sixel_scrub: be a bit more cautious about our jiggery-pokery

src/lib/internal.h

@@ -816,7 +816,7 @@ sprixel_state(const sprixel* s, int y, int x){
   const ncplane* stdn = notcurses_stdplane_const(ncplane_notcurses_const(s->n));
   int localy = y - (s->n->absy - stdn->absy);
   int localx = x - (s->n->absx - stdn->absx);
-//fprintf(stderr, "TAM %d at %d/%d (%d/%d)\n", s->n->tam[localy * s->dimx + localx].state, localy, localx, y, x);
+//fprintf(stderr, "TAM %d at %d/%d (%d/%d, %d/%d)\n", s->n->tam[localy * s->dimx + localx].state, localy, localx, y, x, s->dimy, s->dimx);
   assert(localy >= 0);
   assert(localy < s->dimy);
   assert(localx >= 0);

src/lib/kitty.c

@@ -996,7 +996,7 @@ int kitty_remove(int id, FILE* out){
   return 0;
 }
 
-// damages cells underneath the graphic which weren't SPRIXCELL_OPAQUE
+// damages cells underneath the graphic which were OPAQUE
 int kitty_scrub(const ncpile* p, sprixel* s){
 //fprintf(stderr, "FROM: %d/%d state: %d s->n: %p\n", s->movedfromy, s->movedfromx, s->invalidated, s->n);
   for(int yy = s->movedfromy ; yy < s->movedfromy + s->dimy && yy < p->dimy ; ++yy){

src/lib/sixel.c

@@ -755,12 +755,9 @@ int sixel_blit(ncplane* n, int linesize, const void* data, int leny, int lenx,
   // if we have a sprixel attached to this plane, see if we can reuse it
   // (we need the same dimensions) and thus immediately apply its T-A table.
   if(n->tam){
-//fprintf(stderr, "IT'S A REUSE %d %d\n", rows, cols);
     if(n->leny == rows && n->lenx == cols){
       tam = n->tam;
       reuse = true;
-    }else{
-      // FIXME free up old TAM (well, shrink it anyway)
     }
   }
   if(!reuse){
@@ -806,9 +803,20 @@ int sixel_scrub(const ncpile* p, sprixel* s){
       if(r->sprixel){
         s = r->sprixel;
       }
-      if(s->n){
-        sprixcell_e state = sprixel_state(s, yy - s->movedfromy,
-                                          xx - s->movedfromx);
+      if(!s->n){
+        // need this to damage cells underneath a sprixel we're removing
+        r->s.damaged = 1;
+        continue;
+      }
+      if(yy >= s->n->leny || yy - s->n->absy < 0){
+        r->s.damaged = 1;
+        continue;
+      }
+      if(xx >= s->n->lenx || xx - s->n->absx < 0){
+        r->s.damaged = 1;
+        continue;
+      }
+      sprixcell_e state = sprixel_state(s, yy, xx);
 //fprintf(stderr, "CHECKING %d/%d state: %d %d/%d\n", yy - s->movedfromy - s->n->absy, xx - s->movedfromx - s->n->absx, state, yy, xx);
       if(state == SPRIXCELL_TRANSPARENT || state == SPRIXCELL_MIXED_SIXEL){
         r->s.damaged = 1;
@@ -818,10 +826,6 @@ int sixel_scrub(const ncpile* p, sprixel* s){
         // ahead and damage it.
         r->s.damaged = 1;
       }
-      }else{
-        // need this to damage cells underneath a sprixel we're removing
-        r->s.damaged = 1;
-      }
     }
   }
   return 1;