[royale-asjs] 02/02: try a different virtual scrolling trick. Should fix #554

[aharui]

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aharui pushed a commit to branch develop
in repository https://gitbox.apache.org/repos/asf/royale-asjs.git

commit 73457e254b9872c4d8921fffef9e027cbe2ad836
Author: Alex Harui <aha...@apache.org>
AuthorDate: Tue Nov 12 23:33:05 2019 -0800

    try a different virtual scrolling trick.  Should fix #554
---
 .../beads/layouts/AdvancedDataGridLayout.as        | 41 +++++++++-------------
 1 file changed, 17 insertions(+), 24 deletions(-)

diff --git 
a/frameworks/projects/MXRoyale/src/main/royale/mx/controls/beads/layouts/AdvancedDataGridLayout.as
 
b/frameworks/projects/MXRoyale/src/main/royale/mx/controls/beads/layouts/AdvancedDataGridLayout.as
index 6bf8694..2f2d660 100644
--- 
a/frameworks/projects/MXRoyale/src/main/royale/mx/controls/beads/layouts/AdvancedDataGridLayout.as
+++ 
b/frameworks/projects/MXRoyale/src/main/royale/mx/controls/beads/layouts/AdvancedDataGridLayout.as
@@ -63,10 +63,7 @@ package mx.controls.beads.layouts
         }
         
         COMPILE::JS
-        protected var topSpacer:HTMLDivElement;
-        
-        COMPILE::JS
-        protected var bottomSpacer:HTMLDivElement;
+        protected var spacer:HTMLDivElement;
         
         COMPILE::JS
         private var listening:Boolean;
@@ -108,6 +105,22 @@ package mx.controls.beads.layouts
                 var topSpacerHeight:Number = 
Math.floor(listArea.element.scrollTop / presentationModel.rowHeight)
                     * presentationModel.rowHeight;
                 }
+                var model:IDataGridModel = uiHost.model as IDataGridModel;
+                if (model.dataProvider && model.dataProvider.length)
+                {
+                    var totalHeight:Number = model.dataProvider.length * 
presentationModel.rowHeight;
+                    COMPILE::JS
+                    {
+                        if (!spacer)
+                        {
+                            spacer = document.createElement("div") as 
HTMLDivElement;
+                            listArea.element.appendChild(spacer);
+                        }
+                        // the lists are "absolute" so they float over the 
spacer
+                        spacer.style.height = totalHeight.toString() + "px";
+                        topSpacerHeight = Math.min(topSpacerHeight, 
totalHeight - useHeight);
+                    }
+                }
                 for (var i:int = 0; i < n; i++)
                 {
                     var columnList:UIBase = displayedColumns[i] as UIBase;
@@ -119,26 +132,6 @@ package mx.controls.beads.layouts
                         columnList.dispatchEvent(new Event("layoutNeeded"));
                     }
                 }
-                var model:IDataGridModel = uiHost.model as IDataGridModel;
-                if (model.dataProvider && model.dataProvider.length)
-                {
-                    var totalHeight:Number = model.dataProvider.length * 
presentationModel.rowHeight;
-                    COMPILE::JS
-                    {
-                        if (!topSpacer)
-                        {
-                            topSpacer = document.createElement("div") as 
HTMLDivElement;
-                            listArea.element.insertBefore(topSpacer, (listArea 
as UIBase).internalChildren()[0]);
-                        }
-                        topSpacer.style.height = topSpacerHeight.toString() + 
"px";
-                        if (!bottomSpacer)
-                        {
-                            bottomSpacer = document.createElement("div") as 
HTMLDivElement;
-                            listArea.element.appendChild(bottomSpacer);
-                        }
-                        bottomSpacer.style.height = (totalHeight - useHeight - 
topSpacerHeight).toString() + "px";  
-                    }
-                }
             }            
             return retval;
         }