feat(后端架构): 优化多后端渲染，修复描边与字形校验

ofdgo_render_cache.go

@@ -0,0 +1,68 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ofdgo
+
+import "container/list"
+
+// renderCache 按估算字节数限制派生渲染数据，淘汰不修改源资源
+type renderCache[K comparable, V any] struct {
+	limit, used int
+	entries     map[K]*list.Element
+	order       list.List
+}
+
+// renderCacheEntry 保存缓存值及内存成本
+type renderCacheEntry[K comparable, V any] struct {
+	key   K
+	value V
+	cost  int
+}
+
+// get 读取缓存并更新使用顺序
+// 入参: key 缓存键
+// 返回: V 缓存值, bool 是否命中
+func (c *renderCache[K, V]) get(key K) (V, bool) {
+	if item := c.entries[key]; item != nil {
+		c.order.MoveToFront(item)
+		return item.Value.(renderCacheEntry[K, V]).value, true
+	}
+	var zero V
+	return zero, false
+}
+
+// put 缓存预算内的派生数据，超大单项不进入缓存
+// 入参: key 缓存键, value 缓存值, cost 字节成本
+func (c *renderCache[K, V]) put(key K, value V, cost int) {
+	if item := c.entries[key]; item != nil {
+		c.used -= item.Value.(renderCacheEntry[K, V]).cost
+		c.order.Remove(item)
+		delete(c.entries, key)
+	}
+	if cost <= 0 || cost > c.limit {
+		return
+	}
+	if c.entries == nil {
+		c.entries = make(map[K]*list.Element)
+	}
+	for c.used+cost > c.limit {
+		item := c.order.Back()
+		entry := item.Value.(renderCacheEntry[K, V])
+		c.used -= entry.cost
+		delete(c.entries, entry.key)
+		c.order.Remove(item)
+	}
+	c.entries[key] = c.order.PushFront(renderCacheEntry[K, V]{key, value, cost})
+	c.used += cost
+}