feat: add --watch live-reload preview for the TUI#24
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Adds `termdown --watch FILE` (and `watch` config option) so the TUI re-renders whenever the file changes on disk — built for a two-pane "edit in your editor, preview in termdown" workflow. - notify-based watcher on the parent directory (survives editor atomic save / rename), drained in the existing 50ms event-loop tick - reload_active_doc rebuilds the doc in place, preserving scroll position (via top-logical anchor), ToC/metadata fold state, and any active search query - process-global heading-image cache keyed on (level, theme, text): a body-only edit re-renders near-instantly; only changed headings are re-rasterized - [watch] status-bar indicator; extract renumber_doc_images helper Tests: heading cache keying/determinism, renumber_doc_images id remap, viewport top_logical round-trip.
Address review findings on the --watch live-reload feature: - Watcher now retargets on link/back/forward navigation (new LiveWatch with an Arc<Mutex> target shared with the callback thread), so live reload follows the on-screen doc instead of staying bound to the initial file. - Preserve the current search match across reload via SearchState::rebuilt_for / nearest_match_index, rather than resetting focus to the top. - Include a font fingerprint in the heading-image cache key so distinct font configs can't alias the same cached PNG.
reload_active_doc reads the active file via read_to_string; on Linux/inotify that surfaces as Access(Open) (and, via atime, Modify(Metadata)) for the target, re-triggering reload and spinning a self-sustaining loop. Filter both kinds in the watch callback; real content changes (Create/Modify(Data/Name/Any)/Remove and the coarse Any/Other macOS FSEvents emits) still reload.
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What & why
Adds
termdown --watch FILE(and awatchconfig option) so the interactive TUI re-renders whenever the file changes on disk. Built for a two-pane workflow: edit the Markdown in your editor (e.g. vim) on one side, keeptermdown --watchopen on the other for a live preview.Motivated by the "edit on the left, preview on the right" request — implemented with performance as the primary constraint.
How it works
notify): watches the file's parent directory non-recursively and filters events to the target path, so editor atomic saves (write-temp-then-rename, which swaps the inode) keep firing. The watcher pings anmpscchannel that the existing 50 msevent::pollloop drains each tick (burst events from one save are coalesced into a single reload).reload_active_doc: re-reads the file and rebuilds the doc in place, preserving:Viewport::top_logical()anchor + the existingvisual_line_for_logical()SearchStatenow retains its query so matches rebuild against new content)(level, theme, text), mirroring the existingFONT_DATA_CACHE. PNG rasterization is the dominant render cost (~150–240 ms on a heading-heavy doc), so a save that only touches body text now re-renders in ~5–35 ms; only headings whose text actually changed are re-rasterized.[watch]marker in the status bar;renumber_doc_imagesextracted frompush_new_docand reused by reload.--watchis TUI-only — it warns and falls back to cat mode for piped/stdin input. Default off; opt in via-w/--watchorwatch = truein config.Tests
make checkis green (clippy-D warnings, 119 tests). New unit tests:(level, theme, text), byte-identical on hitrenumber_doc_images: id remap + span/LineKindref patching, allocator advanceViewport::top_logical: round-trips withvisual_line_for_logicalManual verification (needs a Kitty-graphics terminal)
termdown --watch README.mdin one pane; edit + save in another. Confirm: body-only edit reloads instantly with scroll kept; editing one heading re-rasterizes only that heading; works with both:set backupcopy=yes(in-place) and default (atomic rename);rm+ recreate recovers without crashing.🤖 Generated with Claude Code