diff --git a/.gitignore b/.gitignore
index 7edc5b7..63ff3ad 100644
--- a/.gitignore
+++ b/.gitignore
@@ -52,3 +52,5 @@ doxygen/
 /src/backtrace-symbols.[ch]
 /compton*.trace
 *.orig
+/tests/log
+/tests/testcases/__pycache__/
diff --git a/src/backend/backend.c b/src/backend/backend.c
index bded608..910c49c 100644
--- a/src/backend/backend.c
+++ b/src/backend/backend.c
@@ -204,16 +204,34 @@ void paint_all_new(session_t *ps, struct managed_win *t, bool ignore_damage) {
 			// itself is not opaque, only the frame is.
 
 			double blur_opacity = 1;
-			if (w->state == WSTATE_MAPPING) {
+			if (w->opacity < (1.0 / MAX_ALPHA)) {
+				// Hide blur for fully transparent windows.
+				blur_opacity = 0;
+			} else if (w->state == WSTATE_MAPPING) {
 				// Gradually increase the blur intensity during
 				// fading in.
+				assert(w->opacity <= w->opacity_target);
 				blur_opacity = w->opacity / w->opacity_target;
 			} else if (w->state == WSTATE_UNMAPPING ||
 			           w->state == WSTATE_DESTROYING) {
 				// Gradually decrease the blur intensity during
 				// fading out.
-				blur_opacity =
-				    w->opacity / win_calc_opacity_target(ps, w, true);
+				assert(w->opacity <= w->opacity_target_old);
+				blur_opacity = w->opacity / w->opacity_target_old;
+			} else if (w->state == WSTATE_FADING) {
+				if (w->opacity < w->opacity_target &&
+				    w->opacity_target_old < (1.0 / MAX_ALPHA)) {
+					// Gradually increase the blur intensity during
+					// fading in.
+					assert(w->opacity <= w->opacity_target);
+					blur_opacity = w->opacity / w->opacity_target;
+				} else if (w->opacity > w->opacity_target &&
+				           w->opacity_target < (1.0 / MAX_ALPHA)) {
+					// Gradually decrease the blur intensity during
+					// fading out.
+					assert(w->opacity <= w->opacity_target_old);
+					blur_opacity = w->opacity / w->opacity_target_old;
+				}
 			}
 			assert(blur_opacity >= 0 && blur_opacity <= 1);
 
diff --git a/src/event.c b/src/event.c
index 87de238..c6e1179 100644
--- a/src/event.c
+++ b/src/event.c
@@ -287,7 +287,7 @@ static inline void ev_map_notify(session_t *ps, xcb_map_notify_event_t *ev) {
 		return;
 	}
 
-	win_queue_update(w, WIN_UPDATE_MAP);
+	win_set_flags(w, WIN_FLAGS_MAPPED);
 
 	// FocusIn/Out may be ignored when the window is unmapped, so we must
 	// recheck focus here
@@ -482,14 +482,7 @@ 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;
-			}
-			if (!ps->redirected) {
-				CHECK(!win_skip_fading(ps, w));
-			}
+			win_update_opacity_target(ps, w);
 		}
 	}
 
diff --git a/src/picom.c b/src/picom.c
index b4a4d49..bbade20 100644
--- a/src/picom.c
+++ b/src/picom.c
@@ -1309,12 +1309,6 @@ static void handle_new_windows(session_t *ps) {
 }
 
 static void refresh_windows(session_t *ps) {
-	win_stack_foreach_managed_safe(w, &ps->window_stack) {
-		win_process_updates(ps, w);
-	}
-}
-
-static void refresh_stale_images(session_t *ps) {
 	win_stack_foreach_managed(w, &ps->window_stack) {
 		win_process_flags(ps, w);
 	}
@@ -1351,7 +1345,13 @@ static void handle_pending_updates(EV_P_ struct session *ps) {
 		// Call fill_win on new windows
 		handle_new_windows(ps);
 
-		// Process window updates
+		// Handle screen changes
+		// This HAS TO be called before refresh_windows, as handle_root_flags
+		// could call configure_root, which will release images and mark them
+		// stale.
+		handle_root_flags(ps);
+
+		// Process window flags
 		refresh_windows(ps);
 
 		{
@@ -1363,15 +1363,6 @@ static void handle_pending_updates(EV_P_ struct session *ps) {
 			free(r);
 		}
 
-		// Handle screen changes
-		// This HAS TO be called before refresh_stale_images, as handle_root_flags
-		// could call configure_root, which will release images and mark them
-		// stale.
-		handle_root_flags(ps);
-
-		// Refresh pixmaps and shadows
-		refresh_stale_images(ps);
-
 		e = xcb_request_check(ps->c, xcb_ungrab_server_checked(ps->c));
 		if (e) {
 			log_fatal_x_error(e, "failed to ungrab x server");
diff --git a/src/win.c b/src/win.c
index a27643c..28d84ed 100644
--- a/src/win.c
+++ b/src/win.c
@@ -46,9 +46,6 @@
 // TODO Make more window states internal
 struct managed_win_internal {
 	struct managed_win base;
-
-	/// A bit mask of unhandled window updates
-	uint_fast32_t pending_updates;
 };
 
 #define OPAQUE (0xffffffff)
@@ -247,6 +244,7 @@ static inline void win_release_pixmap(backend_t *base, struct managed_win *w) {
 	if (w->win_image) {
 		base->ops->release_image(base, w->win_image);
 		w->win_image = NULL;
+		// Bypassing win_set_flags, because `w` might have been destroyed
 		w->flags |= WIN_FLAGS_PIXMAP_NONE;
 	}
 }
@@ -256,6 +254,7 @@ static inline void win_release_shadow(backend_t *base, struct managed_win *w) {
 	if (w->shadow_image) {
 		base->ops->release_image(base, w->shadow_image);
 		w->shadow_image = NULL;
+		// Bypassing win_set_flags, because `w` might have been destroyed
 		w->flags |= WIN_FLAGS_SHADOW_NONE;
 	}
 }
@@ -276,11 +275,11 @@ static inline bool win_bind_pixmap(struct backend_base *b, struct managed_win *w
 	    b->ops->bind_pixmap(b, pixmap, x_get_visual_info(b->c, w->a.visual), true);
 	if (!w->win_image) {
 		log_error("Failed to bind pixmap");
-		w->flags |= WIN_FLAGS_IMAGE_ERROR;
+		win_set_flags(w, WIN_FLAGS_IMAGE_ERROR);
 		return false;
 	}
 
-	w->flags &= ~WIN_FLAGS_PIXMAP_NONE;
+	win_clear_flags(w, WIN_FLAGS_PIXMAP_NONE);
 	return true;
 }
 
@@ -294,13 +293,13 @@ bool win_bind_shadow(struct backend_base *b, struct managed_win *w, struct color
 		log_error("Failed to bind shadow image, shadow will be disabled for "
 		          "%#010x (%s)",
 		          w->base.id, w->name);
-		w->flags |= WIN_FLAGS_SHADOW_NONE;
+		win_set_flags(w, WIN_FLAGS_SHADOW_NONE);
 		w->shadow = false;
 		return false;
 	}
 
 	log_debug("New shadow for %#010x (%s)", w->base.id, w->name);
-	w->flags &= ~WIN_FLAGS_SHADOW_NONE;
+	win_clear_flags(w, WIN_FLAGS_SHADOW_NONE);
 	return true;
 }
 
@@ -310,40 +309,38 @@ void win_release_images(struct backend_base *backend, struct managed_win *w) {
 	// But if we are not releasing any images anyway, we don't care about the stale
 	// flags.
 
-	if ((w->flags & WIN_FLAGS_PIXMAP_NONE) == 0) {
-		assert((w->flags & WIN_FLAGS_PIXMAP_STALE) == 0);
+	if (!win_check_flags_all(w, WIN_FLAGS_PIXMAP_NONE)) {
+		assert(!win_check_flags_all(w, WIN_FLAGS_PIXMAP_STALE));
 		win_release_pixmap(backend, w);
 	}
 
-	if ((w->flags & WIN_FLAGS_SHADOW_NONE) == 0) {
-		assert((w->flags & WIN_FLAGS_SHADOW_STALE) == 0);
+	if (!win_check_flags_all(w, WIN_FLAGS_SHADOW_NONE)) {
+		assert(!win_check_flags_all(w, WIN_FLAGS_SHADOW_STALE));
 		win_release_shadow(backend, w);
 	}
 }
 
 void win_process_flags(session_t *ps, struct managed_win *w) {
-	// Make sure all pending window updates are processed before this. Making this
-	// assumption simplifies some checks (e.g. whether window is mapped)
-	assert(((struct managed_win_internal *)w)->pending_updates == 0);
-
-	if (!w->flags || (w->flags & WIN_FLAGS_IMAGE_ERROR) != 0) {
-		return;
+	if (win_check_flags_all(w, WIN_FLAGS_MAPPED)) {
+		map_win_start(ps, w);
 	}
+	win_clear_flags(w, WIN_FLAGS_MAPPED);
 
 	// Not a loop
-	while ((w->flags & WIN_FLAGS_IMAGES_STALE) != 0) {
+	while (win_check_flags_any(w, WIN_FLAGS_IMAGES_STALE) &&
+	       !win_check_flags_all(w, WIN_FLAGS_IMAGE_ERROR)) {
 		// Image needs to be updated, update it.
 		if (!ps->backend_data) {
 			// We are using legacy backend, nothing to do here.
 			break;
 		}
 
-		if ((w->flags & WIN_FLAGS_PIXMAP_STALE) != 0) {
+		if (win_check_flags_all(w, WIN_FLAGS_PIXMAP_STALE)) {
 			// Check to make sure the window is still mapped, otherwise we
 			// won't be able to rebind pixmap after releasing it, yet we might
 			// still need the pixmap for rendering.
 			assert(w->state != WSTATE_UNMAPPING && w->state != WSTATE_DESTROYING);
-			if ((w->flags & WIN_FLAGS_PIXMAP_NONE) == 0) {
+			if (!win_check_flags_all(w, WIN_FLAGS_PIXMAP_NONE)) {
 				// Must release images first, otherwise breaks
 				// NVIDIA driver
 				win_release_pixmap(ps->backend_data, w);
@@ -351,8 +348,8 @@ void win_process_flags(session_t *ps, struct managed_win *w) {
 			win_bind_pixmap(ps->backend_data, w);
 		}
 
-		if ((w->flags & WIN_FLAGS_SHADOW_STALE) != 0) {
-			if ((w->flags & WIN_FLAGS_SHADOW_NONE) == 0) {
+		if (win_check_flags_all(w, WIN_FLAGS_SHADOW_STALE)) {
+			if (!win_check_flags_all(w, WIN_FLAGS_SHADOW_NONE)) {
 				win_release_shadow(ps->backend_data, w);
 			}
 			if (w->shadow) {
@@ -370,7 +367,7 @@ void win_process_flags(session_t *ps, struct managed_win *w) {
 	}
 
 	// Clear stale image flags
-	w->flags &= ~WIN_FLAGS_IMAGES_STALE;
+	win_clear_flags(w, WIN_FLAGS_IMAGES_STALE);
 }
 
 /**
@@ -582,18 +579,17 @@ winmode_t win_calc_mode(const struct managed_win *w) {
  *
  * @param ps           current session
  * @param w            struct _win object representing the window
- * @param ignore_state whether window state should be ignored in opacity calculation
  *
  * @return target opacity
  */
-double win_calc_opacity_target(session_t *ps, const struct managed_win *w, bool ignore_state) {
+double win_calc_opacity_target(session_t *ps, const struct managed_win *w) {
 	double opacity = 1;
 
-	if (w->state == WSTATE_UNMAPPED && !ignore_state) {
+	if (w->state == WSTATE_UNMAPPED) {
 		// be consistent
 		return 0;
 	}
-	if ((w->state == WSTATE_UNMAPPING || w->state == WSTATE_DESTROYING) && !ignore_state) {
+	if (w->state == WSTATE_UNMAPPING || w->state == WSTATE_DESTROYING) {
 		return 0;
 	}
 	// Try obeying opacity property and window type opacity firstly
@@ -694,7 +690,7 @@ static void win_set_shadow(session_t *ps, struct managed_win *w, bool shadow_new
 		w->shadow = shadow_new;
 		assert(!w->shadow_image);
 		assert(!w->win_image);
-		assert(w->flags & WIN_FLAGS_IMAGES_NONE);
+		assert(win_check_flags_all(w, WIN_FLAGS_IMAGES_NONE));
 		return;
 	}
 
@@ -720,14 +716,14 @@ static void win_set_shadow(session_t *ps, struct managed_win *w, bool shadow_new
 	// asserting the existence of the shadow image.
 	if (w->shadow) {
 		// Mark the new extents as damaged if the shadow is added
-		assert(!w->shadow_image || (w->flags & WIN_FLAGS_SHADOW_STALE) ||
+		assert(!w->shadow_image || win_check_flags_all(w, WIN_FLAGS_SHADOW_STALE) ||
 		       !ps->o.experimental_backends);
 		pixman_region32_clear(&extents);
 		win_extents(w, &extents);
 		add_damage_from_win(ps, w);
 	} else {
 		// Mark the old extents as damaged if the shadow is removed
-		assert(w->shadow_image || (w->flags & WIN_FLAGS_SHADOW_STALE) ||
+		assert(w->shadow_image || win_check_flags_all(w, WIN_FLAGS_SHADOW_STALE) ||
 		       !ps->o.experimental_backends);
 		add_damage(ps, &extents);
 	}
@@ -737,7 +733,7 @@ static void win_set_shadow(session_t *ps, struct managed_win *w, bool shadow_new
 	// Delayed update of shadow image
 	// By setting WIN_FLAGS_SHADOW_STALE, we ask win_process_flags to re-create or
 	// release the shaodw in based on whether w->shadow is set.
-	w->flags |= WIN_FLAGS_SHADOW_STALE;
+	win_set_flags(w, WIN_FLAGS_SHADOW_STALE);
 	ps->pending_updates = true;
 }
 
@@ -915,18 +911,7 @@ void win_on_factor_change(session_t *ps, struct managed_win *w) {
 		w->unredir_if_possible_excluded =
 		    c2_match(ps, w, ps->o.unredir_if_possible_blacklist, NULL);
 
-	auto opacity_target_old = w->opacity_target;
-	w->opacity_target = win_calc_opacity_target(ps, w, false);
-	if (opacity_target_old != w->opacity_target && w->state == WSTATE_MAPPED) {
-		// Only MAPPED can transition to FADING
-		assert(w->opacity == opacity_target_old);
-		w->state = WSTATE_FADING;
-		log_debug("Window %#010x (%s) opactiy %f, opacity target %f", w->base.id,
-		          w->name, w->opacity, w->opacity_target);
-		if (!ps->redirected) {
-			CHECK(!win_skip_fading(ps, w));
-		}
-	}
+	win_update_opacity_target(ps, w);
 
 	w->reg_ignore_valid = false;
 }
@@ -945,7 +930,7 @@ void win_on_win_size_change(session_t *ps, struct managed_win *w) {
 	// Invalidate the shadow we built
 	if (w->state == WSTATE_MAPPED || w->state == WSTATE_MAPPING ||
 	    w->state == WSTATE_FADING) {
-		w->flags |= WIN_FLAGS_IMAGES_STALE;
+		win_set_flags(w, WIN_FLAGS_IMAGES_STALE);
 		ps->pending_updates = true;
 	} else {
 		assert(w->state == WSTATE_UNMAPPED);
@@ -1301,7 +1286,6 @@ struct win *fill_win(session_t *ps, struct win *w) {
 	// Allocate and initialize the new win structure
 	auto new_internal = cmalloc(struct managed_win_internal);
 	auto new = (struct managed_win *)new_internal;
-	new_internal->pending_updates = 0;
 
 	// Fill structure
 	// We only need to initialize the part that are not initialized
@@ -1599,7 +1583,7 @@ void win_update_bounding_shape(session_t *ps, struct managed_win *w) {
 		// Note we only do this when screen is redirected, because
 		// otherwise win_data is not valid
 		assert(w->state != WSTATE_UNMAPPING && w->state != WSTATE_DESTROYING);
-		w->flags |= WIN_FLAGS_IMAGES_STALE;
+		win_set_flags(w, WIN_FLAGS_IMAGES_STALE);
 		ps->pending_updates = true;
 	}
 	free_paint(ps, &w->paint);
@@ -1713,7 +1697,7 @@ static void unmap_win_finish(session_t *ps, struct managed_win *w) {
 	free_paint(ps, &w->shadow_paint);
 
 	// Try again at binding images when the window is mapped next time
-	w->flags &= ~WIN_FLAGS_IMAGE_ERROR;
+	win_clear_flags(w, WIN_FLAGS_IMAGE_ERROR);
 }
 
 /// Finish the destruction of a window (e.g. after fading has finished).
@@ -1886,14 +1870,15 @@ bool destroy_win_start(session_t *ps, struct win *w) {
 	}
 
 	if (w->managed) {
+		// Clear PIXMAP_STALE flag, since the window is destroyed there is no
+		// pixmap available so STALE doesn't make sense.
+		// Do this before changing the window state to destroying
+		win_clear_flags(mw, WIN_FLAGS_PIXMAP_STALE);
+
 		// Update state flags of a managed window
 		mw->state = WSTATE_DESTROYING;
 		mw->a.map_state = XCB_MAP_STATE_UNMAPPED;
 		mw->in_openclose = true;
-
-		// Clear PIXMAP_STALE flag, since the window is destroyed there is no
-		// pixmap available so STALE doesn't make sense.
-		mw->flags &= ~WIN_FLAGS_PIXMAP_STALE;
 	}
 
 	// don't need win_ev_stop because the window is gone anyway
@@ -1913,7 +1898,6 @@ bool destroy_win_start(session_t *ps, struct win *w) {
 }
 
 void unmap_win_start(session_t *ps, struct managed_win *w) {
-	auto internal_w = (struct managed_win_internal *)w;
 	assert(w);
 	assert(w->base.managed);
 	assert(w->a._class != XCB_WINDOW_CLASS_INPUT_ONLY);
@@ -1926,8 +1910,9 @@ void unmap_win_start(session_t *ps, struct managed_win *w) {
 	}
 
 	if (unlikely(w->state == WSTATE_UNMAPPING || w->state == WSTATE_UNMAPPED)) {
-		if (internal_w->pending_updates & WIN_UPDATE_MAP) {
-			internal_w->pending_updates &= ~(unsigned long)WIN_UPDATE_MAP;
+		if (win_check_flags_all(w, WIN_FLAGS_MAPPED)) {
+			// Clear the pending map as this window is now unmapped
+			win_clear_flags(w, WIN_FLAGS_MAPPED);
 		} else {
 			log_warn("Trying to unmapping an already unmapped window %#010x "
 			         "\"%s\"",
@@ -1942,11 +1927,12 @@ void unmap_win_start(session_t *ps, struct managed_win *w) {
 
 	w->a.map_state = XCB_MAP_STATE_UNMAPPED;
 	w->state = WSTATE_UNMAPPING;
-	w->opacity_target = win_calc_opacity_target(ps, w, false);
+	w->opacity_target_old = fmax(w->opacity_target, w->opacity_target_old);
+	w->opacity_target = win_calc_opacity_target(ps, w);
 
 	// Clear PIXMAP_STALE flag, since the window is unmapped there is no pixmap
 	// available so STALE doesn't make sense.
-	w->flags &= ~WIN_FLAGS_PIXMAP_STALE;
+	win_clear_flags(w, WIN_FLAGS_PIXMAP_STALE);
 
 	// don't care about properties anymore
 	win_ev_stop(ps, &w->base);
@@ -2053,8 +2039,7 @@ void map_win_start(session_t *ps, struct managed_win *w) {
 	}
 
 	assert(w->state == WSTATE_UNMAPPED);
-	assert((w->flags & WIN_FLAGS_IMAGES_NONE) == WIN_FLAGS_IMAGES_NONE ||
-	       !ps->o.experimental_backends);
+	assert(win_check_flags_all(w, WIN_FLAGS_IMAGES_NONE) || !ps->o.experimental_backends);
 
 	// We stopped processing window size change when we were unmapped, refresh the
 	// size of the window
@@ -2127,7 +2112,8 @@ void map_win_start(session_t *ps, struct managed_win *w) {
 	// XXX We need to make sure that win_data is available
 	// iff `state` is MAPPED
 	w->state = WSTATE_MAPPING;
-	w->opacity_target = win_calc_opacity_target(ps, w, false);
+	w->opacity_target_old = 0;
+	w->opacity_target = win_calc_opacity_target(ps, w);
 
 	log_debug("Window %#010x has opacity %f, opacity target is %f", w->base.id,
 	          w->opacity, w->opacity_target);
@@ -2148,7 +2134,7 @@ void map_win_start(session_t *ps, struct managed_win *w) {
 	// the window's image will be bound
 	win_update_bounding_shape(ps, w);
 
-	assert((w->flags & WIN_FLAGS_IMAGES_STALE) == WIN_FLAGS_IMAGES_STALE);
+	assert(win_check_flags_all(w, WIN_FLAGS_IMAGES_STALE));
 
 #ifdef CONFIG_DBUS
 	// Send D-Bus signal
@@ -2162,6 +2148,60 @@ void map_win_start(session_t *ps, struct managed_win *w) {
 	}
 }
 
+/**
+ * Update target window opacity depending on the current state.
+ */
+void win_update_opacity_target(session_t *ps, struct managed_win *w) {
+	auto opacity_target_old = w->opacity_target;
+	w->opacity_target = win_calc_opacity_target(ps, w);
+
+	if (opacity_target_old == w->opacity_target) {
+		return;
+	}
+
+	if (w->state == WSTATE_MAPPED) {
+		// Opacity target changed while MAPPED. Transition to FADING.
+		assert(w->opacity == opacity_target_old);
+		w->opacity_target_old = opacity_target_old;
+		w->state = WSTATE_FADING;
+		log_debug("Window %#010x (%s) opacity %f, opacity target %f, set "
+		          "old target %f",
+		          w->base.id, w->name, w->opacity, w->opacity_target,
+		          w->opacity_target_old);
+	} else if (w->state == WSTATE_MAPPING) {
+		// Opacity target changed while fading in.
+		if (w->opacity >= w->opacity_target) {
+			// Already reached new target opacity. Transition to
+			// FADING.
+			map_win_finish(w);
+			w->opacity_target_old = fmax(opacity_target_old, w->opacity);
+			w->state = WSTATE_FADING;
+			log_debug("Window %#010x (%s) opacity %f already reached "
+			          "new opacity target %f while mapping, set old "
+			          "target %f",
+			          w->base.id, w->name, w->opacity, w->opacity_target,
+			          w->opacity_target_old);
+		}
+	} else if (w->state == WSTATE_FADING) {
+		// Opacity target changed while FADING.
+		if ((w->opacity < opacity_target_old && w->opacity > w->opacity_target) ||
+		    (w->opacity > opacity_target_old && w->opacity < w->opacity_target)) {
+			// Changed while fading in and will fade out or while
+			// fading out and will fade in.
+			w->opacity_target_old = opacity_target_old;
+			log_debug("Window %#010x (%s) opacity %f already reached "
+			          "new opacity target %f while fading, set "
+			          "old target %f",
+			          w->base.id, w->name, w->opacity, w->opacity_target,
+			          w->opacity_target_old);
+		}
+	}
+
+	if (!ps->redirected) {
+		CHECK(!win_skip_fading(ps, w));
+	}
+}
+
 /**
  * Find a managed window from window id in window linked list of the session.
  */
@@ -2284,31 +2324,33 @@ win_is_fullscreen_xcb(xcb_connection_t *c, const struct atom *a, const xcb_windo
 	return false;
 }
 
-/// Queue an update on a window. A series of sanity checks are performed
-void win_queue_update(struct managed_win *_w, enum win_update update) {
-	auto w = (struct managed_win_internal *)_w;
-	assert(popcount(update) == 1);
-	assert(update == WIN_UPDATE_MAP);        // Currently the only supported update
-
-	if (unlikely(_w->state == WSTATE_DESTROYING)) {
-		log_error("Updates queued on a destroyed window %#010x (%s)", _w->base.id,
-		          _w->name);
+/// Set flags on a window. Some sanity checks are performed
+void win_set_flags(struct managed_win *w, uint64_t flags) {
+	if (unlikely(w->state == WSTATE_DESTROYING)) {
+		log_error("Flags set on a destroyed window %#010x (%s)", w->base.id, w->name);
 		return;
 	}
 
-	w->pending_updates |= update;
+	w->flags |= flags;
 }
 
-/// Process pending updates on a window. Has to be called in X critical section
-void win_process_updates(struct session *ps, struct managed_win *_w) {
-	assert(ps->server_grabbed);
-	auto w = (struct managed_win_internal *)_w;
-
-	if (w->pending_updates & WIN_UPDATE_MAP) {
-		map_win_start(ps, _w);
+/// Clear flags on a window. Some sanity checks are performed
+void win_clear_flags(struct managed_win *w, uint64_t flags) {
+	if (unlikely(w->state == WSTATE_DESTROYING)) {
+		log_error("Flags cleared on a destroyed window %#010x (%s)", w->base.id,
+		          w->name);
+		return;
 	}
 
-	w->pending_updates = 0;
+	w->flags = w->flags & (~flags);
+}
+
+bool win_check_flags_any(struct managed_win *w, uint64_t flags) {
+	return (w->flags & flags) != 0;
+}
+
+bool win_check_flags_all(struct managed_win *w, uint64_t flags) {
+	return (w->flags & flags) == flags;
 }
 
 /**
@@ -2364,7 +2406,6 @@ win_stack_find_next_managed(const session_t *ps, const struct list_node *i) {
 
 /// Return whether this window is mapped on the X server side
 bool win_is_mapped_in_x(const struct managed_win *w) {
-	auto iw = (const struct managed_win_internal *)w;
 	return w->state == WSTATE_MAPPING || w->state == WSTATE_FADING ||
-	       w->state == WSTATE_MAPPED || (iw->pending_updates & WIN_UPDATE_MAP);
+	       w->state == WSTATE_MAPPED || (w->flags & WIN_FLAGS_MAPPED);
 }
diff --git a/src/win.h b/src/win.h
index d3d9071..d6778b6 100644
--- a/src/win.h
+++ b/src/win.h
@@ -131,7 +131,7 @@ struct managed_win {
 	/// See above about coordinate systems.
 	region_t bounding_shape;
 	/// Window flags. Definitions above.
-	int_fast16_t flags;
+	uint64_t flags;
 	/// The region of screen that will be obscured when windows above is painted,
 	/// in global coordinates.
 	/// We use this to reduce the pixels that needed to be paint when painting
@@ -192,6 +192,8 @@ struct managed_win {
 	double opacity;
 	/// Target window opacity.
 	double opacity_target;
+	/// Previous window opacity.
+	double opacity_target_old;
 	/// true if window (or client window, for broken window managers
 	/// not transferring client window's _NET_WM_OPACITY value) has opacity prop
 	bool has_opacity_prop;
@@ -252,12 +254,8 @@ struct managed_win {
 #endif
 };
 
-/// Process pending updates on a window. Has to be called in X critical section
-void win_process_updates(struct session *ps, struct managed_win *_w);
 /// Process pending images flags on a window. Has to be called in X critical section
 void win_process_flags(session_t *ps, struct managed_win *w);
-/// Queue an update on a window. A series of sanity checks are performed
-void win_queue_update(struct managed_win *_w, enum win_update update);
 /// Bind a shadow to the window, with color `c` and shadow kernel `kernel`
 bool win_bind_shadow(struct backend_base *b, struct managed_win *w, struct color c,
                      struct conv *kernel);
@@ -291,6 +289,7 @@ void win_set_focused(session_t *ps, struct managed_win *w);
 bool attr_pure win_should_fade(session_t *ps, const struct managed_win *w);
 void win_update_prop_shadow_raw(session_t *ps, struct managed_win *w);
 void win_update_prop_shadow(session_t *ps, struct managed_win *w);
+void win_update_opacity_target(session_t *ps, struct managed_win *w);
 void win_on_factor_change(session_t *ps, struct managed_win *w);
 /**
  * Update cache data in struct _win that depends on window size.
@@ -311,12 +310,10 @@ bool win_get_class(session_t *ps, struct managed_win *w);
  *
  * @param ps           current session
  * @param w            struct _win object representing the window
- * @param ignore_state whether window state should be ignored in opacity calculation
  *
  * @return target opacity
  */
-double attr_pure win_calc_opacity_target(session_t *ps, const struct managed_win *w,
-                                         bool ignore_state);
+double attr_pure win_calc_opacity_target(session_t *ps, const struct managed_win *w);
 bool attr_pure win_should_dim(session_t *ps, const struct managed_win *w);
 void win_update_screen(session_t *, struct managed_win *);
 /**
@@ -434,6 +431,14 @@ bool win_is_mapped_in_x(const struct managed_win *w);
 // Find the managed window immediately below `w` in the window stack
 struct managed_win *attr_pure win_stack_find_next_managed(const session_t *ps,
                                                           const struct list_node *w);
+/// Set flags on a window. Some sanity checks are performed
+void win_set_flags(struct managed_win *w, uint64_t flags);
+/// Clear flags on a window. Some sanity checks are performed
+void win_clear_flags(struct managed_win *w, uint64_t flags);
+/// Returns true if any of the flags in `flags` is set
+bool win_check_flags_any(struct managed_win *w, uint64_t flags);
+/// Returns true if all of the flags in `flags` are set
+bool win_check_flags_all(struct managed_win *w, uint64_t flags);
 
 /// Free all resources in a struct win
 void free_win_res(session_t *ps, struct managed_win *w);
diff --git a/src/win_defs.h b/src/win_defs.h
index 2a18e4b..f8494bb 100644
--- a/src/win_defs.h
+++ b/src/win_defs.h
@@ -27,11 +27,6 @@ typedef enum {
 	WMODE_SOLID,              // The window is opaque including the frame
 } winmode_t;
 
-/// Pending window updates
-enum win_update {
-	WIN_UPDATE_MAP = 1,
-};
-
 /// Transition table:
 /// (DESTROYED is when the win struct is destroyed and freed)
 /// ('o' means in all other cases)
@@ -45,8 +40,8 @@ enum win_update {
 /// |  DESTROYING |    -    |    o     |   -   |  -    |   -    |  -     | Fading  |
 /// |             |         |          |       |       |        |        |finished |
 /// +-------------+---------+----------+-------+-------+--------+--------+---------+
-/// |   MAPPING   | Window  |  Window  |   o   |  -    |   -    | Fading |    -    |
-/// |             |unmapped |destroyed |       |       |        |finished|         |
+/// |   MAPPING   | Window  |  Window  |   o   |Opacity|   -    | Fading |    -    |
+/// |             |unmapped |destroyed |       |change |        |finished|         |
 /// +-------------+---------+----------+-------+-------+--------+--------+---------+
 /// |    FADING   | Window  |  Window  |   -   |  o    |   -    | Fading |    -    |
 /// |             |unmapped |destroyed |       |       |        |finished|         |
@@ -86,9 +81,11 @@ enum win_flags {
 	WIN_FLAGS_SHADOW_STALE = 8,
 	/// shadow has not been generated
 	WIN_FLAGS_SHADOW_NONE = 16,
+	/// the window is mapped by X, we need to call map_win_start for it
+	WIN_FLAGS_MAPPED = 64,
 };
 
-static const int_fast16_t WIN_FLAGS_IMAGES_STALE =
+static const uint64_t WIN_FLAGS_IMAGES_STALE =
     WIN_FLAGS_PIXMAP_STALE | WIN_FLAGS_SHADOW_STALE;
 
 #define WIN_FLAGS_IMAGES_NONE (WIN_FLAGS_PIXMAP_NONE | WIN_FLAGS_SHADOW_NONE)
diff --git a/tests/configs/issue314.conf b/tests/configs/issue314.conf
index ce71a3e..bb3c4cb 100644
--- a/tests/configs/issue314.conf
+++ b/tests/configs/issue314.conf
@@ -1,5 +1,5 @@
 fading = true
-fade-in-step = 1
+fade-in-step = 0.01
 fade-out-step = 0.01
 inactive-opacity = 0
 blur-background = true
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index 53292ca..9f3c9e4 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -10,3 +10,5 @@ cd $(dirname $0)
 ./run_one_test.sh $exe configs/issue239_3.conf testcases/issue239_3.py
 ./run_one_test.sh $exe configs/issue239_3.conf testcases/issue239_3_norefresh.py
 ./run_one_test.sh $exe configs/issue314.conf testcases/issue314.py
+./run_one_test.sh $exe configs/issue314.conf testcases/issue314_2.py
+./run_one_test.sh $exe configs/issue314.conf testcases/issue314_3.py
diff --git a/tests/testcases/issue314.py b/tests/testcases/issue314.py
index de7226b..ee29fc4 100755
--- a/tests/testcases/issue314.py
+++ b/tests/testcases/issue314.py
@@ -12,11 +12,11 @@ visual = setup.roots[0].root_visual
 depth = setup.roots[0].root_depth
 x = xproto.xprotoExtension(conn)
 
-# issue 239 is caused by a window gaining a shadow during its fade-out transition
+# issue 314 is caused by changing a windows target opacity during its fade-in/-out transition
 wid1 = conn.generate_id()
 print("Window 1: ", hex(wid1))
 wid2 = conn.generate_id()
-print("Window 1: ", hex(wid2))
+print("Window 2: ", hex(wid2))
 
 # Create windows
 conn.core.CreateWindowChecked(depth, wid1, root, 0, 0, 100, 100, 0, xproto.WindowClass.InputOutput, visual, 0, []).check()
@@ -26,20 +26,19 @@ conn.core.CreateWindowChecked(depth, wid2, root, 0, 0, 100, 100, 0, xproto.Windo
 set_window_name(conn, wid1, "Test window 1")
 set_window_name(conn, wid2, "Test window 2")
 
-print("mapping 1")
+# Check updating opacity while UNMAPPING/DESTROYING windows
+print("Mapping 1")
 conn.core.MapWindowChecked(wid1).check()
-print("mapping 2")
+print("Mapping 2")
 conn.core.MapWindowChecked(wid2).check()
-
 time.sleep(0.5)
 
 x.SetInputFocusChecked(0, wid1, xproto.Time.CurrentTime).check()
-
 time.sleep(0.5)
 
 # Destroy the windows
+print("Destroy 1 while fading out")
 conn.core.DestroyWindowChecked(wid1).check()
-
 x.SetInputFocusChecked(0, wid2, xproto.Time.CurrentTime).check()
 time.sleep(1)
 conn.core.DestroyWindowChecked(wid2).check()
diff --git a/tests/testcases/issue314_2.py b/tests/testcases/issue314_2.py
new file mode 100755
index 0000000..01192de
--- /dev/null
+++ b/tests/testcases/issue314_2.py
@@ -0,0 +1,46 @@
+#!/usr/bin/env python
+
+import xcffib.xproto as xproto
+import xcffib
+import time
+from common import set_window_name, trigger_root_configure
+
+conn = xcffib.connect()
+setup = conn.get_setup()
+root = setup.roots[0].root
+visual = setup.roots[0].root_visual
+depth = setup.roots[0].root_depth
+x = xproto.xprotoExtension(conn)
+
+opacity_80 = [int(0xffffffff * 0.8), ]
+opacity_single = [int(0xffffffff * 0.002), ]
+
+# issue 314 is caused by changing a windows target opacity during its fade-in/-out transition
+wid1 = conn.generate_id()
+print("Window 1: ", hex(wid1))
+
+atom = "_NET_WM_WINDOW_OPACITY"
+opacity_atom = conn.core.InternAtom(False, len(atom), atom).reply().atom
+
+# Create windows
+conn.core.CreateWindowChecked(depth, wid1, root, 0, 0, 100, 100, 0, xproto.WindowClass.InputOutput, visual, 0, []).check()
+
+# Set Window names
+set_window_name(conn, wid1, "Test window 1")
+
+# Check updating opacity while MAPPING windows
+print("Mapping window")
+conn.core.MapWindowChecked(wid1).check()
+time.sleep(0.5)
+
+print("Update opacity while fading in")
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_80).check()
+time.sleep(0.2)
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_single).check()
+time.sleep(1)
+
+conn.core.DeletePropertyChecked(wid1, opacity_atom).check()
+time.sleep(0.5)
+
+# Destroy the windows
+conn.core.DestroyWindowChecked(wid1).check()
diff --git a/tests/testcases/issue314_3.py b/tests/testcases/issue314_3.py
new file mode 100755
index 0000000..8e5d62d
--- /dev/null
+++ b/tests/testcases/issue314_3.py
@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+
+import xcffib.xproto as xproto
+import xcffib
+import time
+from common import set_window_name, trigger_root_configure
+
+conn = xcffib.connect()
+setup = conn.get_setup()
+root = setup.roots[0].root
+visual = setup.roots[0].root_visual
+depth = setup.roots[0].root_depth
+x = xproto.xprotoExtension(conn)
+
+opacity_100 = [0xffffffff, ]
+opacity_80 = [int(0xffffffff * 0.8), ]
+opacity_single = [int(0xffffffff * 0.002), ]
+opacity_0 = [0, ]
+
+# issue 314 is caused by changing a windows target opacity during its fade-in/-out transition
+wid1 = conn.generate_id()
+print("Window 1: ", hex(wid1))
+
+atom = "_NET_WM_WINDOW_OPACITY"
+opacity_atom = conn.core.InternAtom(False, len(atom), atom).reply().atom
+
+# Create windows
+conn.core.CreateWindowChecked(depth, wid1, root, 0, 0, 100, 100, 0, xproto.WindowClass.InputOutput, visual, 0, []).check()
+
+# Set Window names
+set_window_name(conn, wid1, "Test window 1")
+
+# Check updating opacity while FADING windows
+print("Mapping window")
+conn.core.MapWindowChecked(wid1).check()
+time.sleep(1.2)
+
+print("Update opacity while fading out")
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_single).check()
+time.sleep(0.2)
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_0).check()
+time.sleep(1)
+
+print("Change from fading in to fading out")
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_80).check()
+time.sleep(0.5)
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_0).check()
+time.sleep(1)
+
+print("Update opacity while fading in")
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_80).check()
+time.sleep(0.2)
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_100).check()
+time.sleep(1)
+
+print("Change from fading out to fading in")
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_0).check()
+time.sleep(0.5)
+conn.core.ChangePropertyChecked(xproto.PropMode.Replace, wid1, opacity_atom, xproto.Atom.CARDINAL, 32, 1, opacity_80).check()
+time.sleep(1)
+
+# Destroy the windows
+conn.core.DestroyWindowChecked(wid1).check()