Fast current_indent (resolves #649)

doc/indent_blankline.txt

@@ -201,6 +201,9 @@ config                                                            *ibl.config*
    • {scope}            (|ibl.config.scope|)
                         Configures the scope
 
+   • {current_indent}   (|ibl.config.current_indent|)
+                        Configures the current_indent
+
    • {exclude}          (|ibl.config.exclude|)
                         Configures what is excluded from indent-blankline
 
@@ -211,6 +214,7 @@ config                                                            *ibl.config*
        indent = { char = "|" },
        whitespace = { highlight = { "Whitespace", "NonText" } },
        scope = { exclude = { language = { "lua" } } },
+       current_indent = { enabled = true },
    }
 <
 
@@ -541,6 +545,92 @@ config.scope.exclude                                *ibl.config.scope.exclude*
    }
 <
 
+config.current_indent                                *ibl.config.current_indent*
+
+ Configures the current indent
+
+ The current indent *is* the current indentation level (unlike scope).
+
+ Example: ~
+
+ In Python, using the same example as above, current_indent will highlight the
+ current inner most indentation guide. With scope disabled, this will look like
+ this:
+ >python
+ def foo();
+     if True:
+     ┋   a = "foo █ar"
+     ┋   #        ↳ cursor here
+     print(a)
+<
+ If we have the same code with scope enabled, it will look like this:
+ >python
+ def foo();
+ ┋   if True:
+ ┋   ┋   a = "foo █ar"
+ ┋   ┋   #        ↳ cursor here
+ ┋   print(a)
+<
+ If you have both scope and current_indent enabled and the two overlap, the
+ scope will take priority by default. So the Rust example from above will look
+ identical since the scope matches the current indent level. To make
+ current_indent take priority, make sure that its priority is set to a higher
+ value than scope's priority.
+ (this code would not compile)
+ >rust
+ fn foo() {
+     if true {
+     ┋    let a = "foo █ar";
+     ┋   //           ↳ cursor here
+     }
+     print(a);
+ }
+<
+ Fields: ~
+                                           *ibl.config.current_indent.enabled*
+   • {enabled}             (boolean)
+                           Enables or disables current_indent
+
+                           Default: `false` ~
+
+                                              *ibl.config.current_indent.char*
+   • {char}                (string)
+                           Character that gets used to display the current
+                           indents indentation guide
+                           Each character has to have a display width
+                           of 0 or 1
+
+                           Default: |ibl.config.indent.char| ~
+
+
+                                        *ibl.config.current_indent.highlight*
+   • {highlight}           (string)
+                           Highlight group that gets applied to the current
+                           indent
+
+                           Default: |hl-IblCurrentIndent| ~
+
+                                        *ibl.config.current_indent.show_start*
+   • {show_start}          (boolean)
+                           Shows an underline on the line above the current
+                           indent level
+
+                           Default: `true` ~
+
+                                         *ibl.config.current_indent.show_end*
+   • {show_end}            (boolean)
+                           Shows an underline on the line below the current
+                           indent level
+
+                           Default: `true` ~
+
+                                         *ibl.config.current_indent.priority*
+   • {priority}            (number)
+                           Virtual text priority for the current_indent
+
+                           Default: `64` ~
+
+
 config.exclude                                            *ibl.config.exclude*
 
  Configures what is excluded from indent-blankline

lua/ibl/config.lua

@@ -62,6 +62,14 @@ M.default_config = {
             },
         },
     },
+    current_indent = {
+        enabled = false,
+        char = nil,
+        highlight = "IblCurrentIndent",
+        show_start = false,
+        show_end = false,
+        priority = 64,
+    },
     exclude = {
         filetypes = {
             "lspinfo",
@@ -116,6 +124,7 @@ local validate_config = function(config)
         indent = { config.indent, "table", true },
         whitespace = { config.whitespace, "table", true },
         scope = { config.scope, "table", true },
+        current_indent = { config.current_indent, "table", true },
         exclude = { config.exclude, "table", true },
     }, config, "ibl.config")
 
@@ -229,6 +238,26 @@ local validate_config = function(config)
         end
     end
 
+    if config.current_indent then
+        utils.validate({
+            enabled = { config.current_indent.enabled, "boolean", true },
+            char = { config.current_indent.char, "string", true },
+            highlight = { config.current_indent.highlight, "string", true },
+            show_start = { config.current_indent.show_start, "boolean", true },
+            show_end = { config.current_indent.show_end, "boolean", true },
+            priority = { config.current_indent.priority, "number", true },
+        }, config.current_indent, "ibl.config.current_indent")
+        if config.current_indent.char then
+            vim.validate {
+                char = {
+                    config.current_indent.char,
+                    validate_char,
+                    "current_indent.char to have a display width of 0 or 1",
+                },
+            }
+        end
+    end
+
     if config.exclude then
         if config.exclude then
             utils.validate({

lua/ibl/config.types.lua

@@ -15,6 +15,8 @@
 ---@field whitespace ibl.config.whitespace?
 --- Configures the scope
 ---@field scope ibl.config.scope?
+--- Configures the current_indent
+---@field current_indent ibl.config.current_indent?
 --- Configures what is excluded from indent-blankline
 ---@field exclude ibl.config.exclude?
 
@@ -109,6 +111,22 @@
 --- </code>
 ---@field node_type table<string, string[]>?
 
+---@class ibl.config.current_indent
+--- Enables or disables current_indent
+---@field enabled boolean?
+--- Character that gets used to display the current_indent indentation guide
+---
+--- The character has to have a display width of 0 or 1
+---@field char string?
+--- Highlight group that get applied to the current_indent
+---@field highlight string?
+--- Shows an underline on the first line of the current_indent
+---@field show_start boolean?
+--- Shows an underline on the last line of the current_indent
+---@field show_end boolean?
+--- Virtual text priority for the current_indent
+---@field priority number?
+
 ---@class ibl.config.exclude
 --- List of `filetypes` for which indent-blankline is disabled
 ---@field filetypes string[]?
@@ -130,7 +148,9 @@
 --- Configures the whitespace
 ---@field whitespace ibl.config.full.whitespace: ibl.config.whitespace
 --- Configures the scope
----@field scope ibl.config.full.scope: ig.config.scope
+---@field scope ibl.config.full.scope: ibl.config.scope
+--- Configures the current_indent
+---@field current_indent ibl.config.full.current_indent: ibl.config.current_indent
 --- Configures what is excluded from indent-blankline
 ---@field exclude ibl.config.full.exclude: ibl.config.exclude
 
@@ -225,6 +245,22 @@
 --- </code>
 ---@field node_type table<string, string[]>
 
+---@class ibl.config.full.current_indent: ibl.config.current_indent
+--- Enables or disables current_indent
+---@field enabled boolean
+--- Character that gets used to display the current_indent indentation guide
+---
+--- The character has to have a display width of 0 or 1
+---@field char string?
+--- Highlight group that get applied to the current_indent
+---@field highlight string
+--- Shows an underline on the first line of the current_indent
+---@field show_start boolean
+--- Shows an underline on the last line of the current_indent
+---@field show_end boolean
+--- Virtual text priority for the current_indent
+---@field priority number
+
 ---@class ibl.config.full.exclude: ibl.config.exclude
 --- List of `filetypes` for which indent-blankline is disabled
 ---@field filetypes string[]

lua/ibl/highlights.lua

@@ -12,6 +12,8 @@ local M = {
     whitespace = {},
     ---@type ibl.highlight[]
     scope = {},
+    ---@type ibl.highlight[]
+    current_indent = {},
 }
 
 ---@param name string
@@ -33,9 +35,11 @@ end
 local setup_builtin_hl_groups = function()
     local whitespace_hl = get "Whitespace"
     local line_nr_hl = get "LineNr"
+    local cursor_line_nr_hl = get "CursorLineNr"
     local ibl_indent_hl_name = "IblIndent"
     local ibl_whitespace_hl_name = "IblWhitespace"
     local ibl_scope_hl_name = "IblScope"
+    local ibl_current_indent_hl_name = "IblCurrentIndent"
 
     if not_set(get(ibl_indent_hl_name)) then
         vim.api.nvim_set_hl(0, ibl_indent_hl_name, whitespace_hl)
@@ -46,6 +50,9 @@ local setup_builtin_hl_groups = function()
     if not_set(get(ibl_scope_hl_name)) then
         vim.api.nvim_set_hl(0, ibl_scope_hl_name, line_nr_hl)
     end
+    if not_set(get(ibl_current_indent_hl_name)) then
+        vim.api.nvim_set_hl(0, ibl_current_indent_hl_name, cursor_line_nr_hl)
+    end
 end
 
 M.setup = function()
@@ -107,6 +114,20 @@ M.setup = function()
         vim.api.nvim_set_hl(0, M.scope[i].char, char_hl)
         vim.api.nvim_set_hl(0, M.scope[i].underline, { sp = char_hl.fg, underline = true })
     end
+
+    local current_indent_highlights = config.current_indent.highlight
+    M.current_indent = {}
+    local char_hl = get(current_indent_highlights)
+    if not_set(char_hl) then
+        error(string.format("No highlight group '%s' found", current_indent_highlights))
+    end
+    char_hl.nocombine = true
+    M.current_indent = {
+        char = "@ibl.current_indent.char",
+        underline = "@ibl.current_indent.underline",
+    }
+    vim.api.nvim_set_hl(0, M.current_indent.char, char_hl)
+    vim.api.nvim_set_hl(0, M.current_indent.underline, { sp = char_hl.fg, underline = true })
 end
 
 return M

lua/ibl/indent.lua

@@ -45,6 +45,7 @@ M.get = function(whitespace, opts, indent_state)
     if shiftwidth == 0 then
         shiftwidth = tabstop
     end
+
     local whitespace_tbl = {}
 
     for ch in whitespace:gmatch "." do