## 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
### Summary
Fixes weapons not serializing lesser poison.
> [!NOTE]
> Dev Note: After applying this fix, fix weapons already in-game using the following command
> `[global set poison lesser where baseweapon poison = null poisoncharges > 0`
## Summary
### Changes
- Adds `[IgnoreDupe]` and `[SerializedIgnoreDupe]`
- Updates all _known_ classes that need the attribute. Some might be missing, please helps us find them!
- Adds `Item.Dupe()` command and encapsulates `CopyProperties` and `OnAfterDuped`. This is also overridable.
- Updates Dupe command to use the new logic.
- Fixes duping multiple kinds of objects that used to be outright broken.
### Bug Fixes
- Fixes issue with durability after duping
- Fixes issue with hue after duping
> [!Note]
> **Developer Note**
> Customizing how duping an item works now requires two steps:
> 1. Add `[IgnoreDupe]` or `[SerializedIgnoreDupe]` to the property/field
> 2. Add custom logic in an `OnAfterDuped` override
>
> When do you need to do this?
> *When the property being copied is not a primitive, and you need to manually deep-clone the contents of the property such as with Lists, Dictionaries, or sub classes.*
> [!IMPORTANT]
> Please read through these changes, as they changed certain expectations for how the internal AI thinking/movement work.
> Note that some mobs still don't have smooth movement on ClassicUO due to how the client handles animations/movement.
### Summary
- **Important Change**: Mobs will now move at a more regular pace. If the OnThink results in a move, but the cooldown would otherwise prevent the move, then the movement is scheduled on another timer.
- Added a 400ms delay to mobs turning to face a player to attack in order to avoid glitching between moving and turning.
- Reverted AI thinking speeds back to RunUO specific speeds.
- Reverted the AI thinking to moving conversion delays back to RunUO.
- For thinking speeds that are not exactly the predefined speeds from RunUO, there is a new calculation to determine the correct conversion to movement speed. This stops speeds like `0.35` from being faster than `0.3`
> [!NOTE]
> **Developer Note**
> BaseAI.CheckMove() no longer contains the check for whether or not a mob is on movement cooldown. This function can now be overwritten without causing issues to figuring out that cooldown.
### Summary
- [X] Lightning arrow no longer allows SDI
- [X] Lightning arrow now proc's even without arrows
- [X] Fixed NPE with lightning arrow when a monster is already killed.
### Summary
Eliminates `IPooledEnumerable<T>` and `eable.Free()` from `Map` for mobiles. This drastically simplifies code that iterates in range, for example:
```cs
foreach (var m in m.GetMobilesInRange(5))
{
}
```
The code above no longer requires an eable and calling `Free()`.
- [X] Fixed several locations where an NPC that was damaged would cause a server crash.
- [X] Removed an unnecessary allocation in guard fake calls (NPCs calling guards on you)
- [X] Fixes damage precision loss in Poison Strike Spell
- [X] BogThing no longer attempts to "search" for boglings to eat when it is at full health
### Summary
- [X] Fixed a bug where entity persistence was serialized out of order, causing world corruption.
- [X] Fixed LastSerialized not being utilized properly and dangling references still becoming an issue.
- [X] Added a new `GenericEntityPersistence<T>` type to encapsulate `ISerializable` serialization.
- [X] Removing the custom logic and moved Items, Mobiles, Guilds, and Accounts to GenericEntityPersistence.
- [X] Changed serialization to use the singleton pattern to reduce calling methods from stored variables.
## MAJOR CHANGE (API BREAKING)
Moved the virtues to it's own system _VirtueSystem_. This should make it easier to extend or remove the virtue system. Virtues will be saved to a new folder called _Virtues_.
### Motivation
The motivation was also two-fold, performance/stability, and to fix bugs.
First, virtues is the second system (first is murders), that has a pre-world-save check on _every mobile in the game_ to atrophy virtue stats. This is taxing since it freexes the world and makes world saves take longer. Every mobile had Gain/Loss dates for each virtue, whether they needed them or not. Most players don't even use the virtue system, so this will increase performance considerably.
Second, when I tried to optimize/refactor the code, I found several bugs that needed to be fixed.
### Major API Changes
- [X] The properties on players related to virtues are gone. Use `pm.GetVirtues()?.<PropertyName>` instead.
- [X] Virtues were removed from non-player Mobiles.
- [X] `pm.JusticeProtectors` was removed. Use `JusticeVirtue.GetProtector()` or `JusticeVirtue.GetProtected()` instead.
### Screenshots
<img width="221" alt="Props-1" src="https://github.com/modernuo/ModernUO/assets/3953314/5c09cb83-b8d5-44a2-b899-a7ed7cd736ac">
<img width="220" alt="props-2" src="https://github.com/modernuo/ModernUO/assets/3953314/aeade4d3-8df0-47bd-955a-a864d0946cf7">
* Movie ignore mobiles to Mobile class
* Allow necromancer familiars to ignore mobiles
* ChampionSpawn should not quietly fail when creating new spawn
* Fix client party crash bug: 2 people partied, the leader logs out, other client is hung
* Fix spellbooks creating with magery/meditation only and creating magery multiple times
* Fix BaseRunicTool.GetRandomSlayer() creating more undead slayers than intended
* Do not allow players to dismount each other whilst mounted
* Fix AOS onwards damage increase tooltip and wrong formula in AOS
* Fix monsters killing other monster revenants + animate dead should not attack player pets + other animates
* Fix fire steed having loot pack added twice
* Fix oaks spawn not able to create Unicorns + Kirins via Activator.CreateInstace() due to constructor having name as parametr
* Fix ignoreMobiles flag not propagated to client for non-players.
* Fix harrower tents not leeching from players
* Fix boats speedhacking around the map
* Fix bless, agility etc. not renewing duration
* Fix reveal always worked
* Fix empty constructor for steeds so they don't throw now.
## Changes
- [X] Adds OPL convenience methods
- `opl.Add(cliloc, value)` and `opl.Add(value)` - value as an integer or string works just like `opl.Add(cliloc, $"{value}")`
- `opl.AddLocalized(cliloc, clilocValue)` - works the same as `opl.Add(cliloc, $"#{clilocValue}");`
- [X] Simplifies basic `list.Add()` situations
- [X] Changes cliloc as an argument so it works with custom IPropertyList implementations (HTML)
- [X] Fixes plants so they support the old localization and new (changed in 7.0.12.0+)
- [X] Exposes more methods to override for Item to make creating custom OPL possible.
## Important Notes
* Using a ternary as an argument, like this `opl.Add(number, showType ? $"{type}\t{value}" : $"{value}");` _will not use the correct string interpolation_. This means if you use a custom PropertyList (for HTML or some other purpose), the property list won't be localized properly.
* All localization values must be interpolated, even if they are literal strings, or integers. Example: `opl.Add(number, $"{"Charges"}\t{m_Charges}");` is correct. Using the following: `$"Charges\t{m_Charges}"` will not work for custom PropertyList implementations!
## Breaking Changes (New API)
ObjectPropertyList supports the following API:
```cs
list.Add(500000);
list.Add(500001, stringArgument);
list.Add("Some text");
list.Add($"Some text with {argument}");
list.Add(500002, $"{arg1}\t{arg2}");
```
## Notes
1. All API uses that require a formatter like this:
```cs
list.Add(500002, "{0}\t{1}", arg1, arg2);
```
Should be changed to use string interpolation, for example:
```cs
list.Add(500002, $"{arg1}\t{arg2}");
```
2. The following paradigm should no longer be used:
```cs
list.Add(1061170, prop.ToString()); // strength requirement ~1_val~
```
The new string interpolation API will avoid having to convert the argument to a string before writing it to the packet. Instead use the following:
```cs
list.Add(1061170, $"{prop}"); // strength requirement ~1_val~
```
### Benchmarks
```cs
| Method | Mean | Error | StdDev | Gen 0 | Allocated |
|------------------------------- |---------:|--------:|--------:|-------:|----------:|
| BenchmarkOldOPL | 241.0 ns | 0.56 ns | 0.47 ns | 0.0105 | 88 B |
| BenchmarkStringInterpolatedOPL | 199.9 ns | 2.44 ns | 2.39 ns | - | - |
```
### Changes
- [X] Removes crash in STArray.Return when array is null.
- [X] Fixes NPE in OPL when entity is null. Serial in packet will be 0 when entity is null.
- [X] Fixes NPE in AosAttributes when Parent is null.
- [X] Changes OPL to use string interpolation.
- [X] Introduces `IPropertyList` to allow extending PropertyList for other uses.
