From bf28e7e680f599af6037b6c6cdc384f6b06f75b9 Mon Sep 17 00:00:00 2001
From: Jordan Eldredge <jordan@jordaneldredge.com>
Date: Sat, 22 Dec 2018 11:43:05 -0800
Subject: [PATCH] Scroll to skin if needed

---
 src/SkinTable.js       | 56 ++++++++++++++++++++++++++++++++++++------
 src/redux/selectors.js |  5 +++-
 2 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/src/SkinTable.js b/src/SkinTable.js
index 8c98748e..aa69c799 100644
--- a/src/SkinTable.js
+++ b/src/SkinTable.js
@@ -52,6 +52,7 @@ class SkinTable extends React.Component {
     // Our initial render may have caused the scrollbar to appear. So we
     // remeasure.
     this._handleResize();
+    this._scrollToSelectedSkinIfNeeded();
   }
 
   componentWillUnmount() {
@@ -59,6 +60,32 @@ class SkinTable extends React.Component {
     window.removeEventListener("resize", this._handleResize);
   }
 
+  componentDidUpdate() {
+    this._scrollToSelectedSkinIfNeeded();
+  }
+
+  _scrollToSelectedSkinIfNeeded() {
+    if (this.props.selectedSkinHash == null) {
+      return;
+    }
+
+    const selectedHashIndex = this.props.skinHashes.indexOf(
+      this.props.selectedSkinHash
+    );
+
+    const { start, end } = this._rangeToRender();
+    if (selectedHashIndex < start || selectedHashIndex > end) {
+      const { columnCount, rowHeight } = this._getTableDimensions();
+      const row = Math.floor(selectedHashIndex / columnCount);
+      const scrollTop =
+        row * rowHeight - (this.state.windowHeight - rowHeight) / 2;
+      window.scrollTo({
+        left: 0,
+        top: scrollTop
+      });
+    }
+  }
+
   _handleScroll() {
     // If there's a timer, cancel it
     if (this._timeout) {
@@ -82,14 +109,27 @@ class SkinTable extends React.Component {
     return { columnWidth, rowHeight, columnCount };
   }
 
-  render() {
-    const { columnWidth, rowHeight, columnCount } = this._getTableDimensions();
+  _rangeToRender() {
+    const { rowHeight, columnCount } = this._getTableDimensions();
     const hashes = this.props.skinHashes;
     // Add one since we might be showing half a row at the top, and half a row at the bottom
     const visibleRows = Math.ceil(this.state.windowHeight / rowHeight) + 1;
 
     const topRow = Math.floor(this.state.scrollTop / rowHeight);
 
+    const firstHashToRender = topRow * columnCount;
+    const lastHashToRender = Math.min(
+      firstHashToRender + visibleRows * columnCount,
+      hashes.length
+    );
+
+    return { start: firstHashToRender, end: lastHashToRender };
+  }
+
+  render() {
+    const { columnWidth, rowHeight, columnCount } = this._getTableDimensions();
+    const hashes = this.props.skinHashes;
+
     const overscanRowsDown =
       this.state.scrollDirection === "DOWN"
         ? OVERSCAN_ROWS_LEADING
@@ -99,11 +139,10 @@ class SkinTable extends React.Component {
         ? OVERSCAN_ROWS_LEADING
         : OVERSCAN_ROWS_TRAILING;
 
-    const firstHashToRender = topRow * columnCount;
-    const lastHashToRender = Math.min(
-      firstHashToRender + visibleRows * columnCount,
-      hashes.length
-    );
+    const {
+      start: firstHashToRender,
+      end: lastHashToRender
+    } = this._rangeToRender();
 
     const firstOverscanHashToRender = Math.max(
       firstHashToRender - overscanRowsUp * columnCount,
@@ -154,7 +193,8 @@ class SkinTable extends React.Component {
 
 const mapStateToProps = state => ({
   skinHashes: Selectors.getMatchingSkinHashes(state),
-  skins: Selectors.getSkins(state)
+  skins: Selectors.getSkins(state),
+  selectedSkinHash: Selectors.getSelectedSkinHash(state)
 });
 
 const mapDispatchToProps = dispatch => ({
diff --git a/src/redux/selectors.js b/src/redux/selectors.js
index c622b427..c2e440d2 100644
--- a/src/redux/selectors.js
+++ b/src/redux/selectors.js
@@ -48,7 +48,10 @@ export const getMatchingSkinHashes = createSelector(
 
 // We should be careful _not_ to memoize this function since it's non determinisitc
 export function getRandomSkinHash(state) {
-  const skinHashes = getSkinHashes(state);
+  const matchingHashes = getMatchingHashes(state);
+  const skinHashes = matchingHashes
+    ? Array.from(matchingHashes)
+    : getSkinHashes(state);
   const numberOfSkins = skinHashes.length;
   const randomIndex = Math.floor(Math.random() * numberOfSkins);
   return skinHashes[randomIndex];