When the browser dropped the page's WebGPU device or WebGL context, the
editor kept running but nothing it drew reached the screen: Chrome and
WebKit showed a frozen, stale canvas and Firefox a blank page, while
edits and Save went on.
- ui-egui: new `graphics` module. `GraphicsLoss` carries a loss report
from any thread (wgpu's device-lost callback, the canvas's
`webglcontextlost` event) to the UI thread. `VectorcraftApp::
graphics_lost` writes Data Recovery copies of the modified documents at
once. The app now notices when the host hands it a new egui context and
uploads everything again (fonts and theme, the canvas, place cursor
thumbnails); every per-thread texture cache (layer, symbol, swatch,
style, asset and glyph thumbnails, previews, font samples, Navigator,
Flattener Preview) is a `TexCache` that empties for a new context.
Without this, the moved app drew stale or wrong textures and egui
panicked on its missing font families.
- web: the shell watches both loss signals; on a loss it puts a fresh
canvas in place of the dead one and starts the same `WebRunner` again,
handing over the same app (documents, undo, panels), with services made
for the new context and a status-bar note. If no new graphics can be had
(or after three losses) it removes the stale canvas, lets go of the
recovery copies and says to reload.
- engine: `recovery::leave` lets go of a session's area but keeps its
copies, so the reloaded page offers them at once instead of after the
heartbeat goes stale.
- desktop: eframe can't give a window a new device, so a lost device
(driver reset) is logged, the copies are written and the status bar says
to save and restart; closing then skips the Save Changes question it
can't show.
- Tests: loss reporting across threads, `TexCache` emptying, the app
uploading the canvas, a cached preview, theme and fonts again in a new
context (fails without the fix), copies written on loss, and
`recovery::leave` offering copies at once with both lock and heartbeat
stores. docs/development.md (web section) and ROADMAP updated.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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