On Rendering Diffs :: Pierre Computer Company
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ON RENDERING DIFFS
Posted on May 29, 2026 by @amadeus
в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•— в–Ҳв–Ҳв•—в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•—в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•—в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•—
в–Ҳв–Ҳв•”в•җв•җв–Ҳв–Ҳв•—в–Ҳв–Ҳв•‘в–Ҳв–Ҳв•”в•җв•җв•җв•җв•қв–Ҳв–Ҳв•”в•җв•җв•җв•җв•қв–Ҳв–Ҳв•”в•җв•җв•җв•җв•қ
в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•— в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв•‘в–Ҳв–Ҳв•‘в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•— в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•— в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•—
в•ҡв•җв•җв•җв•җв•җв•җв•җв•җв•җв•қ в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв•‘в–Ҳв–Ҳв•‘в–Ҳв–Ҳв•”в•җв•җв•қ в–Ҳв–Ҳв•”в•җв•җв•қ в•ҡв•җв•җв•җв•җв–Ҳв–Ҳв•‘
в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•”в•қв–Ҳв–Ҳв•‘в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•‘
в•ҡв•җв•җв•җв•җв•җв•қ в•ҡв•җв•қв•ҡв•җв•қ в•ҡв•җв•қ в•ҡв•җв•җв•җв•җв•җв•җв•қ
в–Ҳв–Ҳв•— в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•— в–Ҳв–Ҳв•—в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•—в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•—в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•—
в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв•”в•җв•җв–Ҳв–Ҳв•—в–Ҳв–Ҳв•‘в–Ҳв–Ҳв•”в•җв•җв•җв•җв•қв–Ҳв–Ҳв•”в•җв•җв•җв•җв•қв–Ҳв–Ҳв•”в•җв•җв•җв•җв•қ
в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•— в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв•‘в–Ҳв–Ҳв•‘в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•— в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•— в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•—
в•ҡв•җв•җв•җв–Ҳв–Ҳв•”в•җв•җв•җв•қ в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв•‘в–Ҳв–Ҳв•‘в–Ҳв–Ҳв•”в•җв•җв•қ в–Ҳв–Ҳв•”в•җв•җв•қ в•ҡв•җв•җв•җв•җв–Ҳв–Ҳв•‘
в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•”в•қв–Ҳв–Ҳв•‘в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв•‘ в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв•‘
в•ҡв•җв•қ в•ҡв•җв•җв•җв•җв•җв•қ в•ҡв•җв•қв•ҡв•җв•қ в•ҡв•җв•қ в•ҡв•җв•җв•җв•җв•җв•җв•қ
You open a pull request expecting to understand what changed.
For small and medium changes, everything works. The code is readable, the files are there,
you scroll around, add comments, and itвҖҷs all pretty seamless.
Then you open something larger. Maybe an agent generated the implementation, tests,
fixtures, and snapshots. Maybe the branch just touched more files than expected. Either way,
the review surface starts to degrade. It might only show you one file at a time, or require
each file to be loaded separately before you can read it, or even make basic navigation feel
sluggish.
Some of these are reasonable trade-offs for genuinely hard problems. But they still have a
cost: reviewers feel the limits of the tool, and product teams have to build workarounds for
these limits.
Diff rendering matters, but for most tools it is not the product. The product is what
happens around the code: review workflows, automation, agent output, CI results, and
collaboration. Code review should support that work, not become something every team has to
build from scratch.
That is why, about 6 months ago, we released
Diffs. Our goal was to make
the code and diff rendering part just work, so teams could spend their time on the product
around it.
Originally we launched with just the basic pieces: File and
FileDiff components. We quickly got feedback about performance issues, so we
followed up with a simple virtualizer that avoided rendering code when it was out of view
and an API to move syntax highlighting into worker threads. The simple virtualizer helped,
but it was a stopgap. There was still a lot of O(n×m) complexity, high memory usage, and virtualization blanking. What was missing was a
higher-level component that could manage an entire review surface and handle the hard
problems related to scale.
That missing layer became CodeView: a virtualization-first component for
reviewing code and diffs. And we built it around a deliberately impossible goal:
You should be able to just render any diff.
Not literally, of course. There are physical limits to browsers, compute, and memory. But
practically speaking, I think weвҖҷve come pretty close, and IвҖҷd like to share a bit about how
we got there.
If you find long-form blog posts boring, go check out the CodeView playground
at DiffsHub.com where you can pretty
much view any PR or diff that GitHub will send our way. Nearly any diff, at any scale,
nearly instantly.
diffshub[dot]com Take any public diff from GitHub and virtualize it nearly
instantly, no matter how large, with DiffsHub. Built to show off our brand new CodeView
component. To try it out, replace `github` with `diffshub` in your address
bar. pic.twitter.com/5X30YwbpHn
— Pierre (@pierrecomputer)
May 20, 2026
You can check out the CodeView component and more in the latest version of the diffs package
on npm:
@pierre/diffs, or
read the docs.
DIFFS LOOK SIMPLE UNTIL THEY ARE NOT
On the surface, rendering diffs in a browser may not seem very hard. ItвҖҷs just text, right?
Browsers are purpose-built to take raw HTML and turn that into something you can look at and
interact with. Code is just text, after all.
But a good review surface needs more than text. It needs syntax highlighting, line numbers,
annotations, comments, theming, split and unified layouts, wrapping modes, and enough
customization to fit into someone elseвҖҷs product. Each of those features adds cost and
complexity. Syntax highlighting adds processing time and inflates DOM count. Comments
involve additional layout complexity that we canвҖҷt fully control, and they still have to
work seamlessly with your existing design system.
With CodeView, we take that per-file complexity and scale it up; work that was
cheap for a single diff now has meaningful cost across a large review. We can roughly break
down the problems into three categories:
RenderingвҖүвҖ”вҖүDOM complexity grows quickly, and the browser can become
overloaded while scrolling or interacting with the page.
ProcessingвҖүвҖ”вҖүEvery file or diff operation gets multiplied, so work that
was fast in isolation can become expensive when repeated thousands of times.
MemoryвҖүвҖ”вҖүLarge files and diffs get transformed into rendering data
structures, which can push against browser memory limits and make garbage collection more
frequent.
Our simple virtualizer helped with some rendering problems, and moving highlighting off the
main thread helped with parts of the processing problem. But CodeView needed to
treat rendering, memory, and processing as connected parts of the same problem.
VIRTUALIZATION
Virtualization, or windowing, is a way of tackling the rendering problem. In its simplest
form, the idea is to only render the part of the content near the viewport. As you scroll,
the virtualizer renders the new content coming into view and removes content that has moved
off screen.
Keeping the DOM small has a lot of benefits: lower memory usage, less layout work, less
paint work, and fewer elements for the browser to manage. The trade-off is that the
virtualizer has to estimate or measure how tall everything is, and it must coordinate those
changes dynamically.
One thing that adds to this complexity is that browsers generally manage scroll compositing
separately from JavaScript execution. This can help scrolling feel more responsive to user
interactions, but it also means that JavaScript can easily lag behind scroll updates. This
is often most noticeable when using the scrollbar to make large jumps or scrolling extremely
quicklyвҖүвҖ”вҖүthe virtualizer canвҖҷt keep up and youвҖҷll scroll into blank regions before the
JavaScript has time to render the updated content.
Click to see blanking in the old virtualizer
Common Virtualization Techniques
There are a few common ways to virtualize content in a browser, and each comes with its own
set of trade-offs.
The most common approach is to create a real scrollable region with the full estimated
height of the content, then position the visible items where they belong. This keeps
scrolling native: the scrollbar, momentum, input handling, and accessibility all stay with
the browser. The trade-off is that the rendered window can fall behind the visual scroll
position. Fast scrolls and large scrollbar jumps can expose blank space before JavaScript
has a chance to render the next range. You can reduce that by rendering a larger buffer
outside the viewport, but that gives back some of the DOM, layout, and memory savings that
virtualization was supposed to buy you.
Another approach is to keep the visible content in a sticky or fixed container and update
what it shows with requestAnimationFrame. In this model, blanking is
impossible: the content container cannot scroll out of view because itвҖҷs not moving with the
scroll position; it just looks like it is. However, if JavaScript cannot keep up, then
scrolling can hitch or stutter because JavaScript is now part of the render update path.
Browser behavior matters here too. Safari, for example, currently caps
requestAnimationFrame at 60Hz even on higher refresh-rate displays, which makes
this approach feel worse than native scrolling on those devices.
A more extreme version is to emulate scrolling entirely: no native scrollable region, just a
custom viewport, a fake scrollbar, and content updated via
requestAnimationFrame as the user moves through the document. This can
avoid browser scroll-size limits because the scroll position is now your own state, not the
browserвҖҷs. But the cost is larger: you now own the details of making scrolling feel native,
accessible, and correct across different operating systems and browsers.
The Inverse Sticky Technique
For CodeView, many of those virtualization trade-offs were not acceptable.
Native browser scrolling mattered. WebKit-based environments needed to feel good because
Tauri is a common target for developer tools. And blanking was not an option.
This left us stuck between different approaches that werenвҖҷt quite right. After some
experimentation and frustration, we figured out a hybrid approach that could keep scrolling
native, mostly decouple positioning from requestAnimationFrame updates, and
make blanking effectively impossible.
WeвҖҷve called our new technique the Inverse Sticky Technique, but before we talk
about how it works, first a quick primer on how sticky positioning works. The
typical use case for sticky positioning is ensuring that section headers in a scrollable
list stay in view as you scroll through it. You set position: sticky; top: 0 on
your section headers and then when they should normally be scrolled out of view, they stay
fixed to the top of the scroll view as the content below scrolls underneath.
Section Title 1 (stuck)
Item 1
Item 2
Item 3
Item 4
Item 5
Section Title 2 (stuck)
Item 6
Item 7
Item 8
Item 9
Item 10
Section Title 3 (stuck)
Item 11
Item 12
Item 13
Item 14
Item 15
Item 16
Item 17
Item 18
Item 19
Item 20
For CodeView, we invert the usual sticky behavior. Instead of pinning the top
of the rendered content to the top of the viewport as you scroll down, the bottom edge of
the rendered region sticks to the bottom of the viewport when you scroll past it. When you
scroll back up, the top edge sticks to the top of the viewport.
This gives us native scrolling while the viewport is inside the rendered range. If
JavaScript falls behind, the rendered region sticks to one edge instead of scrolling away
and exposing blank space. We can get that behavior with negative top and
bottom sticky offsets, both calculated with the same formula:
(contentHeight - viewportHeight) * -1.
Pre Content Buffer
HereвҖҷs a quick demo showing the Inverse Sticky Technique. We are
currently halfway scrolled down a larger scroll region.
Try scrolling up or down. This content scrolls with you until you hit the sticky
bounds, at which point this content will get stuck to the top or bottom.
Post Content Buffer
So to circle back to the goals we set for ourselves: we preserve native scrolling, render
updates do not need to be frame-perfect to keep scrolling feeling smooth, and even large
jumps cannot scroll past the rendered content into blank space.
в”Ңв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”җ
в”Ӯ в”Ңв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”җ в”Ӯ
в”Ӯ в”Ӯ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ Full-height content element в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
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в”Ӯ в”Ӯ в–“в–“в–“в–“в–“ в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“ Buffer element в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“ before virtualized content в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“ в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“в–“ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в”Ңв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”җ в”Ӯ в”Ӯ
в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ
в”Ңв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв•–
в”Ӯ в–Җ в–Җ в–Җ в–“в–“в–“ Browser в–“в–“в–“ в•‘
в”ңв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв•ў
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘ в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘ Rendered content в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘ в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в”Ӯ в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ в”Ӯ в•‘
в•ҳв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•қ
в”Ӯ в”Ӯ в”Ӯв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в”Ӯ в”Ӯ |
в”Ӯ в”Ӯ в””в”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”ҳ в”Ӯ |
в”Ӯ в”Ӯ в”Ӯ |
в”Ӯ в”Ӯ в”Ӯ |
в”Ӯ в”Ӯ в”Ӯ |
в”Ӯ в”Ӯ в”Ӯ |
в”Ӯ в”Ӯ в”Ӯ |
в”Ӯ в”Ӯ в”Ӯ |
в”Ӯ в”Ӯ в”Ӯ |
в”Ӯ в””в”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”ҳ |
в””в”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”ҳ
While we were shooting for impossible to blank, Safari still found a way to
break our hearts. Under sufficiently aggressive scrolling, it can get backed up at the
compositing layer and expose blank space. It usually takes some work to pull off, but it is
still technically possible.
SCALABLE LAYOUTS
With virtualization in place, the next problem was calculating the layout and size of the
scrollable region. A virtualizer works best when its estimates are close to reality. Bad
estimates mean more corrective work after render: measuring DOM, updating item positions,
adjusting scroll height, and sometimes fixing the scroll offset to keep the current content
in place. The more often that happens, the more likely the page is to stutter or make the
scrollbar jump around.
Fortunately, the first pass is pretty cheap. Files are basically
lineHeight * totalLines. Diffs are only a little more complex because we
already have the parsed line counts and hunk metadata. From there, we just add the hunk
separators into the estimate. Simplified, it looks like this:
(lineHeight * diff.splitLineCount) + (diff.hunks.length * hunkSeparatorHeight).
Rendering Line Ranges
With our rough estimates in place, CodeView can determine which files should be
rendered. From there, each rendered file or diff gets the viewport size and position, and
uses that to decide which lines should be rendered internally.
This architecture came from the previous Virtualizer, but
CodeView pushed us to optimize some of the expensive paths. The old
implementation could end up iterating through a file or diff from the beginning to find
where the rendered range should start and end. For most files and diffs, that cost was
effectively invisible. But once we started testing much larger change sets, it became a
problem. A hunk with hundreds of thousands of lines could become pathologically expensive
because the lookup still had to start from zero.
To work around this, we added a cached position to line checkpoint system. That
lets us use binary search to find a closer starting point before doing the remaining range
search.
Once a line range is rendered, each file can verify its internal estimate against the actual
DOM and store any deltas. That lets the first-pass layout stay cheap while still correcting
the cases where the estimate was wrong.
Scroll Anchoring
Scroll anchoring is less about raw performance and more about keeping the view stable while
layout changes. If content above your scroll position changes height, the browser normally
tries to preserve what you were looking at instead of letting it jump around.
Browsers have built-in scroll anchoring for this, but virtualized views make that mostly
impossible. The mounted DOM is constantly changing, and the browser cannot make a safe
decision about which element to anchor to. For CodeView, we disable the
browserвҖҷs built-in anchoring with overflow-anchor: none and handle it
ourselves.
The core idea is that CodeView can choose an anchor from its own layout model
before committing DOM changes. It does not need to ask the DOM what the user is looking at;
it already knows which file or line should be visible at each scroll position.
A typical render update looks roughly like this:
Find the first fully visible line or file.
Store that line or file, along with its viewport offset, as the anchor.
Commit DOM changes for the new rendered range.
Reconcile any measured height changes.
Check whether the anchor is still at the same viewport offset.
If it moved, adjust the scroll position to put it back.
Taken together, rough estimates, line-range rendering optimizations, incrementally measured
deltas, and scroll anchoring let CodeView stay fast even with very large diffs,
without requiring perfect layout information up front.
DONвҖҷT FORGET ABOUT MEMORY
At this point CodeView was in a pretty good place. It could render diffs as
large as BunвҖҷs
Zig to Rust rewrite
or an even larger Node.js
V8 update without
falling over.
So, in typical Pierre fashion, we found a larger diff and kept going (weвҖҷre probably
hiring btw). The next set of work
came from trying to render the diff between Linux
v6 and v7
more efficiently.
Detaching Parsed Strings
Pathological cases like the Linux diff above can mean more than 700 MB of patch content to
parse and render. One of the first things our diff renderers need is a data structure built
from that patch file: line content and hunk metadata needed to render them efficiently and
correctly.
The subtle problem is that parsed strings can keep more memory alive than you expect.
Depending on how the JavaScript engine represents substrings, a small string can still
reference the much larger string it came from. That means you can parse a huge patch, keep
only the lines you need, and still accidentally retain the original giant input string.
In that case, copying strings can actually save memory. By forcing the parsed line content
to detach from the original patch input, Diffs can keep the data they need without keeping
the entire source string alive.
This was a good fit for an agent loop because the problem was narrow and easy to test. We
had a clear hypothesis, a parser function with well-tested inputs and outputs, and an easy
way to check whether each change improved memory usage and parse time.
в”Ңв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв•–
в”Ӯ в•‘
в”Ӯ Memory usage compared (Linux v6...v7 diff) в•‘
в”Ӯ в•‘
в”ңв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв•ў
в”Ӯ в•‘
в”Ӯ в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–‘в–‘ в•‘
в”Ӯ в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–‘в–‘ в•‘
в”Ӯ в•‘
в”Ӯ Original (2.4 GB) в•‘
в”Ӯ в•‘
в”Ӯ в”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җв”Җ в•‘
в”Ӯ в•‘
в”Ӯ в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘ в•‘
в”Ӯ в–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–Ҳв–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘в–‘ в•‘
в”Ӯ в•‘
в”Ӯ Optimized (1.15 GB) в•‘
в”Ӯ в•‘
в•ҳв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•җв•қ
After about an hour of iteration, we had some clear wins. Memory usage on the Linux diff
dropped from 2.4 GB to around 1.15 GB, and parse time dropped by about 80%.
Pooling DOM Elements
Virtualization keeps the mounted DOM small, but it can also create a lot of DOM element
churn. During aggressive scrolling, CodeView may remove one set of file or diff
elements and mount another. Those allocations do not disappear for free: JavaScript objects,
derived data, event handlers, and DOM nodes all eventually have to be cleaned up, and enough
garbage collection can show up as main-thread pauses.
There was also repeated setup work every time a new file or diff was rendered. Each one
lives inside a Shadow DOM wrapper that includes things like stylesheets, theme styles, and
an SVG icon atlas. Recreating all of that every time an item scrolled in or out of view was
unnecessary work.
So we added a pool for those containers. Instead of throwing the whole wrapper away,
CodeView can clean out the item-specific DOM and reuse the shell for the next
file or diff. That reduces allocation churn, avoids rebuilding the same wrapper structure
over and over, and keeps garbage collection further away from the scrolling path.
A nice side effect of building the pool was that it forced us to be more deliberate about
cleanup. Reusing containers safely meant being explicit about clearing references and
removing item-specific state, which helped patch a few leaks along the way.
Sharing options State
While we were testing against the
Linux diff, one thing we noticed was that configuration changes were extremely expensive.
File and FileDiff were originally designed to each have their own
options object. That worked well for rendering a single file or diff, but it
scaled poorly once CodeView was managing tens of thousands of them. Options
include things like split or unified layout, line numbers, line wrapping, and other display
settings. When one of those values changed, we would end up walking every file or diff
instance to give it a newly spread options object.
With enough instances, that became expensive quickly.
The fix was to keep the options shape, but change where the state actually
lived. Instead of giving every file or diff its own fresh config object,
CodeView owns the current options as the source of truth. Each rendered item
gets a stable options object with specialized getters that read from that shared state.
From the itemвҖҷs perspective, it still reads options like normal. Underneath,
those values are always coming from the latest CodeView configuration.
That means cosmetic changes no longer require rewriting configuration across every item in
the review. CodeView can update the shared state, re-render the mounted range,
and let the visible files and diffs read the latest values through the same options object.
Layout-affecting changes may still need to invalidate estimates, but we already spent time
making those much more efficient earlier in the post. Anecdotally, we also noticed a 20-30
MB memory reduction on the Linux diff after implementing this.
Deferred Syntax Highlighting
This is a feature weвҖҷve had in Diffs for a while, but it is still an important piece of
making large reviews feel smooth. Syntax highlighting is one of the most expensive
processing tasks we do. We use
Shiki because it is fast enough for most
cases, has a ton of language support, and can run in a variety of contexts: the browser, web
workers, and server-side rendering.
But вҖңfast enoughвҖқ changes when you multiply it across a large review. A 2,000-line
TypeScript file might only take a few milliseconds to highlight, but that is still expensive
inside a strict frame budget, especially when many files are being rendered or updated at
once and the main thread is already busy with rendering and virtualization work.
WhatвҖҷs important is that highlighting is deferred. Files and diffs can render first as plain
text, then request highlighted output from the worker pool. Each worker owns its own Shiki
highlighter, keeping the expensive work off the main thread while still allowing multiple
highlight jobs to make progress.
Additionally, we keep an LRU cache of highlighted results and provide APIs to
prime the highlight cache if we know a file will be rendered soon. That helps
avoid repeating work when code comes back into view, while still putting a hard limit on how
much highlighted output can be retained.
The goal is for highlighting to improve the review surface, not block it. Code is readable
immediately, and highlighting can progressively enhance the experience.
WRAP THIS UP ALREADY
If youвҖҷve made it this far: damn, thank you. вҷҘ
This has been a large project, with a lot of complicated work behind it. IвҖҷm proud of what
weвҖҷve managed to pull off inside the confines of a browser. Should all of this be happening
in a browser? Probably not. But, you know, challenge accepted.
So far, weвҖҷve mostly talked about the wins: the virtualization techniques, layout
estimation, memory improvements, DOM pooling, shared options, and deferred highlighting.
Those are real improvements, but there are still plenty of rough edges.
One of the bigger ones is CSS. Some of the most expensive parts of the virtualization system
now come from layout and paint. In normal use, thatвҖҷs usually fine. During aggressive
scrolling, though, those costs can become the majority of the work. WeвҖҷve thrown some
agentic research loops
at this, but so far we havenвҖҷt made much progress.
Another unresolved issue is serialization in the highlighting pipeline. If you
syntax-highlight a file with tens of thousands of lines, sending that data back and forth
through the worker pool gets noticeably expensive. At times, itвҖҷs enough to dominate the
main thread. This is probably an area where a more server-based streaming approach would
make sense.
Finally, while we do line-based virtualization, we donвҖҷt virtualize horizontal scrolling or
extremely long lines, like you might see in minified JS or CSS. That means mounting one of
those lines can still create a sizable DOM hit. We do have safeguards to stop the
highlighter from crashing on very long lines, but thatвҖҷs a separate problem.
Future plans for Diffs include things like lightweight editing, semantic diffs, and maybe
even moving some of this work onto the server where it makes sense. In the meantime:
You should be able to just render any diff.
So
hit play on Sandstorm
and scroll some diffs.
P.S. Apple, Safari, Please
Before I wrap this up, I wanted to end on a quick note about Safari. A lot of
CodeView is built on browser primitives that worked consistently across Chrome
and Firefox. In WebKit, that was not always the experience. Between poor performance and
limited observability, many wins felt like one step forward and then a half step back.
This is not meant as a dunk on Safari. WebKit is an important target for us, especially
because of macOS and the popularity of Tauri. I want nothing more than to build first-class
experiences on WebKit.
HereвҖҷs a non-exhaustive list of issues weвҖҷve run into while developing
CodeView and Diffs:
Sticky compositing performance that appears significantly worse than Chrome or Firefox
(cases where the Inverse Sticky Technique can still blank under aggressive
scrolling).
Developer tools that make it difficult to trace performance issues across JavaScript,
layout, paint, and compositing.
What does the gray other represent in frame timelines, and why is it often
blowing up our frame buffers?
Off-screen compositing rules that were difficult to predict
Deep scrolling/layout bugs when injecting slot containers. See
https://bugs.webkit.org/show_bug.cgi?id=308027.
requestAnimationFrame still being capped at 60Hz, even on higher refresh-rate
displays.
Work on Safari or on WebKit? Would love to talkвҖүвҖ”вҖүemail amadeuspierre.co.
вҶҗ Back to Home |
The development of diff rendering systems, as explored by Pierre Computer Company, addresses the complexity of displaying code differences within a browser by focusing on virtualization and scalable layout management. The initial goal was to make the code and diff rendering functional, allowing developers to focus on the surrounding review workflows rather than the technical implementation of rendering. Early attempts involved basic components but quickly encountered performance issues related to the complexity added by features like syntax highlighting, line numbers, and unified layouts, which introduce costs across rendering, processing, and memory.
To manage this complexity, the team developed CodeView, a virtualization-first component designed to handle large-scale review surfaces. This involved addressing three primary technical bottlenecks: DOM complexity, processing cost, and memory usage. Virtualization, or windowing, was introduced to only render content visible in the viewport, aiming to reduce the load on the browser by minimizing the number of elements managed. However, achieving smooth scrolling without visible blanking posed specific challenges related to the interplay between JavaScript execution and browser compositing.
Multiple virtualization techniques were explored, including creating a real scrollable region, using sticky containers updated with requestAnimationFrame, and full emulation of scrolling. The chosen approach for CodeView was the Inverse Sticky Technique, which preserves native scrolling while ensuring that when content scrolls out of view, the rendered region sticks to the viewport's boundary rather than exposing empty space. This technique achieves the goal of preventing blanking while maintaining native scroll behavior.
Scaling the layout presented further challenges. Virtualization requires accurate estimates of content size, and poor estimates lead to layout inconsistencies. To optimize this, the system developed a method to estimate layout based on line heights and hunk metadata, and subsequently implemented optimizations for rendering line ranges, introducing a cached position system with binary search to accelerate lookups for large change sets. Scroll anchoring was also managed by disabling the browser's native anchoring and implementing a custom mechanism where CodeView determines the anchor point based on its internal layout model before committing DOM changes, thus ensuring stability during layout shifts.
Further performance gains were realized through architectural refinements. A significant source of overhead was the constant creation and destruction of DOM elements within the virtualization process. To mitigate this element churn, the team implemented a pool for container elements, allowing shells to be reused across different file or diff renderings, which reduced allocation overhead and improved garbage collection efficiency. Furthermore, managing layout-affecting options, such as line wrapping and layout styles, was refined by making the state shared across all rendered items. Instead of duplicating configuration objects for every file, CodeView established a shared state for options, allowing rendered items to read these values through specialized getters, which drastically reduced the cost of cosmetic updates.
Syntax highlighting, being an expensive processing task, was handled through deferred execution. Instead of calculating highlighting on the main thread, files render as plain text first, and highlighting results are requested asynchronously from a worker pool. The system also incorporates an LRU cache for highlighted results and caching mechanisms to avoid redundant computations when code reappears in the viewport.
Despite these significant gains, lingering challenges remain. Performance costs related to layout and painting during aggressive scrolling must continue to be addressed. Serialization within the highlighting pipeline, where transferring large amounts of highlighted data between the worker pool and the main thread can become performance-intensive, suggests a need for alternative streaming approaches. Finally, the virtualization framework currently handles line-based scrolling but does not virtualize horizontal scrolling or extremely long lines, which can still incur significant DOM costs. Future work is directed toward lightweight editing, semantic diffs, and potentially offloading processing to the server.
The project also highlighted platform-specific issues, noting that performance and observability within WebKit environments, particularly concerning sticky compositing and requestAnimationFrame capping, presented distinct difficulties compared to environments like Chrome and Firefox. |