fix: tick native watchdog before SetFormat to prevent black screen

When the surface is born as RGB565 on Vulkan, the RGB565 guard in
SurfaceChanged calls SetFormat(RGBA8888) which triggers a synchronous
surface teardown on the UI thread. This blocks the UI thread for hundreds
of milliseconds, preventing the Update thread from sending heartbeats to
the native watchdog. The native watchdog (10s default) then fires, killing
the process and producing a black screen.

The fix calls NativeWatchdog.Heartbeat() right before SetFormat to reset
the watchdog timer from the UI thread. The native watchdog checks
g_lastHeartbeatMonotonicSec which is updated by a simple atomic store
— safe to call from any thread and never throws.

This is safer than the previous approach of setting surfaceEvent before
SetFormat, which introduced a data race between the draw thread reading
surfaceGlobalRef and SurfaceDestroyed freeing it.

Author: Ubuntu

osu.Android/OsuGameActivity.cs

@@ -21,6 +21,7 @@
 using osu.Framework.Android;
 using osu.Game.Database;
 using osu.Framework.Logging;
+using osu.Android.Native;
 
 namespace osu.Android
 {
@@ -899,18 +900,25 @@ public void SurfaceChanged(ISurfaceHolder holder, global::Android.Graphics.Forma
                 Logger.Log(rgb565Message, LoggingTarget.Runtime, LogLevel.Important);
                 Logger.Log(rgb565Message, LoggingTarget.Performance, LogLevel.Important);
 
-                // Set the surface event BEFORE calling SetFormat so the draw thread can
-                // proceed with the current (soon-to-be-recreated) surface. Without this,
-                // the draw thread blocks on surfaceEvent.Wait(5000) while SetFormat triggers
-                // a synchronous surface teardown on the UI thread, blocking the entire
-                // managed runtime from sending heartbeats. The native watchdog then fires
-                // at 10s because no managed heartbeat is observed.
-                // The new surface will trigger another SurfaceChanged which will set
-                // surfaceEvent again with the correct RGBA8888 format.
-                if (width > 0 && height > 0)
+                // Tick the native watchdog BEFORE calling SetFormat. SetFormat triggers a
+                // synchronous surface teardown on the UI thread that can block for hundreds
+                // of milliseconds. During this window the Update thread may not get a chance
+                // to send a heartbeat (especially during startup when the runtime is under
+                // heavy load), and the native watchdog (10s default) would fire, killing the
+                // process and producing a black screen.
+                //
+                // Calling Heartbeat() here resets the watchdog timer from the UI thread,
+                // giving SetFormat time to complete without triggering a false positive.
+                // The native watchdog checks g_lastHeartbeatMonotonicSec which is updated
+                // by a simple atomic store — safe to call from any thread.
+                try
+                {
+                    NativeWatchdog.Heartbeat();
+                    Debug.WriteLine("[osu!] Native watchdog heartbeat ticked before SetFormat(RGBA8888)");
+                }
+                catch (Exception e)
                 {
-                    surfaceEvent.Set();
-                    Debug.WriteLine($"[osu!] Native surface signal set before format change (size: {width}x{height})");
+                    Debug.WriteLine($"[osu!] NativeWatchdog.Heartbeat failed (non-fatal): {e.Message}");
                 }
 
                 try