feat(hardcopy): check gui colours for highlights first

Previously, :hardcopy would only use terminal highlight colours, with a
fixed mapping table, despite internally supporting true colour. This
patch looks at the guifg colour first while coming up with the printing
highlight colours, then falls back to the terminal ones.

I have passed through the modec argument in this change because it was
there before, but it could be deleted and hardcoded to 'c' since nobody
sets it to anything else anywhere.

1 files changed, 28 insertions, 15 deletions

diff --git a/src/nvim/hardcopy.c b/src/nvim/hardcopy.c
index 6fc70144ac..eb10c65be9 100644
--- a/src/nvim/hardcopy.c
+++ b/src/nvim/hardcopy.c
@@ -386,30 +386,43 @@ static uint32_t prt_get_term_color(int colorindex)
   return cterm_color_8[colorindex % 8];
 }
 
-static void prt_get_attr(int hl_id, prt_text_attr_T *pattr, int modec)
+static uint32_t prt_get_color(int hl_id, int modec)
 {
   int colorindex;
   uint32_t fg_color;
 
+  const char *color = highlight_color(hl_id, "fg#", 'g');
+  if (color != NULL) {
+    RgbValue rgb = name_to_color(color);
+    if (rgb != -1) {
+      return (uint32_t)rgb;
+    }
+  }
+
+  color = highlight_color(hl_id, "fg", modec);
+  if (color == NULL) {
+    colorindex = 0;
+  } else {
+    colorindex = atoi(color);
+  }
+
+  if (colorindex >= 0 && colorindex < t_colors) {
+    fg_color = prt_get_term_color(colorindex);
+  } else {
+    fg_color = PRCOLOR_BLACK;
+  }
+
+  return fg_color;
+}
+
+static void prt_get_attr(int hl_id, prt_text_attr_T *pattr, int modec)
+{
   pattr->bold = (highlight_has_attr(hl_id, HL_BOLD, modec) != NULL);
   pattr->italic = (highlight_has_attr(hl_id, HL_ITALIC, modec) != NULL);
   pattr->underline = (highlight_has_attr(hl_id, HL_UNDERLINE, modec) != NULL);
   pattr->undercurl = (highlight_has_attr(hl_id, HL_UNDERCURL, modec) != NULL);
 
-  {
-    const char *color = highlight_color(hl_id, "fg", modec);
-    if (color == NULL) {
-      colorindex = 0;
-    } else {
-      colorindex = atoi(color);
-    }
-
-    if (colorindex >= 0 && colorindex < t_colors) {
-      fg_color = prt_get_term_color(colorindex);
-    } else {
-      fg_color = PRCOLOR_BLACK;
-    }
-  }
+  uint32_t fg_color = prt_get_color(hl_id, modec);
 
   if (fg_color == PRCOLOR_WHITE) {
     fg_color = PRCOLOR_BLACK;