feat: Improve LaTeX compatibility for more advanced converters

## Details

The current LaTeX parsing logic trims each line to remove spaces.

This is okay for simple converters, but multi-line converters will
use spaces to position components.

Instead of removing the whitespace around each line, use the trimempty
option to remove leading and trailing fully empty lines only. From
there each line is left as returned from the converter.

Add `latex.top_pad` and `latex.bottom_pad` options to allow users to
specify how much spacing they want around the rendered LaTeX blocks.

Co-Authored-By: joshuarayton <[email protected]>

Author: MeanderingProgrammer

Diff for: README.md

@@ -184,6 +184,10 @@ require('render-markdown').setup({
         converter = 'latex2text',
         -- Highlight for LaTeX blocks
         highlight = 'RenderMarkdownMath',
+        -- Amount of empty lines above LaTeX blocks
+        top_pad = 0,
+        -- Amount of empty lines below LaTeX blocks
+        bottom_pad = 0,
     },
     heading = {
         -- Turn on / off heading icon & background rendering

Diff for: doc/render-markdown.txt

@@ -225,6 +225,10 @@ Full Default Configuration ~
             converter = 'latex2text',
             -- Highlight for LaTeX blocks
             highlight = 'RenderMarkdownMath',
+            -- Amount of empty lines above LaTeX blocks
+            top_pad = 0,
+            -- Amount of empty lines below LaTeX blocks
+            bottom_pad = 0,
         },
         heading = {
             -- Turn on / off heading icon & background rendering

Diff for: lua/render-markdown/handler/latex.lua

@@ -32,8 +32,13 @@ function M.parse(root, buf)
     local expressions = cache.expressions[info.text]
     if expressions == nil then
         local raw_expression = vim.fn.system(latex.converter, info.text)
-        local parsed_expressions = vim.split(vim.trim(raw_expression), '\n', { plain = true })
-        expressions = vim.tbl_map(vim.trim, parsed_expressions)
+        expressions = vim.split(raw_expression, '\n', { plain = true, trimempty = true })
+        for _ = 1, latex.top_pad do
+            table.insert(expressions, 1, '')
+        end
+        for _ = 1, latex.bottom_pad do
+            table.insert(expressions, '')
+        end
         cache.expressions[info.text] = expressions
     end
 

Diff for: lua/render-markdown/init.lua

@@ -96,6 +96,8 @@ local M = {}
 ---@field public enabled? boolean
 ---@field public converter? string
 ---@field public highlight? string
+---@field public top_pad? integer
+---@field public bottom_pad? integer
 
 ---@class render.md.UserAntiConceal
 ---@field public enabled? boolean
@@ -208,6 +210,10 @@ M.default_config = {
         converter = 'latex2text',
         -- Highlight for LaTeX blocks
         highlight = 'RenderMarkdownMath',
+        -- Amount of empty lines above LaTeX blocks
+        top_pad = 0,
+        -- Amount of empty lines below LaTeX blocks
+        bottom_pad = 0,
     },
     heading = {
         -- Turn on / off heading icon & background rendering

Diff for: lua/render-markdown/state.lua

@@ -117,6 +117,8 @@ function state.validate()
         enabled = { latex.enabled, 'boolean' },
         converter = { latex.converter, 'string' },
         highlight = { latex.highlight, 'string' },
+        top_pad = { latex.top_pad, 'number' },
+        bottom_pad = { latex.bottom_pad, 'number' },
     })
 
     local heading = config.heading

Diff for: lua/render-markdown/types.lua

@@ -81,6 +81,8 @@
 ---@field public enabled boolean
 ---@field public converter string
 ---@field public highlight string
+---@field public top_pad integer
+---@field public bottom_pad integer
 
 ---@class render.md.AntiConceal
 ---@field public enabled boolean

Diff for: tests/latex_spec.lua

@@ -46,7 +46,7 @@ async_tests.describe('latex.md', function()
             -- Inline
             latex(2, 2, 0, 21, { '√(3x-1)+(1+x)^2' }),
             -- Block
-            latex(4, 7, 0, 2, { 'f(x,y) = x + √(y)', 'f(x,y) = √(y) + x^2/4y' }),
+            latex(4, 7, 0, 2, { '    f(x,y) = x + √(y)', '    f(x,y) = √(y) + x^2/4y' }),
         })
 
         local actual = util.get_actual_marks()