Build interactive native workspace vertical slice

spikes/gpui-accessibility-probe/README.md

@@ -0,0 +1,83 @@
+# GPUI accessibility and input probe
+
+This independent workspace answers one narrow question: can the GPUI version
+currently used by Zed expose the minimum semantic tree Lumbridge needs for a
+workspace and terminal pane, while accepting real platform IME input?
+
+## Reproducibility
+
+- Upstream: `https://github.com/zed-industries/zed`
+- Commit: `ce48461eaadd16c65c31f835511ab96bd3b6e746`
+- GPUI license at this commit: Apache-2.0
+- Rust: 1.97.1, matching the upstream `rust-toolchain.toml`
+
+Both `gpui` and `gpui_platform` are pinned to the full commit. This directory is
+an independent Cargo workspace, so its toolchain and dependency graph do not
+change Lumbridge's root MSRV or release graph.
+
+## Semantics under test
+
+The rendered tree contains:
+
+- an application named `Lumbridge accessibility probe`;
+- a stable, externally identifiable `Region` named `Lumbridge workspace`;
+- a stable, focusable `Pane` named `Local terminal pane`;
+- `selected = true` on the pane;
+- real GPUI keyboard focus tracked on the pane;
+- the description `Needs input: choose whether to run the proposed command`;
+- a `Terminal` child named `Terminal output` for the pane's content.
+
+Current GPUI exposes these through its AccessKit integration using `role`,
+`accessibility_id`, `aria_label`, `aria_description`, `aria_selected`,
+`focusable`, and `track_focus`. The deterministic unit test checks the exact
+AccessKit role and properties. The binary compile-checks GPUI's element wiring;
+a platform screen reader remains necessary for end-to-end AT-SPI/VoiceOver
+validation.
+
+## Input and IME proof
+
+The focused pane also installs a real `ElementInputHandler<ImeTextReceiver>`
+during element paint. `ImeTextReceiver` implements GPUI's
+`EntityInputHandler`, including text queries, UTF-16 selection, marked-text
+composition, replacement, unmarking, selection updates, editable length, and
+IME candidate bounds. This is the code path GPUI's platform adapters call for
+composed operating-system text input.
+
+The backing buffer stores UTF-8 only at valid scalar boundaries and translates
+the platform's UTF-16 ranges before mutation. Deterministic tests cover:
+
+- replacing a selected decomposed `e` plus combining acute accent with `é`;
+- a marked decomposed-accent IME composition and commit;
+- inserting, selecting, and replacing the multi-codepoint grapheme `👩🏽‍💻`;
+- collapsed selection placement after every replacement.
+
+These tests prove range conversion and composed-text preservation without
+splitting UTF-8. An actual keyboard IME on X11/Wayland and macOS remains an
+end-to-end platform test, not a unit-test claim.
+
+## Commands
+
+```bash
+cargo check --locked
+cargo test --locked
+cargo clippy --locked --all-targets -- -D warnings
+```
+
+The first command installs the pinned Rust toolchain if rustup does not already
+have it and downloads Zed's GPUI dependency closure.
+
+On Ubuntu hosts that have only the runtime libraries, checks work with
+`RUST_FONTCONFIG_DLOPEN=1`. Linking a test or binary additionally needs the
+unversioned linker names normally installed by `libxcb1-dev`,
+`libxkbcommon-dev`, and `libxkbcommon-x11-dev`. The amd-server validation used
+temporary symlinks under the ignored `target/native-libs` directory and set
+`LIBRARY_PATH` to that directory; no system packages or root files changed.
+
+## Observed local cost
+
+On amd-server, the first successful check required roughly 90 seconds after
+installing/fetching, with some Cargo-cache contention from concurrent work. The
+lockfile contains 691 packages. After check, test, Clippy, and a debug build,
+the isolated target directory was 4.4 GiB and the debug binary was 535 MiB. The
+minimal Rust 1.97.1 toolchain occupies 624 MiB. These are development costs, not
+optimized release measurements.