Hl Usages: don't calculate definitions again if on the same node (#22)

Closes #21

Author: stsewd

Diff for: README.md

@@ -25,7 +25,11 @@ Highlights definition and usages of the current symbol under the cursor.
 lua <<EOF
 require'nvim-treesitter.configs'.setup {
   refactor = {
-    highlight_definitions = { enable = true },
+    highlight_definitions = {
+      enable = true,
+      -- Set to false if you have an `updatetime` of ~100.
+      clear_on_cursor_move = true,
+    },
   },
 }
 EOF

Diff for: doc/nvim-treesitter-refactor.txt

@@ -26,12 +26,19 @@ Query files: `locals.scm`.
 Supported options:
 - enable: `true` or `false`.
 - disable: list of languages.
+- clear_on_cursor_move: `true` or `false` if highlights should be cleared
+  when the cursor is moved. If your 'updatetime' is around `100`
+  you can set this to false to have a less laggy experience.
 
 >
   lua <<EOF
   require'nvim-treesitter.configs'.setup {
     refactor = {
-      highlight_definitions = { enable = true },
+      highlight_definitions = {
+        enable = true,
+        -- Set to false if you have an `updatetime` of ~100.
+        clear_on_cursor_move = true,
+      },
     },
   }
   EOF

Diff for: lua/nvim-treesitter-refactor.lua

@@ -10,6 +10,7 @@ function M.init()
         enable = false,
         disable = {},
         is_supported = queries.has_locals,
+        clear_on_cursor_move = true,
       },
       highlight_current_scope = {
         module_path = "nvim-treesitter-refactor.highlight_current_scope",

Diff for: lua/nvim-treesitter-refactor/highlight_definitions.lua

@@ -1,6 +1,7 @@
 -- This module highlights reference usages and the corresponding
 -- definition on cursor hold.
 
+local configs = require "nvim-treesitter.configs"
 local ts_utils = require "nvim-treesitter.ts_utils"
 local locals = require "nvim-treesitter.locals"
 local api = vim.api
@@ -9,14 +10,19 @@ local cmd = api.nvim_command
 local M = {}
 
 local usage_namespace = api.nvim_create_namespace "nvim-treesitter-usages"
+local last_nodes = {}
 
 function M.highlight_usages(bufnr)
-  M.clear_usage_highlights(bufnr)
-
   local node_at_point = ts_utils.get_node_at_cursor()
-  local references = locals.get_references(bufnr)
+  -- Don't calculate usages again if we are on the same node.
+  if node_at_point and node_at_point == last_nodes[bufnr] and M.has_highlights(bufnr) then
+    return
+  else
+    last_nodes[bufnr] = node_at_point
+  end
 
-  if not node_at_point or not vim.tbl_contains(references, node_at_point) then
+  M.clear_usage_highlights(bufnr)
+  if not node_at_point then
     return
   end
 
@@ -34,11 +40,16 @@ function M.highlight_usages(bufnr)
   end
 end
 
+function M.has_highlights(bufnr)
+  return #api.nvim_buf_get_extmarks(bufnr, usage_namespace, 0, -1, {}) > 0
+end
+
 function M.clear_usage_highlights(bufnr)
   api.nvim_buf_clear_namespace(bufnr, usage_namespace, 0, -1)
 end
 
 function M.attach(bufnr)
+  local config = configs.get_module "refactor.highlight_definitions"
   cmd(string.format("augroup NvimTreesitterUsages_%d", bufnr))
   cmd "au!"
   -- luacheck: push ignore 631
@@ -49,13 +60,15 @@ function M.attach(bufnr)
       bufnr
     )
   )
-  cmd(
-    string.format(
-      [[autocmd CursorMoved <buffer=%d> lua require'nvim-treesitter-refactor.highlight_definitions'.clear_usage_highlights(%d)]],
-      bufnr,
-      bufnr
+  if config.clear_on_cursor_move then
+    cmd(
+      string.format(
+        [[autocmd CursorMoved <buffer=%d> lua require'nvim-treesitter-refactor.highlight_definitions'.clear_usage_highlights(%d)]],
+        bufnr,
+        bufnr
+      )
     )
-  )
+  end
   cmd(
     string.format(
       [[autocmd InsertEnter <buffer=%d> lua require'nvim-treesitter-refactor.highlight_definitions'.clear_usage_highlights(%d)]],
@@ -72,6 +85,7 @@ function M.detach(bufnr)
   cmd(string.format("autocmd! NvimTreesitterUsages_%d CursorHold", bufnr))
   cmd(string.format("autocmd! NvimTreesitterUsages_%d CursorMoved", bufnr))
   cmd(string.format("autocmd! NvimTreesitterUsages_%d InsertEnter", bufnr))
+  last_nodes[bufnr] = nil
 end
 
 return M