wip: kind of working

Author: sudo-tee

docs/virtualized-renderer-plan.md

@@ -0,0 +1,167 @@
+Virtualized Renderer Migration Plan
+=================================
+
+Goal
+----
+
+- Move from event-driven buffer mutations to a component-style renderer that produces reusable "RenderBlock" objects (message/part/overlay), then apply a visible slice to the output buffer via a backend.
+- Keep `state.messages` as the single source of truth.
+- Add virtualization by message first, then optionally by viewport.
+
+High-level Direction
+--------------------
+
+- Keep data model (`state.messages`) and formatter functions.
+- Build components that render messages/parts into independent payloads (`Output` / `RenderBlock`).
+- Add a cache for rendered blocks keyed by message/part identity and content fingerprint.
+- Select a visible slice of blocks (message-based virtualization) and apply them to the buffer with a backend applier that can later be upgraded to a patcher.
+
+Component Model (concept)
+-------------------------
+
+- RenderBlock example:
+
+```
+{
+  key = "message:msg_123",
+  kind = "message",
+  message_id = "msg_123",
+  line_count = 12,
+  output = Output.new(), -- lines/extmarks/actions
+}
+```
+
+Phase-by-phase Plan
+-------------------
+
+Phase 1 — Pure Render Functions
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Files to change / add:
+  - `lua/opencode/ui/formatter.lua`
+    - Split/ensure functions are pure and return `Output` objects.
+    - Provide `render_message_header(message) -> Output` and `render_part(part, message, ctx) -> Output`.
+  - `lua/opencode/ui/output.lua` — keep as transport object for lines/extmarks/actions.
+  - Add `lua/opencode/ui/renderer/components/message.lua` (new)
+    - `render(message, opts) -> RenderBlock` combines header + parts into a block.
+  - Add `lua/opencode/ui/renderer/components/part.lua` (new)
+    - Thin wrapper around part formatting and cache keys.
+  - Add `lua/opencode/ui/renderer/components/overlays.lua` (new)
+    - Renders revert/question/permission/hidden-history blocks.
+
+Phase 2 — Block Cache and Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Files to change / add:
+  - `lua/opencode/ui/render_state.lua`
+    - Extend to track blocks: `set_block`, `get_block`, `set_message_block`, etc.
+    - Preserve existing line-based APIs during migration.
+  - Add `lua/opencode/ui/renderer/cache.lua` (new)
+    - Cache rendered blocks by `message.id` and `part.id`.
+    - Provide `get_message_block(message)`, `set_message_block(message, block)`, `invalidate_message(message_id)`, `invalidate_part(part_id)`.
+
+Phase 3 — Session View + Virtualization Selector
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Files to add:
+  - `lua/opencode/ui/renderer/session_view.lua` (new)
+    - Build ordered list of blocks from `state.messages` and inject synthetic blocks (hidden notice, revert banner).
+    - API: `build_blocks(messages, opts) -> RenderBlock[]`.
+  - `lua/opencode/ui/renderer/virtualize.lua` (new)
+    - Select visible blocks given budgets: `select_visible_blocks(blocks, { max_lines, max_messages }) -> VisibleRender`.
+
+- Adjust `lua/opencode/ui/renderer.lua` (coordinator):
+  - Full-session render: fetch -> build_blocks -> select_visible_blocks -> backend.apply
+  - Keep event-by-event path until migration stabilizes.
+
+Phase 4 — Backend & Buffer Application
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Files to change / add:
+  - `lua/opencode/ui/renderer/buffer.lua`
+    - Convert to backend applier that flattens visible blocks into a single `Output` and applies it.
+  - Add `lua/opencode/ui/renderer/backend.lua` (new)
+    - Start with `apply_full(visible_render)` (full replace) and later add `apply_patch(prev_visible, next_visible)`.
+  - `lua/opencode/ui/output_window.lua` unchanged role but add helpers for chunk/range updates.
+
+Phase 5 — Event Handling & Scheduler
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Files to change / add:
+  - `lua/opencode/ui/renderer/events.lua`
+    - Stop direct buffer edits; instead mutate message state, mark blocks dirty, and schedule a render pass.
+  - Add `lua/opencode/ui/renderer/scheduler.lua` (new)
+    - Batch event bursts and choose incremental vs full visible recompose.
+  - `lua/opencode/ui/renderer/ctx.lua` becomes render-pass transient state (prev visible keys, guards).
+
+Phase 6 — Viewport Virtualization & Measurement
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Files to add:
+  - `lua/opencode/ui/renderer/measure.lua` (new)
+    - Track message/block heights (measured or estimated).
+  - `lua/opencode/ui/renderer/viewport.lua` (new)
+    - Compute which blocks to mount around scroll position. API: `get_visible_range(blocks, scroll_top, win_height, overscan)`.
+  - Extend `virtualize.lua` to use viewport computations.
+
+File-by-File Summary
+--------------------
+
+- Modify:
+  - `lua/opencode/ui/formatter.lua` — make pure builders for message/part
+  - `lua/opencode/ui/render_state.lua` — add block metadata API
+  - `lua/opencode/ui/renderer.lua` — coordinator, route full/session rendering through session_view/virtualize/backend
+  - `lua/opencode/ui/renderer/buffer.lua` — convert to applier/patch utilities
+  - `lua/opencode/ui/renderer/events.lua` — mutate state + invalidate + schedule
+  - `lua/opencode/ui/renderer/ctx.lua` — render-pass context only
+
+- Add:
+  - `lua/opencode/ui/renderer/components/message.lua`
+  - `lua/opencode/ui/renderer/components/part.lua`
+  - `lua/opencode/ui/renderer/components/overlays.lua`
+  - `lua/opencode/ui/renderer/cache.lua`
+  - `lua/opencode/ui/renderer/session_view.lua`
+  - `lua/opencode/ui/renderer/virtualize.lua`
+  - `lua/opencode/ui/renderer/backend.lua`
+  - `lua/opencode/ui/renderer/scheduler.lua`
+  - `lua/opencode/ui/renderer/measure.lua` (later)
+  - `lua/opencode/ui/renderer/viewport.lua` (later)
+
+Recommended Migration Order
+--------------------------
+
+1. Add `RenderBlock` components and cache helpers; don't change existing behavior.
+2. Route full-session rendering through `session_view` but keep old event handlers for incremental updates (feature flag by path).
+3. Implement message-level virtualization (tail-only) and replace the previous trimming code with the new selector.
+4. Replace event handlers to mark blocks dirty + scheduled render passes.
+5. Add backend patcher (diff by block key) and minimize buffer updates.
+6. Add measurement/viewport virtualization and support arbitrary scroll position (harder step).
+
+Testing Plan
+------------
+
+- Unit tests to add:
+  - `tests/unit/renderer/cache_spec.lua` — cache hit/miss/invalidate
+  - `tests/unit/renderer/virtualize_spec.lua` — visible block selection
+  - `tests/unit/renderer/session_view_spec.lua` — block building + synthetic overlays
+  - Extend `tests/unit/render_state_spec.lua` to cover block indexing/invalidation
+
+- Keep existing `tests/replay/renderer_spec.lua` fixtures and run them during migration to ensure parity. Migrate tests gradually from the old full-session path to the new pipeline.
+
+Practical First Implementation Tasks (low-risk)
+-----------------------------------------------
+
+1. Implement `components/message.lua` and `components/part.lua` that call `formatter` and return `RenderBlock`.
+2. Implement `renderer/cache.lua` and add simple cache APIs.
+3. Implement `renderer/session_view.lua` that composes blocks from `state.messages` and returns ordered blocks including hidden-history/revert overlays.
+4. Modify `renderer._render_full_session_data` to call `session_view.build_blocks` and then `virtualize.select_visible_blocks` (initially a simple `select tail N messages` using `max_rendered_lines`), and pass to `buffer.apply_full`.
+
+Notes / Tips
+-----------
+
+- Virtualize by message first — it keeps block math manageable and preserves test fixtures.
+- Keep extmarks/actions separate from text lines in patch calculations.
+- Avoid doing heavy Levenshtein diffs over the whole buffer until you have a stable block-level pipeline; ultimately you can diff blocks or block text to further reduce updates.
+- Add a small interactive "load older" action on the hidden-history notice to re-mount older messages on demand.
+
+If you want, I can scaffold the new file stubs and implement the first 3 small files (`components/message.lua`, `components/part.lua`, `renderer/cache.lua`) to get started.

lua/opencode/config.lua

@@ -150,6 +150,10 @@ M.defaults = {
         show_reasoning_output = true,
       },
       always_scroll_to_bottom = false,
+      viewport = {
+        enabled = true,
+        overscan = 8,
+      },
     },
     questions = {
       use_vim_ui_select = false, -- If true, render questions with vim.ui.select instead of in the output buffer

lua/opencode/ui/dialog.lua

@@ -260,11 +260,11 @@ function Dialog:format_dialog(output, config)
 
   local end_line = output:get_line_count()
 
+  output:add_line('')
+
   if config.border_hl then
     formatter.add_vertical_border(output, start_line + 1, end_line, config.border_hl, -2)
   end
-
-  output:add_line('')
 end
 
 ---Format options list with selection indicator

lua/opencode/ui/formatter.lua

@@ -243,11 +243,7 @@ function M.render_message_header(message, render_ctx)
     if mode and mode ~= '' then
       display_name = mode:upper()
     else
-      -- For the most recent assistant message, show current_mode if mode is missing
-      -- This handles new messages that haven't been stamped yet
-      local messages = render_ctx.messages or {}
-      local is_last_message = #messages == 0 or message.info.id == messages[#messages].info.id
-      if is_last_message and render_ctx.current_mode and render_ctx.current_mode ~= '' then
+      if render_ctx.current_mode and render_ctx.current_mode ~= '' then
         display_name = render_ctx.current_mode:upper()
       else
         display_name = 'ASSISTANT'
@@ -338,17 +334,12 @@ function M._format_user_prompt(output, text, message)
 
   local end_line = output:get_line_count()
 
-  local end_line_extmark_offset = 0
-
   local mentions = {}
   if message and message.parts then
     -- message.parts will only be filled out on a re-render
     -- we need to collect the mentions here
     for _, part in ipairs(message.parts) do
       if part.type == 'file' then
-        -- we're rerendering this part and we have files, the space after the user prompt
-        -- also needs an extmark
-        end_line_extmark_offset = 1
         if part.source and part.source.text then
           table.insert(mentions, part.source.text)
         end
@@ -364,7 +355,7 @@ function M._format_user_prompt(output, text, message)
     mention.highlight_mentions_in_output(output, text, mentions, start_line)
   end
 
-  M.add_vertical_border(output, start_line, end_line + end_line_extmark_offset, 'OpencodeMessageRoleUser', -3)
+  M.add_vertical_border(output, start_line, end_line, 'OpencodeMessageRoleUser', -3)
 end
 
 ---@param output Output Output object to write to

lua/opencode/ui/formatter/tools/task.lua

@@ -79,8 +79,8 @@ function M.format(output, part, get_child_parts)
     type = 'select_child_session',
     args = {},
     key = 'S',
-    display_line = start_line - 1,
-    range = { from = start_line, to = end_line },
+    display_line = start_line,
+    range = { from = start_line + 1, to = end_line + 1 },
   })
 end
 

lua/opencode/ui/output.lua

@@ -102,6 +102,7 @@ function Output:add_extmark(idx, extmark)
   if not self.extmarks[idx] then
     self.extmarks[idx] = {}
   end
+
   table.insert(self.extmarks[idx], extmark)
 end