Util: Factor out gcd code

include/mgba-util/math.h

@@ -58,6 +58,19 @@ static inline uint32_t toPow2(uint32_t bits) {
 	return 1 << (32 - lz);
 }
 
+static inline int reduceFraction(int* num, int* den) {
+	int n = *num;
+	int d = *den;
+	while (d != 0) {
+		int temp = n % d;
+		n = d;
+		d = temp;
+	}
+	*num /= n;
+	*den /= n;
+	return n;
+}
+
 CXX_GUARD_END
 
 #endif

src/platform/qt/VideoView.cpp

@@ -10,6 +10,8 @@
 #include "GBAApp.h"
 #include "LogController.h"
 
+#include <mgba-util/math.h>
+
 #include <QMap>
 
 using namespace QGBA;
@@ -396,15 +398,7 @@ void VideoView::updateAspectRatio(int width, int height, bool force) {
 	} else {
 		int w = m_width;
 		int h = m_height;
-		// Get greatest common divisor
-		while (w != 0) {
-			int temp = h % w;
-			h = w;
-			w = temp;
-		}
-		int gcd = h;
-		w = m_width / gcd;
-		h = m_height / gcd;
+		reduceFraction(&h, &w);
 		safelySet(m_ui.wratio, w);
 		safelySet(m_ui.hratio, h);
 	}