feat(dap.hover): update buffer incrementally on expand/collapse

lua/ow/dap/hover.lua

@@ -1,4 +1,5 @@
 -- DAP hover implementation with tree-based display
+local Content = require("ow.dap.hover.content")
 local Item = require("ow.dap.item")
 local Tree = require("ow.dap.hover.tree")
 local log = require("ow.log")
@@ -45,6 +46,7 @@ function Window.show(lines, content)
     local orig_buf = vim.api.nvim_get_current_buf()
     local buf = vim.api.nvim_create_buf(false, true)
     vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+    vim.api.nvim_set_option_value("modifiable", false, { buf = buf })
 
     -- Create window (initially hidden for size calculation)
     local win = vim.api.nvim_open_win(buf, false, {
@@ -66,7 +68,7 @@ function Window.show(lines, content)
     })
 
     -- Apply syntax highlighting
-    content:apply_highlights(Window.ns_id, buf)
+    content:apply_highlights(Window.ns_id, buf, 0)
 
     -- Store window reference
     Window.current_win = win
@@ -94,6 +96,17 @@ function Window.show(lines, content)
     end, { buffer = buf, nowait = true })
 end
 
+---@param buf integer
+---@param callback fun()
+function Window.update_buffer(buf, callback)
+    local prev_scrolloff = vim.wo[Window.current_win].scrolloff
+    vim.wo[Window.current_win].scrolloff = 0
+    vim.bo[buf].modifiable = true
+    callback()
+    vim.bo[buf].modifiable = false
+    vim.wo[Window.current_win].scrolloff = prev_scrolloff
+end
+
 ---Expand/collapse item at cursor position
 ---@param buf integer
 function Window.expand_at_cursor(buf)
@@ -105,36 +118,40 @@ function Window.expand_at_cursor(buf)
     coroutine.wrap(function()
         local ok, err = xpcall(function()
             -- Toggle expansion
-            local cursor = vim.api.nvim_win_get_cursor(Window.current_win)
+            local lnum = vim.api.nvim_win_get_cursor(Window.current_win)[1]
-            local success = Window.tree:toggle_at_line(cursor[1])
+            local node = Window.tree:get_node_at_line(lnum)
+            if not node or not node:is_container() then
+                return
+            end
+
+            local prev_node_count = Window.tree:count_subtree_nodes(node)
+
+            local success = Window.tree:toggle_node(node)
             if not success then
                 return
             end
 
-            local content = Window.tree:render()
+            local content = Content.new()
+            Window.tree:render_subtree(node, content)
             local lines = content:get_lines()
 
-            -- TODO: possible to only update the affected lines?
+            Window.update_buffer(buf, function()
-            -- Update buffer content
+                vim.api.nvim_buf_set_lines(
-            vim.api.nvim_set_option_value(
+                    buf,
-                "scrolloff",
+                    lnum - 1,
-                0,
+                    lnum - 1 + prev_node_count,
-                { win = Window.current_win }
+                    true,
-            )
+                    lines
-            vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
-            vim.api.nvim_set_option_value(
-                "scrolloff",
-                vim.o.scrolloff,
-                { win = Window.current_win }
                 )
+            end)
 
-            -- Re-apply highlights
+            -- Apply highlights
-            vim.api.nvim_buf_clear_namespace(buf, -1, 0, -1) -- Clear old highlights
+            content:apply_highlights(Window.ns_id, buf, lnum - 1)
-            content:apply_highlights(Window.ns_id, buf)
 
             -- Adjust window size
+            local all_lines = vim.api.nvim_buf_get_lines(buf, 0, -1, true)
             vim.api.nvim_win_set_config(Window.current_win, {
-                width = Window.compute_width(lines),
+                width = Window.compute_width(all_lines),
             })
             local text_height =
                 vim.api.nvim_win_text_height(Window.current_win, {}).all
@@ -152,7 +169,7 @@ function Window.expand_at_cursor(buf)
     end)()
 end
 
----Main hover entry point (async)
+---Main hover entry point
 ---@async
 ---@param expr string Expression to evaluate
 ---@param session dap.Session DAP session
@@ -207,6 +224,7 @@ local function hover_eval(
 end
 
 ---Public hover function
+---@async
 local function hover_async()
     -- Check if hover window is already open - focus it instead
     if Window.current_win and vim.api.nvim_win_is_valid(Window.current_win) then

lua/ow/dap/hover/content.lua

@@ -125,14 +125,15 @@ end
 ---Apply highlights to a buffer
 ---@param ns_id integer
 ---@param buf integer Buffer handle
-function Content:apply_highlights(ns_id, buf)
+---@param row_offset integer
+function Content:apply_highlights(ns_id, buf, row_offset)
     for _, highlight in ipairs(self.highlights) do
         vim.hl.range(
             buf,
             ns_id,
             highlight.group,
-            { highlight.start_row, highlight.start_col },
+            { row_offset + highlight.start_row, highlight.start_col },
-            { highlight.end_row, highlight.end_col }
+            { row_offset + highlight.end_row, highlight.end_col }
         )
     end
 end

lua/ow/dap/hover/tree.lua

@@ -4,9 +4,7 @@ local Node = require("ow.dap.hover.node")
 
 ---@class ow.dap.hover.Tree
 ---@field session dap.Session
----@field root_node ow.dap.hover.Node?
+---@field root ow.dap.hover.Node?
----@field line_to_node table<integer, ow.dap.hover.Node> Map line numbers to nodes
----@field extmark_to_node table<integer, ow.dap.hover.Node> Map extmark IDs to nodes
 local Tree = {}
 Tree.__index = Tree
 
@@ -22,20 +20,19 @@ function Tree.new(session)
     }, Tree)
 end
 
----Build the tree from a DAP item (async)
+---Build the tree from a DAP item
 ---@async
 ---@param item ow.dap.Item Root item to build tree from
----@return ow.dap.hover.Node
 function Tree:build(item)
-    local root = Node.new(item, nil)
+    self.root = Node.new(item, nil)
-    self.root_node = root
 
-    -- For now, start with everything collapsed
+    if self.root:is_container() then
-    -- Later we can add logic to expand first level by default
+        self:load_children(self.root)
-    return root
+        self.root.is_expanded = true
+    end
 end
 
----Load children for a node (async)
+---Load children for a node
 ---@async
 ---@param node ow.dap.hover.Node
 ---@return boolean success Whether loading succeeded
@@ -80,14 +77,13 @@ end
 ---@async
 ---@return ow.dap.hover.Content
 function Tree:render()
-    if not self.root_node then
+    if not self.root then
         return Content.new()
     end
 
     local content = Content.new()
-    self.line_to_node = {}
 
-    self:render_subtree(self.root_node, content)
+    self:render_subtree(self.root, content)
     return content
 end
 
@@ -96,9 +92,6 @@ end
 ---@param node ow.dap.hover.Node
 ---@param content ow.dap.hover.Content
 function Tree:render_subtree(node, content)
-    -- Store line mapping
-    self.line_to_node[content:current_line()] = node
-
     -- Format this node
     node:format_into(self.session, content)
 
@@ -111,18 +104,53 @@ function Tree:render_subtree(node, content)
     end
 end
 
----Toggle expansion state of node at given line
+---@param node ow.dap.hover.Node
----@async
+---@return integer
----@param line_number integer
+function Tree:count_subtree_nodes(node)
----@return boolean success Whether toggle succeeded
+    local count = 1
-function Tree:toggle_at_line(line_number)
+
-    local node = self.line_to_node[line_number]
+    if node.is_expanded then
-    if not node or not node:is_container() then
+        for _, child in ipairs(node.children) do
-        return false
+            count = count + self:count_subtree_nodes(child)
+        end
     end
 
+    return count
+end
+
+---@param target_line integer
+---@return ow.dap.hover.Node?
+function Tree:get_node_at_line(target_line)
+    local current_line = 0
+
+    ---@param node ow.dap.hover.Node
+    local function search(node)
+        current_line = current_line + 1
+        if current_line == target_line then
+            return node
+        end
+
+        if node.is_expanded and node.children then
+            for _, child in ipairs(node.children) do
+                local found = search(child)
+                if found then
+                    return found
+                end
+            end
+        end
+    end
+
+    if self.root then
+        return search(self.root)
+    end
+end
+
+---Toggle expansion state of node at given line
+---@async
+---@param node ow.dap.hover.Node
+---@return boolean success Whether toggle succeeded
+function Tree:toggle_node(node)
     if not node.is_expanded then
-        -- Expanding: load children if needed
         local success = self:load_children(node)
         if not success then
             return false