Fix bug with sticky headers that listen to onLayout

Summary:
Wrapping them in ScrollViewStickyHeader broken the onLayout and would always give y = 0
because it is now relative to the wrapper.

This uses some not-so-great react magic, but fixes the bugs with no aparent side-effects.

Note we also need to kill the StaticRenderer wrapper that ListView introduces. I think this was
probably a premature optimization anyway since there are usually not many headers and they are
usually pretty cheap to render. If people care, they can use `shouldComponentUpdate` with the
rendered components.

Reviewed By: yungsters

Differential Revision: D4654622

fbshipit-source-id: 1ea557ef64327d1f4df53b22fedd678da1549288

Libraries/Components/ScrollView/ScrollViewStickyHeader.js

@@ -42,6 +42,10 @@ class ScrollViewStickyHeader extends React.Component {
     });
 
     this.props.onLayout(event);
+    const child = React.Children.only(this.props.children);
+    if (child.props.onLayout) {
+      child.props.onLayout(event);
+    }
   };
 
   render() {
@@ -85,7 +89,8 @@ class ScrollViewStickyHeader extends React.Component {
         onLayout={this._onLayout}
         style={[child.props.style, styles.header, {transform: [{translateY}]}]}>
         {React.cloneElement(child, {
-          style: styles.fill,
+          style: styles.fill, // We transfer the child style to the wrapper.
+          onLayout: undefined, // we call this manually through our this._onLayout
         })}
       </Animated.View>
     );

Libraries/CustomComponents/ListView/ListView.js

@@ -403,6 +403,8 @@ var ListView = React.createClass({
     var rowCount = 0;
     var stickySectionHeaderIndices = [];
 
+    const {renderSectionHeader} = this.props;
+
     var header = this.props.renderHeader && this.props.renderHeader();
     var footer = this.props.renderFooter && this.props.renderFooter();
     var totalIndex = header ? 1 : 0;
@@ -426,20 +428,14 @@ var ListView = React.createClass({
         }
       }
 
-      if (this.props.renderSectionHeader) {
-        var shouldUpdateHeader = rowCount >= this._prevRenderedRowsCount &&
-          dataSource.sectionHeaderShouldUpdate(sectionIdx);
-        bodyComponents.push(
-          <StaticRenderer
-            key={'s_' + sectionID}
-            shouldUpdate={!!shouldUpdateHeader}
-            render={this.props.renderSectionHeader.bind(
-              null,
-              dataSource.getSectionHeaderData(sectionIdx),
-              sectionID
-            )}
-          />
-        );
+      if (renderSectionHeader) {
+        bodyComponents.push(React.cloneElement(
+          renderSectionHeader(
+            dataSource.getSectionHeaderData(sectionIdx),
+            sectionID
+          ),
+          {key: 's_' + sectionID},
+        ));
         if (this.props.stickySectionHeadersEnabled) {
           stickySectionHeaderIndices.push(totalIndex++);
         }