Allow to use different chars to render the tab character

Signed-off-by: yuguorui <yuguorui@pku.edu.cn>

Author: yuguorui

docs/en/blank.md

@@ -7,8 +7,9 @@ blank have four configurable items
 1. enable
 2. notify
 3. chars
-4. style
-5. exclude_filetype
+4. tab_chars
+5. style
+6. exclude_filetype
 
 `enable` is used to control whether enable hl_blank, if set it to false, its usercmd and autocmd will not set, so it will not work
 
@@ -27,6 +28,8 @@ chars = {
 },
 ```
 
+`tab_chars` is used to configure what char to render the `<Tab>`, it is a table likes the `chars` table.
+
 `style` is a RGB string or RGB string list, if it is a table, it will choice different color to render different blank (indent)
 
 `exclude_filetype` is opposite of support_filetypes, it is a lua table like this, same as chunk mod

docs/zh_CN/blank.md

@@ -7,8 +7,9 @@ blank mod 有四个配置项
 1. enable
 2. notify
 3. chars
-4. style
-5. exclude_filetype
+4. tab_chars
+5. style
+6. exclude_filetype
 
 `enable` 是用来控制该 mod 是否启动的，如果设置为 false，其所携带的 usercmd 和 autocmd 均不会产生，此时该 mod 关闭
 
@@ -27,6 +28,8 @@ chars = {
 },
 ```
 
+`tab_chars` 是一个 lua 表，其中的字符用来指示如何渲染 `<Tab>` 字符，它和`chars`类似。
+
 `style` 是一个 RGB 字符串或者一个表，如果是表，他将会使用不同颜色来渲染 blank
 
 `exclude_filetype` 是 support_filetype 的反面，用来控制在哪些文件类型不渲染 blank，默认的 exclude_filetypes 可以在 [default config](../../lua/hlchunk/utils/filetype.lua) 中找到

lua/hlchunk/mods/blank.lua

@@ -21,6 +21,7 @@ local blank_mod = BaseMod:new({
         chars = {
             "․",
         },
+        tab_chars = {},
         style = {
             api.nvim_get_hl(0, { name = "Whitespace" }),
         },
@@ -38,8 +39,16 @@ function blank_mod:render_line(index, indent)
     local render_char_num = math.floor(indent / shiftwidth)
     local win_info = fn.winsaveview()
     local text = ""
-    for _ = 1, render_char_num do
-        text = text .. "." .. (" "):rep(shiftwidth - 1)
+
+    local space_tab = ("\t"):rep(vim.o.tabstop)
+    local line_val = fn.getline(index):gsub("\t", space_tab)
+    for i = 1, render_char_num do
+        local char = line_val:sub(shiftwidth * i - 1, shiftwidth * i - 1)
+        if char == "\t" then
+            text = text .. ("t") .. (" "):rep(shiftwidth - 1)
+        else
+            text = text .. "." .. (" "):rep(shiftwidth - 1)
+        end
     end
     text = text:sub(win_info.leftcol + 1)
 
@@ -50,7 +59,14 @@ function blank_mod:render_line(index, indent)
             count = count + 1
             local Blank_chars_num = Array:from(self.options.chars):size()
             local Blank_style_num = Array:from(self.options.style):size()
-            local char = self.options.chars[(count - 1) % Blank_chars_num + 1]:rep(shiftwidth)
+
+            local char
+            if self.options.tab_chars and c:match("t") then
+                char = self.options.tab_chars[(count - 1) % Blank_chars_num + 1]:rep(shiftwidth)
+            else
+                char = self.options.chars[(count - 1) % Blank_chars_num + 1]:rep(shiftwidth)
+            end
+
             local style = "HLBlank" .. tostring((count - 1) % Blank_style_num + 1)
             row_opts.virt_text = { { char, style } }
             row_opts.virt_text_win_col = i - 1