I was searching for what's the latest in emacs widgets developments because I was interested in using widgets. Emacs Customize for example, renders text-based widgets in an editable buffer, which is very uncommon nowadays. Emacs seems like the best candidate for this kind of interactivity. I'm sure it's possible in other editors, but with significantly more effort and significantly slower rendering. I also considered lem, but the barrier also seems much higher.
His post also led me to his vui.el project, but I ended up not trying it, since after understanding the tradeoffs, I pushed the widget code creation to an LLM. I still get frequent unbalanced parentheses errors so I still stay close to the defaults.
The PoC is about testing a method to render a widgets-based, json-schema-validated input form that you can embed dynamically into an emacs buffer, enter the data, then do something post-validation. If anyone's interested, here's the latest state of the LLM-generated and human-fixed code: https://gist.github.com/whacked/6875c5117b48528e619755e13e24...
On the unbalanced parentheses from LLMs - I've found Claude Code with Opus 4.5 is generally quite good at keeping them balanced, fwiw.
Curious about this though:
> after understanding the tradeoffs, I pushed the widget code creation to an LLM
What tradeoffs made you go with raw widget.el over vui.el? Genuine question - that's exactly the kind of feedback that helps me understand if vui.el is solving the right problems or missing something.
Your gist essentially reimplements some things vui.el provides generically (state tracking, inline form lifecycle, cleanup). Would be interesting to see if vui.el could simplify the widget/state parts while you focus on the schema translation - or learn what's missing if it can't.
If having conversation here is not convenient, we can continue under your gist or via email. Let me know if you are interested :) If not - that's also fine :)
Staying vanilla reduces dependencies, which also makes testing easier during iteration. I forgot which agent (CC or codex) I used for the bulk of the code generation, but some times I manually do some one-off dialog and those get unbalanced parens.
In the agent I ask it to do `emacs -q -nw -l ...` to iterate, so it starts a bare emacs instance. This seems to have worked well when adding [Submit and Close] and [Cancel] buttons, as well as "move the cursor into the first text input widget when inserting a new array item" (the default action is to keep the cursor on the [INS] widget after inserting the list item).
The next consideration is just that I am less confident in the agent's ability to just ingest a .el library and use it correctly vs something more popular like python. Maybe it can, I just wanted results fast and not have to dig too deep myself. I had to go in and do some (setq debug-on-error t) toggles a few times while it was figuring out the json schema load into alist/hashmap differences and I didn't want to spend more time doing plumbing.
But as you probably can imagine, dynamic inline forms immediate gives us state issues, so I asked the agent to create a buffer-local alist (or hashmap?) to track the states of the form input, so it can be cleaned up on close. It's a bit unreliable now. If vui.el already has a solution I'll switch over next.
His posts are very insightful.
I couldn't tell from the list of blog posts about on non-Emacs topics.
I'm not sure what to tell authors of such pages...
update: added; turns out I almost finished it before on a local branch but didn't push to master
- vui.el seems like the right idea - You have a widget library, and then you add state management, you add layout management etc. It's sort of a blessing widget is simple enough to be reused this way
- ECS and inheritance. I have personally never really hit on this limitation. It's there in the abstract.. but don't GUIs generally fit the OO paradigm pretty well? Looking at the class tree for JavaFX, I don't see any really awkward widgets that are ambiguously placed.
- State Management. This can be bolted on - like with vui.el. But to me this feels like something that should be independent of GUIs. Something like Pathom looks more appealing to me here
- "Not a full reactive framework - Emacs doesn't need that complexity" .. why not? Maybe the library internals are complex, but it makes user code much simpler, no?
On vui.el's approach - yes, the blessing is that widget.el is simple enough to build on. It does the "rendering" and some "behaviour", vui.el handles the rest.
On ECS vs OO - I'll admit I don't have enough experience to speak about UI paradigms in general. But my critique of widget.el is that inheritance hierarchies don't compose well when you need orthogonal behaviors. Composition feels more natural to me - could be just how my brain works, but it scales better in my experience.
On state management being independent - I'd be curious to hear more. Pathom is interesting for data-driven architectures. vui.el's state is intentionally minimal and Emacs-native, but you're right it could potentially be decoupled further.
On "why not full reactive" - to clarify what vui.el has: React-style hooks with explicit dependency tracking (vui-use-effect, vui-use-memo, etc.), state changes trigger re-renders, batching for multiple updates. What it doesn't have: automatic dependency inference or fine-grained reactivity where only specific widgets update. The tradeoff was debuggability - explicit deps are easier to trace than magic. But I'm open to being wrong here. What would you want from a reactive layer?
> Pathom is interesting for data-driven architectures. vui.el's state is intentionally minimal and Emacs-native, but you're right it could potentially be decoupled further.
I'll be honest, I haven't yet written a Pathom-backed GUI. But I'm hoping to experiment with this in the coming weeks :)) cljfx is structured in such a way that you can either use the provided subscription system or you can roll your own.
> What it doesn't have: automatic dependency inference or fine-grained reactivity where only specific widgets update
So all the derived states are recalculated? Probably in the 95% case this i fine
In the big picture I enjoyed the cljfx subscription system so much, that I'd like to use a "reactive layer" at the REPL and in general applications. You update some input and only the parts that are relevant get updated. With a subscription-style system the downside is that the code is effectively "instrumented" with subscription calls to the state. You aren't left with easily testable function calls and it's a bit uglier.
Pathom kind of solves this and introduces several awesome additional features. Now your "resolvers" can behave like dumb functions that take a map-of-input and return a map-of-output. They're nicer to play with at the REP and are more idiomatic Clojure. On top of that your code turns in to pipelines that can be injected in to at any point (so the API becomes a lot more flexible). And finally, the resolvers can auto parallelized as the engine can see which parts of the dependency graph (for the derived state you're prompting) can be run in parallel.
The downsides are mostly related to caching of results. You need an "engine" that has to run all the time to find "given my inputs, how do I construct the derived state the user wants". In theory these can be cached, but the cache is easily invalidated. You add a key on the input, and the engine has to rerun everything (maybe this can be bypassed somehow?). You also can concoct complex scenarios where the caching of the derived states is non-trivial. Derived state values are cached by the resolvers themselved, but they have a limited view of how often and where they're needed. If two derived states use one intermediary resolver but with different inputs, you need to find a way to adjust the cache size.. Unclear to me how to do this tbh
:ascii
+---------+--------+
| Summary | |
+---------+--------+
| RMS | 4.1620 |
| AVG | 3.9558 |
+---------+--------+
┌─────────┬────────┐
│ Summary │ │
├─────────┼────────┤
│ RMS │ 4.1620 │
│ AVG │ 3.9558 │
└─────────┴────────┘
Doesn't emacs lag like crazy in files with large lines. Why is this still a problem? Every modern editor handles this gracefully. I remember reading something about using regexes for syntax highlighting. This looks like a problem in the rendering layer which shouldn't be too hard to fix without touching the core engine. Are there any other problems that make it difficult to fix without disabling any useful features?
Emacs is now capable of editing files with very long lines. The display of long lines has been optimized, and Emacs should no longer choke when a buffer on display contains long lines. The variable 'long-line-threshold' controls whether and when these display optimizations are in effect.
A companion variable 'large-hscroll-threshold' controls when another set of display optimizations are in effect, which are aimed specifically at speeding up display of long lines that are truncated on display.
If you still experience slowdowns while editing files with long lines, this may be due to line truncation, or to one of the enabled minor modes, or to the current major mode. Try turning off line truncation with 'C-x x t', or try disabling all known slow minor modes with 'M-x so-long-minor-mode', or try disabling both known slow minor modes and the major mode with 'M-x so-long-mode', or visit the file with 'M-x find-file-literally' instead of the usual 'C-x C-f'.
In buffers in which these display optimizations are in effect, the 'fontification-functions', 'pre-command-hook' and 'post-command-hook' hooks are executed on a narrowed portion of the buffer, whose size is controlled by the variables 'long-line-optimizations-region-size' and 'long-line-optimizations-bol-search-limit', as if they were in a 'with-restriction' form. This may, in particular, cause occasional mis-fontifications in these buffers. Modes which are affected by these optimizations and by the fact that the buffer is narrowed, should adapt and either modify their algorithm so as not to expect the entire buffer to be accessible, or, if accessing outside of the narrowed region doesn't hurt performance, use the 'without-restriction' form to temporarily lift the restriction and access portions of the buffer outside of the narrowed region.
The new function 'long-line-optimizations-p' returns non-nil when these optimizations are in effect in the current buffer.
I do agree that Emacs can be slower than the terminal when handling long lines/files, although (depending on your case) this can be easily mitigated by running a terminal inside of Emacs.
Generally though, for everyday use, Emacs feels a lot snappier than VSCode.
> Generally though, for everyday use, Emacs feels a lot snappier than VSCode.
+1
When you're building a UI, you control the content. Lines are short by design (form fields, buttons, lists). The pathological case of a 50KB minified JSON line simply doesn't occur.
The long-line problem stems from how Emacs calculates display width for bidirectional text and variable-pitch fonts - it needs to scan the entire line. That's orthogonal to rendering widgets or interactive buffers.
The author is known in the community as a mere packager whose knowledge of the nitty-gritty derives entirely from hearsay. Perhaps he read the long-winded preamble to xdisp.c written in 1995 boasting of all manner of optimisations. But they were written so long ago, almost no one believes most of them matter anymore, what with thirty years of bitrot.