feat: allow TS users to highlight marker delimiters

This permits those of us who use treesitter to change the highlights
surrounding markers. E.g. for the "verbatim" marker we can now highlight
the "=" characters individually instead of the entire chunk being the
same highlight.

This is particularly useful in tables with lots of code elements, this
makes it easier to tell the delimiter characters apart from the primary
marker.

lua/orgmode/colors/markup_highlighter.lua

@@ -9,58 +9,58 @@ local valid_post_marker_chars =
 local markers = {
   ['*'] = {
     hl_name = 'org_bold',
-    hl_cmd = 'hi def org_bold term=bold cterm=bold gui=bold',
+    hl_cmd = 'hi def %s term=bold cterm=bold gui=bold',
     nestable = true,
     type = 'text',
   },
   ['/'] = {
     hl_name = 'org_italic',
-    hl_cmd = 'hi def org_italic term=italic cterm=italic gui=italic',
+    hl_cmd = 'hi def %s term=italic cterm=italic gui=italic',
     nestable = true,
     type = 'text',
   },
   ['_'] = {
     hl_name = 'org_underline',
-    hl_cmd = 'hi def org_underline term=underline cterm=underline gui=underline',
+    hl_cmd = 'hi def %s term=underline cterm=underline gui=underline',
     nestable = true,
     type = 'text',
   },
   ['+'] = {
     hl_name = 'org_strikethrough',
-    hl_cmd = 'hi def org_strikethrough term=strikethrough cterm=strikethrough gui=strikethrough',
+    hl_cmd = 'hi def %s term=strikethrough cterm=strikethrough gui=strikethrough',
     nestable = true,
     type = 'text',
   },
   ['~'] = {
     hl_name = 'org_code',
-    hl_cmd = 'hi def link org_code String',
+    hl_cmd = 'hi def link %s String',
     nestable = false,
     spell = false,
     type = 'text',
   },
   ['='] = {
     hl_name = 'org_verbatim',
-    hl_cmd = 'hi def link org_verbatim String',
+    hl_cmd = 'hi def link %s String',
     nestable = false,
     spell = false,
     type = 'text',
   },
   ['\\('] = {
     hl_name = 'org_latex',
-    hl_cmd = 'hi def link org_latex OrgTSLatex',
+    hl_cmd = 'hi def link %s OrgTSLatex',
     nestable = false,
     spell = false,
     type = 'latex',
   },
   ['\\{'] = {
     hl_name = 'org_latex',
-    hl_cmd = 'hi def link org_latex OrgTSLatex',
+    hl_cmd = 'hi def link %s OrgTSLatex',
     nestable = false,
     type = 'latex',
   },
   ['\\s'] = {
     hl_name = 'org_latex',
-    hl_cmd = 'hi def link org_latex OrgTSLatex',
+    hl_cmd = 'hi def link %s OrgTSLatex',
     nestable = false,
     type = 'latex',
   },
@@ -357,10 +357,29 @@ local function apply(namespace, bufnr, line_index)
   local hide_markers = config.org_hide_emphasis_markers
 
   for _, range in ipairs(result.ranges) do
+    -- Main body highlight
+    vim.api.nvim_buf_set_extmark(bufnr, namespace, range.from.start.line, range.from.start.character + 1, {
+      ephemeral = true,
+      end_col = range.to['end'].character - 1,
+      hl_group = markers[range.type].hl_name,
+      spell = markers[range.type].spell,
+      priority = 110 + range.from.start.character,
+    })
+
+    -- Leading delimiter
     vim.api.nvim_buf_set_extmark(bufnr, namespace, range.from.start.line, range.from.start.character, {
+      ephemeral = true,
+      end_col = range.from.start.character + 1,
+      hl_group = markers[range.type].hl_name .. '_delimiter',
+      spell = markers[range.type].spell,
+      priority = 110 + range.from.start.character,
+    })
+
+    -- Closing delimiter
+    vim.api.nvim_buf_set_extmark(bufnr, namespace, range.from.start.line, range.to['end'].character - 1, {
       ephemeral = true,
       end_col = range.to['end'].character,
-      hl_group = markers[range.type].hl_name,
+      hl_group = markers[range.type].hl_name .. '_delimiter',
       spell = markers[range.type].spell,
       priority = 110 + range.from.start.character,
     })
@@ -423,8 +442,10 @@ local function apply(namespace, bufnr, line_index)
 end
 
 local function setup()
-  for _, marker in pairs(markers) do
-    vim.cmd(marker.hl_cmd)
+  for delimiter, marker in pairs(markers) do
+    vim.cmd(string.format(marker.hl_cmd, marker.hl_name))
+    vim.cmd(string.format('syn keyword %s_delimiter %s', marker.hl_name, delimiter))
+    vim.cmd(string.format(marker.hl_cmd, marker.hl_name .. '_delimiter'))
   end
   vim.cmd('hi def link org_hyperlink Underlined')
   load_deps()