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Show Positron's Viewer stop button for Quarto previews - #1193
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seeM
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Works well! I left a review with some feedback in the Positron PR.
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…stoppable`) (#16602) - Addresses #10753 - Related to quarto-dev/quarto#1193 ### Summary Extensions that show content with `positron.window.createPreviewPanel` can now show a stop button in the Viewer, with the first example being the Quarto extension. <img width="1476" height="946" alt="Screenshot 2026-10-12 at 6 21 49 PM" src="https://github.com/user-attachments/assets/83dd4d91-c355-442b-ae7a-e6f73bf760a0" /> Before this PR, the Viewer had no stop button for a Quarto preview. This PR adds two members to `PreviewPanel`: - `stoppable`: the extension sets this to `true` while its process runs, and to `false` when the process stops. While it is `true`, the Viewer shows a toolbar with a stop button and a clear button. - `onDidRequestStop`: fires when the user clicks the stop button. The Viewer hides the button before it fires the event. The extension stops its process, and also decides if the preview closes. The Viewer does not try to find out if the process runs and instead, the extension owns that state. Panels from `previewUrl` keep their current stop button, which uses a `PreviewSource`. ### The approaches I tried before I had tried some other approaches for this, and WOW, they did not work out well. In one version, I gave `createPreviewPanel` panels a `PreviewSource`, the same as `previewUrl` panels. Positron found the terminal from the PID and watched it, showing the button while a process ran in the terminal, sending <kbd>Ctrl+C</kbd> on a click, and closing the preview when the process stopped. It did NOT work well and was QUITE a lot of code; having the extension in charge here turned out a lot better. ### Release Notes #### New Features - Extensions that use `positron.window.createPreviewPanel` can show a stop button in the Viewer with `PreviewPanel.stoppable` and `onDidRequestStop` (#10753) #### Bug Fixes - N/A ### Validation Steps @:viewer @:apps @:quarto Together with the Quarto PR at quarto-dev/quarto#1193: 1. Install the Quarto extension from the branch of the Quarto PR. 2. Open a `.qmd` file and run _Quarto: Preview_. 3. Make sure that the Viewer shows a stop button on the right side of its toolbar. 4. Save the document. Make sure that the button stays and that the toolbar does not move. 5. Click the stop button. Make sure that the preview server stops and that the preview closes. 6. Run _Quarto: Preview_ again. Press <kbd>Ctrl+C</kbd> in the Quarto Preview terminal. 7. Make sure that the stop button goes away and that the preview stays open. 8. Start a Shiny or Streamlit app with the App Launcher. Make sure that the URL bar and its stop button work as before.
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PreviewPanel.stoppable) posit-dev/positron#16602In Positron, the Viewer now shows a stop button for Quarto previews. Before this PR, the only way to stop
quarto previewwas to find the Quarto Preview terminal and press Ctrl+C or close the terminal.The Positron PR adds
PreviewPanel.stoppableandonDidRequestStopto the Positron API. The extension setsstoppablewhile the preview server runs, and Positron shows the button and reports clicks. Quarto starts and stops the server, so Quarto decides when the button shows.The extension uses feature detection (
"onDidRequestStop" in panel), not a version check. On older Positron versions and in VS Code, nothing changes. A local type covers the new members until@posit-dev/positronships them, soengines.positrondoes not change.Some known limitations:
cmdpath), Ctrl+C in the terminal leaves the button visible until the terminal closes. A click on this button does no harm, and it closes the preview.Verification
yarn build-test: passes, includingtsc --noEmit.yarn test(labelmain): the 6 new tests pass. 178 passing, 3 pending, 1 failing. The failure is the notebook renderer build test, which fails on stale chunks in my localout/markdownit. This PR does not change that code.