SDL: Fix scroll wheel handling in testmouse

From df05d5eff45d15eff45cdae9f65e2ab4c3fd8e07 Mon Sep 17 00:00:00 2001
From: Cameron Cawley <[EMAIL REDACTED]>
Date: Tue, 28 Nov 2023 22:15:18 +0000
Subject: [PATCH] Fix scroll wheel handling in testmouse

---
 test/testmouse.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/testmouse.c b/test/testmouse.c
index b7852e7442d7..18efbc0eb67b 100644
--- a/test/testmouse.c
+++ b/test/testmouse.c
@@ -125,10 +125,10 @@ static void loop(void *arg)
                 /* "positive to the right and negative to the left"  */
                 wheel_x += event.wheel.x * 10.0f;
             }
-            if (event.wheel.x != 0.0f) {
+            if (event.wheel.y != 0.0f) {
                 wheel_y_active = SDL_TRUE;
                 /* "positive away from the user and negative towards the user" */
-                wheel_y -= event.wheel.x * 10.0f;
+                wheel_y -= event.wheel.y * 10.0f;
             }
             break;