fix: top & bottom padding for latex

## Details

The previous change to latex rendering did not correctly handle all the
edge cases around how a formula could be rendered. In particular if
we've added a line above and inlined a formula then padding below should
insert a virtual line below, the current implementation added a gap to
the bottom of the line above.

The fix is pretty simple, add padding to the output directly, rather
than trying to capture all the possible conditions and manipulating the
final virtual lines.

Added unit tests to validate this new behavior, as well as behavior
introduced in the previous change. Minor refactor to test directory,
store tests that use demo files as input in a subdirectory, avoids some
clutter.

Author: MeanderingProgrammer

CHANGELOG.md

@@ -6,6 +6,8 @@
 
 - remove delimiters around latex text before converting [2c6cf12](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/2c6cf127c577712bd29d38f6391b3045c5f0180a)
 - convert latex asynchronously [44cbac6](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/44cbac697e50ae32e4644652da08cf692b9a5a57)
+- combine latex virtual lines use center positioning [#520](https://github.com/MeanderingProgrammer/render-markdown.nvim/issues/520)
+  [9a746ff](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/9a746ff62a482f5eb722b3bfc7eefb2e9d638858)
 
 ### Bug Fixes
 

lua/render-markdown/handler/latex.lua

@@ -141,6 +141,14 @@ function Handler:render(row, nodes)
     for _, node in ipairs(nodes) do
         local output = str.split(Handler.cache[Handler.text(node)], '\n', true)
 
+        -- add top and bottom padding around output
+        for _ = 1, self.config.top_pad do
+            table.insert(output, 1, '')
+        end
+        for _ = 1, self.config.bottom_pad do
+            output[#output + 1] = ''
+        end
+
         -- pad lines to the same width
         local width = vim.fn.max(iter.list.map(output, str.width))
         for i, line in ipairs(output) do
@@ -218,19 +226,11 @@ function Handler:render(row, nodes)
     end
 
     ---@param lines string[]
-    ---@param top boolean
-    ---@param bottom boolean
     ---@param above boolean
-    local function add_lines(lines, top, bottom, above)
+    local function add_lines(lines, above)
         if #lines == 0 then
             return
         end
-        for _ = 1, (top and self.config.top_pad or 0) do
-            table.insert(lines, 1, '')
-        end
-        for _ = 1, (bottom and self.config.bottom_pad or 0) do
-            lines[#lines + 1] = ''
-        end
         self.marks:add(self.config, 'virtual_lines', row, 0, {
             virt_lines = iter.list.map(lines, function(line)
                 return indent:copy():text(line, self.config.highlight):get()
@@ -239,8 +239,8 @@ function Handler:render(row, nodes)
         })
     end
 
-    add_lines(lines_above, true, #lines_below == 0, true)
-    add_lines(lines_below, #lines_above == 0, true, false)
+    add_lines(lines_above, true)
+    add_lines(lines_below, false)
 end
 
 ---@private

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '8.8.6'
+M.version = '8.8.7'
 
 function M.check()
     M.start('versions')

tests/conceal_level_spec.lua

@@ -2,19 +2,19 @@
 
 local util = require('tests.util')
 
-describe('table.md conceallevel', function()
-    local lines = {
-        '',
-        '| Heading 1 | `Heading 2`            |',
-        '| --------- | ---------------------: |',
-        '| `Item 行` | [link](https://行.com) |',
-        '| <1> | ==Itém 2==             |',
-        '',
-        '| Heading 1 | Heading 2 |',
-        '| --------- | --------- |',
-        '| Item 1    | Item 2    |',
-    }
+local lines = {
+    '',
+    '| Heading 1 | `Heading 2`            |',
+    '| --------- | ---------------------: |',
+    '| `Item 行` | [link](https://行.com) |',
+    '| <1> | ==Itém 2==             |',
+    '',
+    '| Heading 1 | Heading 2 |',
+    '| --------- | --------- |',
+    '| Item 1    | Item 2    |',
+}
 
+describe('table conceallevel', function()
     it('0', function()
         util.setup.text(lines, {
             win_options = { conceallevel = { rendered = 0 } },

tests/custom_handler_spec.lua

@@ -2,6 +2,11 @@
 
 local util = require('tests.util')
 
+local lines = {
+    '`Inline` code',
+    '\\$1.50 \\$3.55',
+}
+
 ---@param ctx render.md.handler.Context
 ---@return render.md.Mark[]
 local function conceal_escape(ctx)
@@ -23,11 +28,6 @@ local function conceal_escape(ctx)
 end
 
 describe('custom handler', function()
-    local lines = {
-        '`Inline` code',
-        '\\$1.50 \\$3.55',
-    }
-
     it('default', function()
         util.setup.text(lines)
         -- inline code + no backslash escapes

tests/box_dash_quote_spec.lua tests/demo/box_dash_quote_spec.luatests/box_dash_quote_spec.lua renamed to tests/demo/box_dash_quote_spec.lua

@@ -2,7 +2,7 @@
 
 local util = require('tests.util')
 
-describe('box_dash_quote.md', function()
+describe('demo/box_dash_quote.md', function()
     it('default', function()
         util.setup.file('demo/box_dash_quote.md')
 

tests/callout_spec.lua tests/demo/callout_spec.luatests/callout_spec.lua renamed to tests/demo/callout_spec.lua

@@ -2,7 +2,7 @@
 
 local util = require('tests.util')
 
-describe('callout.md', function()
+describe('demo/callout.md', function()
     it('default', function()
         util.setup.file('demo/callout.md')
 

tests/heading_code_spec.lua tests/demo/heading_code_spec.luatests/heading_code_spec.lua renamed to tests/demo/heading_code_spec.lua

@@ -2,7 +2,7 @@
 
 local util = require('tests.util')
 
-describe('heading_code.md', function()
+describe('demo/heading_code.md', function()
     it('default', function()
         util.setup.file('demo/heading_code.md')
 

tests/latex_spec.lua tests/demo/latex_spec.luatests/latex_spec.lua renamed to tests/demo/latex_spec.lua

@@ -8,7 +8,7 @@ local function join(lines)
     return table.concat(lines, '\n')
 end
 
-describe('latex.md', function()
+describe('demo/latex.md', function()
     it('default', function()
         local inline = {
             raw = '\\sqrt{3x-1}+(1+x)^2',

tests/list_table_spec.lua tests/demo/list_table_spec.luatests/list_table_spec.lua renamed to tests/demo/list_table_spec.lua

@@ -62,7 +62,7 @@ local function shared()
     return marks
 end
 
-describe('list_table.md', function()
+describe('demo/list_table.md', function()
     it('default', function()
         util.setup.file('demo/list_table.md')