Use an extra bit in the button status byte to flag whether the

controls/button.c

@@ -137,27 +137,31 @@ static inline LRESULT WINAPI ButtonWndProc_locked(WND* wndPtr, UINT uMsg,
         break;
 
     case WM_LBUTTONDBLCLK:
-	if(wndPtr->dwStyle & BS_NOTIFY || 
-		style==BS_RADIOBUTTON ||
-		style==BS_USERBUTTON ||
-		style==BS_OWNERDRAW){
-	    SendMessageA( GetParent(hWnd), WM_COMMAND,
-		    MAKEWPARAM( wndPtr->wIDmenu, BN_DOUBLECLICKED ), hWnd);
-	    break;
-	}
-	/* fall through */
+        if(wndPtr->dwStyle & BS_NOTIFY || 
+                style==BS_RADIOBUTTON ||
+                style==BS_USERBUTTON ||
+                style==BS_OWNERDRAW) {
+            SendMessageA( GetParent(hWnd), WM_COMMAND,
+                    MAKEWPARAM( wndPtr->wIDmenu, BN_DOUBLECLICKED ), hWnd);
+            break;
+        }
+        /* fall through */
     case WM_LBUTTONDOWN:
         SetCapture( hWnd );
         SetFocus( hWnd );
         SendMessageA( hWnd, BM_SETSTATE, TRUE, 0 );
+        infoPtr->state |= BUTTON_BTNPRESSED;
         break;
 
     case WM_LBUTTONUP:
-	/* FIXME: real windows uses extra flags in the status for this */
-        if (GetCapture() != hWnd) break;
-        ReleaseCapture();
-        if (!(infoPtr->state & BUTTON_HIGHLIGHTED)) break;
+        if (!(infoPtr->state & BUTTON_BTNPRESSED)) break;
+        infoPtr->state &= BUTTON_NSTATES;
+        if (!(infoPtr->state & BUTTON_HIGHLIGHTED)) {
+            ReleaseCapture();
+            break;
+        }
         SendMessageA( hWnd, BM_SETSTATE, FALSE, 0 );
+        ReleaseCapture();
         GetClientRect( hWnd, &rect );
         if (PtInRect( &rect, pt ))
         {
@@ -181,6 +185,14 @@ static inline LRESULT WINAPI ButtonWndProc_locked(WND* wndPtr, UINT uMsg,
         }
         break;
 
+    case WM_CAPTURECHANGED:
+        if (infoPtr->state & BUTTON_BTNPRESSED) {
+            infoPtr->state &= BUTTON_NSTATES;
+            if (infoPtr->state & BUTTON_HIGHLIGHTED) 
+                SendMessageA( hWnd, BM_SETSTATE, FALSE, 0 );
+        }
+        break;
+
     case WM_MOUSEMOVE:
         if (GetCapture() == hWnd)
         {

include/button.h

@@ -26,6 +26,11 @@ typedef struct
 #define BUTTON_3STATE          0x02
 #define BUTTON_HIGHLIGHTED     0x04
 #define BUTTON_HASFOCUS        0x08
+#define BUTTON_NSTATES         0x0F
+  /* undocumented flags */
+#define BUTTON_BTNPRESSED      0x40
+#define BUTTON_UNKNOWN2        0x20
+#define BUTTON_UNKNOWN3        0x10
 
 #define BUTTON_STATE(hwnd)     ((WIN_FindWndPtr(hwnd))->wExtra[0])