2126da777ab1677598eeb020127005477ee51ac9
braney
  Tue Mar 2 14:49:29 2021 -0800
when counting overlaps for density coverage, make zero width elements
cover a single base.

diff --git src/hg/hgTracks/simpleTracks.c src/hg/hgTracks/simpleTracks.c
index 07d9b09..67ee538 100644
--- src/hg/hgTracks/simpleTracks.c
+++ src/hg/hgTracks/simpleTracks.c
@@ -4461,30 +4461,32 @@
 unsigned *counts = needHugeZeroedMem(size * sizeof(unsigned));
 extern int linkedFeaturesItemStart(struct track *tg, void *item);
 boolean isLinkedFeature = ( track->itemStart == linkedFeaturesItemStart);
 
 for (item = items; item; item = item->next)
     {
     if (isLinkedFeature)
         {
         struct linkedFeatures *lf = (struct linkedFeatures *)item;
         struct simpleFeature *sf;
 
         for (sf = lf->components; sf != NULL; sf = sf->next)
             {
             unsigned start = sf->start;
             unsigned end = sf->end;
+            if (start == end)
+                end++;
             if (positiveRangeIntersection(start, end, winStart, winEnd) <= 0)
                 continue;
 
             int x1 = max((int)start - (int)winStart, 0);
             int x2 = min((int)end - (int)winStart, size);
 
             for(; x1 < x2; x1++)
                 counts[x1]++;
             }
         }
     else
         {
         unsigned start = track->itemStart(track, item);
         unsigned end = track->itemEnd(track, item);
         if (positiveRangeIntersection(start, end, winStart, winEnd) <= 0)