improve:PPT墨迹加载

Ink Canvas/MainWindow_cs/MW_PPT.cs

@@ -835,27 +835,26 @@ namespace Ink_Canvas
                     var previousSlide = _currentSlideShowPosition > 0 ? _currentSlideShowPosition : 
                                        (_pptManager?.GetCurrentSlideNumber() ?? 0);
 
-                    // 先保存当前页墨迹的副本
+                    if (_isInkClearedByButton)
+                    {
+                        _isInkClearedByButton = false;
+                    }
+                    else
+                    {
                         StrokeCollection strokesToSave = null;
                         if (previousSlide > 0 && previousSlide != currentSlide && inkCanvas.Strokes.Count > 0)
                         {
                             strokesToSave = inkCanvas.Strokes.Clone();
                         }
 
-                    if (_isInkClearedByButton)
-                    {
-                        _isInkClearedByButton = false;
-                    }
-                    else if (inkCanvas.Strokes.Count > 0)
+                        // 清除墨迹
+                        if (inkCanvas.Strokes.Count > 0)
                         {
                             ClearStrokes(true);
                             timeMachine.ClearStrokeHistory();
                         }
 
-                    // 更新当前播放页码
-                    _currentSlideShowPosition = currentSlide;
-
-                    // 异步保存之前页面的墨迹（不阻塞翻页操作）
+                        // 异步保存之前页面的墨迹
                         if (strokesToSave != null && previousSlide > 0 && previousSlide != currentSlide)
                         {
                             Task.Run(() =>
@@ -877,7 +876,12 @@ namespace Ink_Canvas
                                 }
                             });
                         }
-                    LoadCurrentSlideInk(currentSlide, skipClear: true); // 跳过清除，因为已在上面清除
+                    }
+
+                    // 更新当前播放页码
+                    _currentSlideShowPosition = currentSlide;
+
+                    LoadCurrentSlideInk(currentSlide, skipClear: true);
                     _pptUIManager?.UpdateCurrentSlideNumber(currentSlide, totalSlides);
 
                 });