darkfi/openspec/changes/app-chatview/proposal.md

Why

The app's chat UI duplicates a full screen (layer tree, ChatView, kv tree, mesh caches) for every joined channel, scrolls with costs that grow linearly with buffer size, keeps render resources (meshes, glyphs, textures, layouts) forever once messages scroll out of view, and conflates every scroll gesture into a single velocity scalar — making animated wheel paging, stable anchoring, and richer content (images, expandable rich messages, stickers) progressively harder to bolt on. The full requirements list agreed during exploration is captured in this change's design.md and spec; this change implements it as a ground-up chatview2 with the current implementation serving as the functional spec (feature parity, no regressions).

What Changes

• New src/ui/chatview2/ module in bin/app: modular chatview — buffer (ordered arena + Fenwick height index), scroll controller, background loader, virtualizing view, and per-type message nodes.
• BREAKING (internal scene API): the old src/ui/chatview/ is removed once parity is reached; src/app/schema/chat.rs moves from one duplicated screen per channel to a single chat screen with the chatview retargeted via set_channel.
• Message system: one scene sub-node per message type (not per message), carrying type-specific styling properties, signals, and methods with msg ids in payloads; messages are records in the buffer plus per-id render state owned by the type node.
• Property inheritance: shared styling (font_size, line_height, timestamp styling, selection color) defined once on the chatview2 node; type nodes define only type-specific properties; property handles passed into the msg type's new(); .regen() rebuilds rendered state (used for both styling changes and async content updates).
• Storage: keep kvdb (no custom format); kv key stays the (timestamp, msg_id) composite; value becomes a type ID followed by type-owned bytes; unconfirmed messages are persisted with a confirmed flag.
• Scrolling: pixel scroll from bottom (scroll=0 is always the bottom), 1:1 finger drag, animated half-page mouse-wheel jumps, flick inertia as distinct states of a scroll controller fed by the new ui/gesture subsystem (drag lifecycle events, release velocity on DragEnd); the controller owns physics only — recognition, slop, long-press timers, and velocity sampling are session-provided; compensation rule for height changes below the viewport; per-channel scroll restore (anchor msg id + offset) on re-entry.
• Performance: visible-range lookup, total height, and position queries are O(log n) in buffer size; only visible messages (soft window + LRU budget) hold render resources; loading is a single async background pipeline; no hard buffer cap in v1.
• Runtime-settable message filter callback applied in the load pipeline.
• Privmsg v1 ships plain text + nicks + URLs plus capped-height with expand; the rich span/block body model (quotes, styling, code, math) is deferred but the APIs are shaped for it.
• Message types take the i18n_fish for translation support.

Capabilities

New Capabilities

• chatview: the chatview2 widget — scene API (properties, methods, signals, per-type message sub-nodes), buffer and geometry semantics (ordering, insertion, dedup, heights), scrolling behavior (gestures, animation, clamping, anchoring, restore), storage format, background loading, filter, resource eviction, and feature parity with the current chatview (URL clicks, selection/copy, file messages, notices/actions, unconfirmed messages, date separators, keyboard scrolling).

Modified Capabilities

(none — no existing specs in this repo; the chat screen rework in src/app/schema/ is part of this change's tasks and is exercised through the chatview capability.)

Impact

• bin/app/src/ui/chatview2/ (new module), bin/app/src/ui/chatview/ (removed at switchover), bin/app/src/ui/mod.rs.
• bin/app/src/app/schema/chat.rs (single screen, channel switching), bin/app/src/app/schema/mod.rs (per-channel screen creation loop), bin/app/src/app/node.rs (node factories), bin/app/src/main.rs (message relay paths), bin/app/src/plugin/darkirc.rs, bin/app/src/plugin/fud.rs (insert/status paths, unconfirmed persistence).
• Per-channel kv trees: value format gains a type ID tag; keys unchanged. Existing history remains readable (v1 privmsg payload is the current nick, text encoding plus a confirmed flag).
• bin/app/src/ui/gesture/ (applied by the app-gesture change) is consumed as-is, not modified: chatview2 implements gesture_set/ gesture_hit_test/handle_gesture instead of the removed handle_touch; overlaying interactive layers (scroll-to-bottom arrow, cmd hints) need explicit node priority above the chatview for the gesture session's priority-ordered targeting.
• Build/test via bin/app Makefile targets (make compile-dev, compile-apk); no changes outside bin/app, no new dependencies.