feat: implement per-frame mouse look for reduced input latency on Windows

Minecraft.Client/Input.cpp

@@ -128,17 +128,23 @@ void Input::tick(LocalPlayer *player)
 	player->interpolateTurn(tx * abs(tx) * turnSpeed, ty * abs(ty) * turnSpeed);
 
 #ifdef _WINDOWS64
-	// Mouse look (added after stick-based turn)
+	// Mouse look is now handled per-frame in Minecraft::applyFrameMouseLook()
+	// to eliminate the 20Hz tick delay. Only flush any remaining delta here
+	// as a safety measure.
 	if (iPad == 0 && KMInput.IsCaptured())
 	{
-		float mouseSensitivity = 0.5f;
 		float rawDx, rawDy;
 		KMInput.ConsumeMouseDelta(rawDx, rawDy);
-		float mdx = rawDx * mouseSensitivity;
-		float mdy = -rawDy * mouseSensitivity;
-		if (app.GetGameSettings(iPad, eGameSetting_ControlInvertLook))
-			mdy = -mdy;
-		player->interpolateTurn(mdx, mdy);
+		// Delta should normally be 0 since applyFrameMouseLook() already consumed it
+		if (rawDx != 0.0f || rawDy != 0.0f)
+		{
+			float mouseSensitivity = 0.5f;
+			float mdx = rawDx * mouseSensitivity;
+			float mdy = -rawDy * mouseSensitivity;
+			if (app.GetGameSettings(iPad, eGameSetting_ControlInvertLook))
+				mdy = -mdy;
+			player->interpolateTurn(mdx, mdy);
+		}
 	}
 #endif
 

Minecraft.Client/Minecraft.cpp

@@ -1223,6 +1223,53 @@ void Minecraft::createPrimaryLocalPlayer(int iPad)
 	}
 }
 
+#ifdef _WINDOWS64
+void Minecraft::applyFrameMouseLook()
+{
+	// Per-frame mouse look: consume mouse deltas every frame instead of waiting
+	// for the 20Hz game tick. Apply the same delta to both xRot/yRot AND xRotO/yRotO
+	// so the render interpolation instantly reflects the change without waiting for a tick.
+	if (level == NULL) return;
+
+	for (int i = 0; i < XUSER_MAX_COUNT; i++)
+	{
+		if (localplayers[i] == NULL) continue;
+		int iPad = localplayers[i]->GetXboxPad();
+		if (iPad != 0) continue;  // Mouse only applies to pad 0
+
+		if (!KMInput.IsCaptured()) continue;
+		if (localgameModes[iPad] == NULL) continue;
+
+		float rawDx, rawDy;
+		KMInput.ConsumeMouseDelta(rawDx, rawDy);
+		if (rawDx == 0.0f && rawDy == 0.0f) continue;
+
+		float mouseSensitivity = 0.5f;
+		float mdx = rawDx * mouseSensitivity;
+		float mdy = -rawDy * mouseSensitivity;
+		if (app.GetGameSettings(iPad, eGameSetting_ControlInvertLook))
+			mdy = -mdy;
+
+		// Apply 0.15f scaling (same as Entity::interpolateTurn / Entity::turn)
+		float dyaw = mdx * 0.15f;
+		float dpitch = -mdy * 0.15f;
+
+		// Apply to both current and old rotation so render interpolation
+		// reflects the change immediately (no 50ms tick delay)
+		localplayers[i]->yRot += dyaw;
+		localplayers[i]->yRotO += dyaw;
+		localplayers[i]->xRot += dpitch;
+		localplayers[i]->xRotO += dpitch;
+
+		// Clamp pitch
+		if (localplayers[i]->xRot < -90.0f) localplayers[i]->xRot = -90.0f;
+		if (localplayers[i]->xRot > 90.0f) localplayers[i]->xRot = 90.0f;
+		if (localplayers[i]->xRotO < -90.0f) localplayers[i]->xRotO = -90.0f;
+		if (localplayers[i]->xRotO > 90.0f) localplayers[i]->xRotO = 90.0f;
+	}
+}
+#endif
+
 void Minecraft::run_middle()
 {
 	static __int64 lastTime = 0;

Minecraft.Client/Minecraft.h

@@ -217,6 +217,9 @@ public:
 	static Minecraft *GetInstance();
 	void run_middle();
 	void run_end();
+#ifdef _WINDOWS64
+	void applyFrameMouseLook();  // Per-frame mouse look to reduce input latency
+#endif
 
 	void emergencySave();
 

Minecraft.Client/Windows64/Windows64_Minecraft.cpp

@@ -1077,6 +1077,7 @@ int APIENTRY _tWinMain(_In_ HINSTANCE hInstance,
 		// Render game graphics.
 		if(app.GetGameStarted())
 		{
+			pMinecraft->applyFrameMouseLook();  // Per-frame mouse look (before ticks + render)
 			pMinecraft->run_middle();
 			app.SetAppPaused( g_NetworkManager.IsLocalGame() && g_NetworkManager.GetPlayerCount() == 1 && ui.IsPauseMenuDisplayed(ProfileManager.GetPrimaryPad()) );
 		}