add preserve cursor behavior

Author: joaopluigi

docs/configuration.md

@@ -149,6 +149,7 @@ require("eca").setup({
           expanded_label = "- view diff",  -- Label when the diff is expanded
           expanded = false,                -- When true, tool diffs start expanded
         },
+        preserve_cursor = true,            -- When true, cursor stays in place when expanding/collapsing
       },
 
       -- Reasoning ("Thinking") block behavior
@@ -260,6 +261,24 @@ require("eca").setup({
 })
 ```
 
+### Tool Call Behavior
+
+```lua
+-- Keep cursor in place when expanding/collapsing tool calls
+require("eca").setup({
+  windows = {
+    chat = {
+      tool_call = {
+        preserve_cursor = true,  -- Don't move cursor on expand/collapse
+        diff = {
+          expanded = true,       -- Start with diffs expanded
+        },
+      },
+    },
+  },
+})
+```
+
 ---
 
 ## Migration Guide

lua/eca/config.lua

@@ -90,6 +90,7 @@ M._defaults = {
           expanded_label = "- view diff",  -- Label when the diff is expanded
           expanded = false,                -- When true, tool diffs start expanded
         },
+        preserve_cursor = true,           -- When true, cursor position is preserved when expanding/collapsing
       },
       reasoning = {
         expanded = false,              -- When true, "Thinking" blocks start expanded

lua/eca/sidebar.lua

@@ -2517,6 +2517,13 @@ function M:_expand_tool_call(call)
     return
   end
 
+  -- Save cursor position before expansion (if configured)
+  local saved_cursor = nil
+  local preserve_cursor = Utils.should_preserve_cursor()
+  if preserve_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    saved_cursor = vim.api.nvim_win_get_cursor(chat.winid)
+  end
+
   -- Reasoning ("Thinking") entries behave slightly differently: we never
   -- wrap them in code fences and the streaming handler is responsible for
   -- keeping the body up to date. Here we just insert the current body once.
@@ -2552,7 +2559,15 @@ function M:_expand_tool_call(call)
     call.expanded = true
     self:_update_tool_call_header_line(call)
 
-    if chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    -- Restore cursor position or move to last line based on config
+    if saved_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+      -- Adjust cursor row if it was after the insertion point
+      if saved_cursor[1] > call.header_line then
+        saved_cursor[1] = saved_cursor[1] + count
+      end
+      vim.api.nvim_win_set_cursor(chat.winid, saved_cursor)
+    elseif not preserve_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+      -- Default behavior: move cursor to last line of expanded content
       local last_line = call.header_line + (call._last_arguments_count or 0)
       vim.api.nvim_win_set_cursor(chat.winid, { last_line, 0 })
       vim.api.nvim_win_call(chat.winid, function()
@@ -2588,8 +2603,15 @@ function M:_expand_tool_call(call)
   -- Update header arrow
   self:_update_tool_call_header_line(call)
 
-  -- Move cursor to show the full arguments block
-  if chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+  -- Restore cursor position or move to last line based on config
+  if saved_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    -- Adjust cursor row if it was after the insertion point
+    if saved_cursor[1] > call.header_line then
+      saved_cursor[1] = saved_cursor[1] + count
+    end
+    vim.api.nvim_win_set_cursor(chat.winid, saved_cursor)
+  elseif not preserve_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    -- Default behavior: move cursor to last line of expanded content
     local last_line = call.header_line + count
     vim.api.nvim_win_set_cursor(chat.winid, { last_line, 0 })
     vim.api.nvim_win_call(chat.winid, function()
@@ -2609,6 +2631,13 @@ function M:_collapse_tool_call(call)
     return
   end
 
+  -- Save cursor position before collapsing (if configured)
+  local saved_cursor = nil
+  local preserve_cursor = Utils.should_preserve_cursor()
+  if preserve_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    saved_cursor = vim.api.nvim_win_get_cursor(chat.winid)
+  end
+
   local count = call.arguments_lines and #call.arguments_lines or 0
   if count == 0 then
     call.expanded = false
@@ -2633,6 +2662,19 @@ function M:_collapse_tool_call(call)
 
   -- Update header arrow
   self:_update_tool_call_header_line(call)
+
+  -- Restore cursor position, adjusting if it was after the collapsed region
+  if saved_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    -- If cursor was inside the collapsed region, move it to the header
+    if saved_cursor[1] > call.header_line and saved_cursor[1] <= call.header_line + count then
+      saved_cursor[1] = call.header_line
+      saved_cursor[2] = 0
+    -- If cursor was after the collapsed region, adjust it up
+    elseif saved_cursor[1] > call.header_line + count then
+      saved_cursor[1] = saved_cursor[1] - count
+    end
+    vim.api.nvim_win_set_cursor(chat.winid, saved_cursor)
+  end
 end
 
 -- Expand a tool call's diff, inserting it below the diff label
@@ -2646,6 +2688,13 @@ function M:_expand_tool_call_diff(call)
     return
   end
 
+  -- Save cursor position before expansion (if configured)
+  local saved_cursor = nil
+  local preserve_cursor = Utils.should_preserve_cursor()
+  if preserve_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    saved_cursor = vim.api.nvim_win_get_cursor(chat.winid)
+  end
+
   call.diff_lines = call.diff_lines or self:_build_tool_call_diff_lines(call.details)
   local count = call.diff_lines and #call.diff_lines or 0
   if count == 0 then
@@ -2664,6 +2713,15 @@ function M:_expand_tool_call_diff(call)
 
   -- Update the diff label to show the collapse indicator
   self:_update_tool_call_diff_label_line(call)
+
+  -- Restore cursor position (no default cursor movement for diff expansion)
+  if saved_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    -- Adjust cursor row if it was after the insertion point
+    if saved_cursor[1] > call.label_line then
+      saved_cursor[1] = saved_cursor[1] + count
+    end
+    vim.api.nvim_win_set_cursor(chat.winid, saved_cursor)
+  end
 end
 
 -- Collapse a tool call's diff, removing it from the buffer
@@ -2677,6 +2735,13 @@ function M:_collapse_tool_call_diff(call)
     return
   end
 
+  -- Save cursor position before collapsing (if configured)
+  local saved_cursor = nil
+  local preserve_cursor = Utils.should_preserve_cursor()
+  if preserve_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    saved_cursor = vim.api.nvim_win_get_cursor(chat.winid)
+  end
+
   local count = call.diff_lines and #call.diff_lines or 0
   if count == 0 then
     call.diff_expanded = false
@@ -2696,6 +2761,19 @@ function M:_collapse_tool_call_diff(call)
 
   -- Update the diff label to show the expand indicator again
   self:_update_tool_call_diff_label_line(call)
+
+  -- Restore cursor position, adjusting if it was after the collapsed region
+  if saved_cursor and chat.winid and vim.api.nvim_win_is_valid(chat.winid) then
+    -- If cursor was inside the collapsed region, move it to the label
+    if saved_cursor[1] > call.label_line and saved_cursor[1] <= call.label_line + count then
+      saved_cursor[1] = call.label_line
+      saved_cursor[2] = 0
+    -- If cursor was after the collapsed region, adjust it up
+    elseif saved_cursor[1] > call.label_line + count then
+      saved_cursor[1] = saved_cursor[1] - count
+    end
+    vim.api.nvim_win_set_cursor(chat.winid, saved_cursor)
+  end
 end
 
 -- Toggle tool call details at the current cursor position in the chat window

lua/eca/utils.lua

@@ -189,6 +189,15 @@ function M.should_start_diff_expanded()
   return diff_cfg.expanded == true
 end
 
+---Check if cursor position should be preserved when expanding/collapsing tool calls
+---@return boolean
+function M.should_preserve_cursor()
+  local chat_cfg = M.get_chat_config()
+  local cfg = chat_cfg.tool_call or {}
+
+  return cfg.preserve_cursor == true
+end
+
 ---Get reasoning labels configuration
 ---@return table
 function M.get_reasoning_labels()