Enable autodetection of upscaling filter

client/renderSDL/ScreenHandler.cpp

@@ -335,25 +335,22 @@ EUpscalingFilter ScreenHandler::loadUpscalingFilter() const
 	if (filter != EUpscalingFilter::AUTO)
 		return filter;
 
-	// for now - always fallback to no filter
-	return EUpscalingFilter::NONE;
-
 	// else - autoselect
-//	Point outputResolution = getRenderResolution();
-//	Point logicalResolution = getPreferredLogicalResolution();
-//
-//	float scaleX = static_cast<float>(outputResolution.x) / logicalResolution.x;
-//	float scaleY = static_cast<float>(outputResolution.x) / logicalResolution.x;
-//	float scaling = std::min(scaleX, scaleY);
-//
-//	if (scaling <= 1.0f)
-//		return EUpscalingFilter::NONE;
-//	if (scaling <= 2.0f)
-//		return EUpscalingFilter::XBRZ_2;
-//	if (scaling <= 3.0f)
-//		return EUpscalingFilter::XBRZ_3;
-//
-//	return EUpscalingFilter::XBRZ_4;
+	Point outputResolution = getRenderResolution();
+	Point logicalResolution = getPreferredLogicalResolution();
+
+	float scaleX = static_cast<float>(outputResolution.x) / logicalResolution.x;
+	float scaleY = static_cast<float>(outputResolution.x) / logicalResolution.x;
+	float scaling = std::min(scaleX, scaleY);
+
+	if (scaling <= 1.001f)
+		return EUpscalingFilter::NONE; // running at original resolution or even lower than that - no need for xbrz
+	if (scaling <= 2.001f)
+		return EUpscalingFilter::XBRZ_2; // resolutions below 1200p (including 1080p / FullHD)
+	if (scaling <= 3.001f)
+		return EUpscalingFilter::XBRZ_3; // resolutions below 2400p (including 1440p and 2160p / 4K)
+
+	return EUpscalingFilter::XBRZ_4; // Only for massive displays, e.g. 8K
 }
 
 void ScreenHandler::selectUpscalingFilter()