dotnet/wpf

TextFormatter.FormatLine has O(n^2) performance when called multiple times

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#6,304 建立於 2022年3月23日

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Performancehelp wanted

描述

  • .NET Core Version: .net 6
  • Windows version: 11
  • Does the bug reproduce also in WPF for .NET Framework 4.8?: Yes
  • Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc...)? no

Actual behavior:

TextFormatter.FormatLine has O(n^2) performance

Expected behavior:

TextFormatter.FormatLine exhibits linear performance

Minimal repro: WpfFontRepro.zip

Remarks

Disposing the formatted lines or creating new TextFormatter instances prevents the O(n^2) behavior.

貢獻者指南

技術棧
csharp
領域
desktopperformance
議題類型
performance
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-2 days
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
stale
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
C#WPFPerformance profiling
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
35
研究方向
Investigate the TextFormatter.FormatLine method in the WPF codebase (likely in TextFormatter.cs). The issue suggests that creating new TextFormatter instances or disposing formatted lines avoids the O(n^2) behavior, indicating improper caching or resource management. Review how FormattedLine objects are stored and disposed, and consider implementing a fix that ensures linear time complexity across multiple calls. The minimal repro provided in the issue can be used to validate the fix.