add ncchannel_rgb(), use it in channels_blend()

USAGE.md

@@ -3174,14 +3174,32 @@ ncchannels_bg_alpha(uint64_t channels){
   return ncchannel_alpha(channels_bchannel(channels));
 }
 
+// Extract the 24-bit RGB value from a 32-bit channel.
+// Only valid if ncchannel_rgb_p() would return true for the channel.
+static inline uint32_t
+ncchannel_rgb(uint32_t channel){
+  return channel & NC_BG_RGB_MASK;
+}
+
+// Extract the three 8-bit R/G/B components from a 32-bit channel.
+// Only valid if ncchannel_rgb_p() would return true for the channel.
+static inline uint32_t
+ncchannel_rgb8(uint32_t channel, unsigned* restrict r, unsigned* restrict g,
+               unsigned* restrict b){
+  *r = ncchannel_r(channel);
+  *g = ncchannel_g(channel);
+  *b = ncchannel_b(channel);
+  return channel;
+}
+
 // Extract 24 bits of foreground RGB from 'channels', split into subchannels.
-static inline unsigned
+static inline uint32_t
 ncchannels_fg_rgb8(uint64_t channels, unsigned* r, unsigned* g, unsigned* b){
   return ncchannel_rgb8(channels_fchannel(channels), r, g, b);
 }
 
 // Extract 24 bits of background RGB from 'channels', split into subchannels.
-static inline unsigned
+static inline uint32_t
 ncchannels_bg_rgb8(uint64_t channels, unsigned* r, unsigned* g, unsigned* b){
   return ncchannel_rgb8(channels_bchannel(channels), r, g, b);
 }

doc/man/man3/notcurses_channels.3.md

@@ -25,6 +25,8 @@ notcurses_channels - operations on notcurses channels
 
 **uint32_t ncchannel_b(uint32_t ***channel***);**
 
+**uint32_t ncchannel_rgb(uint32_t ***channel***);**
+
 **uint32_t ncchannel_rgb8(uint32_t ***channel***, uint32_t* restrict ***r***, uint32_t* restrict ***g***, uint32_t* restrict ***b***);**
 
 **int ncchannel_set_rgb8(uint32_t* ***channel***, unsigned ***r***, unsigned ***g***, unsigned ***b***);**

include/notcurses/notcurses.h

@@ -222,9 +222,16 @@ ncchannel_b(uint32_t channel){
   return (channel & 0x0000ffu);
 }
 
+// Extract the 24-bit RGB value from a 32-bit channel.
+// Only valid if ncchannel_rgb_p() would return true for the channel.
+static inline uint32_t
+ncchannel_rgb(uint32_t channel){
+  return channel & NC_BG_RGB_MASK;
+}
+
 // Extract the three 8-bit R/G/B components from a 32-bit channel.
 // Only valid if ncchannel_rgb_p() would return true for the channel.
-static inline unsigned
+static inline uint32_t
 ncchannel_rgb8(uint32_t channel, unsigned* RESTRICT r, unsigned* RESTRICT g,
                unsigned* RESTRICT b){
   *r = ncchannel_r(channel);
@@ -404,13 +411,13 @@ ncchannels_bg_palindex(uint64_t channels){
 // Extract 24 bits of foreground RGB from 'channels', shifted to LSBs.
 static inline uint32_t
 ncchannels_fg_rgb(uint64_t channels){
-  return ncchannels_fchannel(channels) & NC_BG_RGB_MASK;
+  return ncchannel_rgb(ncchannels_fchannel(channels));
 }
 
 // Extract 24 bits of background RGB from 'channels', shifted to LSBs.
 static inline uint32_t
 ncchannels_bg_rgb(uint64_t channels){
-  return ncchannels_bchannel(channels) & NC_BG_RGB_MASK;
+  return ncchannel_rgb(ncchannels_bchannel(channels));
 }
 
 // Extract 24 bits of foreground RGB from 'channels', split into subchannels.

src/lib/internal.h

@@ -1353,16 +1353,14 @@ channels_blend(notcurses* nc, unsigned c1, unsigned c2, unsigned* blends){
     }else if(c2palette){
       ncchannel_set_palindex(&c1, ncchannel_palindex(c2));
     }else{
-      ncchannel_set(&c1, c2 & NC_BG_RGB_MASK);
+      ncchannel_set(&c1, ncchannel_rgb(c2));
     }
     ncchannel_set_alpha(&c1, ncchannel_alpha(c2));
   }else if(!c2default && !ncchannel_default_p(c1)){
     unsigned rsum, gsum, bsum;
     if(c2palette){
-      uint32_t rgb = nc->palette.chans[ncchannel_palindex(c2)];
-      bsum = rgb & 0xff;
-      gsum = (rgb >> 8u) & 0xff;
-      rsum = (rgb >> 16u) & 0xff;
+      ncchannel_rgb8(nc->palette.chans[ncchannel_palindex(c2)],
+                     &rsum, &gsum, &bsum);
     }else{
       ncchannel_rgb8(c2, &rsum, &gsum, &bsum);
     }