Elide unnecessary sprixel invalidations

When the damaged cell of a sprixel is actually entirely
transparent (or annihilated), there's no need to invalidate
it. Check for this in the TAM in sprixel_invalidate(). Good
optimization, and eliminates a lot of the flicker in `xray`
on Kitty described in #1522.

src/lib/internal.h

@@ -56,7 +56,8 @@ typedef enum {
 typedef enum {
   SPRIXCELL_NORMAL,         // no transparent pixels in this cell
   SPRIXCELL_CONTAINS_TRANS, // this cell has transparent pixels
-  SPRIXCELL_ANNIHILATED,    // this cell has been wiped
+  SPRIXCELL_ALL_TRANS,      // all pixels are naturally transparent
+  SPRIXCELL_ANNIHILATED,    // this cell has been wiped (all trans)
 } sprixcell_e;
 
 // there is a context-wide set of displayed pixel glyphs ("sprixels"); i.e.
@@ -831,7 +832,7 @@ int sprite_kitty_cell_wipe(const notcurses* nc, sprixel* s, int y, int x);
 int sixel_wipe(const notcurses* nc, sprixel* s, int ycell, int xcell);
 int sprite_destroy(const struct notcurses* nc, const struct ncpile* p, FILE* out, sprixel* s);
 void sprixel_free(sprixel* s);
-void sprixel_invalidate(sprixel* s);
+void sprixel_invalidate(sprixel* s, int y, int x);
 void sprixel_movefrom(sprixel* s, int y, int x);
 void sprixel_hide(sprixel* s);
 int sprite_draw(const notcurses* n, const ncpile *p, sprixel* s, FILE* out);
@@ -848,7 +849,6 @@ int sprite_kitty_annihilate(const notcurses* nc, const ncpile* p, FILE* out, spr
 int sprite_kitty_init(int fd);
 int sprite_sixel_init(int fd);
 int sprite_init(const notcurses* nc);
-void sprixel_invalidate(sprixel* s);
 int kitty_shutdown(int fd);
 int sixel_shutdown(int fd);
 sprixel* sprixel_by_id(const notcurses* nc, uint32_t id);

src/lib/kitty.c

@@ -153,6 +153,7 @@ int sprite_kitty_cell_wipe(const notcurses* nc, sprixel* s, int ycell, int xcell
 //fprintf(stderr, "CACHED WIPE %d %d/%d\n", s->id, ycell, xcell);
     return 0; // already annihilated, needn't draw glyph in kitty
   }
+//fprintf(stderr, "NEW WIPE %d %d/%d\n", s->id, ycell, xcell);
   const int totalpixels = s->pixy * s->pixx;
   const int xpixels = nc->tcache.cellpixx;
   const int ypixels = nc->tcache.cellpixy;
@@ -271,13 +272,21 @@ write_kitty_data(FILE* fp, int linesize, int leny, int lenx,
         const uint32_t* line = data + (linesize / sizeof(*data)) * y;
         source[e] = line[x];
 //fprintf(stderr, "%u/%u/%u -> %c%c%c%c %u %u %u %u\n", r, g, b, b64[0], b64[1], b64[2], b64[3], b64[0], b64[1], b64[2], b64[3]);
-        int tyx = (x / cdimx) + (y / cdimy) * cols;
+        int xcell = x / cdimx;
+        int ycell = y / cdimy;
+        int tyx = xcell + ycell * cols;
 //fprintf(stderr, "Tyx: %d y: %d (%d) * %d x: %d (%d)\n", tyx, y, y / cdimy, cols, x, x / cdimx);
         if(tacache[tyx] == SPRIXCELL_ANNIHILATED){
           wipe[e] = 1;
         }else{
           wipe[e] = 0;
           if(rgba_trans_p(source[e], transcolor)){
+            if(x % cdimx == 0 && y % cdimy == 0){
+              tacache[tyx] = SPRIXCELL_ALL_TRANS;
+            }else if(tacache[tyx] == SPRIXCELL_NORMAL){
+              tacache[tyx] = SPRIXCELL_CONTAINS_TRANS;
+            }
+          }else if(tacache[tyx] == SPRIXCELL_ALL_TRANS){
             tacache[tyx] = SPRIXCELL_CONTAINS_TRANS;
           }
         }

src/lib/render.c

@@ -1084,7 +1084,7 @@ rasterize_core(notcurses* nc, const ncpile* p, FILE* out, unsigned phase){
         }
 //fprintf(stderr, "RAST %08x [%s] to %d/%d cols: %u %016lx\n", srccell->gcluster, pool_extended_gcluster(&nc->pool, srccell), y, x, srccell->width, srccell->channels);
         if(rvec[damageidx].sprixel){
-          sprixel_invalidate(rvec[damageidx].sprixel);
+          sprixel_invalidate(rvec[damageidx].sprixel, y, x);
         }
         if(term_putc(out, &nc->pool, srccell)){
           return -1;

src/lib/sprite.c

@@ -60,9 +60,17 @@ void sprixel_hide(sprixel* s){
   }
 }
 
-void sprixel_invalidate(sprixel* s){
-  if(s->invalidated != SPRIXEL_HIDE){
-    s->invalidated = SPRIXEL_INVALIDATED;
+// y and x are absolute coordinates
+void sprixel_invalidate(sprixel* s, int y, int x){
+//fprintf(stderr, "INVALIDATING AT %d/%d\n", y, x);
+  if(s->invalidated != SPRIXEL_HIDE && s->n){
+    int localy = y - s->n->absy;
+    int localx = x - s->n->absx;
+//fprintf(stderr, "INVALIDATING AT %d/%d (%d/%d) TAM: %d\n", y, x, localy, localx, s->n->tacache[localy * s->dimx + localx]);
+    if(s->n->tacache[localy * s->dimx + localx] != SPRIXCELL_ALL_TRANS &&
+       s->n->tacache[localy * s->dimx + localx] != SPRIXCELL_ALL_TRANS){
+      s->invalidated = SPRIXEL_INVALIDATED;
+    }
   }
 }