版本记录

日期	版本	说明	作者
2019-11-25	0.1	文档初始版本	李俊

原理

rebuild过程
- 正确算出来 canvasrenderer mesh， material
- Graphic rebuild
- Graphic ugui中显示的基类
- Image 图片
- Text 文字

RectTransform.widthGraphic.OnRectTransformDimensionsChangeGraphic.SetVerticesDirtyCanvasUpdateRegistry.RegisterCanvasElementForGraphicRebuildCanvasUpdateRegistry.PerformUpdateGraphic.RebuildGraphic.UpdateGeometry&UpdateMaterialcanvasRenderer.SetMesh&SetMaterial&SetTexturegraph TB A[RectTransform.width] B[Graphic.OnRectTransformDimensionsChange] C[Graphic.SetVerticesDirty] D[CanvasUpdateRegistry.RegisterCanvasElementForGraphicRebuild] E[CanvasUpdateRegistry.PerformUpdate] F[Graphic.Rebuild] G[Graphic.UpdateGeometry&UpdateMaterial] H[canvasRenderer.SetMesh&SetMaterial&SetTexture] A-->B B-->C C-->D D-->E E-->F F-->G G-->H

Layout Rebuild
- 计算子节点的recttransfrom
- ILayoutGroup 布局接口
- LayoutGroup 布局基类
- GridLayoutGroup 格子布局
- HorizontalLayoutGroup 水平布局

RectTransform.OnRectTransformDimensionsChangeLayoutGroup.SetDirtyLayoutRebuilder.MarkLayoutForRebuildLayoutRebuilder.MarkLayoutRootForRebuildCanvasUpdateRegistry.TryRegisterCanvasElementForLayoutRebuildLayoutRebuilder.RebuildILayoutElement.CalculateLayoutInputHorizontal&SetLayoutHorizontal&CalculateLayoutInputVertical&SetLayoutVerticalgraph TB A[RectTransform.OnRectTransformDimensionsChange] B[LayoutGroup.SetDirty] C[LayoutRebuilder.MarkLayoutForRebuild] D[LayoutRebuilder.MarkLayoutRootForRebuild] E[CanvasUpdateRegistry.TryRegisterCanvasElementForLayoutRebuild] F[LayoutRebuilder.Rebuild] G[ILayoutElement.CalculateLayoutInputHorizontal&SetLayoutHorizontal&CalculateLayoutInputVertical&SetLayoutVertical] A-->B B-->C C-->D D-->E E-->F F-->G

核心代码 CanvasUpdateRegistry.PerformUpdate

private void PerformUpdate()
        {
            UISystemProfilerApi.BeginSample(UISystemProfilerApi.SampleType.Layout);
            CleanInvalidItems();
  m_PerformingLayoutUpdate = true;   m_LayoutRebuildQueue.Sort(s_SortLayoutFunction);  for (int i = 0; i <= (int)CanvasUpdate.PostLayout; i++)  {  for (int j = 0; j < m_LayoutRebuildQueue.Count; j++)  {  var rebuild = instance.m_LayoutRebuildQueue[j];  try  {  if (ObjectValidForUpdate(rebuild))  rebuild.Rebuild((CanvasUpdate)i);  }  catch (Exception e)  {  Debug.LogException(e, rebuild.transform);  }  }  }   for (int i = 0; i < m_LayoutRebuildQueue.Count; ++i)  m_LayoutRebuildQueue[i].LayoutComplete();   instance.m_LayoutRebuildQueue.Clear();  m_PerformingLayoutUpdate = false;   // now layout is complete do culling...  ClipperRegistry.instance.Cull();   m_PerformingGraphicUpdate = true;  for (var i = (int)CanvasUpdate.PreRender; i < (int)CanvasUpdate.MaxUpdateValue; i++)  {  for (var k = 0; k < instance.m_GraphicRebuildQueue.Count; k++)  {  try  {  var element = instance.m_GraphicRebuildQueue[k];  if (ObjectValidForUpdate(element))  element.Rebuild((CanvasUpdate)i);  }  catch (Exception e)  {  Debug.LogException(e, instance.m_GraphicRebuildQueue[k].transform);  }  }  }   for (int i = 0; i < m_GraphicRebuildQueue.Count; ++i)  m_GraphicRebuildQueue[i].GraphicUpdateComplete();   instance.m_GraphicRebuildQueue.Clear();  m_PerformingGraphicUpdate = false;  UISystemProfilerApi.EndSample(UISystemProfilerApi.SampleType.Layout);  }

batch过程合并canvaserender里的mesh,这个过程在其他线程，没有源码，不可见
1. 根据层次结构（深度优先）拿到所有canvasrenderer
2. 从下而上遍历List,检测当前renderer和下边的renderer相交
  - 没有相交, depth = 0
  - 相交，其实深度值最大的为depthi,则检测是否能batch,能depth = depthi, 不能depth = depthi+1
3. 所有renderer根据depth排序，depth相同的根据mat id,再根据texture id
4. 相邻renderer如果能batch就合批