sane.ds: Fix a subtle bug that prevented the float scrollbar from incrementing by one.

dlls/sane.ds/ui.c

@@ -853,10 +853,14 @@ static INT_PTR InitializeDialog(HWND hwnd)
                 dd = SANE_UNFIX(*sf);
                 HeapFree(GetProcessHeap(),0,sf);
 
+                /* Note that conversion of float -> SANE_Fixed is lossy;
+                 *   and when you truncate it into an integer, you can get
+                 *   unfortunate results.  This calculation attempts
+                 *   to mitigate that harm */
                 if (s_quant)
-                    pos = (dd / s_quant);
+                    pos = ((dd + (s_quant/2.0)) / s_quant);
                 else
-                    pos = dd / 0.01;
+                    pos = (dd + 0.005) / 0.01;
 
                 SendMessageW(control, SBM_SETPOS, pos, TRUE);