/// PainterContext
void paintChild(RenderObject child, Offset offset) {
    assert(() {
        debugOnProfilePaint?.call(child);
        return true;
    }());

    if (child.isRepaintBoundary) {
        stopRecordingIfNeeded();
        _compositeChild(child, offset);
    } else {
        child._paintWithContext(this, offset);
    }
}

  void _compositeChild(RenderObject child, Offset offset) {
    assert(!_isRecording);
    assert(child.isRepaintBoundary);
    assert(_canvas == null || _canvas!.getSaveCount() == 1);

    // Create a layer for our child, and paint the child into it.
    // 给子节点创建一个layer，然后在上面绘制
    if (child._needsPaint) {
      repaintCompositedChild(child, debugAlsoPaintedParent: true);
    } else {
      assert(() {
        // register the call for RepaintBoundary metrics
        child.debugRegisterRepaintBoundaryPaint();
        child._layerHandle.layer!.debugCreator = child.debugCreator ?? child;
        return true;
      }());
    }
    assert(child._layerHandle.layer is OffsetLayer);
    final OffsetLayer childOffsetLayer = child._layerHandle.layer! as OffsetLayer;
    childOffsetLayer.offset = offset;
    appendLayer(childOffsetLayer);
  }

  void markNeedsPaint() {
    assert(!_debugDisposed);
    assert(owner == null || !owner!.debugDoingPaint);
    if (_needsPaint)
      return;
    _needsPaint = true;
    //如果RenderObject.isRepaintBoundary 为true,则该RenderObject拥有layer，直接绘制
    if (isRepaintBoundary) {
      assert(() {
        if (debugPrintMarkNeedsPaintStacks)
          debugPrintStack(label: 'markNeedsPaint() called for $this');
        return true;
      }());
      // If we always have our own layer, then we can just repaint
      // ourselves without involving any other nodes.
      assert(_layerHandle.layer is OffsetLayer);
      if (owner != null) {
          //找到最近的layer，绘制
        owner!._nodesNeedingPaint.add(this);
        owner!.requestVisualUpdate();
      }
    } else if (parent is RenderObject) {
// 没有自己的layer, 会和一个祖先节点共用一个layer 
      final RenderObject parent = this.parent! as RenderObject;
      parent.markNeedsPaint();
      assert(parent == this.parent);
    } else {
      assert(() {
        if (debugPrintMarkNeedsPaintStacks)
          debugPrintStack(label: 'markNeedsPaint() called for $this (root of render tree)');
        return true;
      }());
      // If we're the root of the render tree (probably a RenderView),
      // then we have to paint ourselves, since nobody else can paint
      // us. We don't add ourselves to _nodesNeedingPaint in this
      // case, because the root is always told to paint regardless.
      if (owner != null)
      // 如果直到根节点也没找到一个Layer，那么便需要绘制自身，因为没有其它节点可以绘制根节点。
        owner!.requestVisualUpdate();
    }
  }

// 当前 app module
include ':app'

/**
 * 1、读取android/local.properties文件内容
 * 2、获取flutter.sdk的值，也就是你本地flutter SDK安装目录
 * 3、gradle 脚本常规操作 apply flutter SDK路径下/packages/flutter_tools/gradle/app_plugin_loader.gradle文件 
 */
def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
def properties = new Properties()

assert localPropertiesFile.exists()
localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }

def flutterSdkPath = properties.getProperty("flutter.sdk")
assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"

/// Parent data used by [RenderBox] and its subclasses.
class BoxParentData extends ParentData {
  /// The offset at which to paint the child in the parent's coordinate system.
  Offset offset = Offset.zero;

  @override
  String toString() => 'offset=$offset';
}