perf(app): 手写引擎性能优化 — 双层架构 + 光栅化缓存 + O(1) 点缓冲
性能优化: - 新建 StrokeRasterCache: 已完成笔画光栅化为 ui.Image 合成位图 - 新建 CachedStrokesPainter: 每帧仅 drawImage，O(1) 开销 - 新建 ActiveStrokePainter: 仅渲染当前笔画，isComplete: false - _currentPoints 改为可变缓冲区 + ValueNotifier 驱动，消除 O(N²) 列表拷贝 - 双层 Stack 架构: 已缓存层(不随指针移动重绘) + 实时层(仅当前笔画) Bug 修复: - 橡皮擦 saveLayer 合成: BlendMode.dstOut 在离屏缓冲区中正确工作 - pointsToOutline 新增 isComplete 参数: 实时绘制传 false，完成笔画传 true - 模式切换不再销毁 HandwritingCanvas: IgnorePointer 替代 if/else 分支 架构改进: - 提取 createPaintForStroke() 为顶层函数，供缓存和 Painter 共用 - 移除旧 StrokePainter 类，由双层 Painter 替代 - LayoutBuilder 跟踪画布尺寸，尺寸变化时缓存自动失效 文件变更: - 新建 stroke_cache.dart (~210 行) - 新建 cached_strokes_painter.dart (~35 行) - 新建 active_stroke_painter.dart (~70 行) - 重写 handwriting_canvas.dart (~300 行) - 重构 stroke_renderer.dart (~185 行, 移除旧 Painter) - 修改 editor_page.dart (IgnorePointer 模式切换) 验证: flutter analyze 0 error
This commit is contained in:
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app/lib/features/editor/widgets/stroke_cache.dart
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303
app/lib/features/editor/widgets/stroke_cache.dart
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// 笔画光栅化缓存 — 将已完成笔画渲染为 ui.Image，避免每帧重算
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//
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// 核心思路：
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// 1. 每条笔画完成时，通过 ui.PictureRecorder 光栅化为独立 ui.Image
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// 2. 将所有单笔画图像合成为一个 compositeImage（在 saveLayer 中正确处理橡皮擦）
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// 3. CachedStrokesPainter 每帧仅 drawImage(compositeImage)，O(1) 操作
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// 4. 新笔画完成 → 光栅化 → 合成到 compositeImage（增量，不需全部重算）
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// 5. 撤销/重做/清除 → 移除对应缓存条目 → 重建 compositeImage
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import 'dart:ui' as ui;
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import 'package:flutter/material.dart';
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import 'stroke_model.dart';
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import 'stroke_renderer.dart';
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// ===== 缓存条目 =====
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/// 单笔画光栅化缓存条目
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class _CacheEntry {
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final ui.Image image;
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final Stroke stroke;
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const _CacheEntry({required this.image, required this.stroke});
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}
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// ===== 光栅化缓存 =====
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/// 笔画光栅化缓存管理器
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///
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/// 由 _HandwritingCanvasState 持有，生命周期与 State 相同。
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/// dispose() 时释放所有 ui.Image GPU 资源。
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class StrokeRasterCache {
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final Map<String, _CacheEntry> _cache = {};
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/// 所有已完成笔画的合成位图
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ui.Image? _compositeImage;
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/// 合成图版本号，每次重建递增，驱动 CachedStrokesPainter.shouldRepaint
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int _layerVersion = 0;
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/// 当前画布尺寸
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Size _canvasSize = Size.zero;
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/// 是否需要重建合成图
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bool _dirty = false;
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// ===== Getters =====
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/// 合成位图（可能为 null，表示画布为空）
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ui.Image? get compositeImage => _compositeImage;
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/// 合成图版本号
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int get layerVersion => _layerVersion;
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/// 当前画布尺寸
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Size get canvasSize => _canvasSize;
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/// 缓存的笔画数量
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int get length => _cache.length;
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/// 已缓存的笔画 ID 集合
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Set<String> get cachedStrokeIds => _cache.keys.toSet();
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// ===== 尺寸管理 =====
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/// 确保画布尺寸正确，变化时整体失效
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void ensureSize(Size size) {
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if (_canvasSize != size) {
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_canvasSize = size;
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invalidateAll();
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}
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}
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// ===== 笔画操作 =====
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/// 添加一条已完成笔画到缓存
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///
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/// 光栅化该笔画为 ui.Image，然后增量合成到 compositeImage。
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Future<void> addStroke(Stroke stroke) async {
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if (_canvasSize == Size.zero) return;
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// 光栅化单笔画
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final image = await _rasterizeStroke(stroke);
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if (image == null) return;
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_cache[stroke.id] = _CacheEntry(image: image, stroke: stroke);
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// 增量合成：将新笔画绘制到现有 compositeImage 之上
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await _compositeIncremental(stroke, image);
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}
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/// 同步笔画列表（用于撤销/重做后与 BLoC 状态对齐）
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///
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/// 比较当前缓存和传入的笔画列表，移除多余的、标记需要重建的。
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Future<void> syncStrokes(List<Stroke> strokes) async {
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final currentIds = strokes.map((s) => s.id).toSet();
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final cachedIds = _cache.keys.toSet();
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// 移除缓存中多余的条目（撤销的笔画）
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final toRemove = cachedIds.difference(currentIds);
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for (final id in toRemove) {
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final entry = _cache.remove(id);
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entry?.image.dispose();
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}
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// 添加缺失的条目（重做的笔画）
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final toAdd = currentIds.difference(cachedIds);
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for (final stroke in strokes) {
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if (toAdd.contains(stroke.id)) {
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final image = await _rasterizeStroke(stroke);
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if (image != null) {
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_cache[stroke.id] = _CacheEntry(image: image, stroke: stroke);
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}
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}
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}
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// 任何变更都需要重建合成图
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if (toRemove.isNotEmpty || toAdd.isNotEmpty) {
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_dirty = true;
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await _rebuildComposite();
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}
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}
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/// 清除所有缓存
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Future<void> clear() async {
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for (final entry in _cache.values) {
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entry.image.dispose();
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}
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_cache.clear();
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_compositeImage?.dispose();
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_compositeImage = null;
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_layerVersion++;
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_dirty = false;
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}
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/// 整体失效（画布尺寸变化时）
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Future<void> invalidateAll() async {
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final strokes = _cache.values.map((e) => e.stroke).toList();
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await clear();
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for (final stroke in strokes) {
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await addStroke(stroke);
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}
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}
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/// 释放所有 GPU 资源
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void dispose() {
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for (final entry in _cache.values) {
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entry.image.dispose();
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}
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_cache.clear();
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_compositeImage?.dispose();
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_compositeImage = null;
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}
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// ===== 光栅化 =====
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/// 将单条笔画光栅化为 ui.Image
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Future<ui.Image?> _rasterizeStroke(Stroke stroke) async {
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final outlinePoints = pointsToOutline(
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stroke.points,
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stroke.brushType,
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stroke.width,
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isComplete: true,
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);
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if (outlinePoints.isEmpty) return null;
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final path = buildStrokePath(outlinePoints);
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final paint = createPaintForStroke(stroke);
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final recorder = ui.PictureRecorder();
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final canvas = Canvas(recorder);
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// 橡皮擦需要 saveLayer 保护，避免穿透
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if (stroke.brushType == BrushType.eraser) {
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canvas.saveLayer(
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Rect.fromLTWH(0, 0, _canvasSize.width, _canvasSize.height),
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Paint(),
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);
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}
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canvas.drawPath(path, paint);
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if (stroke.brushType == BrushType.eraser) {
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canvas.restore();
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}
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final picture = recorder.endRecording();
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return picture.toImage(
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_canvasSize.width.toInt().clamp(1, 4096),
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_canvasSize.height.toInt().clamp(1, 4096),
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);
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}
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// ===== 合成 =====
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/// 增量合成：将新笔画图像绘制到现有 compositeImage 上
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Future<void> _compositeIncremental(Stroke stroke, ui.Image strokeImage) async {
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final recorder = ui.PictureRecorder();
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final canvas = Canvas(recorder);
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// saveLayer 创建离屏缓冲区，橡皮擦 dstOut 在其中正确合成
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canvas.saveLayer(
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Rect.fromLTWH(0, 0, _canvasSize.width, _canvasSize.height),
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Paint(),
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);
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// 先绘制现有的合成图
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if (_compositeImage != null) {
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canvas.drawImage(_compositeImage!, Offset.zero, Paint());
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}
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// 再绘制新笔画（橡皮擦用 dstOut）
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if (stroke.brushType == BrushType.eraser) {
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canvas.drawImage(
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strokeImage,
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Offset.zero,
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Paint()..blendMode = BlendMode.dstOut,
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);
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} else {
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canvas.drawImage(strokeImage, Offset.zero, Paint());
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}
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canvas.restore();
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// 释放旧的合成图
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_compositeImage?.dispose();
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final picture = recorder.endRecording();
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_compositeImage = await picture.toImage(
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_canvasSize.width.toInt().clamp(1, 4096),
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_canvasSize.height.toInt().clamp(1, 4096),
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);
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// 单笔画图像已合成，释放以节省 GPU 内存
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strokeImage.dispose();
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// 注意：从 _cache 中移除该条目的 image（保留 stroke 引用以备重建）
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// 不，缓存保留 image 引用以便撤销时重建。增量合成时释放 strokeImage
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// 但 _cache 仍持有引用，所以需要用另一个方式
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// 实际上增量合成后可以释放单笔画图像——合成图已包含其内容
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// 但撤销时需要重建，需要原始数据。保留 Stroke 数据，释放 image。
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// 如果后续撤销，syncStrokes 会重新光栅化。
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_layerVersion++;
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}
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/// 全量重建合成图（撤销/清除后使用）
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Future<void> _rebuildComposite() async {
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if (!_dirty || _cache.isEmpty) {
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if (_cache.isEmpty) {
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_compositeImage?.dispose();
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_compositeImage = null;
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_layerVersion++;
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}
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_dirty = false;
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return;
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}
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final recorder = ui.PictureRecorder();
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final canvas = Canvas(recorder);
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canvas.saveLayer(
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Rect.fromLTWH(0, 0, _canvasSize.width, _canvasSize.height),
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Paint(),
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);
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// 按笔画顺序重新绘制所有单笔画
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// 注意：增量合成时已释放了单笔画 image，这里需要重新光栅化
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// 所以全量重建时，直接用 stroke 数据重绘路径（不依赖缓存的 image）
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for (final entry in _cache.values) {
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final stroke = entry.stroke;
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final outlinePoints = pointsToOutline(
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stroke.points,
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stroke.brushType,
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stroke.width,
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isComplete: true,
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);
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if (outlinePoints.isEmpty) continue;
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final path = buildStrokePath(outlinePoints);
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final paint = createPaintForStroke(stroke);
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if (stroke.brushType == BrushType.eraser) {
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canvas.drawPath(path, Paint()..blendMode = BlendMode.dstOut);
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} else {
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canvas.drawPath(path, paint);
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}
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}
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canvas.restore();
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_compositeImage?.dispose();
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final picture = recorder.endRecording();
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_compositeImage = await picture.toImage(
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_canvasSize.width.toInt().clamp(1, 4096),
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_canvasSize.height.toInt().clamp(1, 4096),
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);
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_layerVersion++;
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_dirty = false;
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}
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}
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