feat(homework_review): 优化批注绘制与坐标换算，提升交互流畅度

- 批注绘制改为 Path 聚合一次性绘制
- 移除高频 print，开启 CustomPaint isComplex/willChange
- 无变换时跳过逆矩阵
- 回滚不必要的 RepaintBoundary/低过滤
- 调整 Path 判空判断写法

making_school_asignment_app/lib/page/home_page/children/homework_review/components/question_paper_view.dart

@@ -518,7 +518,7 @@ class QuestionImageView extends HookWidget with EventBusMixin<BottomOperationBar
         if (activePointers.value > 0) {
           activePointers.value = activePointers.value - 1;
         }
-        print("---进入：onPointerUp ${activePointers.value}");
+        // 移除高频日志，避免导致掉帧
         timerRef.value?.cancel();
         if (!annotationState.pen.value) return;
 
@@ -526,7 +526,7 @@ class QuestionImageView extends HookWidget with EventBusMixin<BottomOperationBar
         sateData.handwritings = vnHandWritings.value; // 添加笔迹数据
       },
       onPointerMove: (PointerMoveEvent event) {
-        print("进入：onPointerMove ${activePointers.value}");
+        // 移除高频日志，避免导致掉帧
         if (activePointers.value != 1) return;
         startTimerForHandwriting(vnHandWritings);
         if (!annotationState.pen.value) return;
@@ -555,9 +555,24 @@ class QuestionImageView extends HookWidget with EventBusMixin<BottomOperationBar
         // (dy / theScale) - (max(0, imageHeightOffsetStart) / theScale) + ((sateData.zoomOffset?.dy.abs() ?? 0) / theScale),
 
         // 屏幕坐标 -> 图片坐标（通过逆矩阵）
-        final inv = Matrix4.inverted(matrix);
-        final v = inv.transform3(Vector3(localPosition.dx, localPosition.dy, 0));
-        localPosition = Offset(v.x, v.y);
+        // final inv = Matrix4.inverted(matrix);
+        // final v = inv.transform3(Vector3(localPosition.dx, localPosition.dy, 0));
+        // localPosition = Offset(v.x, v.y);
+
+        /// 屏幕坐标 -> 图片坐标（通过逆矩阵）。当无缩放/平移时走快速路径，避免不必要求逆
+        /// 它们是 Matrix4 内部 4x4 矩阵的平移分量（列主序存储）。
+        /// storage[12] 是平移的 x 分量，storage[13] 是平移的 y 分量（storage[14] 则是 z）。
+        /// 因为 Matrix4 采用列主序，索引计算为 index = col * 4 + row，平移在第 4 列的前 3 行，所以是 12、13、14。
+        /// 用途：当 theScale == 1.0 && storage[12] == 0.0 && storage[13] == 0.0 时，可判定无缩放/平移，走快速路径跳过逆矩阵。
+        final double tx = matrix.storage[12];
+        final double ty = matrix.storage[13];
+        if (theScale == 1.0 && tx == 0.0 && ty == 0.0) {
+          // identity 变换，局部坐标无需转换
+        } else {
+          final inv = Matrix4.inverted(matrix);
+          final v = inv.transform3(Vector3(localPosition.dx, localPosition.dy, 0));
+          localPosition = Offset(v.x, v.y);
+        }
 
         // 在图片坐标系做边界校验（更直观）：0..maxWidth、0..actualHeight
         if (localPosition.dy < 0 || localPosition.dy > actualHeight) return;
@@ -625,7 +640,8 @@ class QuestionImageView extends HookWidget with EventBusMixin<BottomOperationBar
                     RepaintBoundary(
                       key: logic.pictureOverviewKey,
                       child: CustomPaint(
-                        // isComplex: true,
+                        isComplex: true,
+                        willChange: true,
                         size: Size(maxWidth, actualHeight),
                         foregroundPainter: DrawingPainter(ctrl: vnHandWritings),
                         // child: $TheCachedNetworkImage(
@@ -658,19 +674,40 @@ class DrawingPainter extends CustomPainter {
   final Paint paintBrush = Paint()
     ..color = Colors.red
     ..strokeCap = StrokeCap.round
-    ..strokeWidth = 0.7.sp;
+    ..strokeJoin = StrokeJoin.round
+    ..isAntiAlias = true
+    ..strokeWidth = 0.7.sp
+    ..style = PaintingStyle.stroke;
   DrawingPainter({required this.ctrl}) : super(repaint: ctrl);
 
   @override
   void paint(Canvas canvas, Size size) {
-    var points = ctrl.value;
-    var pointsLength = points.length;
-    for (int i = 0; i < pointsLength; i++) {
-      Offset? offsetData = points[i];
-      Offset? nextOffsetData = pointsLength - 1 == i ? null : points[i + 1];
-      if (offsetData != null && nextOffsetData != null) {
-        canvas.drawLine(offsetData, nextOffsetData, paintBrush);
+    final List<dynamic> points = ctrl.value;
+    if (points.isEmpty) return;
+
+    Path path = Path();
+    Offset? previous;
+    for (int i = 0; i < points.length; i++) {
+      final Offset? current = points[i] as Offset?;
+      if (current == null) {
+        // 提交当前子路径
+        if (path.computeMetrics().isNotEmpty) {
+          canvas.drawPath(path, paintBrush);
+        }
+        path = Path();
+        previous = null;
+        continue;
       }
+      if (previous == null) {
+        path.moveTo(current.dx, current.dy);
+      } else {
+        path.lineTo(current.dx, current.dy);
+      }
+      previous = current;
+    }
+    // 绘制最后的子路径
+    if (path.computeMetrics().isNotEmpty) {
+      canvas.drawPath(path, paintBrush);
     }
   }