Fixed Hypergrid scroll stuttering

packages/perspective-viewer-hypergrid/src/js/PerspectiveDataModel.js

@@ -124,7 +124,8 @@ module.exports = require("datasaur-local").extend("PerspectiveDataModel", {
 
         try {
             await Promise.all(promises);
-            resolve(false);
+            const rects = getSubrects.call(this.grid.renderer);
+            resolve(!!rects.find(uncachedRow, this));
         } catch (e) {
             resolve(true);
         } finally {
@@ -152,7 +153,7 @@ module.exports = require("datasaur-local").extend("PerspectiveDataModel", {
 function uncachedRow(rect) {
     let start_row = this.data[rect.origin.y];
     let end_row = this.data[Math.min(rect.corner.y, this.getRowCount() - 1)];
-    return !(start_row && start_row[rect.origin.x] !== undefined && end_row && end_row[rect.corner.x] !== undefined);
+    return !(start_row && start_row[rect.origin.x] !== undefined && end_row && end_row[rect.corner.x - 1] !== undefined);
 }
 
 function cellStyle(gridCellConfig) {

packages/perspective/src/js/perspective.js

@@ -343,17 +343,18 @@ export default function(Module) {
                 formatter.addRow(data, row);
             }
         } else if (this.sides() === 1) {
+            // TODO slice.column_names should return the column names in the slice, respecting start_col and end_col
             const col_names = extract_vector(slice.get_column_names());
             for (let ridx = start_row; ridx < end_row; ridx++) {
                 const row = formatter.initRowValue();
                 for (let cidx = start_col; cidx < end_col; cidx++) {
                     const col_name = col_names[cidx];
-                    if (cidx === 0) {
+                    if (cidx === start_col) {
                         const row_path = slice.get_row_path(ridx);
-                        formatter.initColumnValue(data, row, col_name);
+                        formatter.initColumnValue(data, row, "__ROW_PATH__");
                         for (let i = 0; i < row_path.size(); i++) {
                             const value = __MODULE__.scalar_vec_to_val(row_path, i);
-                            formatter.addColumnValue(data, row, col_name, value);
+                            formatter.addColumnValue(data, row, "__ROW_PATH__", value);
                         }
                         row_path.delete();
                     } else {

packages/perspective/test/js/to_format.js

@@ -50,6 +50,17 @@ module.exports = perspective => {
             }
         });
 
+        it("one-sided views with start_col > 0 should have row paths", async function() {
+            let table = perspective.table(int_float_string_data);
+            let view = table.view({
+                row_pivot: ["int"]
+            });
+            let json = await view.to_json({start_col: 1});
+            for (let d of json) {
+                expect(d.__ROW_PATH__).toBeDefined();
+            }
+        });
+
         it("one-sided column-only views should not have row paths", async function() {
             let table = perspective.table(int_float_string_data);
             let view = table.view({