Merge pull request #567 from matrix-org/luke/fix-agressive-unpagination

Make the unpagination process less aggressive

Author: richvdh

src/components/structures/ScrollPanel.js

@@ -25,7 +25,10 @@ var DEBUG_SCROLL = false;
 
 // The amount of extra scroll distance to allow prior to unfilling.
 // See _getExcessHeight.
-const UNPAGINATION_PADDING = 500;
+const UNPAGINATION_PADDING = 1500;
+// The number of milliseconds to debounce calls to onUnfillRequest, to prevent
+// many scroll events causing many unfilling requests.
+const UNFILL_REQUEST_DEBOUNCE_MS = 200;
 
 if (DEBUG_SCROLL) {
     // using bind means that we get to keep useful line numbers in the console
@@ -361,7 +364,15 @@ module.exports = React.createClass({
         }
 
         if (markerScrollToken) {
-            this.props.onUnfillRequest(backwards, markerScrollToken);
+            // Use a debouncer to prevent multiple unfill calls in quick succession
+            // This is to make the unfilling process less aggressive
+            if (this._unfillDebouncer) {
+                clearTimeout(this._unfillDebouncer);
+            }
+            this._unfillDebouncer = setTimeout(() => {
+                this._unfillDebouncer = null;
+                this.props.onUnfillRequest(backwards, markerScrollToken);
+            }, UNFILL_REQUEST_DEBOUNCE_MS);
         }
     },
 

test/components/structures/TimelinePanel-test.js

@@ -341,8 +341,9 @@ describe('TimelinePanel', function() {
             var events = scryEventTiles(panel);
             expect(events[0].props.mxEvent).toBe(timeline.getEvents()[0]);
 
-            // Expect to be able to paginate forwards, having unpaginated a few events
-            expect(panel.state.canForwardPaginate).toBe(true);
+            // At this point, we make no assumption that unpagination has happened. This doesn't
+            // mean that we shouldn't be able to scroll all the way down to the bottom to see the
+            // most recent event in the timeline.
 
             // scroll all the way to the bottom
             return scrollDown();