Automatically focus the WYSIWYG composer when you enter a room

src/components/views/rooms/wysiwyg_composer/WysiwygComposer.tsx

@@ -15,15 +15,16 @@ limitations under the License.
 */
 
 import React, { useCallback, useEffect } from 'react';
-import { useWysiwyg } from "@matrix-org/matrix-wysiwyg";
 import { IEventRelation, MatrixEvent } from 'matrix-js-sdk/src/models/event';
+import { useWysiwyg } from "@matrix-org/matrix-wysiwyg";
 
-import { useRoomContext } from '../../../../contexts/RoomContext';
-import { sendMessage } from './message';
+import { Editor } from './Editor';
+import { FormattingButtons } from './FormattingButtons';
 import { RoomPermalinkCreator } from '../../../../utils/permalinks/Permalinks';
+import { sendMessage } from './message';
 import { useMatrixClientContext } from '../../../../contexts/MatrixClientContext';
-import { FormattingButtons } from './FormattingButtons';
-import { Editor } from './Editor';
+import { useRoomContext } from '../../../../contexts/RoomContext';
+import { useWysiwygActionHandler } from './useWysiwygActionHandler';
 
 interface WysiwygProps {
     disabled?: boolean;
@@ -55,6 +56,8 @@ export function WysiwygComposer(
         ref.current?.focus();
     }, [content, mxClient, roomContext, wysiwyg, props, ref]);
 
+    useWysiwygActionHandler(disabled, ref);
+
     return (
         <div className="mx_WysiwygComposer">
             <FormattingButtons composer={wysiwyg} formattingStates={formattingStates} />

src/components/views/rooms/wysiwyg_composer/useWysiwygActionHandler.ts

@@ -0,0 +1,73 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+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.
+*/
+
+import { useRef } from "react";
+
+import defaultDispatcher from "../../../../dispatcher/dispatcher";
+import { Action } from "../../../../dispatcher/actions";
+import { ActionPayload } from "../../../../dispatcher/payloads";
+import { IRoomState } from "../../../structures/RoomView";
+import { TimelineRenderingType, useRoomContext } from "../../../../contexts/RoomContext";
+import { useDispatcher } from "../../../../hooks/useDispatcher";
+
+export function useWysiwygActionHandler(
+    disabled: boolean,
+    composerElement: React.MutableRefObject<HTMLElement>,
+) {
+    const roomContext = useRoomContext();
+    const timeoutId = useRef<number>();
+
+    useDispatcher(defaultDispatcher, (payload: ActionPayload) => {
+        // don't let the user into the composer if it is disabled - all of these branches lead
+        // to the cursor being in the composer
+        if (disabled) return;
+
+        const context = payload.context ?? TimelineRenderingType.Room;
+
+        switch (payload.action) {
+            case "reply_to_event":
+            case Action.FocusSendMessageComposer:
+                focusComposer(composerElement, context, roomContext, timeoutId);
+                break;
+            // TODO: case Action.ComposerInsert: - see SendMessageComposer
+        }
+    });
+}
+
+function focusComposer(
+    composerElement: React.MutableRefObject<HTMLElement>,
+    renderingType: TimelineRenderingType,
+    roomContext: IRoomState,
+    timeoutId: React.MutableRefObject<number>,
+) {
+    if (renderingType === roomContext.timelineRenderingType) {
+        // Immediately set the focus, so if you start typing it
+        // will appear in the composer
+        composerElement.current?.focus();
+        // If we call focus immediate, the focus _is_ in the right
+        // place, but the cursor is invisible, presumably because
+        // some other event is still processing.
+        // The following line ensures that the cursor is actually
+        // visible in composer.
+        if (timeoutId.current) {
+            clearTimeout(timeoutId.current);
+        }
+        timeoutId.current = setTimeout(
+            () => composerElement.current?.focus(),
+            200,
+        );
+    }
+}

test/components/views/rooms/wysiwyg_composer/WysiwygComposer-test.tsx

@@ -14,15 +14,18 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import "@testing-library/jest-dom";
 import React from "react";
-import { act, render, screen } from "@testing-library/react";
+import { act, render, screen, waitFor } from "@testing-library/react";
 
-import { IRoomState } from "../../../../../src/components/structures/RoomView";
+import MatrixClientContext from "../../../../../src/contexts/MatrixClientContext";
 import RoomContext, { TimelineRenderingType } from "../../../../../src/contexts/RoomContext";
+import defaultDispatcher from "../../../../../src/dispatcher/dispatcher";
+import { Action } from "../../../../../src/dispatcher/actions";
+import { IRoomState } from "../../../../../src/components/structures/RoomView";
 import { Layout } from "../../../../../src/settings/enums/Layout";
-import { createTestClient, mkEvent, mkStubRoom } from "../../../../test-utils";
-import MatrixClientContext from "../../../../../src/contexts/MatrixClientContext";
 import { WysiwygComposer } from "../../../../../src/components/views/rooms/wysiwyg_composer/WysiwygComposer";
+import { createTestClient, mkEvent, mkStubRoom } from "../../../../test-utils";
 
 // The wysiwyg fetch wasm bytes and a specific workaround is needed to make it works in a node (jest) environnement
 // See https://github.com/matrix-org/matrix-wysiwyg/blob/main/platforms/web/test.setup.ts
@@ -92,7 +95,7 @@ describe('WysiwygComposer', () => {
     };
 
     let sendMessage: () => void;
-    const customRender = (onChange = (content: string) => void 0, disabled = false) => {
+    const customRender = (onChange = (_content: string) => void 0, disabled = false) => {
         return render(
             <MatrixClientContext.Provider value={mockClient}>
                 <RoomContext.Provider value={defaultRoomContext}>
@@ -140,5 +143,58 @@ describe('WysiwygComposer', () => {
         expect(mockClient.sendMessage).toBeCalledWith('myfakeroom', null, expectedContent);
         expect(screen.getByRole('textbox')).toHaveFocus();
     });
+
+    it('Should focus when receiving an Action.FocusSendMessageComposer action', async () => {
+        // Given we don't have focus
+        customRender(() => {}, false);
+        expect(screen.getByRole('textbox')).not.toHaveFocus();
+
+        // When we send the right action
+        defaultDispatcher.dispatch({
+            action: Action.FocusSendMessageComposer,
+            context: null,
+        });
+
+        // Then the component gets the focus
+        await waitFor(() => expect(screen.getByRole('textbox')).toHaveFocus());
+    });
+
+    it('Should focus when receiving a reply_to_event action', async () => {
+        // Given we don't have focus
+        customRender(() => {}, false);
+        expect(screen.getByRole('textbox')).not.toHaveFocus();
+
+        // When we send the right action
+        defaultDispatcher.dispatch({
+            action: "reply_to_event",
+            context: null,
+        });
+
+        // Then the component gets the focus
+        await waitFor(() => expect(screen.getByRole('textbox')).toHaveFocus());
+    });
+
+    it('Should not focus when disabled', async () => {
+        // Given we don't have focus and we are disabled
+        customRender(() => {}, true);
+        expect(screen.getByRole('textbox')).not.toHaveFocus();
+
+        // When we send an action that would cause us to get focus
+        defaultDispatcher.dispatch({
+            action: Action.FocusSendMessageComposer,
+            context: null,
+        });
+        // (Send a second event to exercise the clearTimeout logic)
+        defaultDispatcher.dispatch({
+            action: Action.FocusSendMessageComposer,
+            context: null,
+        });
+
+        // Wait for event dispatch to happen
+        await new Promise((r) => setTimeout(r, 200));
+
+        // Then we don't get it because we are disabled
+        expect(screen.getByRole('textbox')).not.toHaveFocus();
+    });
 });