[extract_color_table] work per-cell, facilitating parallelism #2573

src/lib/sixel.c

@@ -738,12 +738,12 @@ preprocess_cell(const uint32_t* data, int linesize, int cols, int leny,
 // we have a 4096-element array that takes the 4-5-3 MSBs from the RGB
 // comoponents. once it's complete, we might need to either merge some
 // chunks, or expand them, converging towards the available number of
-// color registers.
+// color registers. |ccols| is cell geometry; |leny| and |lenx| are pixel
+// geometry, and *do not* include sixel padding.
 static inline int
-extract_color_table(const uint32_t* data, int linesize, int cols,
+extract_color_table(const uint32_t* data, int linesize, int ccols,
                     int leny, int lenx, sixeltable* stab,
                     tament* tam, const blitterargs* bargs){
-  uint64_t pixels = 0;
   uint32_t octets = 0;
   qstate qs;
   if(alloc_qstate(bargs->u.pixel.colorregs, &qs)){
@@ -756,7 +756,6 @@ extract_color_table(const uint32_t* data, int linesize, int cols,
   const int cdimx = bargs->u.pixel.cellpxx;
   // use the cell geometry as computed by the visual layer; leny doesn't
   // include any mandatory sixel padding.
-  const int ccols = bargs->u.pixel.spx->dimx;
   const int crows = bargs->u.pixel.spx->dimy;
   typeof(bargs->u.pixel.spx->needs_refresh) rmatrix;
   rmatrix = malloc(sizeof(*rmatrix) * crows * ccols);
@@ -778,21 +777,11 @@ extract_color_table(const uint32_t* data, int linesize, int cols,
       if(cendx > begx + lenx){
         cendx = begx + lenx;
       }
-fprintf(stderr, "TXYIDX %d (%d/%d) START %d/%d END %d/%d\n", txyidx, y, x, cstarty, cstartx, cendy, cendx);
+      bool firstpix = true;
       for(int visy = cstarty ; visy < cendy ; ++visy){   // current abs pixel row
+        const bool lastrow = visy + 1 == cendy;
         for(int visx = cstartx ; visx < cendx ; ++visx){ // current abs pixel col
-        }
-      }
-    }
-  }
-  for(int visy = begy ; visy < (begy + leny) ; ++visy){ // pixel row
-    for(int visx = begx ; visx < (begx + lenx) ; ++visx){ // pixel column
           const uint32_t* rgb = (data + (linesize / 4 * visy) + visx);
-      int txyidx = (visy / cdimy) * cols + (visx / cdimx);
-      // we can't just check if lastidx != txyidx; that's true for each row
-      // of the cell. this will only be true once.
-      bool firstpix = (visy % cdimy == 0 && visx % cdimx == 0);
-      bool lastrow = visy + 6 >= begy + leny;
           // we do *not* exempt already-wiped pixels from palette creation. once
           // we're done, we'll call sixel_wipe() on these cells. so they remain
           // one of SPRIXCELL_ANNIHILATED or SPRIXCELL_ANNIHILATED_TRANS.
@@ -843,6 +832,7 @@ fprintf(stderr, "TXYIDX %d (%d/%d) START %d/%d END %d/%d\n", txyidx, y, x, cstar
               }
             }
           }
+          firstpix = false;
           if(rgba_trans_p(*rgb, bargs->transcolor)){
             continue;
           }
@@ -850,10 +840,11 @@ fprintf(stderr, "TXYIDX %d (%d/%d) START %d/%d END %d/%d\n", txyidx, y, x, cstar
             free_qstate(&qs);
             return -1;
           }
-      ++pixels;
         }
       }
-  loginfo("octree got %"PRIu32" entries on %"PRIu64" pixels", octets, pixels);
+    }
+  }
+  loginfo("octree got %"PRIu32" entries", octets);
   if(merge_color_table(&qs, &octets, stab->colorregs)){
     free_qstate(&qs);
     return -1;
@@ -1142,7 +1133,6 @@ int sixel_blit(ncplane* n, int linesize, const void* data, int leny, int lenx,
     return -1;
   }
   int cols = bargs->u.pixel.spx->dimx;
-  int rows = bargs->u.pixel.spx->dimy;
   assert(n->tam);
   if(extract_color_table(data, linesize, cols, leny, lenx, &stable, n->tam, bargs)){
     free(bargs->u.pixel.spx->needs_refresh);