From 0810c2b873a754d78c3d269a279f40e2f7ade035 Mon Sep 17 00:00:00 2001
From: Zufu Liu <unknown>
Date: Mon, 14 Oct 2024 08:18:29 +1100
Subject: Bug [#2449]. Fix direction of horizontal scrolling with touchpad.

---
 win32/ScintillaWin.cxx | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'win32')

diff --git a/win32/ScintillaWin.cxx b/win32/ScintillaWin.cxx
index 5fd06cd16..7242f590d 100644
--- a/win32/ScintillaWin.cxx
+++ b/win32/ScintillaWin.cxx
@@ -1645,7 +1645,11 @@ sptr_t ScintillaWin::MouseMessage(unsigned int iMessage, uptr_t wParam, sptr_t l
 
 			MouseWheelDelta &wheelDelta = (iMessage == WM_MOUSEHWHEEL) ? horizontalWheelDelta : verticalWheelDelta;
 			if (wheelDelta.Accumulate(wParam)) {
-				const int charsToScroll = charsPerScroll * wheelDelta.Actions();
+				int charsToScroll = charsPerScroll * wheelDelta.Actions();
+				if (iMessage == WM_MOUSEHWHEEL) {
+					// horizontal scroll is in reverse direction
+					charsToScroll = -charsToScroll;
+				}
 				const int widthToScroll = static_cast<int>(std::lround(charsToScroll * vs.aveCharWidth));
 				HorizontalScrollToClamped(xOffset + widthToScroll);
 			}
-- 
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