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Jaayden Halko
e421c2f747
## Problem The GitPanel's DiffViewer had several performance and correctness issues that manifested as CPU spikes and scrollbar jank, especially on Safari with large diffs: 1. The `onScroll` handler called `getBoundingClientRect()` on every file wrapper per scroll tick (O(N) forced layouts per frame). 2. `setActiveFile()` re-rendered the entire DiffViewer tree on every active file change. 3. `parsePatchFiles()` ran on every render in `LocalDiffPanel`, `RemoteDiffPanel`, and `GitPanel`. 4. File header `rootMargin` used a percentage, which resolves against the root's width (not height), collapsing the observation strip in wide viewports. 5. The IntersectionObserver effect didn't re-run when the viewport mounted after an initial empty state, or when the viewport was resized. ## Fix ### Scroll tracking Replaced the `getBoundingClientRect` scroll handler with an `IntersectionObserver` watching a narrow strip at the top of the viewport. The observation strip is a pixel value derived from `viewport.clientHeight` (the previous `-95%` margin was broken in wide viewports because CSS margin percentages resolve against width). A `ResizeObserver` tracks viewport height so the strip adapts to layout changes, and the effect keys off a stable `fileListKey` string so scroll-driven re-renders don't tear down the observer. ### Memoization: React Compiler `src/pages/AgentsPage/` is opted into the React Compiler via `site/vite.config.mts`. The compiler automatically memoizes values, callbacks, and JSX at build time. This PR removed the manual `useMemo` / `useCallback` wrappers that were added earlier in the review cycle and lets the compiler handle memoization. `React.memo()` is retained on `FileTreeNodeView` and `LazyFileDiff` — the documented list-item exception from `site/AGENTS.md`. Their `memo()` effectiveness depends on the compiler stabilizing prop references; moving these components outside the compiler scope without adding manual memoization would silently regress scroll performance. `useParsedDiff` uses explicit `useMemo` as a documented exception: the compiler cannot prove purity of the external `parsePatchFiles` function from `@pierre/diffs`, so without `useMemo` the parser would run on every render even when inputs are unchanged. ### `activeCommentBoxRef` (stable annotation handler) `CommentableDiffViewer` wraps `activeCommentBox` in a ref that's synced in event handlers (not during render). This gives `renderAnnotation`, `handleSubmitComment`, and the annotation getters stable identities via the compiler, so comment-box toggles no longer force every `LazyFileDiff` to re-render. ### CSS containment for Safari Added `will-change: transform` on the scroll container and `contain: layout style` on each file wrapper. Programmatic `scrollIntoView` / `scrollBy` calls use `behavior: "instant"` to avoid fighting Safari's scroll compositor. ### Hook extraction Extracted `useActiveFileTracking` (observer setup, viewport sizing, scroll-to-file) and `useParsedDiff` (shared diff parsing with memoization) to keep `DiffViewer` focused on layout and eliminate duplication between `LocalDiffPanel` and `RemoteDiffPanel`. ### Testing Added a `LargeDiff` Storybook story (40 files × 60+ context lines, ~2,400 diff lines) with `isExpanded: true` so the observer code path is exercised, plus a `play` function that scrolls the viewport and asserts the sidebar highlight updates. ## Expected impact - Scroll handler: O(N) `getBoundingClientRect` calls per frame → 0 - Re-renders on scroll: full DiffViewer tree → sidebar only - Diff parsing: on every render → only when `diffString` changes
Coder enables organizations to set up development environments in their public or private cloud infrastructure. Cloud development environments are defined with Terraform, connected through a secure high-speed Wireguard® tunnel, and automatically shut down when not used to save on costs. Coder gives engineering teams the flexibility to use the cloud for workloads most beneficial to them.
- Define cloud development environments in Terraform
- EC2 VMs, Kubernetes Pods, Docker Containers, etc.
- Automatically shutdown idle resources to save on costs
- Onboard developers in seconds instead of days
Quickstart
The most convenient way to try Coder is to install it on your local machine and experiment with provisioning cloud development environments using Docker (works on Linux, macOS, and Windows).
# First, install Coder
curl -L https://coder.com/install.sh | sh
# Start the Coder server (caches data in ~/.cache/coder)
coder server
# Navigate to http://localhost:3000 to create your initial user,
# create a Docker template and provision a workspace
Install
The easiest way to install Coder is to use our
install script for Linux
and macOS. For Windows, use the latest ..._installer.exe file from GitHub
Releases.
curl -L https://coder.com/install.sh | sh
You can run the install script with --dry-run to see the commands that will be used to install without executing them. Run the install script with --help for additional flags.
See install for additional methods.
Once installed, you can start a production deployment with a single command:
# Automatically sets up an external access URL on *.try.coder.app
coder server
# Requires a PostgreSQL instance (version 13 or higher) and external access URL
coder server --postgres-url <url> --access-url <url>
Use coder --help to get a list of flags and environment variables. Use our install guides for a complete walkthrough.
Documentation
Browse our docs here or visit a specific section below:
- Templates: Templates are written in Terraform and describe the infrastructure for workspaces
- Workspaces: Workspaces contain the IDEs, dependencies, and configuration information needed for software development
- IDEs: Connect your existing editor to a workspace
- Administration: Learn how to operate Coder
- Premium: Learn about our paid features built for large teams
Support
Feel free to open an issue if you have questions, run into bugs, or have a feature request.
Join our Discord to provide feedback on in-progress features and chat with the community using Coder!
Integrations
We are always working on new integrations. Please feel free to open an issue and ask for an integration. Contributions are welcome in any official or community repositories.
Official
- VS Code Extension: Open any Coder workspace in VS Code with a single click
- JetBrains Toolbox Plugin: Open any Coder workspace from JetBrains Toolbox with a single click
- JetBrains Gateway Plugin: Open any Coder workspace in JetBrains Gateway with a single click
- Dev Container Builder: Build development environments using
devcontainer.jsonon Docker, Kubernetes, and OpenShift - Coder Registry: Build and extend development environments with common use-cases
- Kubernetes Log Stream: Stream Kubernetes Pod events to the Coder startup logs
- Self-Hosted VS Code Extension Marketplace: A private extension marketplace that works in restricted or airgapped networks integrating with code-server.
- Setup Coder: An action to setup coder CLI in GitHub workflows.
Community
- Provision Coder with Terraform: Provision Coder on Google GKE, Azure AKS, AWS EKS, DigitalOcean DOKS, IBMCloud K8s, OVHCloud K8s, and Scaleway K8s Kapsule with Terraform
- Coder Template GitHub Action: A GitHub Action that updates Coder templates
Contributing
We are always happy to see new contributors to Coder. If you are new to the Coder codebase, we have a guide on how to get started. We'd love to see your contributions!
Hiring
Apply here if you're interested in joining our team.