Apply --ozone-platform from electron-flags.conf at startup on Linux by victorwon2001 · Pull Request #18697 · rstudio/rstudio

victorwon2001 · 2026-08-31T17:55:41Z

Intent

Addresses #16594.

On Linux, Chromium picks its Ozone backend before main.ts runs, so an --ozone-platform from electron-flags.conf reached only the child processes. RStudio could then open with a blank window.

Approach

On packaged Linux builds, startup checks for a requested --ozone-platform before anything else starts (R detection, the login-shell query, startup timing). If the request differs from the backend Chromium started with, RStudio relaunches once with the switch placed ahead of the original arguments.

Precedence: an explicit --ozone-platform (or -ozone-platform) on the command line wins, then RSTUDIO_CHROMIUM_ARGUMENTS, then electron-flags.conf. After startup, neither the env var nor the conf file re-applies the switch in any spelling app.commandLine.appendSwitch accepts, so child processes match the browser process.
Only x11 and wayland are accepted. Other values are ignored and logged as warnings, and the relaunch decision is printed to the console.
There's no relaunch for --help, --version, --version-json, or --run-diagnostics, whose output would go to /dev/null in the relaunched process. There's also none in development builds, where exiting stops electron-forge's dev server.
If electron-flags.conf can't be read, the existing startup error dialog reports its path.

The relaunch decision is a pure function, planOzoneRelaunch in electron-flags.ts, so its cases are unit-tested.

Automated Tests

electron-flags.test.ts: conf parsing and loading (including an unreadable file), and the relaunch cases: matching, differing, and absent backends; env over conf; command line wins; switch spellings; arguments around --; unsupported values; dev builds; no second relaunch.
utils.test.ts: augmentCommandLineArguments leaves --ozone-platform unchanged.

npm run typecheck, npm run lint, and npm test pass on macOS. Lint reports no errors and two warnings already on main, in session-launcher.test.ts.

QA Notes

Not yet verified on Linux. With --ozone-platform=wayland in ~/.config/rstudio/electron-flags.conf:

In a Wayland session, the complete IDE opens under Wayland, and project/file arguments are preserved.
In an X11 session, rstudio --ozone-platform=x11 stays on X11.
rstudio --version prints the version and exits without relaunching.
With --ozone-platform=bogus instead, RStudio starts on its default backend and rdesktop.log has the warning.

Checklist

If this PR adds a new feature, or fixes a bug in a previously released version, it includes an entry in NEWS.md
If this PR adds or changes UI, the updated UI meets accessibility standards (no UI changes)
A reviewer is assigned to this PR
This PR passes all local unit tests

gtritchie · 2026-08-31T19:35:35Z

Thanks for the PR, we'll take a look at it as soon as we can.

If you haven't already, please fill out and submit the contributor agreement: https://github.com/rstudio/rstudio/blob/main/CONTRIBUTING.md#contributing-code.

victorwon2001 · 2026-09-01T04:39:30Z

Replaced the unnecessary optional chaining in electron-flags.test.ts. Syntax, focused helper assertions, and whitespace checks passed; lint and the Electron test were unavailable because project-local tools are missing.

kevinushey · 2026-09-08T23:40:12Z

@victorwon2001 can you confirm if you've sent a signed CLA over?

victorwon2001 · 2026-09-09T02:11:03Z

Thanks for checking, @kevinushey. I've just emailed my signed individual CLA to [email protected].

kevinushey · 2026-09-09T17:02:39Z

Perfect, thanks! I can confirm we've received it; I'll do one more review.

kevinushey

Thanks for taking this on -- the diagnosis (Ozone is selected in ElectronBrowserMainParts::PreEarlyInitialization, before the main script can appendSwitch, so only the real argv can influence it) is right, and a one-time relaunch is a reasonable way to get the configured value onto argv.

Review outcome: 4 correctness issues that I think should be addressed before merge (--version/--help now relaunch instead of printing; dev-mode relaunch tears down the forge dev server; an unusable configured value becomes a silent exit 0; conf silently overrides an explicit CLI switch and RSTUDIO_CHROMIUM_ARGUMENTS is not consulted), plus a NEWS placement fix and a few simplifications. Details inline.

Two notes on the PR description:

typecheck, lint, and the unit tests are listed as blocked, but I ran all three on a scratch worktree of this PR's head (04b0075): npm run typecheck and npm run lint are clean, and the new spec passes 8/8 under electron-mocha. So the description and checklist can be updated.
The NEWS entry landed in version/news/os/NEWS-2026.09.0-autumn-hawkbit.md, but this PR targets main (2026.10 / Blue Mistflower), whose notes now live in the root NEWS.md. Please move the entry there (### Fixed).

gtritchie · 2026-10-02T16:16:08Z

Hi, I'm going to make the suggested fixes and push them to your branch, and see if I can get this PR merged today.

- Skip the relaunch for --help, --version, and --version-json, and in development builds, where exiting stops electron-forge's dev server - Ignore and log values other than x11/wayland, trim trailing whitespace from electron-flags.conf lines, and log the relaunch - Give --ozone-platform on the command line precedence over RSTUDIO_CHROMIUM_ARGUMENTS, and that over electron-flags.conf; neither re-applies the switch after startup, so child processes match - Decide before R detection and the login-shell query start, and name the file when electron-flags.conf cannot be read - Read the current backend from app.commandLine and append the switch instead of preserving its argv position Addresses rstudio#16594

- Resolve the config directories inside the error handler, so an appData lookup failure reaches the startup error dialog - Honor a final bare --ozone-platform in RSTUDIO_CHROMIUM_ARGUMENTS and report it as unsupported instead of using an earlier value - Compare the Ozone switch to its initial state in the utils test, since Electron sets it on Linux Addresses rstudio#16594

Chromium stops parsing switches at '--', so appending the switch after an argument list like '-- script.R' left it as a plain argument and the relaunched process kept the old backend. Only packaged builds relaunch, and they make no assumption about argv[1]. Addresses rstudio#16594

Chromium treats everything after '--' as a plain argument, so such an argument should not count as the user choosing a backend and suppress the relaunch. Addresses rstudio#16594

kevinushey

Two startup issues need correction: diagnostics loses its terminal output during relaunch, and accepted alternate Ozone switch spellings can restore the browser/child backend mismatch.

Validation: typecheck and lint passed, with two existing lint warnings. The two changed test files had 37 passing tests and one failure because the review worktree lacks an rsession binary. Linux GUI startup remains unverified.

Chromium reads '-ozone-platform' in argv as well as '--ozone-platform', and app.commandLine.appendSwitch, used for RSTUDIO_CHROMIUM_ARGUMENTS and electron-flags.conf, also drops the prefix and lowercases the name. The matchers knew only '--ozone-platform', so '-ozone-platform=x11' or '--OZONE-PLATFORM=x11' could relaunch into one backend and then switch the child processes to another. Addresses rstudio#16594

Electron's Linux relauncher sends the new process's stdout and stderr to /dev/null, which is where diagnostics reports its progress, its errors, and the rsession output. Diagnostics shows no window, so it does not need the configured backend. Addresses rstudio#16594

Addresses rstudio#16594

gtritchie added bug electron labels Aug 31, 2026

gtritchie added this to the 2026.10 (Blue Mistflower) milestone Aug 31, 2026

gtritchie removed bug electron labels Aug 31, 2026

gtritchie temporarily deployed to e2e-playwright August 31, 2026 22:11 — with GitHub Actions Inactive

gtritchie temporarily deployed to e2e-playwright August 31, 2026 22:13 — with GitHub Actions Inactive

gtritchie temporarily deployed to e2e-playwright August 31, 2026 22:30 — with GitHub Actions Inactive

gtritchie temporarily deployed to e2e-playwright August 31, 2026 22:33 — with GitHub Actions Inactive

victorwon2001 added 2 commits September 1, 2026 13:27

Fix Linux Ozone platform flags from electron-flags.conf

c6da5ca

Address feedback on rstudio#18697

04b0075

victorwon2001 force-pushed the fix/issue-16594 branch from 461d298 to 04b0075 Compare September 1, 2026 04:39

gtritchie self-requested a review September 1, 2026 15:55

victorwon2001 temporarily deployed to e2e-playwright September 2, 2026 17:02 — with GitHub Actions Inactive

victorwon2001 temporarily deployed to e2e-playwright September 2, 2026 17:10 — with GitHub Actions Inactive

victorwon2001 temporarily deployed to e2e-playwright September 2, 2026 17:11 — with GitHub Actions Inactive

victorwon2001 temporarily deployed to e2e-playwright September 2, 2026 17:17 — with GitHub Actions Inactive

kevinushey reviewed Sep 9, 2026

View reviewed changes

gtritchie added 6 commits October 2, 2026 11:12

Merge remote-tracking branch 'origin/main' into fix/issue-16594

98e35b1

Move rstudio#16594 NEWS entry to the Blue Mistflower release notes

03f1f39

Ignore Ozone-like arguments after '--' when checking the command line

801eca2

Chromium treats everything after '--' as a plain argument, so such an argument should not count as the user choosing a backend and suppress the relaunch. Addresses rstudio#16594

gtritchie changed the title ~~Fix #16594: --ozone-platform=wayland works in command line but not elect~~ Apply --ozone-platform from electron-flags.conf at startup on Linux Oct 2, 2026

Merge remote-tracking branch 'origin/main' into fix/issue-16594

72e7738

kevinushey requested changes Oct 2, 2026

View reviewed changes

Comment thread src/node/desktop/src/main/main.ts Outdated

Comment thread src/node/desktop/src/main/electron-flags.ts Outdated

gtritchie added 3 commits October 2, 2026 13:14

Merge remote-tracking branch 'origin/main' into fix/issue-16594

e9bd77b

gtritchie approved these changes Oct 2, 2026

View reviewed changes

gtritchie added 2 commits October 2, 2026 13:35

Credit the contributor in the rstudio#16594 NEWS entry

d8ae7c7

Addresses rstudio#16594

End the rstudio#16594 NEWS credit with a period

f60d120

Addresses rstudio#16594

gtritchie merged commit 69f003e into rstudio:main Oct 2, 2026
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victorwon2001 commented Aug 31, 2026 •

edited by gtritchie

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