From af8f573eb11882f011845a5d1ad1b177b8c34f13 Mon Sep 17 00:00:00 2001
From: inchei <inchei@protonmail.com>
Date: Sun, 20 Sep 2026 19:54:28 +1000
Subject: [PATCH] feat(core): add setEnableDiffSemanticCleanup and honor
 fast-diff templates

Semantic cleanup in diffChanges merged small inline changes into one
block, hiding per-change highlights for text without word boundaries
(e.g. CJK). The cleanup is now opt-out (default on), and prebuilt
fast-diff templates are kept at render time when
setEnableFastDiffTemplate(true) is set.
---
 README.md                               | 11 +++++++++++
 packages/core/src/parse/change-range.ts | 14 +++++++++++++-
 packages/core/src/parse/template.ts     | 11 +++++++++++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index cff330fe..f8418171 100644
--- a/README.md
+++ b/README.md
@@ -189,6 +189,17 @@ import { setEnableFastDiffTemplate } from '@git-diff-view/core';
 setEnableFastDiffTemplate(true);
 ```
 
+By default the inline ranges are merged with a semantic cleanup, which may
+highlight everything between the first and the last change on a line as a
+single block. This is especially visible for text without word boundaries
+(e.g. CJK text). Disable the cleanup to highlight each change separately:
+
+```ts
+import { setEnableDiffSemanticCleanup } from '@git-diff-view/core';
+
+setEnableDiffSemanticCleanup(false);
+```
+
 | Default | FastDiff |
 |---------|----------|
 | ![default](https://raw.githubusercontent.com/MrWangJustToDo/git-diff-view/main/default.png) | ![fastdiff](https://raw.githubusercontent.com/MrWangJustToDo/git-diff-view/main/enableFastDiffTemplate.png) |
diff --git a/packages/core/src/parse/change-range.ts b/packages/core/src/parse/change-range.ts
index 5fbb676c..51d3498d 100644
--- a/packages/core/src/parse/change-range.ts
+++ b/packages/core/src/parse/change-range.ts
@@ -40,6 +40,18 @@ export const resetMaxLengthToIgnoreLineDiff = () => {
 
 export const getMaxLengthToIgnoreLineDiff = () => maxLengthToIgnoreLineDiff;
 
+let enableDiffSemanticCleanup = true;
+
+export const getEnableDiffSemanticCleanup = () => enableDiffSemanticCleanup;
+
+export const setEnableDiffSemanticCleanup = (enable: boolean) => {
+  enableDiffSemanticCleanup = enable;
+};
+
+export const resetEnableDiffSemanticCleanup = () => {
+  enableDiffSemanticCleanup = true;
+};
+
 /** Get the maximum position in the range. */
 function rangeMax(range: IRange["range"]): number {
   return range.location + range.length;
@@ -222,7 +234,7 @@ export function diffChanges(addition: DiffLine, deletion: DiffLine): { addRange:
     };
   }
 
-  const diffRange = fastDiff(delString, addString, 0, true);
+  const diffRange = fastDiff(delString, addString, 0, enableDiffSemanticCleanup);
 
   let aStart = 0;
   let bStart = 0;
diff --git a/packages/core/src/parse/template.ts b/packages/core/src/parse/template.ts
index 11d7581c..91160b3b 100644
--- a/packages/core/src/parse/template.ts
+++ b/packages/core/src/parse/template.ts
@@ -45,6 +45,8 @@ export const getPlainDiffTemplate = ({
 }) => {
   if (diffLine.plainTemplate && diffLine.plainTemplateMode === "relative") return;
 
+  if (diffLine.plainTemplate && diffLine.plainTemplateMode === "fast-diff" && enableFastDiffTemplate) return;
+
   const changes = diffLine.changes;
 
   if (!changes || !changes.hasLineChange || !rawLine) return;
@@ -149,6 +151,15 @@ export const getSyntaxDiffTemplate = ({
   )
     return;
 
+  if (
+    diffLine.syntaxTemplate &&
+    diffLine.syntaxTemplateMode === "fast-diff" &&
+    diffLine.syntaxTemplateName === diffFile._getHighlighterName() &&
+    diffFile._getHighlighterType() === "class" &&
+    enableFastDiffTemplate
+  )
+    return;
+
   const changes = diffLine.changes;
 
   if (!changes || !changes.hasLineChange) return;