Is there a way to cancel/timeout a Map::renderStill?

[xabbu42]

We have a renderserver to render a raster on the server from a maplibre style using HeadlessFrontend::render which itself uses Map::renderStill. To better handle overloads we would like to timeout single render requests and also cancel them as soon as the connection gets closed. Is there a way to do that already?

[louwers]

No, I don't think so. The MapSnapshotter does seem to have something like that though.

maplibre-native/platform/default/src/mbgl/map/map_snapshotter.cpp

Line 291 in 8778246

void cancel() { renderStillCallback.reset(); }

Should be possible to add a method to Map to support it.

[xabbu42]

Sorry for the long silence, was occupied with other things.

I did not understand how MapSnapshotter could do this without support from Map. And in fact adding a test for getting another snapshot after a cancel does trigger the same error we our self did run into namely "Map is currently rendering an image".

[xabbu42]

I also tried calling HeadlessFrontend::reset in a timer after starting a HeadlessFrontend::render. The result is that the render never stops and just busyloops, presumably waiting on an event which will never happen because of the reset. Is that an abuse of the Api or should maybe HeadlessFrontend::reset() abort a running render with an appropriate error?