feat: update Dash rendering logic to support percentage width and alignment style (#272)

* feat: update Dash rendering logic to support percentage width and center alignment

* doc: Updated README.md with additional options for width and alignment in the render-markdown setup.

* fix: Fixed alignment issues in dash rendering.

* CR: Update Dash rendering options and keep consistent with headings & code blocks.

---------

Co-authored-by: Kurama <[email protected]>

Author: Kurama622

README.md

@@ -391,9 +391,13 @@ require('render-markdown').setup({
         -- The icon gets repeated across the window's width
         icon = '─',
         -- Width of the generated line:
-        --  <integer>: a hard coded width value
-        --  full:      full width of the window
+        --  full:     full width of the window
+        --  <number>: a hard coded width value
+        --            If a floating point value < 1 is provided it is treated as a percentage of the available window space
         width = 'full',
+        -- Amount of margin to add to the left of dash
+        -- If a floating point value < 1 is provided it is treated as a percentage of the available window space
+        left_margin = 0,
         -- Highlight for the whole line generated from the icon
         highlight = 'RenderMarkdownDash',
     },

lua/render-markdown/render/dash.lua

@@ -16,17 +16,24 @@ end
 
 function Render:render()
     local width = self.dash.width
-    width = type(width) == 'number' and width or vim.o.columns
-    local virt_text = { self.dash.icon:rep(width), self.dash.highlight }
+    width = type(width) == 'number' and self.context:resolve_offset(width, 0) or vim.o.columns
+    self.dash.left_margin = self.dash.left_margin or 0
+    local margin = self.context:resolve_offset(self.dash.left_margin, width)
+
+    local virt_text = {}
+    if margin > 0 then
+        table.insert(virt_text, self:padding_text(margin))
+    end
+    table.insert(virt_text, { self.dash.icon:rep(width), self.dash.highlight })
 
     local start_row, end_row = self.node.start_row, self.node.end_row - 1
     self.marks:add('dash', start_row, 0, {
-        virt_text = { virt_text },
+        virt_text = virt_text,
         virt_text_pos = 'overlay',
     })
     if end_row > start_row then
         self.marks:add('dash', end_row, 0, {
-            virt_text = { virt_text },
+            virt_text = virt_text,
             virt_text_pos = 'overlay',
         })
     end

lua/render-markdown/types.lua

@@ -120,7 +120,8 @@
 ---@class (exact) render.md.Dash
 ---@field public enabled boolean
 ---@field public icon string
----@field public width 'full'|integer
+---@field public width 'full'|number
+---@field public left_margin number
 ---@field public highlight string
 
 ---@class (exact) render.md.Code