Make sure window cannot enter fading when unredirected

Firstly, this breaks the assumption that when we redirect the screen,
all window is either mapped or unmapped, causing a assertion failure.

Secondly, if transition window into fading when the screen is not
redirected, the fading will not progress until the screen is redirected,
probably not the desired result.

Fixes chjj#246

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/event.c

@@ -468,11 +468,14 @@ static inline void ev_property_notify(session_t *ps, xcb_property_notify_event_t
 			win_update_opacity_prop(ps, w);
 			// we cannot receive OPACITY change when window is destroyed
 			assert(w->state != WSTATE_DESTROYING);
+			w->opacity_target = win_calc_opacity_target(ps, w, false);
 			if (w->state == WSTATE_MAPPED) {
 				// See the winstate_t transition table
 				w->state = WSTATE_FADING;
 			}
-			w->opacity_target = win_calc_opacity_target(ps, w, false);
+			if (!ps->redirected) {
+				CHECK(!win_skip_fading(ps, w));
+			}
 		}
 	}
 

src/win.c

@@ -121,6 +121,9 @@ static void win_update_focused(session_t *ps, struct managed_win *w) {
 	if (opacity_target_old != w->opacity_target && w->state == WSTATE_MAPPED) {
 		// Only MAPPED can transition to FADING
 		w->state = WSTATE_FADING;
+		if (!ps->redirected) {
+			CHECK(!win_skip_fading(ps, w));
+		}
 	}
 }