stops the main loop
+			}
+
+			return Task.FromResult(result);
+		}
+		else
+		{
+			// Fallback
+			return Task.FromResult<string?>(null);
+		}
+	}
+}