clamp Sixel at a multiple of 6 #1560

src/lib/internal.h

@@ -437,6 +437,7 @@ typedef struct tinfo {
   // query the details of the implementation.
   pthread_mutex_t pixel_query; // only query for pixel support once
   int color_registers; // sixel color registers (post pixel_query_done)
+  int sprixel_height_factor; // sprixel height must be multiple of this
   int sixel_maxx, sixel_maxy; // sixel size maxima (post pixel_query_done)
   int sprixelnonce;      // next sprixel id
   int (*pixel_destroy)(const struct notcurses* nc, const struct ncpile* p, FILE* out, sprixel* s);
@@ -957,6 +958,9 @@ clamp_to_sixelmax(const tinfo* t, int* y, int* x){
   if(t->sixel_maxy && *y > t->sixel_maxy){
     *y = t->sixel_maxy;
   }
+  if(*y % t->sprixel_height_factor){
+    *y -= (*y % t->sprixel_height_factor);
+  }
   if(t->sixel_maxx && *x > t->sixel_maxx){
     *x = t->sixel_maxx;
   }

src/lib/terminfo.c

@@ -66,6 +66,7 @@ apply_term_heuristics(tinfo* ti, const char* termname){
     ti->pixel_init = kitty_init;
     ti->pixel_draw = kitty_draw;
     ti->pixel_shutdown = kitty_shutdown;
+    ti->sprixel_height_factor = 1;
     set_pixel_blitter(kitty_blit);
   }else if(strstr(termname, "alacritty")){
     ti->alacritty_sixel_hack = true;
@@ -215,7 +216,9 @@ int interrogate_terminfo(tinfo* ti, int fd, const char* termname, unsigned utf8)
       }
     }
   }
-  // if op is defined as ansi 39 + ansi 49, make the split definitions available
+  // if op is defined as ansi 39 + ansi 49, make the split definitions
+  // available. this ought be asserted by extension capability "ax", but
+  // no terminal i've found seems to do so. =[
   if(ti->op && strcmp(ti->op, "\x1b[39;49m") == 0){
     ti->fgop = "\x1b[39m";
     ti->bgop = "\x1b[49m";
@@ -230,6 +233,7 @@ int interrogate_terminfo(tinfo* ti, int fd, const char* termname, unsigned utf8)
 }
 
 // FIXME need unit tests on this
+// FIXME can read a character not intended for it
 static int
 read_xtsmgraphics_reply(int fd, int* val2){
   char in;
@@ -341,6 +345,7 @@ setup_sixel(tinfo* ti){
   ti->pixel_destroy = sixel_delete;
   ti->pixel_cell_wipe = sixel_wipe;
   ti->pixel_shutdown = sixel_shutdown;
+  ti->sprixel_height_factor = 6;
 }
 
 // query for Sixel support

src/lib/visual.c

@@ -687,6 +687,7 @@ ncplane* ncvisual_render_pixels(notcurses* nc, ncvisual* ncv, const struct blits
   }
   if(flags & NCVISUAL_OPTION_VERALIGNED){
     if(placey == NCALIGN_CENTER){
+      // FIXME why are these calculations structurally different from HORALIGNED above?
       placey = ((ncplane_dim_y(n) * nc->tcache.cellpixy - disprows) / 2) / nc->tcache.cellpixy;
     }else if(placey == NCALIGN_BOTTOM){
       placey = ncplane_dim_y(n) * nc->tcache.cellpixy - disprows / nc->tcache.cellpixy;

src/tests/bitmap.cpp

@@ -219,8 +219,8 @@ TEST_CASE("Bitmaps") {
 
   // verify that the sprixel's TAM is properly initialized
   SUBCASE("PixelTAMSetup") {
-    // first, assemble a visual equivalent to 81 cells
-    auto dimy = 9;
+    // first, assemble a visual equivalent to 54 cells
+    auto dimy = 6;
     auto dimx = 9;
     auto y = dimy * nc_->tcache.cellpixy;
     auto x = dimx * nc_->tcache.cellpixx;