From 0f7a546d9cb38a62a5d626b38e67bcc94f12a0fb Mon Sep 17 00:00:00 2001
From: Robin Dunn <robin@alldunn.com>
Date: Sun, 6 May 2001 00:25:03 +0000
Subject: [PATCH] Fixed HandleMouseWheel to be __WIN32__ sensitive

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@10011 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
---
 src/msw/window.cpp | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/msw/window.cpp b/src/msw/window.cpp
index dadffe9b6a..628d0b76ec 100644
--- a/src/msw/window.cpp
+++ b/src/msw/window.cpp
@@ -3371,16 +3371,31 @@ bool wxWindow::HandleMouseWheel(WXWPARAM wParam, WXLPARAM lParam)
                    GET_X_LPARAM(lParam),
                    GET_Y_LPARAM(lParam),
                    LOWORD(wParam));
-
     event.m_wheelRotation = (short)HIWORD(wParam);
     event.m_wheelDelta = WHEEL_DELTA;
 
-    int linesPer;
-    if (!SystemParametersInfo(SPI_GETWHEELSCROLLLINES, 0, &linesPer, 0))
-        linesPer = 1;
-    event.m_linesPerAction = linesPer;
+#ifdef __WIN32__
+    static int s_linesPerRotation = -1;
+    if ( s_linesPerRotation == -1 )
+    {
+        if ( !::SystemParametersInfo(SPI_GETWHEELSCROLLLINES, 0,
+                                     &s_linesPerRotation, 0))
+        {
+            // this is not supposed to happen
+            wxLogLastError(_T("SystemParametersInfo(GETWHEELSCROLLLINES)"));
+
+            // the default is 3, so use it if SystemParametersInfo() failed
+            s_linesPerRotation = 3;
+        }
+    }
+#else // Win16
+    // no SystemParametersInfo() under Win16
+    static const int s_linesPerRotation = 3;
+#endif
 
+    event.m_linesPerAction = s_linesPerRotation;
     return GetEventHandler()->ProcessEvent(event);
+
 #else
     return FALSE;
 #endif
-- 
2.47.2