From 7d2ec9c1ab62d5ec111106eacd4e6443da9075a8 Mon Sep 17 00:00:00 2001
From: xiepengfei <xiepengfei@uniontech.com>
Date: Fri, 23 Oct 2026 14:41:43 +0800
Subject: [PATCH] fix: reduce print preview delay by yielding UI events
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1. Root cause: updateHighlighterAll() rehighlights every block
   synchronously without yielding, blocking UI thread for ~6s on
   medium files during print preview
2. Fix: call qApp->processEvents() every 100 blocks to keep UI
   responsive, consistent with cloneLargeDocument() pattern
3. Cleanup: remove dead DPrinter printer(QPrinter::HighResolution)
   in popupPrintDialog(), introduced by commit 9fcf3e4c, which
   triggers unnecessary cups plugin load and printer enumeration
4. Impact: print preview opens faster, no behavior change for
   syntax highlighting or print output

Log: 优化打印预览页面打开速度，减少 UI 阻塞

Influence:
1. Test print preview with medium/large syntax-highlighted files
2. Verify syntax highlighting renders correctly in print preview
3. Test print preview with plain text files (no highlighter)
4. Verify no -Wunused-variable warnings after dead code removal

fix: 优化打印预览页面响应速度，减少 UI 线程阻塞

1. 根因：updateHighlighterAll() 同步遍历所有文本块执行语法高亮，
   无 processEvents 间歇，中小文件打印预览时阻塞 UI 线程约 6 秒
2. 方案：循环中每 100 块调用 qApp->processEvents() 保持 UI 响应，
   与 cloneLargeDocument() 现有模式一致
3. 清理：删除 popupPrintDialog() 中 DPrinter printer(QPrinter::
   HighResolution) 死代码，由 commit 9fcf3e4c 引入，会触发不必要的
   cups 插件加载和打印机枚举
4. 影响：打印预览打开速度提升，语法高亮和打印输出行为不变

Log: 优化打印预览页面打开速度，减少 UI 阻塞

Influence:
1. 测试中等/大型语法高亮文件的打印预览
2. 验证打印预览中语法高亮渲染正确
3. 测试纯文本文件（无语法高亮）的打印预览
4. 验证删除死代码后无 -Wunused-variable 告警残留

PMS: BUG-375053
---
 src/editor/editwrapper.cpp | 4 ++++
 src/widgets/window.cpp     | 1 -
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/editor/editwrapper.cpp b/src/editor/editwrapper.cpp
index f8642463..c48eefd8 100644
--- a/src/editor/editwrapper.cpp
+++ b/src/editor/editwrapper.cpp
@@ -1451,8 +1451,12 @@ void EditWrapper::updateHighlighterAll()
             return;
         }
 
+        int blockCount = 0;
         for (QTextBlock var = beginBlock; var != endBlock; var = var.next()) {
             m_pSyntaxHighlighter->rehighlightBlock(var);
+            if (++blockCount % 100 == 0) {
+                qApp->processEvents();
+            }
         }
 
         m_pSyntaxHighlighter->rehighlightBlock(endBlock);
diff --git a/src/widgets/window.cpp b/src/widgets/window.cpp
index 91a9af10..e6a0ad16 100644
--- a/src/widgets/window.cpp
+++ b/src/widgets/window.cpp
@@ -2441,7 +2441,6 @@ void Window::popupPrintDialog()
         return;
     }
 
-    DPrinter printer(QPrinter::HighResolution);
     m_isNewPrint = true;
     m_pPreview = new DPrintPreviewDialog(this);
     m_pPreview->setAttribute(Qt::WA_DeleteOnClose);