feature: Add border style to code blocks, use thin by default

## Details

Request: MeanderingProgrammer#62

Rather than using a highlight group for the entire range of code blocks
allow half height characters to be used when start and end of code
block are entirely concealed.

This involves using the inverse of the code highlight group and
repeating the configured characters across the width.

Allow using the original implementation with `{ border = 'thick' }`.

When rendering the body we now need to be aware of how the language
was rendered, since placing a language above the code block interferes
with the half height row. To fix this we need to handle the language
from the top level code block logic, instead of using 2 separate
capture groups for code block & language.

Add sign configuration to README as well.

README.md

@@ -120,7 +120,6 @@ require('render-markdown').setup({
         (thematic_break) @dash
 
         (fenced_code_block) @code
-        (fenced_code_block (info_string (language) @language))
 
         [
             (list_marker_plus)
@@ -206,6 +205,14 @@ require('render-markdown').setup({
         --  language: adds language icon to sign column and icon + name above code blocks
         --  full: normal + language
         style = 'full',
+        -- Determins how the top / bottom of code block are rendered:
+        --  thick: use the same highlight as the code body
+        --  thin: when lines are empty overlay the above & below icons
+        border = 'thin',
+        -- Used above code blocks for thin border
+        above = '▄',
+        -- Used below code blocks for thin border
+        below = '▀',
         -- Highlight for code blocks & inline code
         highlight = 'ColorColumn',
     },
@@ -414,6 +421,14 @@ require('render-markdown').setup({
         --  language: adds language icon to sign column and icon + name above code blocks
         --  full: normal + language
         style = 'full',
+        -- Determins how the top / bottom of code block are rendered:
+        --  thick: use the same highlight as the code body
+        --  thin: when lines are empty overlay the above & below icons
+        border = 'thin',
+        -- Used above code blocks for thin border
+        above = '▄',
+        -- Used below code blocks for thin border
+        below = '▀',
         -- Highlight for code blocks & inline code
         highlight = 'ColorColumn',
     },
@@ -587,6 +602,23 @@ require('render-markdown').setup({
 })
 ```
 
+## Signs
+
+```lua
+require('render-markdown').setup({
+    sign = {
+        -- Turn on / off sign rendering
+        enabled = true,
+        -- More granular mechanism, disable signs within specific buftypes
+        exclude = {
+            buftypes = { 'nofile' },
+        },
+        -- Applies to background of sign text
+        highlight = 'SignColumn',
+    },
+})
+```
+
 # Additional Info
 
 - [Limitations](doc/limitations.md): Known limitations of this plugin

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*           For 0.10.0           Last change: 2024 July 12
+*render-markdown.txt*           For 0.10.0           Last change: 2024 July 13
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*
@@ -20,6 +20,7 @@ Table of Contents                          *render-markdown-table-of-contents*
   - Tables                                      |render-markdown-setup-tables|
   - Callouts                                  |render-markdown-setup-callouts|
   - Links                                        |render-markdown-setup-links|
+  - Signs                                        |render-markdown-setup-signs|
 7. Additional Info                           |render-markdown-additional-info|
 
 ==============================================================================
@@ -157,7 +158,6 @@ Full Default Configuration ~
             (thematic_break) @dash
 
             (fenced_code_block) @code
-            (fenced_code_block (info_string (language) @language))
 
             [
                 (list_marker_plus)
@@ -243,6 +243,14 @@ Full Default Configuration ~
             --  language: adds language icon to sign column and icon + name above code blocks
             --  full: normal + language
             style = 'full',
+            -- Determins how the top / bottom of code block are rendered:
+            --  thick: use the same highlight as the code body
+            --  thin: when lines are empty overlay the above & below icons
+            border = 'thin',
+            -- Used above code blocks for thin border
+            above = '▄',
+            -- Used below code blocks for thin border
+            below = '▀',
             -- Highlight for code blocks & inline code
             highlight = 'ColorColumn',
         },
@@ -451,6 +459,14 @@ CODE BLOCKS                                *render-markdown-setup-code-blocks*
             --  language: adds language icon to sign column and icon + name above code blocks
             --  full: normal + language
             style = 'full',
+            -- Determins how the top / bottom of code block are rendered:
+            --  thick: use the same highlight as the code body
+            --  thin: when lines are empty overlay the above & below icons
+            border = 'thin',
+            -- Used above code blocks for thin border
+            above = '▄',
+            -- Used below code blocks for thin border
+            below = '▀',
             -- Highlight for code blocks & inline code
             highlight = 'ColorColumn',
         },
@@ -632,6 +648,24 @@ LINKS                                            *render-markdown-setup-links*
 <
 
 
+SIGNS                                            *render-markdown-setup-signs*
+
+>lua
+    require('render-markdown').setup({
+        sign = {
+            -- Turn on / off sign rendering
+            enabled = true,
+            -- More granular mechanism, disable signs within specific buftypes
+            exclude = {
+                buftypes = { 'nofile' },
+            },
+            -- Applies to background of sign text
+            highlight = 'SignColumn',
+        },
+    })
+<
+
+
 ==============================================================================
 7. Additional Info                           *render-markdown-additional-info*
 

lua/render-markdown/colors.lua

@@ -23,6 +23,18 @@ M.combine = function(foreground, background)
     return name
 end
 
+---@param highlight string
+---@return string
+M.inverse = function(highlight)
+    local name = string.format('RenderMd_Inverse_%s', highlight)
+    if not vim.tbl_contains(cache.highlights, name) then
+        local hl = M.get_hl(highlight)
+        vim.api.nvim_set_hl(0, name, { fg = hl.bg, bg = hl.fg })
+        table.insert(cache.highlights, name)
+    end
+    return name
+end
+
 ---@private
 ---@param name string
 ---@return vim.api.keyset.hl_info

lua/render-markdown/handler/markdown.lua

@@ -80,82 +80,28 @@ M.render_node = function(namespace, buf, capture, node)
         if not dash.enabled then
             return
         end
-        local width = vim.api.nvim_win_get_width(util.buf_to_win(buf))
         vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, 0, {
-            virt_text = { { dash.icon:rep(width), dash.highlight } },
+            virt_text = { { dash.icon:rep(util.get_width(buf)), dash.highlight } },
             virt_text_pos = 'overlay',
         })
     elseif capture == 'code' then
-        local code = state.config.code
-        if not code.enabled then
-            return
-        end
-        if not vim.tbl_contains({ 'normal', 'full' }, code.style) then
-            return
-        end
-        vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, 0, {
-            end_row = info.end_row,
-            end_col = 0,
-            hl_group = code.highlight,
-            hl_eol = true,
-        })
-    elseif capture == 'language' then
-        local code = state.config.code
-        if not code.enabled then
-            return
-        end
-        if not vim.tbl_contains({ 'language', 'full' }, code.style) then
-            return
-        end
-        local icon, icon_highlight = icons.get(info.text)
-        if icon == nil or icon_highlight == nil then
-            return
-        end
-        M.render_sign(namespace, buf, info, icon, icon_highlight)
-        -- Requires inline extmarks
-        if not util.has_10 then
-            return
-        end
-
-        local icon_text = icon .. ' '
-        if ts.concealed(buf, info) > 0 then
-            -- Fenced code blocks will pick up varying amounts of leading white space depending on
-            -- the context they are in. This gets lumped into the delimiter node and as a result,
-            -- after concealing, the extmark will be left shifted. Logic below accounts for this.
-            local padding = 0
-            local code_block = ts.parent_in_section(info.node, 'fenced_code_block')
-            if code_block ~= nil then
-                padding = str.leading_spaces(ts.info(code_block, buf).text)
-            end
-            icon_text = str.pad(icon_text .. info.text, padding)
-        end
-
-        local highlight = { icon_highlight }
-        if code.style == 'full' then
-            highlight = { icon_highlight, code.highlight }
-        end
-
-        vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, info.start_col, {
-            virt_text = { { icon_text, highlight } },
-            virt_text_pos = 'inline',
-        })
+        M.render_code(namespace, buf, info)
     elseif capture == 'list_marker' then
         ---@return boolean
         local function sibling_checkbox()
             if not state.config.checkbox.enabled then
                 return false
             end
-            if ts.sibling(info.node, 'task_list_marker_unchecked') ~= nil then
+            if ts.sibling(buf, info, 'task_list_marker_unchecked') ~= nil then
                 return true
             end
-            if ts.sibling(info.node, 'task_list_marker_checked') ~= nil then
+            if ts.sibling(buf, info, 'task_list_marker_checked') ~= nil then
                 return true
             end
-            local paragraph_node = ts.sibling(info.node, 'paragraph')
-            if paragraph_node == nil then
+            local paragraph = ts.sibling(buf, info, 'paragraph')
+            if paragraph == nil then
                 return false
             end
-            local paragraph = ts.info(paragraph_node, buf)
             return component.checkbox(paragraph.text, 'starts') ~= nil
         end
 
@@ -175,7 +121,7 @@ M.render_node = function(namespace, buf, capture, node)
             -- edge cases in the parser: https://github.com/tree-sitter-grammars/tree-sitter-markdown/issues/127
             -- As a result we handle leading spaces here, can remove if this gets fixed upstream
             local leading_spaces = str.leading_spaces(info.text)
-            local level = ts.level_in_section(info.node, 'list')
+            local level = ts.level_in_section(info, 'list')
             local icon = list.cycle(bullet.icons, level)
 
             vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, info.start_col, {
@@ -196,9 +142,9 @@ M.render_node = function(namespace, buf, capture, node)
             return
         end
         local highlight = quote.highlight
-        local quote_node = ts.parent_in_section(info.node, 'block_quote')
-        if quote_node ~= nil then
-            local callout = component.callout(ts.info(quote_node, buf).text, 'contains')
+        local block_quote = ts.parent_in_section(buf, info, 'block_quote')
+        if block_quote ~= nil then
+            local callout = component.callout(block_quote.text, 'contains')
             if callout ~= nil then
                 highlight = callout.highlight
             end
@@ -232,6 +178,98 @@ M.render_node = function(namespace, buf, capture, node)
     end
 end
 
+---@param namespace integer
+---@param buf integer
+---@param info render.md.NodeInfo
+M.render_code = function(namespace, buf, info)
+    local code = state.config.code
+    if not code.enabled then
+        return
+    end
+    if code.style == 'none' then
+        return
+    end
+    local did_render_language = false
+    local code_info = ts.child(buf, info, 'info_string', info.start_row)
+    if code_info ~= nil then
+        local language_info = ts.child(buf, code_info, 'language', code_info.start_row)
+        if language_info ~= nil then
+            did_render_language = M.render_language(namespace, buf, language_info, info)
+        end
+    end
+    if not vim.tbl_contains({ 'normal', 'full' }, code.style) then
+        return
+    end
+    local start_row = info.start_row
+    local end_row = info.end_row
+    -- Do not attempt to render single line code block
+    if start_row == end_row - 1 then
+        return
+    end
+    if code.border == 'thin' then
+        local code_start = ts.child(buf, info, 'fenced_code_block_delimiter', info.start_row)
+        local code_end = ts.child(buf, info, 'fenced_code_block_delimiter', info.end_row - 1)
+        if not did_render_language and ts.hidden(buf, code_info) and ts.hidden(buf, code_start) then
+            start_row = start_row + 1
+            vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, info.start_col, {
+                virt_text = { { code.above:rep(util.get_width(buf)), colors.inverse(code.highlight) } },
+                virt_text_pos = 'overlay',
+            })
+        end
+        if ts.hidden(buf, code_end) then
+            end_row = end_row - 1
+            vim.api.nvim_buf_set_extmark(buf, namespace, info.end_row - 1, info.start_col, {
+                virt_text = { { code.below:rep(util.get_width(buf)), colors.inverse(code.highlight) } },
+                virt_text_pos = 'overlay',
+            })
+        end
+    end
+    vim.api.nvim_buf_set_extmark(buf, namespace, start_row, 0, {
+        end_row = end_row,
+        end_col = 0,
+        hl_group = code.highlight,
+        hl_eol = true,
+    })
+end
+
+---@param namespace integer
+---@param buf integer
+---@param info render.md.NodeInfo
+---@param code_block render.md.NodeInfo
+---@return boolean
+M.render_language = function(namespace, buf, info, code_block)
+    local code = state.config.code
+    if not vim.tbl_contains({ 'language', 'full' }, code.style) then
+        return false
+    end
+    local icon, icon_highlight = icons.get(info.text)
+    if icon == nil or icon_highlight == nil then
+        return false
+    end
+    M.render_sign(namespace, buf, info, icon, icon_highlight)
+    -- Requires inline extmarks
+    if not util.has_10 then
+        return false
+    end
+    local icon_text = icon .. ' '
+    if ts.hidden(buf, info) then
+        -- Code blocks will pick up varying amounts of leading white space depending on the
+        -- context they are in. This gets lumped into the delimiter node and as a result,
+        -- after concealing, the extmark will be left shifted. Logic below accounts for this.
+        local padding = str.leading_spaces(code_block.text)
+        icon_text = str.pad(icon_text .. info.text, padding)
+    end
+    local highlight = { icon_highlight }
+    if code.style == 'full' then
+        highlight = { icon_highlight, code.highlight }
+    end
+    vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, info.start_col, {
+        virt_text = { { icon_text, highlight } },
+        virt_text_pos = 'inline',
+    })
+    return true
+end
+
 ---@param namespace integer
 ---@param buf integer
 ---@param info render.md.NodeInfo