From 0bfa8c33fddda1513e50bcb1fed311e8a2d79779 Mon Sep 17 00:00:00 2001
From: nick black <dankamongmen@gmail.com>
Date: Wed, 30 Jun 2021 23:45:48 -0400
Subject: [PATCH] [sixel] clean up cells even when under a new sixel #1537

---
 src/lib/internal.h |  8 +++++---
 src/lib/sixel.c    | 37 +++++++++++++++++++++----------------
 src/lib/sprite.c   |  2 +-
 3 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/src/lib/internal.h b/src/lib/internal.h
index 2b7cbd561..5ae5f9fa0 100644
--- a/src/lib/internal.h
+++ b/src/lib/internal.h
@@ -792,7 +792,7 @@ uint8_t* kitty_trans_auxvec(const struct tinfo* ti);
 // these three all use absolute coordinates
 void sprixel_invalidate(sprixel* s, int y, int x);
 void sprixel_movefrom(sprixel* s, int y, int x);
-void sprixel_debug(FILE* out, const sprixel* s);
+void sprixel_debug(const sprixel* s, FILE* out);
 void sixelmap_free(struct sixelmap *s);
 
 // create an auxiliary vector suitable for a sprixcell, and zero it out. there
@@ -809,6 +809,8 @@ int kitty_blit(ncplane* nc, int linesize, const void* data, int leny, int lenx,
 
 static inline int
 sprite_destroy(const notcurses* nc, const ncpile* p, FILE* out, sprixel* s){
+//fprintf(stderr, "Destroying sprite %u\n", s->id);
+//sprixel_debug(s, stderr);
   return nc->tcache.pixel_destroy(nc, p, out, s);
 }
 
@@ -816,7 +818,7 @@ sprite_destroy(const notcurses* nc, const ncpile* p, FILE* out, sprixel* s){
 // returns -1 on error, or the number of bytes written.
 static inline int
 sprite_draw(const notcurses* n, const ncpile* p, sprixel* s, FILE* out){
-//sprixel_debug(stderr, s);
+//sprixel_debug(s, stderr);
   return n->tcache.pixel_draw(p, s, out);
 }
 
@@ -824,7 +826,7 @@ sprite_draw(const notcurses* n, const ncpile* p, sprixel* s, FILE* out){
 // returns -1 on error, or the number of bytes written.
 static inline int
 sprite_redraw(const notcurses* n, const ncpile* p, sprixel* s, FILE* out){
-//sprixel_debug(stderr, s);
+//sprixel_debug(s, stderr);
   if(s->invalidated == SPRIXEL_MOVED && n->tcache.pixel_move){
     return n->tcache.pixel_move(p, s, out);
   }else{
diff --git a/src/lib/sixel.c b/src/lib/sixel.c
index 90b13996a..6da773517 100644
--- a/src/lib/sixel.c
+++ b/src/lib/sixel.c
@@ -790,8 +790,12 @@ int sixel_blit(ncplane* n, int linesize, const void* data, int leny, int lenx,
   return r;
 }
 
+// to destroy a sixel, we damage all cells underneath it. we might not have
+// to, though, if we've got a new sixel ready to go where the old sixel was
+// (though we'll still need to if the new sprixcell not opaque, and the
+// old and new sprixcell are different in any transparent pixel).
 int sixel_destroy(const notcurses* nc, const ncpile* p, FILE* out, sprixel* s){
-//fprintf(stderr, "%d] %d %p\n", s->id, s->invalidated, s->n);
+//fprintf(stderr, "DESTROYING %d %d %p at %d/%d (%d/%d)\n", s->id, s->invalidated, s->n, s->movedfromy, s->movedfromx, s->dimy, s->dimx);
   (void)nc;
   (void)out;
   int starty = s->movedfromy;
@@ -800,23 +804,24 @@ int sixel_destroy(const notcurses* nc, const ncpile* p, FILE* out, sprixel* s){
     for(int xx = startx ; xx < startx + s->dimx && xx < p->dimx ; ++xx){
       int ridx = yy * p->dimx + xx;
       struct crender *r = &p->crender[ridx];
-      if(!r->sprixel){
-        if(s->n){
-//fprintf(stderr, "CHECKING %d/%d\n", yy - s->movedfromy, xx - s->movedfromx);
-          sprixcell_e state = sprixel_state(s, yy - s->movedfromy + s->n->absy,
-                                            xx - s->movedfromx + s->n->absx);
-          if(state == SPRIXCELL_OPAQUE_SIXEL || state == SPRIXCELL_MIXED_SIXEL){
-            r->s.damaged = 1;
-          }else if(s->invalidated == SPRIXEL_MOVED){
-            // ideally, we wouldn't damage our annihilated sprixcells, but if
-            // we're being annihilated only during this cycle, we need to go
-            // ahead and damage it.
-            r->s.damaged = 1;
-          }
-        }else{
-          // need this to damage cells underneath a sprixel we're removing
+      if(r->sprixel){
+        s = r->sprixel;
+      }
+      if(s->n){
+        sprixcell_e state = sprixel_state(s, yy - s->movedfromy,
+                                          xx - s->movedfromx);
+//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;
+        }else if(s->invalidated == SPRIXEL_MOVED){
+          // ideally, we wouldn't damage our annihilated sprixcells, but if
+          // we're being annihilated only during this cycle, we need to go
+          // ahead and damage it.
           r->s.damaged = 1;
         }
+      }else{
+        // need this to damage cells underneath a sprixel we're removing
+        r->s.damaged = 1;
       }
     }
   }
diff --git a/src/lib/sprite.c b/src/lib/sprite.c
index c97077335..8060e06be 100644
--- a/src/lib/sprite.c
+++ b/src/lib/sprite.c
@@ -4,7 +4,7 @@
 
 static atomic_uint_fast32_t sprixelid_nonce;
 
-void sprixel_debug(FILE* out, const sprixel* s){
+void sprixel_debug(const sprixel* s, FILE* out){
   fprintf(out, "Sprixel %d (%p) %dB %dx%d (%dx%d) @%d/%d state: %d\n",
           s->id, s, s->glyphlen, s->dimy, s->dimx, s->pixy, s->pixx,
           s->n ? s->n->absy : 0, s->n ? s->n->absx : 0,