avoid delta overflow in countdown draw

diff --git a/movement/watch_faces/complication/countdown_face.c b/movement/watch_faces/complication/countdown_face.c
index be04040e33b7584a3079652ec08bf17249294274..6ae3d935b2e1f2992a28d44772e792d8e06a2fcf 100644 (file)
--- a/movement/watch_faces/complication/countdown_face.c
+++ b/movement/watch_faces/complication/countdown_face.c
@@ -87,7 +87,10 @@ static void draw(countdown_state_t *state, uint8_t subsecond) {
 
     switch (state->mode) {
         case cd_running:
-            delta = state->target_ts - state->now_ts;
+            if (state->target_ts <= state->now_ts)
+                delta = 0;
+            else
+                delta = state->target_ts - state->now_ts;
             result = div(delta, 60);
             state->seconds = result.rem;
             result = div(result.quot, 60);