perf(core): stretch certain marks instead of redraw

editor/example/index.ts

@@ -36,6 +36,7 @@ export type ExampleGroup =
     | 'Coordinated Multiple Views'
     | 'Applications'
     | 'Track Templates'
+    | 'Experimental'
     | 'Doc'
     | 'Unassigned';
 
@@ -75,6 +76,10 @@ export const ExampleGroups: {
         name: 'Track Templates',
         description: 'Built-in track templates that allow creating common tracks, like ideograms and gene annotations.'
     },
+    {
+        name: 'Experimental',
+        description: 'Examples that include experimental features, such as performance improvements.'
+    },
     {
         name: 'Doc',
         description: 'Examples used in the official documentation.'
@@ -412,6 +417,12 @@ export const editorExampleObj: {
         spec: JsonExampleSpecs.EX_SPEC_ALIGNMENT_CHART,
         image: THUMBNAILS.ALIGNMENT
     },
+    PERF_ALIGNMENT: {
+        group: 'Experimental',
+        name: 'Performance Comparison: Stretching Tiles',
+        spec: JsonExampleSpecs.EX_SPEC_PERF_ALIGNMENT,
+        image: THUMBNAILS.PERF_ALIGNMENT
+    },
     CORCES_ET_AL: {
         group: 'Coordinated Multiple Views',
         name: 'Corces et al. 2020',

editor/example/json-spec/index.ts

@@ -24,6 +24,7 @@ import { EX_SPEC_CYTOBANDS } from './ideograms';
 import { EX_SPEC_PILEUP } from './pileup';
 import { EX_SPEC_TEMPLATE } from './track-template';
 import { EX_SPEC_MOUSE_EVENT } from './mouse-event';
+import { EX_SPEC_PERF_ALIGNMENT } from './perf-alignment'
 import { EX_SPEC_DEBUG } from './debug';
 
 export const JsonExampleSpecs = {
@@ -42,6 +43,7 @@ export const JsonExampleSpecs = {
     EX_SPEC_RESPONSIVE_TRACK_WISE_COMPARISON,
     EX_SPEC_ALIGNMENT_CHART,
     EX_SPEC_RESPONSIVE_ALIGNMENT_CHART,
+    EX_SPEC_PERF_ALIGNMENT,
     EX_SPEC_MARK_DISPLACEMENT,
     EX_SPEC_CIRCULAR_OVERVIEW_LINEAR_DETAIL,
     EX_SPEC_SARS_COV_2,

editor/example/json-spec/perf-alignment.ts

@@ -0,0 +1,30 @@
+import type { GoslingSpec } from '@gosling-lang/gosling-schema';
+import { alignmentWithText } from './responsive-alignment';
+
+const commonProps = { width: 800, height: 400, xAxis: false, rowLegend: false, colorLegend: false };
+export const EX_SPEC_PERF_ALIGNMENT: GoslingSpec = {
+    zoomLimits: [1, 396],
+    xDomain: { interval: [350, 396] },
+    assembly: 'unknown',
+    title: 'Smoother Zoom',
+    subtitle: 'Rather than redrawing every element at every frame, we can scale existing elements',
+    views: [
+        {
+            tracks: [
+                {
+                    ...alignmentWithText(commonProps),
+                    title: 'New Approach: Stretching Tiles',
+                    experimental: { stretchGraphics: true }
+                }
+            ]
+        },
+        {
+            tracks: [
+                {
+                    ...alignmentWithText(commonProps),
+                    title: 'Original Approach'
+                }
+            ]
+        }
+    ]
+};

editor/example/thumbnails.ts

@@ -15,6 +15,7 @@ import MARK_DISPLACEMENT from './thumbnails/MARK_DISPLACEMENT.png';
 import MATRIX_HFFC6 from './thumbnails/MATRIX_HFFC6.gif';
 import MATRIX from './thumbnails/MATRIX.png';
 import MOUSE_EVENT from './thumbnails/MOUSE_EVENT.png';
+import PERF_ALIGNMENT from './thumbnails/PERF_ALIGNMENT.png';
 import RESPONSIVE_COMPARATIVE_MATRICES from './thumbnails/RESPONSIVE_COMPARATIVE_MATRICES.gif';
 import RESPONSIVE_IDEOGRAM from './thumbnails/RESPONSIVE_IDEOGRAM.gif';
 import RESPONSIVE_MULTIVEC from './thumbnails/RESPONSIVE_MULTIVEC.gif';
@@ -48,6 +49,7 @@ export const THUMBNAILS = {
     MATRIX_HFFC6,
     MATRIX,
     MOUSE_EVENT,
+    PERF_ALIGNMENT,
     RESPONSIVE_COMPARATIVE_MATRICES,
     RESPONSIVE_IDEOGRAM,
     RESPONSIVE_MULTIVEC,

src/gosling-schema/gosling.schema.ts

@@ -431,6 +431,25 @@ interface SingleTrackBase extends CommonTrackDef {
          * @default false
          */
         performanceMode?: boolean;
+
+        /**
+         * Performance rendering option.
+         * By default, certain marks ('bar', 'line', 'rect', 'area') are stretched when zooming in/out to improve
+         * rendering performance. No marks will be stretched in circular layouts.
+         *
+         * When this option is set to true, all marks will be stretched when zooming in/out.
+         * When this option is set to false, all marks will be rerendered when zooming in/out.
+         *
+         */
+        stretchGraphics?: boolean;
+
+        /**
+         * Threshold for stretching graphics. If the graphics are scaled larger than the threshold, then the graphic
+         * will be rerendered. If the graphics are scaled smaller than 1/threshold (e.g., 1/2), then the graphic will
+         * be rerendered. This is to prevent the graphics from being stretched too much.
+         * @default 1.5
+         */
+        stretchGraphicsThreshold?: number;
     };
 
     // Mark

src/tracks/gosling-track/gosling-track.ts

@@ -333,14 +333,44 @@ const factory: PluginTrackFactory<Tile, GoslingTrackOptions> = (HGC, context, op
         override drawTile(tile: Tile) {
             if (PRINT_RENDERING_CYCLE) console.warn('drawTile(tile)');
 
-            tile.drawnAtScale = this._xScale.copy(); // being used in `super.draw()`
-
+            /**
+             * If we don't have info about the tile, we can't draw anything.
+             */
             const tileInfo = this.#processedTileInfo[tile.tileId];
             if (!tileInfo) {
                 // We do not have a track model prepared to visualize
                 return;
             }
 
+            /**
+             * Add a copy of the track scale to the tile. The tile needs its own scale because we will use it to
+             * determine how much the tile has been stretched (if we are stretching the graphics)
+             */
+            if (!tile.drawnAtScale) {
+                // This is the first time this tile is being drawn
+                tile.drawnAtScale = this._xScale.copy();
+            }
+
+            /**
+             * For certain types of marks and layouts (linear), we can stretch the graphics to avoid redrawing
+             * This is much more performant than redrawing everything at every frame
+             */
+            const [graphicsXScale, graphicsXPos] = this.getXScaleAndOffset(tile.drawnAtScale);
+            const isFirstRender = graphicsXScale === 1; // The graphicsXScale is 1 if first time the tile is being drawn
+            if (!this.#isTooStretched(graphicsXScale) && this.#hasStretchableGraphics() && !isFirstRender) {
+                // Stretch the graphics
+                tile.graphics.scale.x = graphicsXScale;
+                tile.graphics.position.x = graphicsXPos;
+                return;
+            }
+
+            /**
+             * If we can't stretch the graphics, we need to redraw everything!
+             */
+
+            // We need the tile scale to match the scale of the track
+            tile.drawnAtScale = this._xScale.copy();
+            // Clear the graphics and redraw everything
             tile.graphics?.clear();
             tile.graphics?.removeChildren();
 
@@ -1472,6 +1502,43 @@ const factory: PluginTrackFactory<Tile, GoslingTrackOptions> = (HGC, context, op
                 }
             });
         }
+
+        /**
+         * Used in drawTile()
+         * Checks if the track has marks which are stretchable. Stretching
+         * is not supported for circular layouts or 2D tracks
+         */
+        #hasStretchableGraphics() {
+            const hasStretchOption = this.options.spec.experimental?.stretchGraphics;
+            if (hasStretchOption === true) {
+                return true;
+            } else if (hasStretchOption === false) {
+                return false;
+            }
+            // The default behavior is that we stretch when stretching looks acceptable
+            const isFirstTrack1D = !Is2DTrack(this.getResolvedTracks()[0]);
+            const isNotCircularLayout = this.options.spec.layout !== 'circular';
+            const stretchableMarks = ['bar', 'line', 'rect', 'area'];
+            const hasStretchableMark = this.getResolvedTracks().reduce(
+                (acc, spec) => acc && stretchableMarks.includes(spec.mark),
+                true
+            );
+            const noMouseInteractions = !this.options.spec.experimental?.mouseEvents;
+
+            return isFirstTrack1D && isNotCircularLayout && hasStretchableMark && noMouseInteractions;
+        }
+
+        /**
+         * Used in drawTile()
+         * Checks if the tile Graphic is too stretched. If so, it returns true.
+         * @param stretchFactor The factor by which the tile is stretched
+         * @returns True if the tile is too stretched, false otherwise
+         */
+        #isTooStretched(stretchFactor: number) {
+            const defaultThreshold = 1.5;
+            const threshold = this.options.spec.experimental?.stretchGraphicsThreshold ?? defaultThreshold;
+            return stretchFactor > threshold || stretchFactor < 1 / threshold;
+        }
     }
     return new GoslingTrackClass();
 };