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submodules/AsyncDisplayKit/docs/_docs/scroll-node.md

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+---
+title: ASScrollNode
+layout: docs
+permalink: /docs/scroll-node.html
+prevPage: control-node.html
+nextPage: editable-text-node.html
+---
+
+`ASScrollNode` is an `ASDisplayNode` whose underlying view is an `UIScrollView`. This class offers the ability to automatically adopt its `ASLayoutSpec`'s size as the scrollable `contentSize`. 
+
+### automaticallyManagesContentSize
+
+When enabled, the size calculated by the `ASScrolNode`'s layout spec defines the `.contentSize` of the scroll view. This is in contrast to most nodes, where the `layoutSpec` size is applied to the bounds (and in turn, frame). In this mode, the bounds of the scroll view always fills the parent's size. 
+
+`automaticallyManagesContentSize` is useful both for subclasses of `ASScrollNode` implementing `layoutSpecThatFits:` or may also be used as the base class with `.layoutSpecBlock` set. In both cases, it is common use `.automaticallyManagesSubnodes` so that the nodes in the layout spec are added to the scrollable area automatically. 
+
+With this approach there is no need to capture the layout size, use an absolute layout spec as a wrapper, or set `contentSize` anywhere in the code and it will update as the layout changes! Instead, it is very common and useful to simply return an `ASStackLayoutSpec` and the scrollable area will allow you to see all of it. 
+
+### scrollableDirections 
+
+This option is useful when using `automaticallyManagesContentSize`, <b>especially if you want horizontal content (because the default is vertical)</b>.
+
+This property controls how the `constrainedSize` is interpreted when sizing the content. Options include:
+
+<table style="width:100%" class = "paddingBetweenCols">
+  <tr>
+    <td><b>Vertical</b></td>
+    <td>The `constrainedSize` is interpreted as having unbounded `.height` (`CGFLOAT_MAX`), allowing stacks and other content in the layout spec to expand and result in scrollable content.</td> 
+  </tr>
+  <tr>
+    <td><b>Horizontal</b></td>
+    <td>The `constrainedSize` is interpreted as having unbounded `.width` (`CGFLOAT_MAX`).</td> 
+  </tr>
+  <tr>
+    <td><b>Vertical & Horizontal</b></td>
+    <td>The `constrainedSize` is interpreted as unbounded in both directions.</td>
+  </tr>
+</table>
+
+### Example
+
+In case you're not familiar with scroll views, they are basically windows into content that would take up more space than can fit in that area.
+
+Say you have a giant image, but you only want to take up 200x200 pts on the screen.
+
+<div class = "highlight-group">
+<span class="language-toggle"><a data-lang="swift" class="swiftButton">Swift</a><a data-lang="objective-c" class = "active objcButton">Objective-C</a></span>
+
+<div class = "code">
+<pre lang="objc" class="objcCode">
+// NOTE: If you are using a horizontal stack, set scrollNode.scrollableDirections.
+ASScrollNode *scrollNode = [[ASScrollNode alloc] init];
+scrollNode.automaticallyManagesSubnodes = YES;
+scrollNode.automaticallyManagesContentSize = YES;
+
+scrollNode.layoutSpecBlock = ^(ASDisplayNode *node, ASSizeRange constrainedSize){
+  ASStackLayoutSpec *stack = [ASStackLayoutSpec verticalStackLayoutSpec];
+  // Add children to the stack.
+  return stack;
+};
+
+</pre>
+<pre lang="swift" class = "swiftCode hidden">
+// NOTE: If you are using a horizontal stack, set scrollNode.scrollableDirections.
+
+let scrollNode = ASScrollNode()
+scrollNode.automaticallyManagesSubnodes = true
+scrollNode.automaticallyManagesContentSize = true
+
+scrollNode.layoutSpecBlock = { node, constrainedSize in
+  let stack = ASStackLayoutSpec.vertical()
+  // Add children to the stack.
+  return stack
+}
+
+</pre>
+</div>
+</div>