Pan and Zoom
Handle horizontal pan and zoom. Pan and zoom are done smoothly and
linearly, but also can be used in discrete steps via tapping keys.
This implementation is robust to losing focus and not capturing key up
events.
Bug: 111538362
Change-Id: Iafdd937b0c3e78ea24b099d9c841c9a431103e93
diff --git a/ui/src/frontend/animation.ts b/ui/src/frontend/animation.ts
new file mode 100644
index 0000000..c91ad99
--- /dev/null
+++ b/ui/src/frontend/animation.ts
@@ -0,0 +1,66 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+export class Animation {
+ private running = false;
+ private runningStartedMs = 0;
+ private end = Infinity;
+ private requestedAnimationFrame = 0;
+
+ constructor(private onAnimationStep: (timeSinceLastMs: number) => void) {}
+
+ start(durationMs?: number) {
+ if (durationMs !== undefined) {
+ this.end = Date.now() + durationMs;
+ }
+ this.run();
+ }
+
+ stop() {
+ this.running = false;
+ cancelAnimationFrame(this.requestedAnimationFrame);
+ }
+
+ getStartTimeMs(): number {
+ return this.runningStartedMs;
+ }
+
+ private run() {
+ if (this.running) {
+ return;
+ }
+ let lastFrameTimeMs = 0;
+
+ const raf = (timestampMs: number) => {
+ if (!lastFrameTimeMs) {
+ lastFrameTimeMs = timestampMs;
+ }
+ this.onAnimationStep(timestampMs - lastFrameTimeMs);
+ lastFrameTimeMs = timestampMs;
+
+ if (this.running) {
+ if (Date.now() < this.end) {
+ this.requestedAnimationFrame = requestAnimationFrame(raf);
+ } else {
+ this.running = false;
+ }
+ }
+ };
+
+ this.running = true;
+ this.runningStartedMs = Date.now();
+
+ requestAnimationFrame(raf);
+ }
+}
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