feat(api): nvim_set_hl can set "font" #37668

Problem: Cannot set highlight group fonts via API, only via :highlight
command.

Solution: Add font parameter in nvim_set_hl().

runtime/doc/api.txt

@@ -1575,6 +1575,8 @@ nvim_set_hl({ns_id}, {name}, {val})                            *nvim_set_hl()*
                  • fg: color name or "#RRGGBB", see note.
                  • fg_indexed: boolean (default false) If true, fg is a
                    terminal palette index (0-255).
+                 • font: GUI font name (string). Sets |highlight-font|. Use
+                   "NONE" to clear.
                  • force: if true force update the highlight group when it
                    exists.
                  • italic: boolean

runtime/doc/news.txt

@@ -106,7 +106,9 @@ The following new features were added.
 
 API
 
-• todo
+• |vim.lsp.buf.declaration()|, |vim.lsp.buf.definition()|, |vim.lsp.buf.definition()|,
+  and |vim.lsp.buf.implementation()| now follows 'switchbuf'.
+• |nvim_set_hl()| supports "font" key.
 
 BUILD
 

runtime/lua/vim/_meta/api.lua

@@ -2240,6 +2240,7 @@ function vim.api.nvim_set_decoration_provider(ns_id, opts) end
 --- - dim: boolean
 --- - fg: color name or "#RRGGBB", see note.
 --- - fg_indexed: boolean (default false) If true, fg is a terminal palette index (0-255).
+--- - font: GUI font name (string). Sets `highlight-font`. Use "NONE" to clear.
 --- - force: if true force update the highlight group when it exists.
 --- - italic: boolean
 --- - link: Name of highlight group to link to. `:hi-link`

runtime/lua/vim/_meta/api_keysets.lua

@@ -337,6 +337,7 @@ error('Cannot require a meta file')
 --- @field force? boolean
 --- @field update? boolean
 --- @field url? string
+--- @field font? string
 
 --- @class vim.api.keyset.highlight_cterm
 --- @field bold? boolean

src/nvim/api/keysets_defs.h

@@ -208,6 +208,7 @@ typedef struct {
   Boolean force;
   Boolean update;
   String url;
+  String font;
 } Dict(highlight);
 
 typedef struct {

src/nvim/api/vim.c

@@ -156,6 +156,7 @@ DictAs(get_hl_info) nvim_get_hl(Integer ns_id, Dict(get_highlight) *opts, Arena
 ///                - dim: boolean
 ///                - fg: color name or "#RRGGBB", see note.
 ///                - fg_indexed: boolean (default false) If true, fg is a terminal palette index (0-255).
+///                - font: GUI font name (string). Sets |highlight-font|. Use "NONE" to clear.
 ///                - force: if true force update the highlight group when it exists.
 ///                - italic: boolean
 ///                - link: Name of highlight group to link to. |:hi-link|

src/nvim/highlight.c

@@ -41,6 +41,8 @@ static Map(uint64_t, int) combine_attr_entries = MAP_INIT;
 static Map(uint64_t, int) blend_attr_entries = MAP_INIT;
 static Map(uint64_t, int) blendthrough_attr_entries = MAP_INIT;
 static Set(cstr_t) urls = SET_INIT;
+/// Interned font names, referenced by index in HlAttrs.font.
+static Set(cstr_t) fonts = SET_INIT;
 
 #define attr_entry(i) attr_entries.keys[i]
 
@@ -536,6 +538,37 @@ const char *hl_get_url(uint32_t index)
   return urls.keys[index];
 }
 
+// Intern a font name and return its stable index for use in HlAttrs.font.
+///
+/// @param font_name The font name to add
+/// @return Font index, or -1 if font_name is NULL or empty
+int32_t hl_add_font_idx(const char *font_name)
+{
+  if (font_name == NULL || *font_name == '\0') {
+    return -1;
+  }
+
+  MHPutStatus status;
+  uint32_t k = set_put_idx(cstr_t, &fonts, font_name, &status);
+  if (status != kMHExisting) {
+    fonts.keys[k] = xstrdup(font_name);
+  }
+
+  return (int32_t)k;
+}
+
+/// Get a font name by its index.
+///
+/// @param index Font index
+/// @return Font name, or NULL if index is invalid
+const char *hl_get_font(int32_t index)
+{
+  if (index < 0 || !fonts.keys) {
+    return NULL;
+  }
+  return fonts.keys[index];
+}
+
 /// Get attribute code for forwarded :terminal highlights.
 int hl_get_term_attr(HlAttrs *aep)
 {
@@ -551,6 +584,11 @@ void clear_hl_tables(bool reinit)
     xfree((void *)url);
   });
 
+  const char *font = NULL;
+  set_foreach(&fonts, font, {
+    xfree((void *)font);
+  });
+
   if (reinit) {
     set_clear(HlEntry, &attr_entries);
     highlight_init();
@@ -558,6 +596,7 @@ void clear_hl_tables(bool reinit)
     map_clear(uint64_t, &blend_attr_entries);
     map_clear(uint64_t, &blendthrough_attr_entries);
     set_clear(cstr_t, &urls);
+    set_clear(cstr_t, &fonts);
     memset(highlight_attr_last, -1, sizeof(highlight_attr_last));
     highlight_attr_set_all();
     highlight_changed();
@@ -569,6 +608,7 @@ void clear_hl_tables(bool reinit)
     map_destroy(uint64_t, &blendthrough_attr_entries);
     map_destroy(ColorKey, &ns_hls);
     set_destroy(cstr_t, &urls);
+    set_destroy(cstr_t, &fonts);
   }
 }
 
@@ -1021,6 +1061,10 @@ void hlattrs2dict(Dict *hl, Dict *hl_attrs, HlAttrs ae, bool use_rgb, bool short
   if (ae.hl_blend > -1 && (use_rgb || !short_keys)) {
     PUT_C(*hl, "blend", INTEGER_OBJ(ae.hl_blend));
   }
+  const char *font = hl_get_font(ae.font);
+  if (font != NULL) {
+    PUT_C(*hl, "font", STRING_OBJ(cstr_as_string(font)));
+  }
 }
 
 HlAttrs dict2hlattrs(Dict(highlight) *dict, bool use_rgb, int *link_id, HlAttrs *base, Error *err)
@@ -1195,6 +1239,13 @@ HlAttrs dict2hlattrs(Dict(highlight) *dict, bool use_rgb, int *link_id, HlAttrs
     hlattrs.cterm_ae_attr = mask;
   }
 
+  if (HAS_KEY_X(dict, font)) {
+    String str = dict->font;
+    if (str.size > 0 && STRICMP(str.data, "NONE") != 0) {
+      hlattrs.font = hl_add_font_idx(str.data);
+    }
+  }
+
   return hlattrs;
 #undef HAS_KEY_X
 }

src/nvim/highlight_defs.h

@@ -45,6 +45,7 @@ typedef struct {
   int16_t cterm_fg_color, cterm_bg_color;
   int32_t hl_blend;
   int32_t url;
+  int32_t font;
 } HlAttrs;
 
 #define HLATTRS_INIT (HlAttrs) { \
@@ -57,6 +58,7 @@ typedef struct {
   .cterm_bg_color = 0, \
   .hl_blend = -1, \
   .url = -1, \
+  .font = -1, \
 }
 
 /// Values for index in highlight_attr[].

src/nvim/highlight_group.c

@@ -112,6 +112,7 @@ typedef struct {
   int sg_rgb_sp_idx;            ///< RGB special color index
 
   int sg_blend;                 ///< blend level (0-100 inclusive), -1 if unset
+  char *sg_font;                ///< font name, NULL if not set
 
   int sg_parent;                ///< parent of @nested.group
 } HlGroup;
@@ -1339,8 +1340,16 @@ void do_highlight(const char *line, const bool forceit, const bool init)
             hl_table[idx].sg_gui = attr;
           }
         }
-      } else if (strcmp(key, "FONT") == 0) {
-        // in non-GUI fonts are simply ignored
+      } else if (strcmp(key, "FONT") == 0 && (!init || !(hl_table[idx].sg_set & SG_GUI))) {
+        if (!init) {
+          hl_table[idx].sg_set |= SG_GUI;
+        }
+        if (hl_table[idx].sg_font != NULL) {
+          XFREE_CLEAR(hl_table[idx].sg_font);
+        }
+        if (strcmp(arg, "NONE") != 0) {
+          hl_table[idx].sg_font = xstrdup(arg);
+        }
       } else if (strcmp(key, "CTERMFG") == 0 || strcmp(key, "CTERMBG") == 0) {
         if (!init || !(hl_table[idx].sg_set & SG_CTERM)) {
           if (!init) {
@@ -1574,6 +1583,9 @@ static void highlight_clear(int idx)
   hl_table[idx].sg_rgb_bg_idx = kColorIdxNone;
   hl_table[idx].sg_rgb_sp_idx = kColorIdxNone;
   hl_table[idx].sg_blend = -1;
+  if (hl_table[idx].sg_font != NULL) {
+    XFREE_CLEAR(hl_table[idx].sg_font);
+  }
   // Restore default link and context if they exist. Otherwise clears.
   hl_table[idx].sg_link = hl_table[idx].sg_deflink;
   // Since we set the default link, set the location to where the default
@@ -1619,8 +1631,9 @@ static void highlight_list_one(const int id)
   didh = highlight_list_arg(id, didh, LIST_STRING, 0,
                             coloridx_to_name(sgp->sg_rgb_sp_idx, sgp->sg_rgb_sp, hexbuf), "guisp");
 
-  didh = highlight_list_arg(id, didh, LIST_INT,
-                            sgp->sg_blend + 1, NULL, "blend");
+  didh = highlight_list_arg(id, didh, LIST_INT, sgp->sg_blend + 1, NULL, "blend");
+
+  didh = highlight_list_arg(id, didh, LIST_STRING, 0, sgp->sg_font, "font");
 
   if (sgp->sg_link && !got_int) {
     syn_list_header(didh, 0, id, true);
@@ -1948,6 +1961,10 @@ static void set_hl_attr(int idx)
   at_en.rgb_bg_color = sgp->sg_rgb_bg_idx != kColorIdxNone ? sgp->sg_rgb_bg : -1;
   at_en.rgb_sp_color = sgp->sg_rgb_sp_idx != kColorIdxNone ? sgp->sg_rgb_sp : -1;
   at_en.hl_blend = sgp->sg_blend;
+  // Convert font name to index
+  if (sgp->sg_font != NULL) {
+    at_en.font = hl_add_font_idx(sgp->sg_font);
+  }
 
   sgp->sg_attr = hl_get_syn_attr(0, idx + 1, at_en);
 

test/functional/api/highlight_spec.lua

@@ -334,6 +334,29 @@ describe('API: set highlight', function()
     eq(nil, hl.underdouble)
     eq(true, hl.bold)
   end)
+
+  it('can set font', function()
+    local ns = api.nvim_create_namespace('test_font')
+    api.nvim_set_hl(ns, 'TestFont', { fg = '#ff0000', font = 'Courier New 10' })
+    local hl = api.nvim_get_hl(ns, { name = 'TestFont' })
+    eq('Courier New 10', hl.font)
+    eq(16711680, hl.fg)
+
+    api.nvim_set_hl(ns, 'TestFont', { font = 'Monaco' })
+    hl = api.nvim_get_hl(ns, { name = 'TestFont' })
+    eq('Monaco', hl.font)
+
+    -- Clear font with "NONE"
+    api.nvim_set_hl(ns, 'TestFont', { font = 'NONE' })
+    hl = api.nvim_get_hl(ns, { name = 'TestFont' })
+    eq(nil, hl.font)
+
+    -- global namespace
+    api.nvim_set_hl(0, 'TestFontGlobal', { bg = '#00ff00', font = 'JetBrains Mono' })
+    hl = api.nvim_get_hl(0, { name = 'TestFontGlobal' })
+    eq('JetBrains Mono', hl.font)
+    eq(65280, hl.bg)
+  end)
 end)
 
 describe('API: get highlight', function()