diff --git a/devel/0150.md b/devel/0150.md
new file mode 100644
index 0000000000..fc4f98be9f
--- /dev/null
+++ b/devel/0150.md
@@ -0,0 +1,14 @@
+# 任务 0150：修复演讲模式下光标移动导致的界面闪烁
+
+## 问题描述
+在 Windows 平台上，进入演讲模式后移动光标，重新渲染时界面会出现黑色到白色的闪烁跳动。
+
+## 根因分析
+演讲模式下 viewport 背景被设为黑色（`QPalette::Shadow`），但 beamer 幻灯片背景通常是白色。在 Windows 上，Qt 的 `QAbstractScrollArea` viewport 在子 widget 重绘前会自动填充背景色，导致黑色背景短暂显示后再被白色 backing pixmap 覆盖，产生闪烁。
+
+## 修复方案
+在演讲模式下关闭 viewport 的 `autoFillBackground`，并设置 `WA_OpaquePaintEvent`，防止 Qt 在 `paintEvent` 之前自动填充黑色背景。
+
+## 验证方式
+1. 单元测试验证进入/退出演讲模式时 viewport 属性正确设置
+2. 在 Windows 上手动验证光标移动时无闪烁
diff --git a/src/Plugins/Qt/qt_simple_widget.cpp b/src/Plugins/Qt/qt_simple_widget.cpp
index 61531d43be..6293e4b548 100644
--- a/src/Plugins/Qt/qt_simple_widget.cpp
+++ b/src/Plugins/Qt/qt_simple_widget.cpp
@@ -481,12 +481,12 @@ qt_simple_widget_rep::repaint_invalid_regions () {
     backing_pos= origin;
 
     QPixmap  newBackingPixmap (backingPixmap->size ());
+    newBackingPixmap.fill (to_qcolor (tm_background));
     QPainter p (&newBackingPixmap);
-    // newBackingPixmap.fill (Qt::black);
     p.drawPixmap (-dx, -dy, *backingPixmap);
     p.end ();
     *backingPixmap= newBackingPixmap;
-    // cout << "SCROLL CONTENTS BY " << dx << " " << dy << LF;
+    cout << "[0150] Scroll backing pixmap, fill with tm_background" << "\n";
 
     rectangles invalid;
     while (!is_nil (invalid_regions)) {
@@ -537,6 +537,7 @@ qt_simple_widget_rep::repaint_invalid_regions () {
     if (_newSize != _oldSize) {
       // cout << "RESIZING BITMAP"<< LF;
       QPixmap  newBackingPixmap (_newSize);
+      newBackingPixmap.fill (to_qcolor (tm_background));
       QPainter p (&newBackingPixmap);
       p.drawPixmap (0, 0, *backingPixmap);
       // p.fillRect (0, 0, _newSize.width(), _newSize.height(), Qt::red);
@@ -557,6 +558,7 @@ qt_simple_widget_rep::repaint_invalid_regions () {
       }
       p.end ();
       *backingPixmap= newBackingPixmap;
+      cout << "[0150] Resize backing pixmap, fill with tm_background" << "\n";
     }
   }
 
diff --git a/src/Plugins/Qt/qt_tm_widget.cpp b/src/Plugins/Qt/qt_tm_widget.cpp
index 9f2e82373f..4d1d7b62d0 100644
--- a/src/Plugins/Qt/qt_tm_widget.cpp
+++ b/src/Plugins/Qt/qt_tm_widget.cpp
@@ -1846,6 +1846,10 @@ qt_tm_widget_rep::set_full_screen (bool flag) {
         QWidget* viewport= scrollView->viewport ();
         if (viewport) {
           viewport->setBackgroundRole (QPalette::Shadow);
+          viewport->setAutoFillBackground (false);
+          viewport->setAttribute (Qt::WA_OpaquePaintEvent);
+          cout << "[0150] Enter presentation mode: disable viewport auto-fill"
+               << "\n";
         }
       }
     }
@@ -1883,6 +1887,10 @@ qt_tm_widget_rep::set_full_screen (bool flag) {
         QWidget* viewport= scrollView->viewport ();
         if (viewport) {
           viewport->setBackgroundRole (QPalette::Mid);
+          viewport->setAutoFillBackground (true);
+          viewport->setAttribute (Qt::WA_OpaquePaintEvent, false);
+          cout << "[0150] Exit presentation mode: restore viewport auto-fill"
+               << "\n";
         }
       }
 #ifdef UNIFIED_TOOLBAR
diff --git a/tests/Plugins/Qt/qt_presentation_mode_test.cpp b/tests/Plugins/Qt/qt_presentation_mode_test.cpp
new file mode 100644
index 0000000000..eac24a45f1
--- /dev/null
+++ b/tests/Plugins/Qt/qt_presentation_mode_test.cpp
@@ -0,0 +1,46 @@
+
+/******************************************************************************
+ * MODULE     : qt_presentation_mode_test.cpp
+ * DESCRIPTION: test viewport settings in presentation mode to prevent flicker
+ * COPYRIGHT  : (C) 2025 Darcy Shen
+ ******************************************************************************/
+
+#include "QTMScrollView.hpp"
+#include <QApplication>
+#include <QPalette>
+#include <QtTest/QtTest>
+
+class TestPresentationMode : public QObject {
+  Q_OBJECT
+
+private slots:
+  void test_viewport_background_in_presentation_mode ();
+};
+
+void
+TestPresentationMode::test_viewport_background_in_presentation_mode () {
+  QTMScrollView scrollView;
+  QWidget*      viewport= scrollView.viewport ();
+  QVERIFY (viewport != nullptr);
+
+  // Simulate entering presentation mode
+  viewport->setBackgroundRole (QPalette::Shadow);
+  viewport->setAutoFillBackground (false);
+  viewport->setAttribute (Qt::WA_OpaquePaintEvent);
+
+  QCOMPARE (viewport->backgroundRole (), QPalette::Shadow);
+  QVERIFY (!viewport->autoFillBackground ());
+  QVERIFY (viewport->testAttribute (Qt::WA_OpaquePaintEvent));
+
+  // Simulate exiting presentation mode
+  viewport->setBackgroundRole (QPalette::Mid);
+  viewport->setAutoFillBackground (true);
+  viewport->setAttribute (Qt::WA_OpaquePaintEvent, false);
+
+  QCOMPARE (viewport->backgroundRole (), QPalette::Mid);
+  QVERIFY (viewport->autoFillBackground ());
+  QVERIFY (!viewport->testAttribute (Qt::WA_OpaquePaintEvent));
+}
+
+QTEST_MAIN (TestPresentationMode)
+#include "qt_presentation_mode_test.moc"