feat: always indent based on heading level rather than parent sections

## Details

This is a follow up to: #164

Following this PR several edge cases were fixed around intation when
used with heading borders. Along with edge cases when not starting with
an H1 in the document.

However there was still a problem when indentation level was reduced
which caused additional space to be added to the top border.

Rather than patching this I went the direction of unifying the
definition of a heading level. With this content underneath a heading is
always indented to that level, i.e. an H3 will always have 6 starting
spaces. Before this would only happen if an H1 & an H2 were included
before, this is no longer the case. To do this logic to calculate the
change in level between sections was added. Also H1s become less of a
special case, we simply define the default document level as 1 so H1s
end up at the same level leading to no change.

This on its own would cause problems with upper borders since they would
be indented based on the previous section. To fix this the range that a
section covers was changed from what treesitter provides. Empty lines
above a section belong to the lower section making the indentation more
or less just work.

Author: MeanderingProgrammer

CHANGELOG.md

@@ -16,6 +16,11 @@
   [12fdb6f](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/12fdb6f6623cb7e20da75be68858f12e1e578ffd)
 - leading spaces in checkbox bullet [#158](https://github.com/MeanderingProgrammer/render-markdown.nvim/issues/158)
   [06337f6](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/06337f64367ef1f1115f0a9ba41e49b84a04b1a4)
+- heading borders with indentation [#164](https://github.com/MeanderingProgrammer/render-markdown.nvim/pull/164)
+
+### Collaborator Shoutouts
+
+- @lukas-reineke
 
 ## 6.3.0 (2024-08-29)
 

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*         For 0.10.0        Last change: 2024 September 11
+*render-markdown.txt*         For 0.10.0        Last change: 2024 September 12
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*

lua/render-markdown/core/node_info.lua

@@ -53,29 +53,25 @@ function NodeInfo:has_error()
 end
 
 ---@return integer
-function NodeInfo:level()
-    local level = 0
-    local parent = self.node:parent()
-    while parent ~= nil and parent:type() ~= 'document' do
-        if parent:type() == 'section' then
-            local child = parent:child(0)
-            child = child and child:child(0)
-            local is_first_heading = child and child:type() == 'atx_h1_marker'
-            if not is_first_heading then
-                level = level + 1
-            end
-        end
-        parent = parent:parent()
-    end
-    return level
+function NodeInfo:parent_heading_level()
+    local parent = self:parent('section')
+    return parent ~= nil and parent:heading_level() or 1
+end
+
+---@return integer
+function NodeInfo:heading_level()
+    assert(self.type == 'section', 'Node must be a section')
+    local heading = self:child('atx_heading')
+    local node = heading ~= nil and heading.node:child(0) or nil
+    -- Counts the number of hashtags in the heading marker
+    return node ~= nil and #vim.treesitter.get_node_text(node, self.buf) or 1
 end
 
 ---Walk through parent nodes, count the number of target nodes
 ---@param target string
 ---@return integer
 function NodeInfo:level_in_section(target)
-    local level = 0
-    local parent = self.node:parent()
+    local level, parent = 0, self.node:parent()
     while parent ~= nil and in_section(parent) do
         if parent:type() == target then
             level = level + 1
@@ -132,18 +128,20 @@ function NodeInfo:for_each_child(callback)
     end
 end
 
----@param position 'above'|'below'|'on'
+---@param position 'above'|'below'|'first'|'last'
 ---@return string?
 function NodeInfo:line(position)
-    local start_row = nil
+    local row = nil
     if position == 'above' then
-        start_row = self.start_row - 1
+        row = self.start_row - 1
     elseif position == 'below' then
-        start_row = self.end_row + 1
-    else
-        start_row = self.start_row
+        row = self.end_row + 1
+    elseif position == 'first' then
+        row = self.start_row
+    elseif position == 'last' then
+        row = self.end_row - 1
     end
-    return vim.api.nvim_buf_get_lines(self.buf, start_row, start_row + 1, false)[1]
+    return row ~= nil and vim.api.nvim_buf_get_lines(self.buf, row, row + 1, false)[1] or nil
 end
 
 ---@return string[]

lua/render-markdown/handler/markdown.lua

@@ -23,6 +23,7 @@ function Handler.new(buf)
         code = require('render-markdown.render.code'),
         heading = require('render-markdown.render.heading'),
         quote = require('render-markdown.render.quote'),
+        section = require('render-markdown.render.section'),
         table = require('render-markdown.render.table'),
     }
     return self
@@ -38,8 +39,6 @@ function Handler:parse(root)
             if render:setup() then
                 render:render()
             end
-        elseif capture == 'section' then
-            self:section(info)
         elseif capture == 'dash' then
             self:dash(info)
         elseif capture == 'list_marker' then
@@ -55,31 +54,6 @@ function Handler:parse(root)
     return self.marks:get()
 end
 
----@private
----@param info render.md.NodeInfo
-function Handler:section(info)
-    local indent = self.config.indent
-    if not indent.enabled then
-        return
-    end
-
-    -- Do not add any indentation on unknown or first level
-    local heading = info:child('atx_heading')
-    if heading == nil or heading:child('atx_h1_marker') ~= nil then
-        return
-    end
-
-    -- Each level stacks inline marks so we do not need to multiply spaces
-    -- However skipping a level, i.e. 2 -> 5, will only add one level of spaces
-    for row = info.start_row, info.end_row - 1 do
-        self.marks:add(false, row, 0, {
-            priority = 0,
-            virt_text = { { str.spaces(indent.per_level), 'Normal' } },
-            virt_text_pos = 'inline',
-        })
-    end
-end
-
 ---@private
 ---@param info render.md.NodeInfo
 function Handler:dash(info)

lua/render-markdown/handler/markdown_inline.lua

@@ -67,7 +67,7 @@ function Handler:shortcut(info)
         return
     end
 
-    local line = info:line('on')
+    local line = info:line('first')
     if line ~= nil and line:find('[' .. info.text .. ']', 1, true) ~= nil then
         self:wiki_link(info)
         return

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local M = {}
 
 ---@private
 ---@type string
-M.version = '6.3.7'
+M.version = '6.3.8'
 
 function M.check()
     vim.health.start('render-markdown.nvim [version]')

lua/render-markdown/render/base.lua

@@ -41,14 +41,13 @@ end
 
 ---@protected
 ---@param line { [1]: string, [2]: string }[]
----@param level integer?
 ---@return { [1]: string, [2]: string }[]
-function Base:indent_virt_line(line, level)
+function Base:indent_virt_line(line)
     local indent = self.config.indent
     if not indent.enabled then
         return line
     end
-    level = level or self.info:level()
+    local level = self.info:parent_heading_level() - 1
     if level <= 0 then
         return line
     end

lua/render-markdown/render/heading.lua

@@ -175,9 +175,6 @@ function Render:border(width)
         { self.heading.above:rep(width - self.heading.left_pad - prefix), background },
     }
     if str.width(self.info:line('above')) == 0 and self.info.start_row - 1 ~= self.context.last_heading then
-        if self.data.level > 1 then
-            line_above = self:indent_virt_line(line_above, 1)
-        end
         self.marks:add(true, self.info.start_row - 1, 0, {
             virt_text = line_above,
             virt_text_pos = 'overlay',

lua/render-markdown/render/section.lua

@@ -0,0 +1,57 @@
+local Base = require('render-markdown.render.base')
+local str = require('render-markdown.core.str')
+
+---@class render.md.render.Section: render.md.Renderer
+---@field private indent render.md.Indent
+---@field private level_change integer
+local Render = setmetatable({}, Base)
+Render.__index = Render
+
+---@param marks render.md.Marks
+---@param config render.md.buffer.Config
+---@param context render.md.Context
+---@param info render.md.NodeInfo
+---@return render.md.Renderer
+function Render:new(marks, config, context, info)
+    return Base.new(self, marks, config, context, info)
+end
+
+---@return boolean
+function Render:setup()
+    self.indent = self.config.indent
+    if not self.indent.enabled then
+        return false
+    end
+
+    local current_level = self.info:heading_level()
+    local parent_level = self.info:parent_heading_level()
+    self.level_change = current_level - parent_level
+
+    -- Nothing to do if there is not a change in level
+    if self.level_change <= 0 then
+        return false
+    end
+
+    return true
+end
+
+function Render:render()
+    -- Do include empty line in previous section
+    local start_offset = str.width(self.info:line('above')) == 0 and 1 or 0
+    local start_row = math.max(self.info.start_row - start_offset, 0)
+
+    -- Do not include empty line at the end of current section
+    local end_offset = str.width(self.info:line('last')) == 0 and 1 or 0
+    local end_row = self.info.end_row - 1 - end_offset
+
+    -- Each level stacks inline marks so we only need to multiply based on any skipped levels
+    for row = start_row, end_row do
+        self.marks:add(false, row, 0, {
+            priority = 0,
+            virt_text = { { str.spaces(self.indent.per_level * self.level_change), 'Normal' } },
+            virt_text_pos = 'inline',
+        })
+    end
+end
+
+return Render

tests/ad_hoc_spec.lua

@@ -11,17 +11,14 @@ local function setext_heading(start_row, end_row, level)
     local foreground = util.hl(string.format('H%d', level))
     local background = util.hl(string.format('H%dBg', level))
 
-    local result = {}
-
     ---@type render.md.MarkInfo
-    local icon_mark = {
-        row = { start_row, end_row + 1 },
-        col = { 0, 0 },
-        virt_text = { { icon, { foreground, background } } },
-        virt_text_pos = 'inline',
+    local sign_mark = {
+        row = { start_row },
+        col = { 0 },
+        sign_text = '󰫎 ',
+        sign_hl_group = util.hl('_' .. foreground .. '_' .. util.hl('Sign')),
     }
-    table.insert(result, icon_mark)
-
+    local result = { sign_mark }
     for row = start_row, end_row do
         ---@type render.md.MarkInfo
         local background_mark = {
@@ -32,23 +29,21 @@ local function setext_heading(start_row, end_row, level)
         }
         table.insert(result, background_mark)
     end
-
+    ---@type render.md.MarkInfo
+    local icon_mark = {
+        row = { start_row, end_row + 1 },
+        col = { 0, 0 },
+        virt_text = { { icon, { foreground, background } } },
+        virt_text_pos = 'inline',
+    }
+    table.insert(result, 3, icon_mark)
     ---@type render.md.MarkInfo
     local conceal_mark = {
         row = { end_row, end_row },
         col = { 0, 3 },
         conceal = '',
     }
-    table.insert(result, conceal_mark)
-
-    ---@type render.md.MarkInfo
-    local sign_mark = {
-        row = { start_row },
-        col = { 0 },
-        sign_text = '󰫎 ',
-        sign_hl_group = util.hl('_' .. foreground .. '_' .. util.hl('Sign')),
-    }
-    table.insert(result, 3, sign_mark)
+    table.insert(result, #result, conceal_mark)
     return result
 end