feature: Use SignColumn background for signs allow them to be disabled by buftype

# Details

Request: #58

Not all color schemes use the Normal background color for the sign
column. This can lead to some not so great looking icons. Fix this
by combining the color we were going to set with the SignColumn
background. Add a new configuration section 'sign' where this is
defined and moifiable.

While we are adding a new section for signs add 2 other abilities.

- The ability to globally disable them from components that create them
- The ability to disable them within a set of buftypes, use a default
  value of 'nofile' so that signs do not appear in LSP documentation

Author: MeanderingProgrammer

README.md

@@ -327,6 +327,16 @@ require('render-markdown').setup({
         -- Applies to the inlined icon
         highlight = '@markup.link.label.markdown_inline',
     },
+    sign = {
+        -- Turn on / off sign rendering
+        enabled = true,
+        -- More granular mechanism, disable signs within specific buftypes
+        exclude = {
+            buftypes = { 'nofile' },
+        },
+        -- Applies to background of sign text
+        highlight = 'SignColumn',
+    },
     -- Window options to use that change between rendered and raw view
     win_options = {
         -- See :h 'conceallevel'

doc/render-markdown.txt

@@ -364,6 +364,16 @@ Full Default Configuration ~
             -- Applies to the inlined icon
             highlight = '@markup.link.label.markdown_inline',
         },
+        sign = {
+            -- Turn on / off sign rendering
+            enabled = true,
+            -- More granular mechanism, disable signs within specific buftypes
+            exclude = {
+                buftypes = { 'nofile' },
+            },
+            -- Applies to background of sign text
+            highlight = 'SignColumn',
+        },
         -- Window options to use that change between rendered and raw view
         win_options = {
             -- See :h 'conceallevel'

lua/render-markdown/colors.lua

@@ -0,0 +1,33 @@
+---@class render.md.ColorCache
+---@field highlights string[]
+
+---@type render.md.ColorCache
+local cache = {
+    highlights = {},
+}
+
+---@class render.md.Colors
+local M = {}
+
+---@param foreground string
+---@param background string
+---@return string
+M.combine = function(foreground, background)
+    local name = string.format('RenderMd_%s_%s', foreground, background)
+    if not vim.tbl_contains(cache.highlights, name) then
+        local fg = M.get_hl(foreground).fg
+        local bg = M.get_hl(background).bg
+        vim.api.nvim_set_hl(0, name, { fg = fg, bg = bg })
+        table.insert(cache.highlights, name)
+    end
+    return name
+end
+
+---@private
+---@param name string
+---@return vim.api.keyset.hl_info
+M.get_hl = function(name)
+    return vim.api.nvim_get_hl(0, { name = name, link = false })
+end
+
+return M

lua/render-markdown/handler/latex.lua

@@ -2,10 +2,10 @@ local logger = require('render-markdown.logger')
 local state = require('render-markdown.state')
 local ts = require('render-markdown.ts')
 
----@class render.md.Cache
+---@class render.md.LatexCache
 ---@field expressions table<string, string[]>
 
----@type render.md.Cache
+---@type render.md.LatexCache
 local cache = {
     expressions = {},
 }

lua/render-markdown/handler/markdown.lua

@@ -1,3 +1,4 @@
+local colors = require('render-markdown.colors')
 local component = require('render-markdown.component')
 local icons = require('render-markdown.icons')
 local list = require('render-markdown.list')
@@ -53,12 +54,7 @@ M.render_node = function(namespace, buf, capture, node)
             hl_eol = true,
         })
 
-        vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, info.start_col, {
-            end_row = info.end_row,
-            end_col = info.end_col,
-            sign_text = list.cycle(heading.signs, level),
-            sign_hl_group = foreground,
-        })
+        M.render_sign(namespace, buf, info, list.cycle(heading.signs, level), foreground)
     elseif capture == 'dash' then
         local dash = state.config.dash
         if not dash.enabled then
@@ -95,12 +91,7 @@ M.render_node = function(namespace, buf, capture, node)
         if icon == nil or icon_highlight == nil then
             return
         end
-        vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, info.start_col, {
-            end_row = info.end_row,
-            end_col = info.end_col,
-            sign_text = icon,
-            sign_hl_group = icon_highlight,
-        })
+        M.render_sign(namespace, buf, info, icon, icon_highlight)
         -- Requires inline extmarks
         if not util.has_10 then
             return
@@ -221,6 +212,27 @@ M.render_node = function(namespace, buf, capture, node)
     end
 end
 
+---@param namespace integer
+---@param buf integer
+---@param info render.md.NodeInfo
+---@param text string
+---@param highlight string
+M.render_sign = function(namespace, buf, info, text, highlight)
+    local sign = state.config.sign
+    if not sign.enabled then
+        return
+    end
+    if vim.tbl_contains(sign.exclude.buftypes, util.get_buftype(buf)) then
+        return
+    end
+    vim.api.nvim_buf_set_extmark(buf, namespace, info.start_row, info.start_col, {
+        end_row = info.end_row,
+        end_col = info.end_col,
+        sign_text = text,
+        sign_hl_group = colors.combine(highlight, sign.highlight),
+    })
+end
+
 ---@param namespace integer
 ---@param buf integer
 ---@param info render.md.NodeInfo

lua/render-markdown/init.lua

@@ -11,6 +11,11 @@ local M = {}
 ---@field public default any
 ---@field public rendered any
 
+---@class render.md.UserSign
+---@field public enabled? boolean
+---@field public exclude? render.md.UserExclude
+---@field public highlight? string
+
 ---@class render.md.UserLink
 ---@field public enabled? boolean
 ---@field public image? string
@@ -92,6 +97,7 @@ local M = {}
 ---@field public pipe_table? render.md.UserPipeTable
 ---@field public callout? table<string, render.md.UserCustomComponent>
 ---@field public link? render.md.UserLink
+---@field public sign? render.md.UserSign
 ---@field public win_options? table<string, render.md.WindowOption>
 ---@field public custom_handlers? table<string, render.md.Handler>
 
@@ -323,6 +329,16 @@ M.default_config = {
         -- Applies to the inlined icon
         highlight = '@markup.link.label.markdown_inline',
     },
+    sign = {
+        -- Turn on / off sign rendering
+        enabled = true,
+        -- More granular mechanism, disable signs within specific buftypes
+        exclude = {
+            buftypes = { 'nofile' },
+        },
+        -- Applies to background of sign text
+        highlight = 'SignColumn',
+    },
     -- Window options to use that change between rendered and raw view
     win_options = {
         -- See :h 'conceallevel'

lua/render-markdown/manager.lua

@@ -20,8 +20,7 @@ function M.setup()
         group = group,
         pattern = state.config.file_types,
         callback = function(event)
-            local buftype = vim.api.nvim_get_option_value('buftype', { buf = event.buf })
-            if not vim.tbl_contains(state.config.exclude.buftypes, buftype) then
+            if not vim.tbl_contains(state.config.exclude.buftypes, util.get_buftype(event.buf)) then
                 M.attach(group, event.buf)
             end
         end,

lua/render-markdown/state.lua

@@ -81,6 +81,7 @@ function state.validate()
         quote = { config.quote, 'table' },
         callout = { config.callout, 'table' },
         link = { config.link, 'table' },
+        sign = { config.sign, 'table' },
         win_options = { config.win_options, 'table' },
         custom_handlers = { config.custom_handlers, 'table' },
     })
@@ -186,6 +187,17 @@ function state.validate()
         highlight = { link.highlight, 'string' },
     })
 
+    local sign = config.sign
+    append_errors('render-markdown.sign', sign, {
+        enabled = { sign.enabled, 'boolean' },
+        exclude = { sign.exclude, 'table' },
+        highlight = { sign.highlight, 'string' },
+    })
+    local sign_exclude = sign.exclude
+    append_errors('render-markdown.sign.exclude', sign_exclude, {
+        buftypes = string_array(sign_exclude.buftypes),
+    })
+
     for name, win_option in pairs(config.win_options) do
         append_errors('render-markdown.win_options.' .. name, win_option, {
             default = { win_option.default, { 'number', 'string' } },

lua/render-markdown/types.lua

@@ -1,3 +1,8 @@
+---@class render.md.Sign
+---@field public enabled boolean
+---@field public exclude render.md.Exclude
+---@field public highlight string
+
 ---@class render.md.Link
 ---@field public enabled boolean
 ---@field public image string
@@ -79,5 +84,6 @@
 ---@field public pipe_table render.md.PipeTable
 ---@field public callout table<string, render.md.CustomComponent>
 ---@field public link render.md.Link
+---@field public sign render.md.Sign
 ---@field public win_options table<string, render.md.WindowOption>
 ---@field public custom_handlers table<string, render.md.Handler>

lua/render-markdown/util.lua

@@ -34,6 +34,12 @@ M.set_win_option = function(win, name, value)
     logger.debug({ option = name, win = win, before = before, after = value })
 end
 
+---@param buf integer
+---@return any
+M.get_buftype = function(buf)
+    return vim.api.nvim_get_option_value('buftype', { buf = buf })
+end
+
 ---@param win integer
 ---@return integer
 M.get_leftcol = function(win)