From dbfd9105dea8117aad762defe9897ad11fde0de9 Mon Sep 17 00:00:00 2001
From: sudacode <suda@sudacode.com>
Date: Mon, 9 Feb 2026 23:03:40 -0800
Subject: [PATCH] refactor: extract mpv render metrics runtime apply helper

---
 package.json                                  |  2 +-
 .../mpv-render-metrics-service.test.ts        | 37 +++++++++++++++++++
 .../services/mpv-render-metrics-service.ts    | 25 +++++++++++++
 src/main.ts                                   | 24 +-----------
 4 files changed, 65 insertions(+), 23 deletions(-)
 create mode 100644 src/core/services/mpv-render-metrics-service.test.ts

diff --git a/package.json b/package.json
index 2f7de9c..2e67017 100644
--- a/package.json
+++ b/package.json
@@ -16,7 +16,7 @@
     "docs:build": "vitepress build docs",
     "docs:preview": "vitepress preview docs --host 0.0.0.0 --port 4173 --strictPort",
     "test:config": "pnpm run build && node --test dist/config/config.test.js",
-    "test:core": "pnpm run build && node --test dist/cli/args.test.js dist/cli/help.test.js dist/core/services/cli-command-service.test.js dist/core/services/numeric-shortcut-session-service.test.js dist/core/services/secondary-subtitle-service.test.js",
+    "test:core": "pnpm run build && node --test dist/cli/args.test.js dist/cli/help.test.js dist/core/services/cli-command-service.test.js dist/core/services/numeric-shortcut-session-service.test.js dist/core/services/secondary-subtitle-service.test.js dist/core/services/mpv-render-metrics-service.test.js",
     "test:subtitle": "pnpm run build && node --test dist/subtitle/stages.test.js dist/subtitle/pipeline.test.js",
     "generate:config-example": "pnpm run build && node dist/generate-config-example.js",
     "start": "pnpm run build && electron . --start",
diff --git a/src/core/services/mpv-render-metrics-service.test.ts b/src/core/services/mpv-render-metrics-service.test.ts
new file mode 100644
index 0000000..43c9e7e
--- /dev/null
+++ b/src/core/services/mpv-render-metrics-service.test.ts
@@ -0,0 +1,37 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { MpvSubtitleRenderMetrics } from "../../types";
+import { applyMpvSubtitleRenderMetricsPatchService } from "./mpv-render-metrics-service";
+
+const BASE: MpvSubtitleRenderMetrics = {
+  subPos: 100,
+  subFontSize: 38,
+  subScale: 1,
+  subMarginY: 34,
+  subMarginX: 19,
+  subFont: "sans-serif",
+  subSpacing: 0,
+  subBold: false,
+  subItalic: false,
+  subBorderSize: 2.5,
+  subShadowOffset: 0,
+  subAssOverride: "yes",
+  subScaleByWindow: true,
+  subUseMargins: true,
+  osdHeight: 720,
+  osdDimensions: null,
+};
+
+test("applyMpvSubtitleRenderMetricsPatchService returns unchanged on empty patch", () => {
+  const { next, changed } = applyMpvSubtitleRenderMetricsPatchService(BASE, {});
+  assert.equal(changed, false);
+  assert.deepEqual(next, BASE);
+});
+
+test("applyMpvSubtitleRenderMetricsPatchService reports changed when patch modifies value", () => {
+  const { next, changed } = applyMpvSubtitleRenderMetricsPatchService(BASE, {
+    subPos: 95,
+  });
+  assert.equal(changed, true);
+  assert.equal(next.subPos, 95);
+});
diff --git a/src/core/services/mpv-render-metrics-service.ts b/src/core/services/mpv-render-metrics-service.ts
index 271d388..82efd27 100644
--- a/src/core/services/mpv-render-metrics-service.ts
+++ b/src/core/services/mpv-render-metrics-service.ts
@@ -55,3 +55,28 @@ export function updateMpvSubtitleRenderMetricsService(
     osdDimensions: nextOsdDimensions,
   };
 }
+
+export function applyMpvSubtitleRenderMetricsPatchService(
+  current: MpvSubtitleRenderMetrics,
+  patch: Partial<MpvSubtitleRenderMetrics>,
+): { next: MpvSubtitleRenderMetrics; changed: boolean } {
+  const next = updateMpvSubtitleRenderMetricsService(current, patch);
+  const changed =
+    next.subPos !== current.subPos ||
+    next.subFontSize !== current.subFontSize ||
+    next.subScale !== current.subScale ||
+    next.subMarginY !== current.subMarginY ||
+    next.subMarginX !== current.subMarginX ||
+    next.subFont !== current.subFont ||
+    next.subSpacing !== current.subSpacing ||
+    next.subBold !== current.subBold ||
+    next.subItalic !== current.subItalic ||
+    next.subBorderSize !== current.subBorderSize ||
+    next.subShadowOffset !== current.subShadowOffset ||
+    next.subAssOverride !== current.subAssOverride ||
+    next.subScaleByWindow !== current.subScaleByWindow ||
+    next.subUseMargins !== current.subUseMargins ||
+    next.osdHeight !== current.osdHeight ||
+    JSON.stringify(next.osdDimensions) !== JSON.stringify(current.osdDimensions);
+  return { next, changed };
+}
diff --git a/src/main.ts b/src/main.ts
index 59725ad..3413084 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -160,7 +160,7 @@ import {
   MpvIpcClient,
   MPV_REQUEST_ID_SECONDARY_SUB_VISIBILITY,
 } from "./core/services/mpv-service";
-import { updateMpvSubtitleRenderMetricsService } from "./core/services/mpv-render-metrics-service";
+import { applyMpvSubtitleRenderMetricsPatchService } from "./core/services/mpv-render-metrics-service";
 import {
   handleMpvCommandFromIpcService,
 } from "./core/services/ipc-command-service";
@@ -636,30 +636,10 @@ function handleInitialArgs(): void {
 function updateMpvSubtitleRenderMetrics(
   patch: Partial<MpvSubtitleRenderMetrics>,
 ): void {
-  const next = updateMpvSubtitleRenderMetricsService(
+  const { next, changed } = applyMpvSubtitleRenderMetricsPatchService(
     mpvSubtitleRenderMetrics,
     patch,
   );
-
-  const changed =
-    next.subPos !== mpvSubtitleRenderMetrics.subPos ||
-    next.subFontSize !== mpvSubtitleRenderMetrics.subFontSize ||
-    next.subScale !== mpvSubtitleRenderMetrics.subScale ||
-    next.subMarginY !== mpvSubtitleRenderMetrics.subMarginY ||
-    next.subMarginX !== mpvSubtitleRenderMetrics.subMarginX ||
-    next.subFont !== mpvSubtitleRenderMetrics.subFont ||
-    next.subSpacing !== mpvSubtitleRenderMetrics.subSpacing ||
-    next.subBold !== mpvSubtitleRenderMetrics.subBold ||
-    next.subItalic !== mpvSubtitleRenderMetrics.subItalic ||
-    next.subBorderSize !== mpvSubtitleRenderMetrics.subBorderSize ||
-    next.subShadowOffset !== mpvSubtitleRenderMetrics.subShadowOffset ||
-    next.subAssOverride !== mpvSubtitleRenderMetrics.subAssOverride ||
-    next.subScaleByWindow !== mpvSubtitleRenderMetrics.subScaleByWindow ||
-    next.subUseMargins !== mpvSubtitleRenderMetrics.subUseMargins ||
-    next.osdHeight !== mpvSubtitleRenderMetrics.osdHeight ||
-    JSON.stringify(next.osdDimensions) !==
-      JSON.stringify(mpvSubtitleRenderMetrics.osdDimensions);
-
   if (!changed) return;
   mpvSubtitleRenderMetrics = next;
   broadcastToOverlayWindows(