Qt: defer Spark GUI callbacks during validation

[reubenyap]

PR intention

Alternative to #1940 for the Qt freeze during Spark batch verification. Long validation holds cs_main, while the queued incoming-fund scan, auto-mint activation check, and Spark address-book refresh can wait for that lock on the GUI thread.

Code changes brief

Use existing TRY_LOCK and Qt timer patterns to defer these automatic callbacks. The startup scan and each busy address-book page retry after MODEL_UPDATE_DELAY (250 ms); auto-mint retries on its next timer tick. Address choices remain intact while busy. Each page retries independently because the shared refresh may finish when another page succeeds.

Two production files, 25 additions and 3 deletions. Core proof verification remains serialized, preserving master's historical batching and recent-block verification behavior. Independent of #1940, based on master 4f0c771462b2f327e3a7ff7bf2532bc33c727713; deferred-proof drain and recovery-marker improvements remain separate work.

Qt regression tests cover chain/wallet lock contention, automatic retries without another block notification, and preservation of address choices.

Integration with #1914 at 425c6db was checked in an isolated test merge. Production code merges cleanly. Resolve the two conflicts in src/qt/test/CMakeLists.txt and src/qt/test/test_main.cpp by retaining both test suites and #1914's resource/settings setup. The combined GUI has not been built or exercised.

Validation at 82c9f8f (CI run):

• Linux Debug and RelWithDebInfo builds passed. cd build && ctest --output-on-failure passed 94/94 tests in each, including test_firo-qt. qa/pull-tester/rpc-tests.py -extended passed in both configurations.
• Windows and macOS CMake builds passed in both configurations. Jenkins branch validation passed. Four Guix jobs passed; the Windows Guix job is still at Install Guix.
• git diff origin/master...HEAD --check and git merge-tree --write-tree --messages origin/master origin/pr1950-thorough-review passed against the current base. The resolved Qt: Redesign wallet UI with light/dark theme support #1914 integration diff check also passed.

Local Qt development files are unavailable, so no local GUI build/test was run. A live batch-sync GUI run has not been reproduced. Keep this draft until the reported hang is verified fixed; these callbacks are not proven to be its only cause.

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[reubenyap]

@CodeAnt-AI review

[codeant-ai]

🤖 CodeAnt AI — Review Status

Status	Commit	Started (UTC)	Finished (UTC)
✅ Reviewed your PR	cf87a06	Sep 08, 2026 · 02:36	02:38

[codeant-ai]

User description

PR intention

Alternative to #1940 for the Qt freeze during Spark batch verification. Long validation holds cs_main, while the queued incoming-fund scan, auto-mint activation check, and Spark address-book refresh can wait for that lock on the GUI thread. Defer these automatic callbacks when validation is busy.

Code changes brief

Use existing TRY_LOCK and Qt timer patterns. The startup scan retries after MODEL_UPDATE_DELAY; the periodic auto-mint check retries on its next tick; address-book refresh preserves its current choices and returns false so the existing block-tip path retries. Core proof verification stays serialized, with master's historical batching and recent-block verification behavior preserved.

Two production files, 21 additions and 3 deletions. Qt regression tests cover chain/wallet lock contention, retry without another block notification, and preservation of address choices. Independent of #1940, based on master 4f0c771462b2f327e3a7ff7bf2532bc33c727713; the base branch's deferred-proof drain and recovery-marker limitations remain separate work.

Validation: git diff --cached --check passed. Local GUI configuration failed because the Qt development package (6.7.3 or newer) is unavailable. The new test_firo-qt cases and a live batch-sync GUI run have not been run. This draft identifies concrete blocking callbacks from source; it does not establish that these are the only causes of the reported freeze. Require Qt CI and reproduction of the reported hang before replacing #1940.

Local configuration command (PowerShell, MSYS2 UCRT compiler on PATH):

C:\msys64\ucrt64\bin\cmake.exe -G Ninja -S . -B build-qt -DCMAKE_C_COMPILER=C:/msys64/ucrt64/bin/cc.exe -DCMAKE_CXX_COMPILER=C:/msys64/ucrt64/bin/c++.exe -DCMAKE_MAKE_PROGRAM=C:/msys64/ucrt64/bin/ninja.exe -DCMAKE_BUILD_TYPE=Debug -DBUILD_GUI=ON -DBUILD_TESTS=ON -DBUILD_GUI_TESTS=ON -DWITH_ZMQ=OFF -DWITH_QRENCODE=OFF -DWITH_DBUS=OFF

---

CodeAnt-AI Description

Keep the Qt interface responsive while Spark validation is running

What Changed

• Incoming-fund scanning, automatic mint checks, and Spark address updates no longer wait for busy validation operations on the interface thread.
• Deferred startup scans retry automatically without requiring a new block or transaction notification.
• Address selections remain unchanged when an update is deferred, and refresh on the next block-tip update.
• Added regression coverage for chain and wallet lock contention across these Spark actions.

Impact

✅ Fewer Qt freezes during Spark validation
✅ Automatic incoming-fund scans recover without new notifications
✅ Address choices remain intact during busy updates

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[reubenyap]

No additional actionable issues were found at 82c9f8f5c628d7b9f16a54eee15ce698b3ff91cf.

I traced the three GUI callbacks through their callers and lock ordering, checked timer lifetimes, retry behavior, and address-choice preservation, reviewed the contention tests and existing discussion, and confirmed the current Linux Debug/RelWithDebInfo Qt tests passed. git diff --check also passes.