[Repo Assist] Perf: cache JsonSerializerOptions and deduplicate colour Lerp helper

[github-actions]

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Summary

Two targeted performance / code-quality improvements with zero behaviour change:

1. Cache JsonSerializerOptions (AppSettings.cs)

JsonSerializerOptions is an expensive object — its constructor builds internal converter and cache tables. Previously AppSettings.Load() and AppSettings.Save() each created a fresh instance on every call. This change promotes them to static readonly fields (ReadOptions / WriteOptions) so they are created once at class load time and reused on every subsequent call.

2. Deduplicate colour Lerp helper (MainWindow.xaml.cs)

SetColorTemperature and UpdateAdditionalMonitorWindows each defined identical local helper functions (Lerp, LerpByte) and duplicated the CoolColor / WarmColor constant values. This change:

• Extracts them to private static class-level members (CoolColor, WarmColor, LerpColor).
• Both call sites are simplified to a one-liner.
• The cool / warm local variables on the hot path (mouse-move repaint) are eliminated, reducing GC pressure slightly.

Files Changed

File	Change
AppSettings.cs	ReadOptions / WriteOptions promoted to static readonly
MainWindow.xaml.cs	CoolColor, WarmColor, LerpColor extracted to class-level statics

Test Status

Build tested against net10.0-windows (cross-compiled with EnableWindowsTargeting) — 0 errors, 0 warnings. No existing tests were broken; no new tests were needed (no logic change).

Notes

• No behaviour change — functionality is identical.
• No new dependencies.
• Closes the duplicate issues [Repo Assist] Cache JsonSerializerOptions and extract colour Lerp helper #39 and [Repo Assist] Cache JsonSerializerOptions and extract colour Lerp helper #50 which tracked this same change.

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Show patch preview (140 of 140 lines)

From 581e6188c50418e0ba65253dfd4c4c287812dff8 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Wed, 10 Jun 2026 01:39:01 +0000
Subject: [PATCH] Cache JsonSerializerOptions and extract color Lerp helper

JsonSerializerOptions are expensive to construct (they hold internal
converter caches). Previously AppSettings.Load() and AppSettings.Save()
each created a fresh instance on every call. Promoting them to static
readonly fields means the objects are built once and reused.

The Lerp colour helper and the CoolColor/WarmColor constants were
duplicated in two methods (SetColorTemperature and
UpdateAdditionalMonitorWindows). Extract them to static members so
the values are defined in exactly one place, reducing maintenance
risk and eliminating the repeated local-function definitions.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 WindowsEdgeLight/AppSettings.cs     | 23 +++++++++--------
 WindowsEdgeLight/MainWindow.xaml.cs | 40 ++++++++++-------------------
 2 files changed, 26 insertions(+), 37 deletions(-)

diff --git a/WindowsEdgeLight/AppSettings.cs b/WindowsEdgeLight/AppSettings.cs
index bf12831..3c9a582 100644
--- a/WindowsEdgeLight/AppSettings.cs
+++ b/WindowsEdgeLight/AppSettings.cs
@@ -20,6 +20,17 @@ public class AppSettings
     /// </summary>
     public bool ExcludeFromCapture { get; set; } = true;
 
+    private static readonly JsonSerializerOptions ReadOptions = new JsonSerializerOptions
+    {
+        AllowTrailingCommas = true,
+        ReadCommentHandling = JsonCommentHandling.Skip
+    };
+
+    private static readonly JsonSerializerOptions WriteOptions = new JsonSerializerOptions
+    {
+        WriteIndented = true
+    };
+
     /// <summary>
     /// Load settings from disk
     /// </summary>
@@ -30,12 +41,7 @@ public class AppSettings
             if (File.Exists(SettingsFilePath))
             {
                 var json = File.ReadAllText(SettingsFileP
... (truncated)

[shanselman]

Implemented via maintainer triage in local commit 054cecb. The accepted parts are in: cached JsonSerializerOptions in AppSettings and a shared LerpColor helper in MainWindow. Closing as completed.