feat: add cell_offset function to pipe_table configuration

## Details

Adds `pipe_table.cell_offset`, which can be used to adjust the computed
width of table cells based on more user specific behavior. This will be
added directly to the width (can be negative to subtract). The computed
value is not fact checked in any way so if the offset provided results
in distorted rendering it is up to the user to fix it.

Existing logic takes care of treesitter highlighting behavior and
offsets caused by `extmark`s from this plugin. Other plugins are not
accounted for as the behavior is not consistent across all plugins, this
is likely the primary usage of this feature.

Author: MeanderingProgrammer

README.md

@@ -674,6 +674,10 @@ require('render-markdown').setup({
         -- | padded  | raw + cells are padded to maximum visual width for each column             |
         -- | trimmed | padded except empty space is subtracted from visual width calculation      |
         cell = 'padded',
+        -- Adjust the computed width of table cells using custom logic.
+        cell_offset = function()
+            return 0
+        end,
         -- Amount of space to put between cell contents and border.
         padding = 1,
         -- Minimum column width to use for padded or trimmed cell.
@@ -1373,6 +1377,10 @@ require('render-markdown').setup({
         -- | padded  | raw + cells are padded to maximum visual width for each column             |
         -- | trimmed | padded except empty space is subtracted from visual width calculation      |
         cell = 'padded',
+        -- Adjust the computed width of table cells using custom logic.
+        cell_offset = function()
+            return 0
+        end,
         -- Amount of space to put between cell contents and border.
         padding = 1,
         -- Minimum column width to use for padded or trimmed cell.

doc/render-markdown.txt

@@ -740,6 +740,10 @@ Default Configuration ~
             -- | padded  | raw + cells are padded to maximum visual width for each column             |
             -- | trimmed | padded except empty space is subtracted from visual width calculation      |
             cell = 'padded',
+            -- Adjust the computed width of table cells using custom logic.
+            cell_offset = function()
+                return 0
+            end,
             -- Amount of space to put between cell contents and border.
             padding = 1,
             -- Minimum column width to use for padded or trimmed cell.
@@ -1423,6 +1427,10 @@ Table Configuration ~
             -- | padded  | raw + cells are padded to maximum visual width for each column             |
             -- | trimmed | padded except empty space is subtracted from visual width calculation      |
             cell = 'padded',
+            -- Adjust the computed width of table cells using custom logic.
+            cell_offset = function()
+                return 0
+            end,
             -- Amount of space to put between cell contents and border.
             padding = 1,
             -- Minimum column width to use for padded or trimmed cell.

lua/render-markdown/config/pipe_table.lua

@@ -1,6 +1,7 @@
 ---@class (exact) render.md.table.Config: render.md.base.Config
 ---@field preset render.md.table.Preset
 ---@field cell render.md.table.Cell
+---@field cell_offset fun(ctx: render.md.table.cell.Context): integer
 ---@field padding integer
 ---@field min_width integer
 ---@field border string[]
@@ -12,6 +13,9 @@
 ---@field filler string
 ---@field style render.md.table.Style
 
+---@class (exact) render.md.table.cell.Context
+---@field node TSNode
+
 ---@enum render.md.table.Preset
 local Preset = {
     none = 'none',
@@ -56,6 +60,10 @@ M.default = {
     -- | padded  | raw + cells are padded to maximum visual width for each column             |
     -- | trimmed | padded except empty space is subtracted from visual width calculation      |
     cell = 'padded',
+    -- Adjust the computed width of table cells using custom logic.
+    cell_offset = function()
+        return 0
+    end,
     -- Amount of space to put between cell contents and border.
     padding = 1,
     -- Minimum column width to use for padded or trimmed cell.
@@ -94,6 +102,7 @@ function M.validate(spec)
     require('render-markdown.config.base').validate(spec)
     spec:one_of('preset', vim.tbl_values(Preset))
     spec:one_of('cell', vim.tbl_values(Cell))
+    spec:type('cell_offset', 'function')
     spec:type('padding', 'number')
     spec:type('min_width', 'number')
     spec:list('border', 'string')

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '8.7.6'
+M.version = '8.7.7'
 
 function M.check()
     M.start('versions')

lua/render-markdown/render/markdown/table.lua

@@ -171,10 +171,10 @@ function Render:parse_row(node, num_cols)
     for i, cell in ipairs(cells) do
         -- account for double width glyphs by replacing cell range with width
         local start_col, end_col = pipes[i].end_col, pipes[i + 1].start_col
-        local width = end_col - start_col
-        width = width
+        local width = (end_col - start_col)
             - (cell.end_col - cell.start_col)
             + self.context:width(cell)
+            + self.config.cell_offset({ node = cell:get() })
         assert(width >= 0, 'invalid table layout')
         cols[#cols + 1] = {
             row = cell.start_row,
@@ -281,23 +281,32 @@ function Render:row(row)
 
     if vim.tbl_contains({ 'trimmed', 'padded' }, self.config.cell) then
         for i, col in ipairs(row.cols) do
-            local delim_col = self.data.delim.cols[i]
-            -- amount of space needed to get column to target width
-            local fill = delim_col.width - col.width
+            local delim = self.data.delim.cols[i]
+            local space = col.space
+            local fill = delim.width - col.width
+            -- delim(20) : --------------------
+            -- col(4,7,2): ----XXXXXXX--
+            -- fill(7)   :              _______
             if not self.context.conceal:enabled() then
+                -- result: ----XXXXXXX--_______
                 -- without concealing it is impossible to do full alignment
                 self:shift(col, 'right', fill)
-            elseif delim_col.alignment == Alignment.center then
-                local shift =
-                    math.floor((fill + col.space.right - col.space.left) / 2)
+            elseif delim.alignment == Alignment.center then
+                -- (7 + 2 - 4) // 2 = 5 // 2 = 2 -> move two spaces to the right
+                -- result: __----XXXXXXX--_____
+                local shift = math.floor((fill + space.right - space.left) / 2)
                 self:shift(col, 'left', shift)
                 self:shift(col, 'right', fill - shift)
-            elseif delim_col.alignment == Alignment.right then
-                local shift = col.space.right - self.config.padding
+            elseif delim.alignment == Alignment.right then
+                -- 2 - 1 = 1 -> conceal one space on right side
+                -- result: -_______----XXXXXXX-
+                local shift = space.right - self.config.padding
                 self:shift(col, 'left', fill + shift)
                 self:shift(col, 'right', -shift)
             else
-                local shift = col.space.left - self.config.padding
+                -- 4 - 1 = 3 -> conceal three spaces on left side
+                -- result: -XXXXXXX--_______---
+                local shift = space.left - self.config.padding
                 self:shift(col, 'left', -shift)
                 self:shift(col, 'right', fill + shift)
             end

lua/render-markdown/types.lua

@@ -257,6 +257,7 @@
 ---@class (exact) render.md.table.UserConfig: render.md.base.UserConfig
 ---@field preset? render.md.table.Preset
 ---@field cell? render.md.table.Cell
+---@field cell_offset? fun(ctx: render.md.table.cell.Context): integer
 ---@field padding? integer
 ---@field min_width? integer
 ---@field border? string[]