[NTUSER] IntSetTimer(): Use timer IDs range [256,32767] as on Windows (reactos#7277)

Based on the Doug Lyons' test in reactos#7087, I found that my previous fix stopped working partially. Or rather, it would only work until the 32767 indexes were exhausted. It seems to me that the behavior of the bitfield has changed, because when I published the previous patch, it passed my tests.

- Bit array generates free ID cyclically, in the previous code after 32767 indexes expired the same index was returned, because of this the previous fix would stop working after expiration, so change the logic of calculating the next index.
- Change the index range to 256-32767 to match Windows, indexes 0-255 can theoretically be used as reserved for system purposes.

Addendum to fd327db. CORE-9141

Author: turican0

win32ss/user/ntuser/timer.c

@@ -17,7 +17,9 @@ static LIST_ENTRY TimersListHead;
 static LONG TimeLast = 0;
 
 /* Windows 2000 has room for 32768 window-less timers */
-#define NUM_WINDOW_LESS_TIMERS   32768
+/* These values give timer IDs [256,32767], same as on Windows */
+#define MAX_WINDOW_LESS_TIMER_ID  (32768 - 1)
+#define NUM_WINDOW_LESS_TIMERS    (32768 - 256)
 
 #define HINTINDEX_BEGIN_VALUE   0
 
@@ -78,11 +80,12 @@ RemoveTimer(PTIMER pTmr)
      RemoveEntryList(&pTmr->ptmrList);
      if ((pTmr->pWnd == NULL) && (!(pTmr->flags & TMRF_SYSTEM))) // System timers are reusable.
      {
-        UINT_PTR IDEvent;
+        ULONG ulBitmapIndex;
 
-        IDEvent = NUM_WINDOW_LESS_TIMERS - pTmr->nID;
+        ASSERT(pTmr->nID <= MAX_WINDOW_LESS_TIMER_ID);
+        ulBitmapIndex = (ULONG)(MAX_WINDOW_LESS_TIMER_ID - pTmr->nID);
         IntLockWindowlessTimerBitmap();
-        RtlClearBit(&WindowLessTimersBitMap, IDEvent);
+        RtlClearBit(&WindowLessTimersBitMap, ulBitmapIndex);
         IntUnlockWindowlessTimerBitmap();
      }
      UserDereferenceObject(pTmr);
@@ -222,12 +225,8 @@ IntSetTimer( PWND Window,
   {
       IntLockWindowlessTimerBitmap();
 
-      ulBitmapIndex = RtlFindClearBitsAndSet(&WindowLessTimersBitMap, 1, HintIndex++);
-      if (ulBitmapIndex == ULONG_MAX)
-      {
-         HintIndex = HINTINDEX_BEGIN_VALUE;
-         ulBitmapIndex = RtlFindClearBitsAndSet(&WindowLessTimersBitMap, 1, HintIndex++);
-      }
+      ulBitmapIndex = RtlFindClearBitsAndSet(&WindowLessTimersBitMap, 1, HintIndex);
+      HintIndex = (ulBitmapIndex + 1) % NUM_WINDOW_LESS_TIMERS;
       if (ulBitmapIndex == ULONG_MAX)
       {
          IntUnlockWindowlessTimerBitmap();
@@ -237,7 +236,7 @@ IntSetTimer( PWND Window,
       }
 
       ASSERT(ulBitmapIndex < NUM_WINDOW_LESS_TIMERS);
-      IDEvent = NUM_WINDOW_LESS_TIMERS - ulBitmapIndex;
+      IDEvent = MAX_WINDOW_LESS_TIMER_ID - ulBitmapIndex;
       Ret = IDEvent;
 
       IntUnlockWindowlessTimerBitmap();