WIP timestamp events

Author: Susko3

osu.Framework/Platform/SDL3/SDL3Window_Input.cs

@@ -508,6 +508,9 @@ private void handleTextEditingEvent(SDL_TextEditingEvent evtEdit)
 
         private void handleKeyboardEvent(SDL_KeyboardEvent evtKey)
         {
+            // GlobalEventTimestamps.LastTimestamp = (long)evtKey.timestamp;
+            GlobalEventTimestamps.LastTimestamp = GlobalEventTimestamps.GetTimestamp();
+
             Key key = evtKey.ToKey();
 
             if (key == Key.Unknown)
@@ -760,4 +763,15 @@ private void updateConfineMode()
 
         #endregion
     }
+
+    public static class GlobalEventTimestamps
+    {
+        public static long LastTimestamp;
+
+        public static long GetTimestamp() => Stopwatch.GetTimestamp();
+        public static double GetDelta(long t1, long t2) => (double)(t2 - t1) / Stopwatch.Frequency * 1000;
+
+        public static ulong GetTimestamp_SDL() => SDL_GetTicksNS();
+        public static double GetDelta_SDL(ulong t1, ulong t2) => (t2 - t1) / 1e6;
+    }
 }