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Will PflegerandGitHub 3ece4461df feat(desktop): apply WebKit rendering workarounds at startup on Linux (#3271 )

On some Linux GPU/driver/compositor combinations, WebKitGTK's dmabuf
renderer aborts the web process during startup, so Buzz comes up with no
window at all and the user has no way to fix it. Setting
`WEBKIT_DISABLE_DMABUF_RENDERER=1` avoids the abort by falling back to
the shared-memory buffer path.

WebKit reads each of its rendering variables exactly once per process,
so the choice has to be made before anything initializes — there is no
runtime toggle and no second chance later in the same process. This
decides up front from two cheap preflight signals rather than reacting
to a crash:

- **NVIDIA GPU** — any DRM device under `/sys/class/drm` reporting PCI
vendor `0x10de`, the driver family behind most upstream reports.
- **AppImage** — the `APPIMAGE` environment variable. linuxdeploy's
AppRun hook pins `GDK_BACKEND=x11`, and the dmabuf renderer buys nothing
on that XWayland path.

Either signal disables the dmabuf renderer. Neither signal leaves the
environment untouched.

## Escape hatches

`--safe-rendering` forces the safest configuration for one launch —
`WEBKIT_DISABLE_DMABUF_RENDERER` plus `WEBKIT_DISABLE_COMPOSITING_MODE`
— for a machine neither signal recognises.

Any user assignment of a variable this module may set stands the
heuristic down **wholesale**. Presence is the test, not truthiness, so
`VAR=0` and `VAR=` both count: a user asking for the dmabuf renderer
*on* gets it, even on a machine the heuristic would have opted out.
`--safe-rendering` against such an assignment is refused with a
diagnostic naming both the assignment and the key to unset, and exits
non-zero — the flag and the environment are two incompatible answers to
one question, and neither is guessed.

## Placement

`webkit_rendering::apply()` runs at the top of `fn main()`, before
`buzz_lib::run()`. That is the only point where the process is still
single threaded with no GTK object alive, which is what makes
`std::env::set_var` sound; the module doc and the call site both say so.
The whole module is `#[cfg(target_os = "linux")]` — macOS and Windows
compile none of it.

The decision is a pure function of argv, an injected environment lookup,
and an injected DRM root, so all of it is unit-testable without mutating
the process environment.

Closes #2338. Upstream:
[tauri#9394](https://github.com/tauri-apps/tauri/issues/9394). Same
approach and same variable as
[clash-verge-rev](https://github.com/clash-verge-rev/clash-verge-rev/blob/main/src-tauri/src/utils/linux/workarounds.rs)
`workarounds.rs` and
[screenpipe](https://github.com/screenpipe/screenpipe/blob/main/apps/screenpipe-app-tauri/src-tauri/src/linux_webkit_env.rs)
`linux_webkit_env.rs`.

Signed-off-by: Will Pfleger <pfleger.will@gmail.com>

2026-07-28 17:20:29 -04:00