DisableInputWndProc clean up

Source/diablo.cpp

@@ -641,31 +641,32 @@ LRESULT CALLBACK DisableInputWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM
 	case WM_MOUSEMOVE:
 		return 0;
 	case WM_LBUTTONDOWN:
-		if (sgbMouseDown == 0) {
+		if (sgbMouseDown != 0)
+			return 0;
 		sgbMouseDown = 1;
 		SetCapture(hWnd);
-		}
 		return 0;
 	case WM_LBUTTONUP:
-		if (sgbMouseDown == 1) {
+		if (sgbMouseDown != 1)
+			return 0;
 		sgbMouseDown = 0;
 		ReleaseCapture();
-		}
 		return 0;
 	case WM_RBUTTONDOWN:
-		if (sgbMouseDown == 0) {
+		if (sgbMouseDown != 0)
+			return 0;
 		sgbMouseDown = 2;
 		SetCapture(hWnd);
-		}
 		return 0;
 	case WM_RBUTTONUP:
-		if (sgbMouseDown == 2) {
+		if (sgbMouseDown != 2)
+			return 0;
 		sgbMouseDown = 0;
 		ReleaseCapture();
-		}
 		return 0;
 	case WM_CAPTURECHANGED:
-		if (hWnd != (HWND)lParam)
+		if (hWnd == (HWND)lParam)
+			return 0;
 		sgbMouseDown = 0;
 		return 0;
 	}