From 3827007c0c140ecbe605a3dc053760b5acf09a8e Mon Sep 17 00:00:00 2001
From: narzoul <narzoul@users.noreply.github.com>
Date: Thu, 31 Mar 2016 23:00:47 +0200
Subject: [PATCH] Avoid forced invalidation of the scroll bar child control
 when scrolling

This was causing the scroll bar arrows to lose their pressed appearance.
---
 DDrawCompat/CompatGdiWinProc.cpp | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/DDrawCompat/CompatGdiWinProc.cpp b/DDrawCompat/CompatGdiWinProc.cpp
index bc1fddd..95ae4c7 100644
--- a/DDrawCompat/CompatGdiWinProc.cpp
+++ b/DDrawCompat/CompatGdiWinProc.cpp
@@ -19,6 +19,7 @@ namespace
 
 	void disableDwmAttributes(HWND hwnd);
 	void onMenuSelect();
+	void onScroll(HWND hwnd, HWND scrollBar);
 	void onWindowPosChanged(HWND hwnd);
 	void removeDropShadow(HWND hwnd);
 
@@ -45,7 +46,7 @@ namespace
 			}
 			else if (WM_VSCROLL == ret->message || WM_HSCROLL == ret->message)
 			{
-				CompatGdiScrollFunctions::updateScrolledWindow(ret->hwnd);
+				onScroll(ret->hwnd, reinterpret_cast<HWND>(ret->lParam));
 			}
 			else if (WM_COMMAND == ret->message)
 			{
@@ -146,6 +147,21 @@ namespace
 		}
 	}
 
+	void onScroll(HWND hwnd, HWND scrollBar)
+	{
+		if (scrollBar)
+		{
+			UpdateWindow(scrollBar);
+		}
+
+		CompatGdiScrollFunctions::updateScrolledWindow(hwnd);
+
+		if (scrollBar)
+		{
+			ValidateRect(scrollBar, nullptr);
+		}
+	}
+
 	void onWindowPosChanged(HWND hwnd)
 	{
 		CompatGdi::GdiScopedThreadLock lock;