Added click counter reset on window activate/deactivate for Windows Areas.

area_windows.go

@@ -644,7 +644,14 @@ func areaWndProc(s *sysData) func(hwnd _HWND, uMsg uint32, wParam _WPARAM, lPara
 				return 0
 			}
 			return defwndproc()
+		case _WM_ACTIVATE:
+			// don't keep the double-click timer running if the user switched programs in between clicks
+			s.clickCounter.reset()
+			// MSDN says this message will be sent alongside WM_MOUSEACTIVATE, but we'll reset there too, just in case
+			return 0
 		case _WM_MOUSEACTIVATE:
+			// don't keep the double-click timer running if the user switched programs in between clicks
+			s.clickCounter.reset()
 			// transfer keyboard focus to our Area on an activating click
 			// (see http://www.catch22.net/tuts/custom-controls)
 			r1, _, err := _setFocus.Call(uintptr(s.hwnd))

events_windows.go

@@ -203,6 +203,9 @@ const (
 
 // Window keyboard event messages and related constants.
 const (
+	// filed under keyboard events by MSDN
+	_WM_ACTIVATE = 0x0006
+
 	// from winuser.h
 	_WM_KEYDOWN = 0x0100
 	_WM_KEYUP = 0x0101