detect and expose default foreground color #2432

NEWS.md

@@ -8,7 +8,7 @@ rearrangements of Notcurses.
     and `ncplane_autogrow_p()` functions. When autogrow is enabled, the plane
     is automatically enlarged to accommodate output at its right (no scrolling)
     or bottom (scrolling enabled) boundaries.
-  * Added the new function `notcurses_default_background()`.
+  * Added `notcurses_default_background()` and `notcurses_default_foreground()`.
 
 * 3.0.0 (2021-12-01) **"In the A"**
   * Made the ABI/API changes that have been planned/collected during 2.x

USAGE.md

@@ -293,6 +293,11 @@ notcurses_term_dim_yx(const struct notcurses* n, unsigned* restrict rows,
 // current screen geometry is returned in 'y' and 'x', if they are not NULL.
 int notcurses_refresh(struct notcurses* n, unsigned* restrict y, unsigned* restrict x);
 
+// Get the default foreground color, if it is known. Returns -1 on error
+// (unknown foreground). On success, returns 0, writing the RGB value to
+// 'fg' (if non-NULL)
+int notcurses_default_foreground(const struct notcurses* nc, uint32_t* fg);
+
 // Get the default background color, if it is known. Returns -1 on error
 // (unknown background). On success, returns 0, writing the RGB value to
 // 'bg' (if non-NULL) and setting 'bgtrans' high iff the background color

doc/man/man3/notcurses_init.3.md

@@ -53,6 +53,8 @@ typedef struct notcurses_options {
 
 **int notcurses_lex_margins(const char* ***op***, notcurses_options* ***opts***);**
 
+**int notcurses_default_foreground(const struct notcurses* ***nc***, uint32_t* ***fg***);**
+
 **int notcurses_default_background(const struct notcurses* ***nc***, uint32_t* ***bg***, unsigned* ***bgtrans***);**
 
 # DESCRIPTION
@@ -168,8 +170,10 @@ zero. The following flags are defined:
     eventually prevent Notcurses from processing messages from the terminal. It
     will furthermore avoid wasting time processing useless input.
 
-**notcurses_default_background** returns the default background color, and
-whether the terminal treats it as transparent, if this could be detected.
+**notcurses_default_foreground** returns the default foreground color, if it
+could be detected. **notcurses_default_background** returns the default
+background color, and whether the terminal treats it as transparent, if this
+could be detected.
 
 ## Fatal signals
 
@@ -250,6 +254,9 @@ rendered mode to be used as a normal scrolling shell application.
 
 **notcurses_cursor_disable** returns -1 if the cursor is already invisible.
 
+**notcurses_default_foreground** returns -1 if the default foreground color
+could not be detected.
+
 **notcurses_default_background** returns -1 if the default background color
 could not be detected.
 

include/notcurses/notcurses.h

@@ -3629,6 +3629,12 @@ ncbprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec){
   return ncnmetric(val, NCBPREFIXSTRLEN + 1, decimal, buf, omitdec, 1024, 'i');
 }
 
+// Get the default foreground color, if it is known. Returns -1 on error
+// (unknown foreground). On success, returns 0, writing the RGB value to
+// 'fg' (if non-NULL)
+API int notcurses_default_foreground(const struct notcurses* nc, uint32_t* fg)
+  __attribute__ ((nonnull (1)));
+
 // Get the default background color, if it is known. Returns -1 on error
 // (unknown background). On success, returns 0, writing the RGB value to
 // 'bg' (if non-NULL) and setting 'bgtrans' high iff the background color

src/info/main.c

@@ -369,18 +369,23 @@ display_logo(struct ncplane* n, const char* path){
 
 static void
 tinfo_debug_bitmaps(struct ncplane* n, const tinfo* ti, const char* indent){
+  uint32_t fg = 0;
+  int r = notcurses_default_foreground(ncplane_notcurses(n), &fg);
+  if(r){
+    ncplane_printf(n, "%sno known default fg ", indent);
+  }else{
+    ncplane_printf(n, "%sdefault fg 0x%06x ", indent, fg);
+  }
   unsigned bgtrans = 0;
   uint32_t bg = 0;
-  int r = notcurses_default_background(ncplane_notcurses(n), &bg, &bgtrans);
+  r = notcurses_default_background(ncplane_notcurses(n), &bg, &bgtrans);
   if(r){
-    ncplane_printf(n, "couldn't detect default background");
+    ncplane_printf(n, "no known default fg");
   }else{
     if(bgtrans){
-      ncplane_printf(n, "%sdefault background 0x%06lx considered transparent", indent,
-                    ti->bg_collides_default & 0xfffffful);
+      ncplane_printf(n, "default bg 0x%06x (trans)", bg);
     }else{
-      ncplane_printf(n, "%sdefault background 0x%06lx", indent,
-                    ti->bg_collides_default & 0xfffffful);
+      ncplane_printf(n, "default bg 0x%06x", bg);
     }
   }
   finish_line(n);

src/lib/render.c

@@ -1726,6 +1726,16 @@ int ncdirect_set_fg_rgb(ncdirect* nc, unsigned rgb){
   return 0;
 }
 
+int notcurses_default_foreground(const struct notcurses* nc, uint32_t* fg){
+  const tinfo* ti = &nc->tcache;
+  if(ti->fg_default & 0x80000000){
+    logerror("default foreground could not be determined\n");
+    return -1;
+  }
+  *fg = ti->fg_default & NC_BG_RGB_MASK;
+  return 0;
+}
+
 int notcurses_default_background(const struct notcurses* nc,
                                  uint32_t* bg, unsigned* bgtrans){
   const tinfo* ti = &nc->tcache;

src/lib/termdesc.c

@@ -857,6 +857,7 @@ int interrogate_terminfo(tinfo* ti, FILE* out, unsigned utf8,
   }
   *cursor_x = *cursor_y = -1;
   ti->bg_collides_default = 0xfe000000;
+  ti->fg_default = 0xff000000;
   ti->kbdlevel = UINT_MAX; // see comment in tinfo definition
   ti->qterm = TERMINAL_UNKNOWN;
   // we don't need a controlling tty for everything we do; allow a failure here
@@ -1109,6 +1110,9 @@ int interrogate_terminfo(tinfo* ti, FILE* out, unsigned utf8,
       // kitty, we'll add the 0x01000000 in during heuristics.
       ti->bg_collides_default = iresp->bg;
     }
+    if(iresp->got_fg){
+      ti->fg_default = iresp->fg;
+    }
     // kitty trumps sixel, when both are available
     if((kitty_graphics = iresp->kitty_graphics) == 0){
       ti->color_registers = iresp->color_registers;

src/lib/termdesc.h

@@ -123,6 +123,9 @@ typedef struct tinfo {
   // 0xfexxxxxxx (unknown), 0x00RRGGBB (no collide), or 0x01RRGGBB (collides).
   uint32_t bg_collides_default;
 
+  // 0xffxxxxxxx (unknown), or 0x00RRGGBB (foreground)
+  uint32_t fg_default;
+
   // bitmap support. if we support bitmaps, pixel_implementation will be a
   // value other than NCPIXEL_NONE.
   ncpixelimpl_e pixel_implementation;