Throttled progress/cancel callback for load_obj_buf - #79
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LoadOptions gains progress_callback: Option<LoadProgressCallback> (Arc<dyn Fn(&LoadProgress) -> ControlFlow<()> + Send + Sync>, an options field rather than a second _with_progress function), invoked every 1000 lines during load_obj_buf's parse loop. Returning ControlFlow::Break stops the load and returns the new LoadError::Cancelled. No behavior change when progress_callback is None (the default): verified by a test comparing output with and without a no-op callback. load_obj_buf_async is untouched.
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Summary
LoadOptionsgainsprogress_callback: Option<LoadProgressCallback>(Arc<dyn Fn(&LoadProgress) -> ControlFlow<()> + Send + Sync>), an options field rather than a second_with_progressfunction, so a caller can observe throttled progress and cooperatively cancel a load of a large OBJ buffer.load_obj_buf's parse loop. ReturningControlFlow::Breakstops the load and returns the newLoadError::Cancelled.progress_callbackisNone(the default): verified by a test comparing output with and without a no-op callback.load_obj_buf_async(thefutures/tokiovariants) is intentionally untouched — that's a materially different code path deserving its own design pass.LoadOptionsloses itsCopyderive (Arcisn'tCopy); every existing call site in this crate already passes&LoadOptions, so nothing else needed to change.Motivated by a real use case: an interactive mesh-editing tool importing large OBJ files needed a way to show progress and let a user cancel a slow import without the caller being able to observe anything until the whole call returned.
Test plan
cargo test --all-features: 21 lib tests + 5 doctests pass, including 3 new tests (test_progress_callback_noop_matches_no_callback,test_progress_callback_cancels_load,test_progress_callback_is_throttled)cargo fmt --all -- --check: cleancargo clippy --all-targets --all-features -- -D warnings: clean (exit 0)