fix(qt): stable sort for equal items in Coin Control dialog

[UdjinM6]

Issue being fixed or feature implemented

CCoinControlWidgetItem::operator< had no tiebreaker for equal numeric values (amount, date, confirmations, CoinJoin rounds), causing Qt's unstable sort to produce a different ordering on each updateView() call whenever coins with identical values were present.

Noticed while testing #7155 - clicking "(un)lock all" button shifted rows with the same amount when list was sorted by amounts.

What was done?

Add a secondary sort by outpoint (txid:vout), which is unique and stable across view rebuilds.

How Has This Been Tested?

Build it on top of #7155, run and click "(un)lock all" button in Coin Control dialog - should be stable now.

Breaking Changes

n/a

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone

[coderabbitai]

Walkthrough

The change modifies the sorting logic in the coin control dialog to ensure deterministic ordering of items. When primary sort keys (amount, date, confirmations, coinjoin rounds) are equal, the new logic introduces a stable tiebreaker by comparing items based on transaction ID and output index (txid:vout), then by output number (vout). This ensures consistent and reproducible sorting results across identical data.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately reflects the main change: adding stable sorting for equal items in the Coin Control dialog by implementing a tiebreaker mechanism.
Description check	✅ Passed	The description is directly related to the changeset, clearly explaining the sorting instability issue, the fix applied, and how it was tested.

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[coderabbitai]

🧹 Nitpick comments (1)

src/qt/coincontroldialog.cpp (1)

46-51: Optional: tiebreaker is inert for tree-mode parent nodes.

In tree mode, parent (itemWalletAddress) nodes have COLUMN_AMOUNT UserRole data (line 792) but never receive TxHashRole/VOutRole (those are set only on child items at lines 764-767). When two parent nodes share the same total amount, the tiebreaker compares empty strings and then 0 < 0, always returning false — so ordering among same-sum parents is still nondeterministic.

This is a minor edge case (parents represent distinct addresses, so collisions are rare) and doesn't undermine the primary fix. If you ever want full stability, you could fall back to the wallet-address string for parent nodes.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/qt/coincontroldialog.cpp` around lines 46 - 51, The current tiebreaker in
coincontroldialog.cpp compares TxHashRole and VOutRole which are only set on
child items, so parent nodes (itemWalletAddress) with equal amounts compare
empty/zero and remain non-deterministic; update the comparison in the relevant
compare/operator (the block using data(..., TxHashRole) and VOutRole) to detect
missing/empty TxHashRole (or missing VOutRole) and, for those cases (i.e.,
parent nodes), fall back to comparing the address string from COLUMN_ADDRESS (or
another stable identifier like the item text) to produce a deterministic
ordering for parent nodes while keeping the existing child-item outpoint
tiebreaker.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/qt/coincontroldialog.cpp`:
- Around line 46-51: The current tiebreaker in coincontroldialog.cpp compares
TxHashRole and VOutRole which are only set on child items, so parent nodes
(itemWalletAddress) with equal amounts compare empty/zero and remain
non-deterministic; update the comparison in the relevant compare/operator (the
block using data(..., TxHashRole) and VOutRole) to detect missing/empty
TxHashRole (or missing VOutRole) and, for those cases (i.e., parent nodes), fall
back to comparing the address string from COLUMN_ADDRESS (or another stable
identifier like the item text) to produce a deterministic ordering for parent
nodes while keeping the existing child-item outpoint tiebreaker.

[github-actions]

✅ No Merge Conflicts Detected

This PR currently has no conflicts with other open PRs.

[PastaPastaPasta]

utACK

[knst]

utACK 49c3a72