*canvas update system

1 files changed, 44 insertions, 12 deletions

diff --git a/Assets/uGUI-2017.1/UnityEngine.UI/UI/Core/CanvasUpdateRegistry.cs b/Assets/uGUI-2017.1/UnityEngine.UI/UI/Core/CanvasUpdateRegistry.cs
index bc7263b..d03d0e7 100644
--- a/Assets/uGUI-2017.1/UnityEngine.UI/UI/Core/CanvasUpdateRegistry.cs
+++ b/Assets/uGUI-2017.1/UnityEngine.UI/UI/Core/CanvasUpdateRegistry.cs
@@ -4,6 +4,8 @@ using UnityEngine.UI.Collections;
 
 namespace UnityEngine.UI
 {
+    // canvas的不同阶段，用来设置layout、graphic做不同的事情，具体看CanvasUpdateRegistry
+    // prelayout  ->  layout  ->  postlayout  -> prerender  ->  laterender  =>=>=>  render  
     public enum CanvasUpdate
     {
         Prelayout = 0,
@@ -11,13 +13,14 @@ namespace UnityEngine.UI
         PostLayout = 2,
         PreRender = 3,
         LatePreRender = 4,
+
         MaxUpdateValue = 5
     }
 
     public interface ICanvasElement
     {
-        void Rebuild(CanvasUpdate executing);
         Transform transform { get; }
+        void Rebuild(CanvasUpdate executing);
         void LayoutComplete();
         void GraphicUpdateComplete();
         // due to unity overriding null check
@@ -26,6 +29,7 @@ namespace UnityEngine.UI
         bool IsDestroyed();
     }
 
+    // 需要注意整个游戏只有一个单例
     public class CanvasUpdateRegistry
     {
         private static CanvasUpdateRegistry s_Instance;
@@ -38,9 +42,11 @@ namespace UnityEngine.UI
 
         protected CanvasUpdateRegistry()
         {
+            // willRenderCanvases在渲染canvas之前调用，执行PerformUpdate来Rebuild处理m_LayoutRebuildQueue和m_GraphicRebuildQueue
             Canvas.willRenderCanvases += PerformUpdate;
         }
 
+        // 简单单例 
         public static CanvasUpdateRegistry instance
         {
             get
@@ -51,6 +57,7 @@ namespace UnityEngine.UI
             }
         }
 
+        // 检查一下实现了ICanvasElement的对象合法性，实现了ICanvasElement接口的对象必须是Unity Object，
         private bool ObjectValidForUpdate(ICanvasElement element)
         {
             var valid = element != null;
@@ -104,6 +111,8 @@ namespace UnityEngine.UI
         }
 
         private static readonly Comparison<ICanvasElement> s_SortLayoutFunction = SortLayoutList;
+        // 在渲染canvas之前对canvas下的元素进行rebuild
+        // 进行 prelayout -> layout -> postlayout -> prerender -> LatePreRender 流程
         private void PerformUpdate()
         {
             UISystemProfilerApi.BeginSample(UISystemProfilerApi.SampleType.Layout);
@@ -111,8 +120,12 @@ namespace UnityEngine.UI
 
             m_PerformingLayoutUpdate = true;
 
+            // 重建layout
+
+            // 根据父节点从少到多排序，先布局父节点少的，由少到多，由内到外
             m_LayoutRebuildQueue.Sort(s_SortLayoutFunction);
-            for (int i = 0; i <= (int)CanvasUpdate.PostLayout; i++)
+            // prelayout -> layout -> postlayout
+            for (int i = 0; i <= (int)CanvasUpdate.PostLayout; i++) // 不同的阶段
             {
                 for (int j = 0; j < m_LayoutRebuildQueue.Count; j++)
                 {
@@ -129,16 +142,22 @@ namespace UnityEngine.UI
                 }
             }
 
+            // 布局完成
             for (int i = 0; i < m_LayoutRebuildQueue.Count; ++i)
                 m_LayoutRebuildQueue[i].LayoutComplete();
 
+            // 清空队列，重置状态
             instance.m_LayoutRebuildQueue.Clear();
             m_PerformingLayoutUpdate = false;
 
+            // 做剔除（裁剪）
             // now layout is complete do culling...
             ClipperRegistry.instance.Cull();
 
+            // 重建graphic
+
             m_PerformingGraphicUpdate = true;
+            // prerender -> lateprerender
             for (var i = (int)CanvasUpdate.PreRender; i < (int)CanvasUpdate.MaxUpdateValue; i++)
             {
                 for (var k = 0; k < instance.m_GraphicRebuildQueue.Count; k++)
@@ -156,14 +175,21 @@ namespace UnityEngine.UI
                 }
             }
 
+            // graphic设置mesh和材质完成
             for (int i = 0; i < m_GraphicRebuildQueue.Count; ++i)
                 m_GraphicRebuildQueue[i].GraphicUpdateComplete();
 
+            // 清空队列，重置状态
             instance.m_GraphicRebuildQueue.Clear();
             m_PerformingGraphicUpdate = false;
+
+            // 到了这里布局和网格、材质都设置完毕，后面canvas会渲染
+
+            // profiler不用管
             UISystemProfilerApi.EndSample(UISystemProfilerApi.SampleType.Layout);
         }
 
+        // 统计父节点个数
         private static int ParentCount(Transform child)
         {
             if (child == null)
@@ -179,14 +205,27 @@ namespace UnityEngine.UI
             return count;
         }
 
+        // 根据父节点由少到多排序
         private static int SortLayoutList(ICanvasElement x, ICanvasElement y)
         {
             Transform t1 = x.transform;
             Transform t2 = y.transform;
 
             return ParentCount(t1) - ParentCount(t2);
+        }

+

+        public static bool IsRebuildingLayout()
+        {
+            return instance.m_PerformingLayoutUpdate;
         }
 
+        public static bool IsRebuildingGraphics()
+        {
+            return instance.m_PerformingGraphicUpdate;
+        }

+

+#region 将canvas elements注册到队列里的方法
+

         public static void RegisterCanvasElementForLayoutRebuild(ICanvasElement element)
         {
             instance.InternalRegisterCanvasElementForLayoutRebuild(element);
@@ -260,16 +299,9 @@ namespace UnityEngine.UI
             }
             element.GraphicUpdateComplete();
             instance.m_GraphicRebuildQueue.Remove(element);
-        }
+        }

+

+#endregion 
 
-        public static bool IsRebuildingLayout()
-        {
-            return instance.m_PerformingLayoutUpdate;
-        }
-
-        public static bool IsRebuildingGraphics()
-        {
-            return instance.m_PerformingGraphicUpdate;
-        }
     }
 }