feat: dash width function

## Details

Request: #537

Allow `dash.width` to be a function. Function is provided with the
window width in the input context, more fields can be added later if
needed. Allows greater flexibility in user setup.

Author: MeanderingProgrammer

README.md

@@ -525,6 +525,9 @@ require('render-markdown').setup({
         style = 'full',
     },
     dash = {
+        -- Useful context to have when evaluating values.
+        -- | width | width of the current window |
+
         -- Turn on / off thematic break rendering.
         enabled = true,
         -- Additional modes to render dash.
@@ -533,9 +536,11 @@ require('render-markdown').setup({
         -- The icon gets repeated across the window's width.
         icon = '─',
         -- Width of the generated line.
-        -- | <number> | a hard coded width value |
-        -- | full     | full width of the window |
         -- If a float < 1 is provided it is treated as a percentage of available window space.
+        -- Output is evaluated depending on the type.
+        -- | function | `value(context)`    |
+        -- | number   | `value`             |
+        -- | full     | width of the window |
         width = 'full',
         -- Amount of margin to add to the left of dash.
         -- If a float < 1 is provided it is treated as a percentage of available window space.
@@ -1191,6 +1196,9 @@ require('render-markdown').setup({
 ```lua
 require('render-markdown').setup({
     dash = {
+        -- Useful context to have when evaluating values.
+        -- | width | width of the current window |
+
         -- Turn on / off thematic break rendering.
         enabled = true,
         -- Additional modes to render dash.
@@ -1199,9 +1207,11 @@ require('render-markdown').setup({
         -- The icon gets repeated across the window's width.
         icon = '─',
         -- Width of the generated line.
-        -- | <number> | a hard coded width value |
-        -- | full     | full width of the window |
         -- If a float < 1 is provided it is treated as a percentage of available window space.
+        -- Output is evaluated depending on the type.
+        -- | function | `value(context)`    |
+        -- | number   | `value`             |
+        -- | full     | width of the window |
         width = 'full',
         -- Amount of margin to add to the left of dash.
         -- If a float < 1 is provided it is treated as a percentage of available window space.

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*       For NVIM v0.11.4      Last change: 2025 October 09
+*render-markdown.txt*       For NVIM v0.11.4      Last change: 2025 October 13
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*
@@ -589,6 +589,9 @@ Default Configuration ~
             style = 'full',
         },
         dash = {
+            -- Useful context to have when evaluating values.
+            -- | width | width of the current window |
+    
             -- Turn on / off thematic break rendering.
             enabled = true,
             -- Additional modes to render dash.
@@ -597,9 +600,11 @@ Default Configuration ~
             -- The icon gets repeated across the window's width.
             icon = '─',
             -- Width of the generated line.
-            -- | <number> | a hard coded width value |
-            -- | full     | full width of the window |
             -- If a float < 1 is provided it is treated as a percentage of available window space.
+            -- Output is evaluated depending on the type.
+            -- | function | `value(context)`    |
+            -- | number   | `value`             |
+            -- | full     | width of the window |
             width = 'full',
             -- Amount of margin to add to the left of dash.
             -- If a float < 1 is provided it is treated as a percentage of available window space.
@@ -1247,6 +1252,9 @@ Dashed Line Configuration ~
 >lua
     require('render-markdown').setup({
         dash = {
+            -- Useful context to have when evaluating values.
+            -- | width | width of the current window |
+    
             -- Turn on / off thematic break rendering.
             enabled = true,
             -- Additional modes to render dash.
@@ -1255,9 +1263,11 @@ Dashed Line Configuration ~
             -- The icon gets repeated across the window's width.
             icon = '─',
             -- Width of the generated line.
-            -- | <number> | a hard coded width value |
-            -- | full     | full width of the window |
             -- If a float < 1 is provided it is treated as a percentage of available window space.
+            -- Output is evaluated depending on the type.
+            -- | function | `value(context)`    |
+            -- | number   | `value`             |
+            -- | full     | width of the window |
             width = 'full',
             -- Amount of margin to add to the left of dash.
             -- If a float < 1 is provided it is treated as a percentage of available window space.

lua/render-markdown/health.lua

@@ -6,7 +6,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '8.9.5'
+M.version = '8.9.6'
 
 function M.check()
     M.start('versions')

lua/render-markdown/lib/env.lua

@@ -250,6 +250,14 @@ function M.win.view(win)
     return vim.api.nvim_win_call(win, vim.fn.winsaveview)
 end
 
+---@param win integer
+---@return integer
+function M.win.width(win)
+    local infos = vim.fn.getwininfo(win)
+    local textoff = #infos == 1 and infos[1].textoff or 0
+    return vim.api.nvim_win_get_width(win) - textoff
+end
+
 ---@param win integer
 ---@param value number
 ---@param used integer
@@ -260,9 +268,7 @@ function M.win.percent(win, value, used)
     elseif value >= 1 then
         return value
     else
-        local infos = vim.fn.getwininfo(win)
-        local textoff = #infos == 1 and infos[1].textoff or 0
-        local width = vim.api.nvim_win_get_width(win) - textoff - used
+        local width = M.win.width(win) - used
         return math.floor((width * value) + 0.5)
     end
 end

lua/render-markdown/render/markdown/dash.lua

@@ -20,7 +20,7 @@ function Render:setup()
     end
     local width = self:get_width(self.config.width, 0)
     local margin = self:get_width(self.config.left_margin, width)
-    if width <= 0 and margin <= 0 then
+    if width <= 0 then
         return false
     end
     self.data = { width = width, margin = margin }
@@ -34,6 +34,8 @@ end
 function Render:get_width(width, used)
     if type(width) == 'number' then
         return env.win.percent(self.context.win, width, used)
+    elseif type(width) == 'function' then
+        return width({ width = env.win.width(self.context.win) })
     else
         return vim.o.columns
     end

lua/render-markdown/settings.lua

@@ -633,10 +633,19 @@ M.dash = {}
 ---@field left_margin number
 ---@field highlight string
 
----@alias render.md.dash.Width 'full'|number
+---@class (exact) render.md.dash.Context
+---@field width integer
+
+---@alias render.md.dash.Width
+---| 'full'
+---| number
+---| fun(ctx: render.md.dash.Context): integer
 
 ---@type render.md.dash.Config
 M.dash.default = {
+    -- Useful context to have when evaluating values.
+    -- | width | width of the current window |
+
     -- Turn on / off thematic break rendering.
     enabled = true,
     -- Additional modes to render dash.
@@ -645,9 +654,11 @@ M.dash.default = {
     -- The icon gets repeated across the window's width.
     icon = '─',
     -- Width of the generated line.
-    -- | <number> | a hard coded width value |
-    -- | full     | full width of the window |
     -- If a float < 1 is provided it is treated as a percentage of available window space.
+    -- Output is evaluated depending on the type.
+    -- | function | `value(context)`    |
+    -- | number   | `value`             |
+    -- | full     | width of the window |
     width = 'full',
     -- Amount of margin to add to the left of dash.
     -- If a float < 1 is provided it is treated as a percentage of available window space.
@@ -661,7 +672,11 @@ function M.dash.schema()
     return M.base.schema({
         icon = { type = 'string' },
         width = {
-            union = { { enum = { 'full' } }, { type = 'number' } },
+            union = {
+                { enum = { 'full' } },
+                { type = 'number' },
+                { type = 'function' },
+            },
         },
         left_margin = { type = 'number' },
         highlight = { type = 'string' },