## Summary
Migrates 14 ConPVP lobby/tournament gumps from legacy `Gump` to modern `DynamicGump`/`StaticGump<T>`. Layouts move into `BuildLayout(ref DynamicGumpBuilder)`, constructors become private, and validation moves into static `DisplayTo` entry points (empty-gump rule).
**Per-gump base type decisions:**
- `BeginGump` → `StaticGump<BeginGump>`: layout is fully fixed (no dynamic content). All other gumps below are `DynamicGump` because they bake dynamic player names, guild abbreviations, ruleset titles, arena names, tournament participant names, ladder rankings, or per-instance rule modifications. Per the cliloc/dynamic-text rule, dynamic content forces `DynamicGump`.
- `ReadyGump`, `ReadyUpGump` → `DynamicGump` (per-instance participant rosters).
- `AcceptDuelGump`, `AcceptTeamGump`, `ConfirmSignupGump` → `DynamicGump` (challenger/registrar/team names, dynamic rule modifications).
- `PickRulesetGump`, `RulesetGump` → `DynamicGump` (ruleset titles and option labels per instance).
- `ParticipantGump`, `DuelContextGump` → `DynamicGump` (player rosters/team labels).
- `LadderGump` → `DynamicGump` (ladder entries: ranks, levels, guild abbrs, names, wins/losses).
- `ArenaGump` → `DynamicGump` (arena names with active player names).
- `PreferencesGump` → `DynamicGump` (arena name list).
- `TournamentBracketGump` (~1k LOC) → `DynamicGump`. The whole gump is one type-switched view that re-renders on every button press across `Index`, `Rules_Info`, `Participant_List`, `Participant_Info`, `Round_List`, `Round_Info`, `Match_Info`, `Player_Info`. All branches bake per-instance content.
**Refresh-via-this conversions (the big perf wins):**
- `LadderGump`: page +/- now mutates `_page` and calls `from.SendGump(this)` instead of allocating a new `LadderGump`.
- `PickRulesetGump`: ruleset apply / flavor toggle now refreshes via `this`.
- `ParticipantGump`: increase/decrease team size, remove player, target failure all refresh via `this`.
- `DuelContextGump`: failed-start and add-participant refresh via `this`.
- `ConfirmSignupGump`: every signup-validation rejection branch in `OnResponse` and every `AddPlayer_OnTarget` rejection branch refreshes via `this` (was allocating a new gump per branch).
- `TournamentBracketGump`: every navigation button (back/forward, type change, page change, drill-down) mutates `_type`/`_object`/`_list`/`_page` and refreshes via `this`. Previously each click allocated a new 1k LOC gump.
All gumps are `Singleton`, use private constructors with static `DisplayTo` entry points that null-check `NetState` before allocation. External callers in `DuelContext`, `TournamentBracketItem`, `TournamentController`, `TournamentSignupItem`, and the cross-references between `AcceptDuelGump`/`ParticipantGump`/`AcceptTeamGump`/`ConfirmSignupGump` are all updated to use `DisplayTo`. Legacy `m_X` fields renamed to `_x` per coding standards.
## Summary
- **Add a self-referencing `InterpolationHandler` to `ValueStringBuilder`** that writes directly into the builder's buffer — zero intermediate allocation, works with `stackalloc`-backed builders
- **Replace all `System.Text.StringBuilder` usage** across the codebase with `ValueStringBuilder`
- **Convert `ValueStringBuilder.Create()` to `stackalloc`** at 10 sites where output length is provably bounded
- **Convert manual `Dispose()` to `using var`** where possible, and hoist loop-scoped builders outside loops with `Reset()`
- **Convert verbose `Append()` chains to `Append($"...")`** interpolation for readability
- **Add comprehensive documentation** for string handling patterns
## InterpolationHandler Design
`ValueStringBuilder` is a `ref struct`, which creates challenges for C#'s interpolated string handler pattern:
- **`ref` fields to ref structs are not allowed** (CS9050)
- **`[InterpolatedStringHandlerArgument("")]` passes struct receivers by value**, not by ref
- **`ISelfInterpolatedStringHandler` requires boxing** ref structs into interface fields
**Solution: Copy-and-reconcile pattern.** The handler receives a value copy of the builder. The copy shares the same underlying `char` buffer (`Span` points to the same `stackalloc`/pooled memory), so writes go to the original buffer. `Append()` reconciles by `this = handler._builder`, updating `_length` and any buffer references changed by `Grow()`.
This is safe because:
- The game loop is single-threaded — no concurrent access between handler construction and reconciliation
- If `Grow()` occurs in the copy, the original's stale buffer isn't accessed until `Append()` replaces it
- `Dispose()` correctly returns the reconciled buffer to the pool
## Changes by Category
### ValueStringBuilder (`Projects/Server/Buffers/ValueStringBuilder.cs`)
- Added nested `InterpolationHandler` ref struct with copy-and-reconcile pattern
- Added `Append([InterpolatedStringHandlerArgument("")] scoped ref InterpolationHandler)` method
- Removed `RawInterpolatedStringHandler` overloads (new handler replaces them)
- All `AppendFormatted` overloads delegate to existing `Append` methods (no code duplication)
- Alignment support via direct private field access (nested type privilege)
### StringBuilder → ValueStringBuilder (15 files)
Replaced all `new StringBuilder()` with `ValueStringBuilder.Create()` or `stackalloc`:
- ConPVP games: KingOfTheHill, DoubleDom, CTF, BombingRun, TourneyMatch
- ConPVP infrastructure: Tournament, Participant, TourneyParticipant
- ConPVP gumps: ArenaGump, TournamentBracketGump, AcceptTeamGump, ConfirmSignupGump
- Commands: Handlers, Logging, Add
- Other: TownCrier, SpeechLogGump, TestCenter
Key patterns:
- `sb = new StringBuilder()` reassignment → `sb.Reset()`
- `sb.AppendFormat("{0:N0}", value)` → `sb.Append($"{value:N0}")`
- `sb.Append(x).Append(y)` chains → separate statements (VSB returns void)
### Create() → stackalloc (10 files)
Converted heap-allocated builders to stackalloc where output is bounded:
- ClientVersion (32), MapSelection (160), HouseRaffleStone (48)
- HolySense (96), UnholySense (96), ClientVerification (192)
- AcceptTeamGump (64), ConfirmSignupGump (64)
- BaseWeapon (160), BaseArmor (128)
### Loop optimizations (2 files)
Hoisted `ValueStringBuilder` creation outside loops with `Reset()` per iteration:
- TourneyMatch.cs: `using var` inside for loop → stackalloc before loop
- ArenaGump.cs: `Create()` + `Dispose()` per iteration → stackalloc before loop
### Append chain → interpolation (5 files)
Converted multi-line `Append()` chains to `Append($"...")`:
- BountyMessage.cs: title switch (6 cases), paragraph (15→1 Append), description lines, closing
- AcceptTeamGump, ConfirmSignupGump, TournamentBracketGump: tournament type strings
- AdminGump: comment/tag formatting in loops
### Documentation
- `dev-docs/string-handling.md`: Full reference — construction, interpolation, disposal, decision guide
- `dev-docs/claude-skills/modernuo-string-handling.md`: Claude skill with quick reference
- `CLAUDE.md`: Added rule 17 (no StringBuilder), dev-docs table entry, skills table entry
- `dev-docs/code-standards.md`: Updated memory management section
## Test Plan
- [x] `dotnet build` — 0 errors, 0 warnings
- [x] `dotnet test` — 940/940 tests pass
- [x] 28 ValueStringBuilder tests covering all reconciliation scenarios:
- Stackalloc no-grow, stackalloc with grow (→pool transition)
- Heap no-grow, heap with grow, heap double grow
- Pre-existing content with and without grow
- Sequential multiple `Append($"...")` calls
- Mixed plain + interpolated Append
- Empty interpolation, literal-only, format specifiers
- Null string holes, ISpanFormattable types
- Dispose after stackalloc→pool grow
> [!IMPORTANT]
> **Developer Note**
> THIS IS A BREAKING CHANGE TO THE NEW API GUMP.
> Please give us feedback in [discord ](https://muo.gg/discord) if you have issues, need help, or have ideas for a better API change!
### Summary
* Adds support for size/style to dynamic/static builder.
* Drastically simplifies the dynamic/static builder api for AddHtml.
* Cleans up some legacy gump files.
> [!Important]
> **Developer Note**
> This code change will **completely move gumps out of the core**
### Summary
- Adds `GetGumps()` convenience which exposes methods to Find/Close/Send multiple gumps. This helper is a performance improvement by eliminating the Dictionary<Player, List> lookup for gumps.
