fix(virtualization): Use virtual scroll top which takes virtual height to actual height ration when recalculating vertical offset.

MKirova · MayaKirova · commit 819a3d07c76c · 2020-05-12T18:29:32.000+03:00
diff --git a/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.ts b/projects/igniteui-angular/src/lib/directives/for-of/for_of.directive.ts
@@ -1291,7 +1291,7 @@ export class IgxForOfDirective<T> implements OnInit, OnChanges, DoCheck, OnDestr
         let scrollOffset = 0;
         const vScroll =  this.scrollComponent.nativeElement;
         scrollOffset = vScroll && this.scrollComponent.size ?
-            this.scrollPosition - this.sizesCache[this.state.startIndex] : 0;
+            this._virtScrollTop - this.sizesCache[this.state.startIndex] : 0;
         this.dc.instance._viewContainer.element.nativeElement.style.top = -(scrollOffset) + 'px';
     }
     private _updateHScrollOffset() {

Original file line number	Diff line number	Diff line change
`@@ -1291,7 +1291,7 @@ export class IgxForOfDirective<T> implements OnInit, OnChanges, DoCheck, OnDestr`
`1291`	`1291`	`let scrollOffset = 0;`
`1292`	`1292`	`const vScroll = this.scrollComponent.nativeElement;`
`1293`	`1293`	`scrollOffset = vScroll && this.scrollComponent.size ?`
`1294`		`- this.scrollPosition - this.sizesCache[this.state.startIndex] : 0;`
	`1294`	`+ this._virtScrollTop - this.sizesCache[this.state.startIndex] : 0;`
`1295`	`1295`	`this.dc.instance._viewContainer.element.nativeElement.style.top = -(scrollOffset) + 'px';`
`1296`	`1296`	`}`
`1297`	`1297`	`private _updateHScrollOffset() {`