[DRAFT] WIP Qml Load Snapshot Onboarding

[D33r-Gee]

Based on #424. This is a WIP.

UTXO Snapshot Loading with Onboarding Support

Overview

This PR enables loading a signet UTXO snapshot at height 160,000, during the initial onboarding process.

What This PR Does

1. Enables snapshot selection during onboarding, with loading when headers are synced

Implementation Details

Core Components Modified

1. CPP Backend (src/qml/models/nodemodel.cpp)

• Adds support for storing snapshot file path during onboarding
• Implements automatic snapshot loading once headers are synced

2. UI Components (src/qml/components/SnapshotSettings.qml, src/qml/components/ConnectionSettings.qml)

• File selection dialog with onboarding awareness
• Snapshot verification status
• Progress tracking and visualization
• Updated visibility conditions to enable loading during onboarding

Key Design Decisions

1. Onboarding Integration

• Allows users to select snapshot during setup
• Delayed loading until headers are synced
• Proper state handling between onboarding and regular modes

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. Test onboarding flow:

   • Select a snapshot file during initial setup
   • Verify it loads automatically after headers sync

7. 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
• When selected during onboarding, snapshot loads after headers sync

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)

feedback welcome on the approach and implementation details.

[GBKS]

I just tested this, screenshots of my journey are below.

There are various visual tweaks that need to be done to match the design, but those can be done in a follow-up PR. The auto-refresh for when headers are synced is nice. I don't think we covered this state ("headers are syncing") in the design, we should make sure to add it in.

Functionality-wise, the only problem I had was getting a snapshot file that works. The magnet link in the description did not have enough peers, and the one I downloaded here also did not work. Gee then directly sent me the file and that worked.

When using the wrong file, I was expecting a proper error message, but did not get one. The screen just went back to its original state. We should make sure to have good errors here, so people know how to do things correctly. Important requirements that people might frequently stumble over could also be put in the description.

I'll leave it to others to decide whether to merge this in or not, based on more technical evaluations and PR planning.

[D33r-Gee]

When using the wrong file, I was expecting a proper error message, but did not get one. The screen just went back to its original state. We should make sure to have good errors here, so people know how to do things correctly. Important requirements that people might frequently stumble over could also be put in the description.

Thanks @GBKS for testing and reviewing the design! I have incorporated your feedback in #424 since that one has been undrafted.

Will update this PR with the error handling next.

[D33r-Gee]

with cac8de9 rebased on top of #424 to allow for error handling if an incorrect snapshot gets picked. This works with both the Onboarding and post onboarding use cases.

This is a WIP, feedback welcomed!