fix(core): fix #3666 #3531 #3340

thanks to @500tech-user and @Jacquelin for PR's that led to this fix

Author: swalters

src/js/core/directives/ui-grid-render-container.js

@@ -75,7 +75,8 @@
 
                 scrollTop = containerCtrl.viewport[0].scrollTop;
                 // Get the scroll percentage
-                var scrollYPercentage = (scrollTop + scrollYAmount) / rowContainer.getVerticalScrollLength();
+                scrollEvent.verticalScrollLength = rowContainer.getVerticalScrollLength();
+                var scrollYPercentage = (scrollTop + scrollYAmount) / scrollEvent.verticalScrollLength;
 
                 // Keep scrollPercentage within the range 0-1.
                 if (scrollYPercentage < 0) { scrollYPercentage = 0; }
@@ -88,7 +89,8 @@
 
                 // Get the scroll percentage
                 scrollLeft = gridUtil.normalizeScrollLeft(containerCtrl.viewport, grid);
-                var scrollXPercentage = (scrollLeft + scrollXAmount) / (colContainer.getCanvasWidth() - colContainer.getViewportWidth());
+                scrollEvent.horizontalScrollLength = (colContainer.getCanvasWidth() - colContainer.getViewportWidth());
+                var scrollXPercentage = (scrollLeft + scrollXAmount) / scrollEvent.horizontalScrollLength;
 
                 // Keep scrollPercentage within the range 0-1.
                 if (scrollXPercentage < 0) { scrollXPercentage = 0; }

src/js/core/factories/ScrollEvent.js

@@ -53,6 +53,9 @@
         self.x = null;
         self.y = null;
 
+        self.verticalScrollLength = -9999999;
+        self.horizontalScrollLength = -999999;
+
 
         /**
          *  @ngdoc function
@@ -132,19 +135,19 @@
       };
 
       ScrollEvent.prototype.atTop = function(scrollTop) {
-        return (this.y && this.y.percentage === 0 && scrollTop === 0);
+        return (this.y && (this.y.percentage === 0 || this.verticalScrollLength < 0) && scrollTop === 0);
       };
 
       ScrollEvent.prototype.atBottom = function(scrollTop) {
-        return (this.y && this.y.percentage === 1 && scrollTop > 0);
+        return (this.y && (this.y.percentage === 1 || this.verticalScrollLength === 0) && scrollTop > 0);
       };
 
       ScrollEvent.prototype.atLeft = function(scrollLeft) {
-        return (this.x && this.x.percentage === 0 && scrollLeft === 0);
+        return (this.x && (this.x.percentage === 0 || this.horizontalScrollLength < 0) && scrollLeft === 0);
       };
 
       ScrollEvent.prototype.atRight = function(scrollLeft) {
-        return (this.x && this.x.percentage === 1 && scrollLeft > 0);
+        return (this.x && (this.x.percentage === 1 || this.horizontalScrollLength ===0) && scrollLeft > 0);
       };