[Image] Pause and play image gifs

.changeset/olive-cameras-change.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus": patch
+---
+
+[Image] New pause and play functionality for image gifs.

packages/perseus/package.json

@@ -51,6 +51,7 @@
         "@khanacademy/pure-markdown": "workspace:*",
         "@khanacademy/simple-markdown": "workspace:*",
         "@use-gesture/react": "^10.2.27",
+        "gifuct-js": "^2.1.2",
         "mafs": "0.19.0",
         "tiny-invariant": "catalog:prodDeps",
         "uuid": "^10.0.0"
@@ -64,8 +65,8 @@
         "@khanacademy/wonder-blocks-data": "catalog:devDeps",
         "@khanacademy/wonder-blocks-dropdown": "catalog:devDeps",
         "@khanacademy/wonder-blocks-form": "catalog:devDeps",
-        "@khanacademy/wonder-blocks-icon-button": "catalog:devDeps",
         "@khanacademy/wonder-blocks-icon": "catalog:devDeps",
+        "@khanacademy/wonder-blocks-icon-button": "catalog:devDeps",
         "@khanacademy/wonder-blocks-labeled-field": "catalog:devDeps",
         "@khanacademy/wonder-blocks-layout": "catalog:devDeps",
         "@khanacademy/wonder-blocks-link": "catalog:devDeps",

packages/perseus/src/components/__tests__/gif-image.test.tsx

@@ -0,0 +1,301 @@
+import {act, render, screen, waitFor} from "@testing-library/react";
+import {parseGIF, decompressFrames} from "gifuct-js";
+import * as React from "react";
+
+import GifImage from "../gif-image";
+
+jest.mock("gifuct-js");
+
+const GIF_SRC = "https://cdn.kastatic.org/test.gif";
+
+// A minimal fake frame from gifuct-js with a 50ms delay.
+const fakeFrame = {
+    patch: new Uint8ClampedArray(4), // 1x1 RGBA
+    delay: 50,
+    dims: {width: 1, height: 1, top: 0, left: 0},
+    disposalType: 0,
+};
+
+describe("GifImage", () => {
+    beforeEach(() => {
+        // Make gifuct-js return two fake frames (100ms total loop).
+        (parseGIF as jest.Mock).mockReturnValue({});
+        (decompressFrames as jest.Mock).mockReturnValue([fakeFrame, fakeFrame]);
+        // jsdom doesn't implement canvas getContext or ImageData.
+        jest.spyOn(HTMLCanvasElement.prototype, "getContext").mockReturnValue({
+            putImageData: jest.fn(),
+            clearRect: jest.fn(),
+            drawImage: jest.fn(),
+            imageSmoothingEnabled: true,
+        } as Partial<CanvasRenderingContext2D> as CanvasRenderingContext2D);
+        global.fetch = jest.fn(() =>
+            Promise.resolve({
+                ok: true,
+                arrayBuffer: () => Promise.resolve(new ArrayBuffer(0)),
+            }),
+        ) as jest.Mock;
+        // @ts-expect-error - jsdom doesn't have ImageData
+        global.ImageData = class ImageData {
+            data: Uint8ClampedArray;
+            width: number;
+            height: number;
+            constructor(
+                data: Uint8ClampedArray,
+                width: number,
+                height: number,
+            ) {
+                this.data = data;
+                this.width = width;
+                this.height = height;
+            }
+        };
+    });
+
+    it("renders a canvas when paused", () => {
+        // Arrange, Act
+        render(
+            <GifImage
+                src={GIF_SRC}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={false}
+                onPause={jest.fn()}
+            />,
+        );
+
+        // Assert
+        expect(screen.getByTestId("gif-canvas")).toBeInTheDocument();
+    });
+
+    it("renders a canvas when playing", () => {
+        // Arrange, Act
+        render(
+            <GifImage
+                src={GIF_SRC}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={true}
+                onPause={jest.fn()}
+            />,
+        );
+
+        // Assert
+        expect(screen.getByTestId("gif-canvas")).toBeInTheDocument();
+    });
+
+    describe("auto-pause", () => {
+        it("calls onPause after all frames have been rendered", async () => {
+            // Arrange
+            const onPause = jest.fn();
+            render(
+                <GifImage
+                    src={GIF_SRC}
+                    alt="test gif"
+                    width={500}
+                    height={285}
+                    scale={1}
+                    isPlaying={true}
+                    onPause={onPause}
+                />,
+            );
+
+            // Wait for the fetch → decode promise chain to complete.
+            await waitFor(() => {
+                expect(decompressFrames).toHaveBeenCalled();
+            });
+
+            // Act — advance enough for both 50ms frames to render.
+            // RAF fires at ~16ms intervals, so we need enough ticks
+            // for two frames plus the initial timestamp capture.
+            act(() => {
+                jest.advanceTimersByTime(200);
+            });
+
+            // Assert
+            expect(onPause).toHaveBeenCalledTimes(1);
+        });
+
+        it("does not call onPause again after pausing", async () => {
+            // Arrange
+            const onPause = jest.fn();
+            const {rerender} = render(
+                <GifImage
+                    src={GIF_SRC}
+                    alt="test gif"
+                    width={500}
+                    height={285}
+                    scale={1}
+                    isPlaying={true}
+                    onPause={onPause}
+                />,
+            );
+
+            await waitFor(() => {
+                expect(decompressFrames).toHaveBeenCalled();
+            });
+            act(() => {
+                jest.advanceTimersByTime(200);
+            });
+            expect(onPause).toHaveBeenCalledTimes(1);
+
+            // Act - pause the GIF
+            rerender(
+                <GifImage
+                    src={GIF_SRC}
+                    alt="test gif"
+                    width={500}
+                    height={285}
+                    scale={1}
+                    isPlaying={false}
+                    onPause={onPause}
+                />,
+            );
+            act(() => {
+                jest.advanceTimersByTime(200);
+            });
+
+            // Assert - onPause should not have been called again
+            expect(onPause).toHaveBeenCalledTimes(1);
+        });
+    });
+
+    it("resets to frame 0 after loop completes and is replayed", async () => {
+        // Arrange — play through one full loop
+        const onPause = jest.fn();
+        const {rerender} = render(
+            <GifImage
+                src={GIF_SRC}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={true}
+                onPause={onPause}
+            />,
+        );
+
+        await waitFor(() => {
+            expect(decompressFrames).toHaveBeenCalled();
+        });
+        act(() => {
+            jest.advanceTimersByTime(200);
+        });
+        expect(onPause).toHaveBeenCalledTimes(1);
+
+        // Act — sync parent state to paused, then play again
+        rerender(
+            <GifImage
+                src={GIF_SRC}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={false}
+                onPause={onPause}
+            />,
+        );
+        rerender(
+            <GifImage
+                src={GIF_SRC}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={true}
+                onPause={onPause}
+            />,
+        );
+
+        // Advance enough for both frames to render from frame 0.
+        act(() => {
+            jest.advanceTimersByTime(200);
+        });
+        // The loop completed a second time — onPause fires again,
+        // confirming it played through both frames from the start.
+        expect(onPause).toHaveBeenCalledTimes(2);
+    });
+
+    it("renders the hidden base canvas", () => {
+        // Arrange, Act
+        render(
+            <GifImage
+                src={GIF_SRC}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={false}
+                onPause={jest.fn()}
+            />,
+        );
+
+        // Assert
+        const patchCanvas = screen.getByTestId("gif-base-canvas");
+        expect(patchCanvas).toBeInTheDocument();
+        expect(patchCanvas).not.toBeVisible();
+    });
+
+    it("decodes gif frames on mount", async () => {
+        // Arrange, Act
+        render(
+            <GifImage
+                src={GIF_SRC}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={false}
+                onPause={jest.fn()}
+            />,
+        );
+
+        // Assert — wait for the async decode chain to complete.
+        await waitFor(() => {
+            expect(global.fetch).toHaveBeenCalledWith(GIF_SRC);
+        });
+        expect(parseGIF).toHaveBeenCalled();
+        expect(decompressFrames).toHaveBeenCalled();
+    });
+
+    it("re-decodes frames when src changes", async () => {
+        // Arrange
+        const {rerender} = render(
+            <GifImage
+                src={GIF_SRC}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={false}
+                onPause={jest.fn()}
+            />,
+        );
+
+        await waitFor(() => {
+            expect(decompressFrames).toHaveBeenCalled();
+        });
+
+        // Act — change the src
+        const newSrc = "https://cdn.kastatic.org/other.gif";
+        rerender(
+            <GifImage
+                src={newSrc}
+                alt="test gif"
+                width={500}
+                height={285}
+                scale={1}
+                isPlaying={false}
+                onPause={jest.fn()}
+            />,
+        );
+
+        // Assert — wait for the second decode to complete.
+        await waitFor(() => {
+            expect(global.fetch).toHaveBeenCalledWith(newSrc);
+        });
+    });
+});

packages/perseus/src/components/__tests__/svg-image.test.tsx

@@ -1,4 +1,4 @@
-import {act, render} from "@testing-library/react";
+import {act, render, screen} from "@testing-library/react";
 import * as React from "react";
 
 import * as Dependencies from "../../dependencies";
@@ -145,10 +145,9 @@ describe("SvgImage", () => {
         });
 
         // Assert
-        // eslint-disable-next-line testing-library/no-node-access
-        expect(document.getElementsByTagName("img")[0].src).toEqual(
-            "https://www.khanacademy.org/my-test-img.png",
-        );
+        expect(
+            screen.getByRole<HTMLImageElement>("img", {name: "png image"}).src,
+        ).toEqual("https://www.khanacademy.org/my-test-img.png");
     });
 
     describe("Graphie label scaling", () => {