Skip decompressing keyframes that become not-current

If a subsequent transaction makes a pending tile dehydration unnecessary,
skip it to catch up more quickly.

Signed-off-by: Chris Lord <chris.lord@collabora.com>
Change-Id: I3cd76e414536d2a762291ed857eee0dcdd3307ff

Author: Chris Lord

browser/src/app/TilesMiddleware.ts

@@ -512,6 +512,9 @@ class TileManager {
 					message: message,
 					deltas: this.pendingDeltas,
 					tileSize: this.tileSize,
+					current: Object.keys(this.tiles).filter(
+						(k) => this.tiles[k].distanceFromView === 0,
+					),
 				},
 				this.pendingDeltas.map((x: any) => x.rawDelta.buffer),
 			);
@@ -2142,20 +2145,28 @@ class TileManager {
 					}
 
 					let keyframeImage = null;
-					if (x.isKeyframe)
-						keyframeImage = new ImageData(
-							x.keyframeBuffer,
-							e.data.tileSize,
-							e.data.tileSize,
+					if (x.isKeyframe) {
+						if (x.keyframeBuffer)
+							keyframeImage = new ImageData(
+								x.keyframeBuffer,
+								e.data.tileSize,
+								e.data.tileSize,
+							);
+						else {
+							tile.imgDataCache = null;
+							tile.rawDeltas = x.rawDelta;
+						}
+					}
+
+					if (!x.isKeyframe || keyframeImage)
+						this.applyDelta(
+							tile,
+							x.rawDelta,
+							x.deltas,
+							x.keyframeDeltaSize,
+							keyframeImage,
+							x.wireMessage,
 						);
-					this.applyDelta(
-						tile,
-						x.rawDelta,
-						x.deltas,
-						x.keyframeDeltaSize,
-						keyframeImage,
-						x.wireMessage,
-					);
 
 					this.createTileBitmap(tile, x, pendingDeltas, bitmaps);
 				}

browser/src/layer/tile/CanvasTileWorkerSrc.js

@@ -18,6 +18,7 @@ const PROCESS_TIME = 10;
 
 let transactionHandlerId = null;
 const transactions = [];
+let currentKeys = new Set();
 
 function transactionCallback(start_time = null) {
 	if (start_time === null) start_time = performance.now();
@@ -36,6 +37,9 @@ function transactionCallback(start_time = null) {
 		transaction.decompressed.push(tile);
 		transaction.buffers.push(tile.rawDelta.buffer);
 
+		// Skip keyframe tiles that are no longer current
+		if (tile.isKeyframe && !currentKeys.has(tile.key)) continue;
+
 		const deltas = self.fzstd.decompress(tile.rawDelta);
 		tile.keyframeDeltaSize = 0;
 
@@ -104,6 +108,7 @@ if ('undefined' === typeof window) {
 	function onMessage(e) {
 		switch (e.data.message) {
 			case 'endTransaction':
+				currentKeys = new Set(e.data.current);
 				transactions.push({
 					data: e.data,
 					decompressed: [],