Throttle fetch requests in time graph chart

If fetching of rows is already in progress, mark any new fetch requests
as pending. When the current fetching of rows is complete, executing any
pending fetch request.

Signed-off-by: Patrick Tasse <patrick.tasse@gmail.com>

timeline-chart/src/layer/time-graph-chart.ts

@@ -85,6 +85,9 @@ export class TimeGraphChart extends TimeGraphChartLayer {
     private _debouncedMaybeFetchNewDataFine = debounce(() => this.maybeFetchNewData(false, true), 400);
     private _debouncedMaybeFetchNewDataFineFullSearch = debounce(() => this.maybeFetchNewData(false,true,true), 400);
 
+    private _fetchingRows = false;
+    private _pendingFetch: { update: boolean | undefined, fine: boolean | undefined, fullSearch: boolean | undefined } | undefined = undefined;
+
     // Keep track of the most recently clicked point.
     // If clicked again during _multiClickTime duration (milliseconds) record multi-click
     private _recentlyClickedGlobal: PIXI.Point | null = null;
@@ -465,6 +468,14 @@ export class TimeGraphChart extends TimeGraphChartLayer {
     }
 
     protected async maybeFetchNewData(update?: boolean, fine?: boolean, fullSearch?: boolean) {
+        if (this._fetchingRows) {
+            this._pendingFetch = {
+                update: this._pendingFetch?.update || update,
+                fine: this._pendingFetch?.fine || fine,
+                fullSearch: this._pendingFetch?.fullSearch || fullSearch
+            }
+            return;
+        }
         this.rowIds = this.providers.rowProvider().rowIds;
         if (update) {
             // update position of existing rows and remove deleted rows
@@ -525,9 +536,18 @@ export class TimeGraphChart extends TimeGraphChartLayer {
                 for (let i = 0; i < rowIds.length; i++) {
                     try {
                         const request = { worldRange, resolution, rowIds: [rowIds[i]], additionalParams, fullSearch };
+                        this._fetchingRows = true;
                         await this.fetchRows(request, i === rowIds.length -1, fine);
                     } catch(error) {
                         return;
+                    } finally {
+                        this._fetchingRows = false;
+                        if (this._pendingFetch !== undefined) {
+                            const pendingFetch = this._pendingFetch;
+                            this._pendingFetch = undefined;
+                            this.maybeFetchNewData(pendingFetch.update, pendingFetch.fine, pendingFetch.fullSearch);
+                            return;
+                        }
                     }
                 }
                 // When row-by-row fetch is completed (not interrupted by new request), update model with filter
@@ -540,9 +560,17 @@ export class TimeGraphChart extends TimeGraphChartLayer {
             } else {
                 try {
                     const request = { worldRange, resolution, rowIds, additionalParams, fullSearch };
+                    this._fetchingRows = true;
                     await this.fetchRows(request, !fullSearch, fine);
                 } catch(error) {
                     return;
+                } finally {
+                    this._fetchingRows = false;
+                    if (this._pendingFetch !== undefined) {
+                        const pendingUpdate = this._pendingFetch;
+                        this._pendingFetch = undefined;
+                        this.maybeFetchNewData(pendingUpdate.update, pendingUpdate.fine, pendingUpdate.fullSearch);
+                    }
                 }
             }
         } else if (!fine && this._coarseResolutionFactor !== FINE_RESOLUTION_FACTOR) {