[DRAFT] WIP QML Load Snapshot Signet (160,000 height)

[D33r-Gee]

Based on #421. For evaluation purposes only!

GUI Integration for UTXO Snapshot Loading

Overview

This PR adds initial GUI support for loading a signet UTXO snapshot at height 160,000, building on Bitcoin Core's assumeutxo infrastructure.

What This PR Does

1. Adds a basic GUI interface for loading UTXO snapshots via the Connection Settings panel
2. Implements non-blocking snapshot loading via QT Thread
3. Provides visual confirmation of snapshot activation
4. Adds a snapshot progress notifications accessible via a handler

Implementation Details

Core Components Modified

1. Node Interface (src/node/interfaces.cpp)

• Implements snapshotLoad() based on the loadtxoutset RPC
• Uses background QT thread for non-blocking operation

2. QML Integration (src/qml/models/nodemodel.cpp)

• Manages snapshot loading state and progress
• Introduces a worker class to manage snapshot metadata
• Uses Qt's thread system to prevent UI blocking
• Provides progress updates via Qt signals

3. UI Components (src/qml/components/SnapshotSettings.qml)

• File selection dialog
• Snapshot verification status
• Progress tracking and visualization

Key Design Decisions

1. Non-blocking Implementation

• Snapshot loading runs in separate QT thread
• UI remains responsive during load

2. Extensibility

• Interface designed to accommodate future assumeutxo changes
• Error handling framework in place

Testing Instructions

1. Build
2. Launch Bitcoin Core QML GUI
3. Navigate to Connection Settings
4. Test with sample snapshot:

magnet:?xt=urn:btih:9da986cb27b3980ea7fd06b21e199b148d486880&dn=utxo-signet-160000.dat

6. Verify (see screenshots below):
   • "Snapshot Loaded" confirmation appears
   • Block clock shows ~50% progress
   • For errors, check debug.log for [snapshot] or [loadsnapshot] messages

Ubuntu 22.04 Screenshots

Expected Behavior

• File selection dialog works
• Success/failure state properly displayed
• Node becomes usable while background validation continues

Future Work

1. Error Handling

• Add user-facing error messages
• Implement recovery paths
• Add snapshot validation UI once background validation has completed

2. Integration

• Coordinate with upstream assumeutxo changes
• Add support for network-specific snapshots (testnet and mainnet)
• Integrate with initial setup wizard

Notes for Reviewers

Snapshot Compatibility

• Currently only works with signet UTXO snapshot
• Limited to specific 160,000 height
• Validates against chain parameters m_assumeutxo_data (the changes there can be discarded once synced since m_assumeutxo_data is already hardcoded)

This is a work in progress - feedback welcome on the approach and implementation details.