feat: add configurable keyword positioning in search results

1. Added positioningMaxLength parameter to HighlightOptions structure to
allow configuration of keyword positioning window size
2. Modified customHighlight function to accept and use this parameter
for better keyword positioning in search results
3. Enforced minimum window size of 30 characters for proper keyword
visibility
4. Updated all function calls to pass the new parameter
5. Improved documentation for the customHighlight function parameters

Log: Added configurable keyword positioning window for better search
result snippets

Influence:
1. Test search results with different positioningMaxLength values (below
30 and above 30)
2. Verify keyword visibility and snippet positioning in results
3. Check HTML highlighting still works when enabled
4. Test with both short and long content samples
5. Verify behavior with empty content or keyword lists

feat: 添加可配置的关键词定位功能

1. 在HighlightOptions结构中添加positioningMaxLength参数，用于配置关键词
定位窗口大小
2. 修改customHighlight函数以接受并使用此参数，改进搜索结果中的关键词定位
3. 强制30个字符的最小窗口尺寸以确保关键词可见性
4. 更新所有函数调用以传递新参数
5. 改进了customHighlight函数的参数文档

Log: 新增可配置关键词定位窗口，改进搜索结果片段显示

Influence:
1. 使用不同的positioningMaxLength值测试搜索结果(小于30和大于30)
2. 验证结果中的关键词可见性和片段定位
3. 检查启用HTML高亮时是否仍正常工作
4. 测试短内容和长内容样本
5. 验证空内容或关键词列表时的行为

Fixes: #365083

Author: Johnson-zs

include/dfm-search/dfm-search/contentretriever.h

@@ -18,8 +18,9 @@ DFM_SEARCH_BEGIN_NS
  */
 struct HighlightOptions
 {
-    int maxPreviewLength = 200;   ///< Maximum snippet length in characters
-    bool enableHtml = false;   ///< Wrap matched keywords with <b> tags
+    int maxPreviewLength = 200;      ///< Maximum snippet length in characters
+    int positioningMaxLength = 30; ///< Keyword positioning window size (min 30)
+    bool enableHtml = false;         ///< Wrap matched keywords with <b> tags
 };
 
 /**

src/dfm-search/dfm-search-lib/utils/contenthighlighter.cpp

@@ -155,7 +155,7 @@ KeywordMatch findFirstKeywordMatch(const QString &content, const QStringList &ke
 }
 }   // namespace
 
-QString customHighlight(const QStringList &keywords, const QString &content, int maxLength, bool enableHtml)
+QString customHighlight(const QStringList &keywords, const QString &content, int maxLength, bool enableHtml, int positioningMaxLength)
 {
     if (content.isEmpty() || keywords.isEmpty()) {
         return QString();
@@ -191,13 +191,13 @@ QString customHighlight(const QStringList &keywords, const QString &content, int
         return match.keyword;   // Return the keyword as is (original behavior)
     }
 
-    // This is the "30 characters" from the requirement, used for positioning the keyword.
-    const int positioningMaxLength = 30;
+    // Enforce minimum of 30 for the positioning window
+    const int effectivePositioningLength = qMax(30, positioningMaxLength);
 
     // 1. Calculate the optimal start position.
     //    This start position is determined based on making the keyword visible
-    //    and well-positioned within a `positioningMaxLength` (e.g., 80 char) window.
-    int optimalStart = findOptimalStartPosition(content, match.position, positioningMaxLength);
+    //    and well-positioned within the positioning window.
+    int optimalStart = findOptimalStartPosition(content, match.position, effectivePositioningLength);
 
     // 2. Calculate the optimal end position.
     //    This uses the `optimalStart` calculated above and extends the snippet

src/dfm-search/dfm-search-lib/utils/contenthighlighter.h

@@ -33,11 +33,12 @@ namespace ContentHighlighter {
  *
  * @param keywords    A list of search keywords (supports wildcards *, ?).
  * @param content     The original document content to be searched.
- * @param maxLength   The maximum length of the returned snippet (used when no line breaks are present).
- * @param enableHtml  Whether to wrap matched keywords with <b></b> tags for highlighting.
+ * @param maxLength           The maximum length of the returned snippet (used when no line breaks are present).
+ * @param enableHtml          Whether to wrap matched keywords with <b></b> tags for highlighting.
+ * @param positioningMaxLength Keyword positioning window size for finding the optimal snippet start/end (min 30).
  * @return A snippet of content with matched keywords highlighted, or an empty string if no match is found.
  */
-QString customHighlight(const QStringList &keywords, const QString &content, int maxLength, bool enableHtml);
+QString customHighlight(const QStringList &keywords, const QString &content, int maxLength, bool enableHtml, int positioningMaxLength = 30);
 
 }   // namespace ContentHighlighter
 

src/dfm-search/dfm-search-lib/utils/contentretriever.cpp

@@ -219,7 +219,8 @@ QString ContentRetriever::fetchHighlight(const QString &path,
         }
 
         return ContentHighlighter::customHighlight(
-                keywords, content, options.maxPreviewLength, options.enableHtml);
+                keywords, content, options.maxPreviewLength, options.enableHtml,
+                options.positioningMaxLength);
     } catch (const LuceneException &e) {
         qWarning() << "ContentRetriever: error fetching highlight for" << path
                    << QString::fromStdWString(e.getError());
@@ -260,7 +261,8 @@ QMap<QString, QString> ContentRetriever::fetchHighlights(const QStringList &path
             }
 
             results.insert(path, ContentHighlighter::customHighlight(
-                                         keywords, content, options.maxPreviewLength, options.enableHtml));
+                                         keywords, content, options.maxPreviewLength, options.enableHtml,
+                                         options.positioningMaxLength));
         } catch (const LuceneException &e) {
             qWarning() << "ContentRetriever: error for" << path
                        << QString::fromStdWString(e.getError());