[PATCH v2] wintab32: Use 64-bit math in ScaleForContext. - wine-devel

16 Nov 2019

With some tablet configurations, the InExt value passed to
ScaleForContext can be very large, leading to an integer overflow. Using
MulDiv prevents this problem by internally using 64-bit math.
---
 dlls/wintab32/context.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/dlls/wintab32/context.c b/dlls/wintab32/context.c
index 0514dd78b4..ff9a4ca677 100644
--- a/dlls/wintab32/context.c
+++ b/dlls/wintab32/context.c
@@ -178,9 +178,9 @@ int TABLET_PostTabletMessage(LPOPENCONTEXT
newcontext, UINT msg, WPARAM wParam,
 static inline DWORD ScaleForContext(DWORD In, LONG InOrg, LONG InExt,
LONG OutOrg, LONG OutExt)
 {
     if (((InExt > 0 )&&(OutExt > 0)) || ((InExt<0) && (OutExt < 0)))
-        return ((In - InOrg) * abs(OutExt) / abs(InExt)) + OutOrg;
+        return MulDiv(In - InOrg, abs(OutExt), abs(InExt)) + OutOrg;
     else
-        return ((abs(InExt) - (In - InOrg))*abs(OutExt) / abs(InExt)) + OutOrg;
+        return MulDiv(abs(InExt) - (In - InOrg), abs(OutExt),
abs(InExt)) + OutOrg;
 }
LPOPENCONTEXT AddPacketToContextQueue(LPWTPACKET packet, HWND hwnd)
-- 
2.23.0


    