perf(virtual-scroll): fast path for removing

ionic-team · May 4, 2017 · 8baa647 · 8baa647
1 parent 88e5642
commit 8baa647
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Showing 2 changed files with 22 additions and 16 deletions.
diff --git a/src/components/virtual-scroll/test/basic/app.module.ts b/src/components/virtual-scroll/test/basic/app.module.ts
@@ -44,18 +44,19 @@ export class E2EPage {
 
   addRandomItem() {
     const index = Math.floor(Math.random() * this.items.length);
+    console.log('Adding to index: ', index);
     this.items.splice( index, 0, {
       value: Math.floor(Math.random() * 10000),
       someMethod: function() {
         return '!!';
       }
-    }
-    );
+    });
   }
 
   changeItem() {
     const index = Math.floor(Math.random() * this.items.length);
-    this.items[index].value = Math.floor(Math.random() * 10000);
+    console.log('Change to index: ', index);
+    this.items[index] = { value: Math.floor(Math.random() * 10000), someMethod: () => '!!' };
   }
 
   trackByFn(index: number, item: any) {

diff --git a/src/components/virtual-scroll/virtual-scroll.ts b/src/components/virtual-scroll/virtual-scroll.ts
@@ -233,7 +233,8 @@ export class VirtualScroll implements DoCheck, AfterContentInit, OnDestroy {
     scrollTop: 0,
   };
   _queue: number = SCROLL_QUEUE_NO_CHANGES;
-  _recordSize: number = 0;
+
+
   _virtualTrackBy: TrackByFn;
 
   @ContentChild(VirtualItem) _itmTmp: VirtualItem;
@@ -416,21 +417,15 @@ export class VirtualScroll implements DoCheck, AfterContentInit, OnDestroy {
    */
   firstRecord(): number {
     const cells = this._cells;
-    if (cells.length > 0) {
-      return cells[0].record;
-    }
-    return 0;
+    return (cells.length > 0) ? cells[0].record : 0;
   }
 
   /**
    * @hidden
    */
   lastRecord(): number {
     const cells = this._cells;
-    if (cells.length > 0) {
-      return cells[cells.length - 1].record;
-    }
-    return 0;
+    return (cells.length > 0) ? cells[cells.length - 1].record : 0;
   }
 
   /**
@@ -451,15 +446,25 @@ export class VirtualScroll implements DoCheck, AfterContentInit, OnDestroy {
     let needClean = false;
     if (changes) {
       var lastRecord = this.lastRecord() + 1;
-      changes.forEachOperation((item, _, cindex) => {
-        if (item.previousIndex != null || (cindex < lastRecord)) {
+
+      changes.forEachOperation((_, pindex, cindex) => {
+
+        // add new record after current position
+        if (pindex === null && (cindex < lastRecord)) {
+          console.debug('adding record before current position, slow path');
+          needClean = true;
+          return;
+        }
+        // remove record after current position
+        if (pindex < lastRecord && cindex === null) {
+          console.debug('removing record before current position, slow path');
           needClean = true;
+          return;
         }
       });
     } else {
       needClean = true;
     }
-    this._recordSize = this._records.length;
 
     this.readUpdate(needClean);
     this.writeUpdate(needClean);
@@ -555,7 +560,7 @@ export class VirtualScroll implements DoCheck, AfterContentInit, OnDestroy {
           this._itmTmp.viewContainer,
           this._itmTmp.templateRef,
           this._hdrTmp && this._hdrTmp.templateRef,
-          this._ftrTmp && this._ftrTmp.templateRef, needClean,
+          this._ftrTmp && this._ftrTmp.templateRef, needClean
         );
       });