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

MKirova · MayaKirova · commit 40ff730e6116 · 2020-05-12T18:23:22.000+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
@@ -1308,7 +1308,7 @@ 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
`@@ -1308,7 +1308,7 @@ export class IgxForOfDirective<T> implements OnInit, OnChanges, DoCheck, OnDestr`
`1308`	`1308`	`let scrollOffset = 0;`
`1309`	`1309`	`const vScroll = this.scrollComponent.nativeElement;`
`1310`	`1310`	`scrollOffset = vScroll && this.scrollComponent.size ?`
`1311`		`- this.scrollPosition - this.sizesCache[this.state.startIndex] : 0;`
	`1311`	`+ this._virtScrollTop - this.sizesCache[this.state.startIndex] : 0;`
`1312`	`1312`	`this.dc.instance._viewContainer.element.nativeElement.style.top = -(scrollOffset) + 'px';`
`1313`	`1313`	`}`
`1314`	`1314`	`private _updateHScrollOffset() {`