SDL: emscripten: scale mousewheel X coordinates correctly, not just Y coordinates.

SDL Commits
1 
From 4ea26a777104fcd59ddb49d77f4a91a66dee13c9 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Wed, 23 Oct 2024 23:35:02 -0400
Subject: [PATCH] emscripten: scale mousewheel X coordinates correctly, not
 just Y coordinates.

Fixes #10454.
---
 src/video/emscripten/SDL_emscriptenevents.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/video/emscripten/SDL_emscriptenevents.c b/src/video/emscripten/SDL_emscriptenevents.c
index b578128dc455f..18d9117fc3da3 100644
--- a/src/video/emscripten/SDL_emscriptenevents.c
+++ b/src/video/emscripten/SDL_emscriptenevents.c
@@ -360,20 +360,24 @@ static EM_BOOL Emscripten_HandleWheel(int eventType, const EmscriptenWheelEvent
     SDL_WindowData *window_data = userData;
 
     float deltaY = wheelEvent->deltaY;
+    float deltaX = wheelEvent->deltaX;
 
     switch (wheelEvent->deltaMode) {
     case DOM_DELTA_PIXEL:
+        deltaX /= 100; // 100 pixels make up a step
         deltaY /= 100; // 100 pixels make up a step
         break;
     case DOM_DELTA_LINE:
+        deltaX /= 3; // 3 lines make up a step
         deltaY /= 3; // 3 lines make up a step
         break;
     case DOM_DELTA_PAGE:
+        deltaX *= 80; // A page makes up 80 steps
         deltaY *= 80; // A page makes up 80 steps
         break;
     }
 
-    SDL_SendMouseWheel(0, window_data->window, SDL_DEFAULT_MOUSE_ID, (float)wheelEvent->deltaX, -deltaY, SDL_MOUSEWHEEL_NORMAL);
+    SDL_SendMouseWheel(0, window_data->window, SDL_DEFAULT_MOUSE_ID, deltaX, -deltaY, SDL_MOUSEWHEEL_NORMAL);
     return SDL_EventEnabled(SDL_EVENT_MOUSE_WHEEL);
 }