feat: switching slides

Program.cs

@@ -2,7 +2,9 @@
 	class Program {
 		private static async Task Main() {
 			GamepadReader reader = new JoyConRead();
+			SlideSwitcher switcher = new(reader);
 			await reader.Read();
+			switcher.Dispose();
 		}
 	}
 }

SlideSwitcher.cs

@@ -0,0 +1,26 @@
+namespace SwitchSlidePresenter;
+
+public class SlideSwitcher : IDisposable {
+	private readonly GamepadReader _reader;
+
+	public SlideSwitcher(GamepadReader reader) {
+		_reader = reader;
+		_reader.NextSlide += NextSlide;
+		_reader.PrevSlide += PreviousSlide;
+	}
+
+	public void Dispose() {
+		_reader.NextSlide -= NextSlide;
+		_reader.PrevSlide -= PreviousSlide;
+	}
+
+	private void NextSlide() {
+		IntPtr handle = Win32Api.GetForegroundWindow();
+		Win32Api.PostMessage(handle, Win32Api.WM_KEYDOWN, Win32Api.VK_NEXT, 0);
+	}
+
+	private void PreviousSlide() {
+		IntPtr handle = Win32Api.GetForegroundWindow();
+		Win32Api.PostMessage(handle, Win32Api.WM_KEYDOWN, Win32Api.VK_PRIOR, 0);
+	}
+}

Win32Api.cs

@@ -0,0 +1,14 @@
+using System.Runtime.InteropServices;
+
+namespace SwitchSlidePresenter;
+
+public static class Win32Api {
+	public const UInt32 WM_KEYDOWN = 0x0100;
+	public const int VK_NEXT = 0x22;
+	public const int VK_PRIOR = 0x21;
+
+	[DllImport("user32.dll")]
+	public static extern bool PostMessage(IntPtr hWnd, UInt32 Msg, int wParam, int lParam);
+	[DllImport("user32.dll")]
+	public static extern IntPtr GetForegroundWindow();
+}