pixelplot: set primary plane transparent but on top #1382

src/lib/plot.c

@@ -619,6 +619,19 @@ update_sample_double(ncdplot* ncp, int64_t x, double y, bool reset){
   }
 }
 
+static inline int
+create_pixelp(ncplot *p, ncplane* n){
+  if(((p->pixelp = ncplane_dup(n, NULL)) == NULL)){
+    return -1;
+  }
+  ncplane_move_below(p->pixelp, n);
+  uint64_t basechan = 0;
+  ncchannels_set_bg_alpha(&basechan, NCALPHA_TRANSPARENT);
+  ncchannels_set_fg_alpha(&basechan, NCALPHA_TRANSPARENT);
+  ncplane_set_base(n, "", 0, basechan);
+  return 0;
+}
+
 // takes ownership of n on all paths
 ncuplot* ncuplot_create(ncplane* n, const ncplot_options* opts, uint64_t miny, uint64_t maxy){
   ncuplot* ret = malloc(sizeof(*ret));
@@ -633,7 +646,7 @@ ncuplot* ncuplot_create(ncplane* n, const ncplot_options* opts, uint64_t miny, u
     return NULL;
   }
   if(bset->geom == NCBLIT_PIXEL){
-    if(((ret->plot.pixelp = ncplane_dup(n, NULL)) == NULL)){
+    if(create_pixelp(&ret->plot, n)){
       ncuplot_destroy(ret);
       return NULL;
     }
@@ -682,7 +695,7 @@ ncdplot* ncdplot_create(ncplane* n, const ncplot_options* opts, double miny, dou
     return NULL;
   }
   if(bset->geom == NCBLIT_PIXEL){
-    if(((ret->plot.pixelp = ncplane_dup(n, NULL)) == NULL)){
+    if(create_pixelp(&ret->plot, n)){
       ncdplot_destroy(ret);
       return NULL;
     }