JKNandLukas Wirth
eae9f3eed0
# Objective
`gpui_macos` implements `PlatformWindow::render_to_image` — the
MetalRenderer samples an offscreen target, so a **hidden** window can be
captured. `gpui_windows` does not implement it, so the method falls
through to the trait default and returns `Err("render_to_image not
implemented for this platform")`.
That leaves Windows consumers (tests, headless screenshot harnesses) on
`PrintWindow`-style workarounds, which require the window to actually be
on screen: a DirectComposition swap chain that never presents has no
frame to read, so you get a visible flash — or an off-screen parking
trick — for every capture.
This closes the macOS/Windows gap. Linux (`gpui_linux`) still returns
the trait default; a Blade/wgpu readback is the obvious follow-up but is
not in this PR.
## Solution
The DirectX analogue of the Metal path:
- `DirectXRenderer::draw`'s clear, scene upload and batch encoding are
factored into a shared `render(scene, background_appearance)`. `draw` is
now `render` + `present`; `render_to_image` is `render` + readback.
Nothing about how a frame is produced is duplicated between them, so the
two cannot drift.
- `render_to_image` renders into the **existing** render target —
created at window construction, so no window need ever be shown — then
copies it into a `D3D11_USAGE_STAGING` texture, `Map`s it, and converts
BGRA → RGBA. `RowPitch` padding is honoured per row; the copy loop
carries a safety comment.
- It refuses to run while `skip_draws` is set. That flag marks a pending
device-lost recovery, where the atlas still holds tile references from
the previous device — drawing before the forced re-render rebuilds them
panics in `DirectXAtlasState::texture` (the case
`WindowState::force_render_pending` documents). Returning an error beats
panicking in a capture harness.
- Gated on `cfg(any(test, feature = "test-support"))` to match the trait
method. `gpui_platform`'s `test-support` now forwards to
`gpui_windows/test-support`, the way it already does for `gpui_macos`.
No behaviour change outside `test-support`/`cfg(test)` builds beyond the
`render` factoring, which is a pure code move.
## Testing
- **Windows, functional:** an earlier revision of this patch has been in
production use since June in the `--screenshot` harness of a GPUI app I
ship ([Ferail](https://github.com/jonx/Ferail)), capturing a hidden
window (`show: false`) with no flash. BGRA→RGBA output was verified
against the on-screen rendering.
- **This exact revision** has been cross-checked from macOS only: `cargo
clippy -p gpui_windows --no-default-features --features test-support
--target x86_64-pc-windows-msvc -- -D warnings` is clean, both with and
without `test-support` (clang-cl + `xwin`; `--no-default-features` skips
only the `windows-manifest` embed-resource step, which is irrelevant
here). I'm relying on CI for a native Windows build of this revision —
happy to report back from a Windows host if that's a blocker for review.
- **Not covered by an automated test.** The behaviour needs a live D3D11
device, so it can only be exercised by a Windows-hosted test. Happy to
add one under `gpui_windows` if you'd like it — say the word and I'll
push it rather than guess at the shape you want.
- **Reviewers:** the interesting part is the staging-texture readback in
`directx_renderer.rs`. Worth a second pair of eyes on the `skip_draws`
guard and on premultiplied alpha (the swap chain is
`DXGI_ALPHA_MODE_PREMULTIPLIED`, so non-opaque captures come back
premultiplied — same as the macOS path, but it does mean
semi-transparent regions are not straight-alpha).
## Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines) — n/a, no UI surface
- [ ] Tests cover the new/changed behavior — see Testing; needs a
Windows host, happy to add
- [x] Performance impact has been considered and is acceptable — the
readback path is `test-support`-only; `draw` is unchanged apart from the
`render` factoring
## Showcase
<!-- TODO: drop in the headless Windows capture (and the macOS one
beside it) -->
---
Release Notes:
- N/A
Co-authored-by: Lukas Wirth <lukas@zed.dev>
Zed
Welcome to Zed, a high-performance, multiplayer code editor from the creators of Atom and Tree-sitter.
Installation
On macOS, Linux, and Windows you can download Zed directly or install Zed via your local package manager (macOS/Linux/Windows).
Other platforms are not yet available:
- Web (tracking discussion)
Developing Zed
Contributing
See CONTRIBUTING.md for ways you can contribute to Zed.
Also... we're hiring! Check out our jobs page for open roles.
Licensing
Zed source code is licensed primarily under GPL-3.0-or-later, with Apache-2.0 components where marked.
License information for third party dependencies must be correctly provided for CI to pass.
We use cargo-about to automatically comply with open source licenses. If CI is failing, check the following:
- Is it showing a
no license specifiederror for a crate you've created? If so, addpublish = falseunder[package]in your crate's Cargo.toml. - Is the error
failed to satisfy license requirementsfor a dependency? If so, first determine what license the project has and whether this system is sufficient to comply with this license's requirements. If you're unsure, ask a lawyer. Once you've verified that this system is acceptable add the license's SPDX identifier to theacceptedarray inscript/licenses/zed-licenses.toml. - Is
cargo-aboutunable to find the license for a dependency? If so, add a clarification field at the end ofscript/licenses/zed-licenses.toml, as specified in the cargo-about book.
Sponsorship
Zed is developed by Zed Industries, Inc., a for-profit company.
If you’d like to financially support the project, you can do so via GitHub Sponsors. Sponsorships go directly to Zed Industries and are used as general company revenue. There are no perks or entitlements associated with sponsorship.