fix up default elision in alpha channels #143

include/notcurses.h

@@ -700,6 +700,18 @@ channels_get_fchannel(uint64_t channels){
   return channels_get_bchannel(channels >> 32u);
 }
 
+// Set the 32-bit background channel of a channel pair.
+static inline uint64_t
+channels_set_bchannel(uint64_t* channels, uint32_t channel){
+  return *channels = (*channels & 0xffffffff00000000llu) | channel;
+}
+
+// Set the 32-bit foreground channel of a channel pair.
+static inline uint64_t
+channels_set_fchannel(uint64_t* channels, uint32_t channel){
+  return *channels = (*channels & 0xfffffffflu) | ((uint64_t)channel << 32u);
+}
+
 // Extract 24 bits of foreground RGB from 'channels', shifted to LSBs.
 static inline unsigned
 channels_get_fg(uint64_t channels){
@@ -847,6 +859,18 @@ cell_get_fchannel(const cell* cl){
   return channels_get_fchannel(cl->channels);
 }
 
+// Set the 32-bit background channel of a cell.
+static inline uint64_t
+cell_set_bchannel(cell* cl, uint32_t channel){
+  return channels_set_bchannel(&cl->channels, channel);
+}
+
+// Set the 32-bit foreground channel of a cell.
+static inline uint64_t
+cell_set_fchannel(cell* cl, uint32_t channel){
+  return channels_set_fchannel(&cl->channels, channel);
+}
+
 // Extract 24 bits of foreground RGB from 'cell', shifted to LSBs.
 static inline unsigned
 cell_get_fg(const cell* cl){

src/lib/notcurses.c

@@ -1104,13 +1104,13 @@ dig_visible_cell(cell* c, int y, int x, ncplane* p, int falpha, int balpha){
             if( (c->gcluster = vis->gcluster) ){ // index copy only
               lockedglyph = true; // must return this ncplane for this glyph
               c->attrword = vis->attrword;
-              cell_set_fg(c, cell_get_fg(vis)); // FIXME blend it in
+              cell_set_fchannel(c, cell_get_fchannel(vis)); // FIXME blend it in
               falpha -= (CELL_ALPHA_TRANS - nalpha); // FIXME blend it in
             }
           }
         }
         if(balpha > 0 && (nalpha = cell_get_bg_alpha(vis)) < CELL_ALPHA_TRANS){
-          cell_set_bg(c, cell_get_bg(vis)); // FIXME blend it in
+          cell_set_bchannel(c, cell_get_bchannel(vis)); // FIXME blend it in
           balpha -= (CELL_ALPHA_TRANS - nalpha);
         }
         if((falpha > 0 || balpha > 0) && p->z){ // we must go further!