Improve subspaces and some utilities around room/space creation

src/components/views/context_menus/IconizedContextMenu.tsx

@@ -90,10 +90,11 @@ export const IconizedContextMenuCheckbox: React.FC<ICheckboxProps> = ({
     </MenuItemCheckbox>;
 };
 
-export const IconizedContextMenuOption: React.FC<IOptionProps> = ({ label, iconClassName, ...props }) => {
+export const IconizedContextMenuOption: React.FC<IOptionProps> = ({ label, iconClassName, children, ...props }) => {
     return <MenuItem {...props} label={label}>
         { iconClassName && <span className={classNames("mx_IconizedContextMenu_icon", iconClassName)} /> }
         <span className="mx_IconizedContextMenu_label">{ label }</span>
+        { children }
     </MenuItem>;
 };
 

src/components/views/dialogs/AddExistingSubspaceDialog.tsx

@@ -0,0 +1,70 @@
+/*
+Copyright 2021 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 React, { useState } from "react";
+import { Room } from "matrix-js-sdk/src/models/room";
+
+import { _t } from '../../../languageHandler';
+import BaseDialog from "./BaseDialog";
+import AccessibleButton from "../elements/AccessibleButton";
+import MatrixClientContext from "../../../contexts/MatrixClientContext";
+import { SpaceFeedbackPrompt } from "../../structures/SpaceRoomView";
+import { AddExistingToSpace, defaultSpacesRenderer, SubspaceSelector } from "./AddExistingToSpaceDialog";
+
+interface IProps {
+    space: Room;
+    onCreateSubspaceClick(): void;
+    onFinished(added?: boolean): void;
+}
+
+const AddExistingSubspaceDialog: React.FC<IProps> = ({ space, onCreateSubspaceClick, onFinished }) => {
+    const [selectedSpace, setSelectedSpace] = useState(space);
+
+    return <BaseDialog
+        title={(
+            <SubspaceSelector
+                title={_t("Add existing space")}
+                space={space}
+                value={selectedSpace}
+                onChange={setSelectedSpace}
+            />
+        )}
+        className="mx_AddExistingToSpaceDialog"
+        contentId="mx_AddExistingToSpace"
+        onFinished={onFinished}
+        fixedWidth={false}
+    >
+        <MatrixClientContext.Provider value={space.client}>
+            <AddExistingToSpace
+                space={space}
+                onFinished={onFinished}
+                footerPrompt={<>
+                    <div>{ _t("Want to add a new space instead?") }</div>
+                    <AccessibleButton onClick={onCreateSubspaceClick} kind="link">
+                        { _t("Create a new subspace") }
+                    </AccessibleButton>
+                </>}
+                filterPlaceholder={_t("Search for spaces")}
+                spacesRenderer={defaultSpacesRenderer}
+            />
+        </MatrixClientContext.Provider>
+
+        <SpaceFeedbackPrompt onClick={() => onFinished(false)} />
+    </BaseDialog>;
+};
+
+export default AddExistingSubspaceDialog;
+

src/components/views/dialogs/AddExistingToSpaceDialog.tsx

@@ -18,9 +18,9 @@ import React, { ReactNode, useContext, useMemo, useState } from "react";
 import classNames from "classnames";
 import { Room } from "matrix-js-sdk/src/models/room";
 import { sleep } from "matrix-js-sdk/src/utils";
+import { EventType } from "matrix-js-sdk/src/@types/event";
 
 import { _t } from '../../../languageHandler';
-import { IDialogProps } from "./IDialogProps";
 import BaseDialog from "./BaseDialog";
 import Dropdown from "../elements/Dropdown";
 import SearchBox from "../../structures/SearchBox";
@@ -42,12 +42,14 @@ import TruncatedList from "../elements/TruncatedList";
 import EntityTile from "../rooms/EntityTile";
 import BaseAvatar from "../avatars/BaseAvatar";
 
-interface IProps extends IDialogProps {
+interface IProps {
     space: Room;
-    onCreateRoomClick(space: Room): void;
+    onCreateRoomClick(): void;
+    onAddSubspaceClick(): void;
+    onFinished(added?: boolean): void;
 }
 
-const Entry = ({ room, checked, onChange }) => {
+export const Entry = ({ room, checked, onChange }) => {
     return <label className="mx_AddExistingToSpace_entry">
         { room?.isSpaceRoom()
             ? <RoomAvatar room={room} height={32} width={32} />
@@ -65,14 +67,36 @@ const Entry = ({ room, checked, onChange }) => {
 interface IAddExistingToSpaceProps {
     space: Room;
     footerPrompt?: ReactNode;
+    filterPlaceholder: string;
     emptySelectionButton?: ReactNode;
     onFinished(added: boolean): void;
+    roomsRenderer?(
+        rooms: Room[],
+        selectedToAdd: Set<Room>,
+        onChange: undefined | ((checked: boolean, room: Room) => void),
+        truncateAt: number,
+        overflowTile: (overflowCount: number, totalCount: number) => JSX.Element,
+    ): ReactNode;
+    spacesRenderer?(
+        spaces: Room[],
+        selectedToAdd: Set<Room>,
+        onChange?: (checked: boolean, room: Room) => void,
+    ): ReactNode;
+    dmsRenderer?(
+        dms: Room[],
+        selectedToAdd: Set<Room>,
+        onChange?: (checked: boolean, room: Room) => void,
+    ): ReactNode;
 }
 
 export const AddExistingToSpace: React.FC<IAddExistingToSpaceProps> = ({
     space,
     footerPrompt,
     emptySelectionButton,
+    filterPlaceholder,
+    roomsRenderer,
+    dmsRenderer,
+    spacesRenderer,
     onFinished,
 }) => {
     const cli = useContext(MatrixClientContext);
@@ -196,7 +220,7 @@ export const AddExistingToSpace: React.FC<IAddExistingToSpaceProps> = ({
         </>;
     }
 
-    const onChange = !busy && !error ? (checked, room) => {
+    const onChange = !busy && !error ? (checked: boolean, room: Room) => {
         if (checked) {
             selectedToAdd.add(room);
         } else {
@@ -206,83 +230,52 @@ export const AddExistingToSpace: React.FC<IAddExistingToSpaceProps> = ({
     } : null;
 
     const [truncateAt, setTruncateAt] = useState(20);
-    function overflowTile(overflowCount, totalCount) {
+    function overflowTile(overflowCount: number, totalCount: number): JSX.Element {
         const text = _t("and %(count)s others...", { count: overflowCount });
         return (
-            <EntityTile className="mx_EntityTile_ellipsis" avatarJsx={
-                <BaseAvatar url={require("../../../../res/img/ellipsis.svg")} name="..." width={36} height={36} />
-            } name={text} presenceState="online" suppressOnHover={true}
-            onClick={() => setTruncateAt(totalCount)} />
+            <EntityTile
+                className="mx_EntityTile_ellipsis"
+                avatarJsx={
+                    <BaseAvatar url={require("../../../../res/img/ellipsis.svg")} name="..." width={36} height={36} />
+                }
+                name={text}
+                presenceState="online"
+                suppressOnHover={true}
+                onClick={() => setTruncateAt(totalCount)}
+            />
         );
     }
 
+    let noResults = true;
+    if ((roomsRenderer && rooms.length > 0) ||
+        (dmsRenderer && dms.length > 0) ||
+        (!roomsRenderer && !dmsRenderer && spacesRenderer && dms.length > 0) // only count spaces when alone
+    ) {
+        noResults = false;
+    }
+
     return <div className="mx_AddExistingToSpace">
         <SearchBox
             className="mx_textinput_icon mx_textinput_search"
-            placeholder={_t("Filter your rooms and spaces")}
+            placeholder={filterPlaceholder}
             onSearch={setQuery}
             autoComplete={true}
             autoFocus={true}
         />
         <AutoHideScrollbar className="mx_AddExistingToSpace_content">
-            { rooms.length > 0 ? (
-                <div className="mx_AddExistingToSpace_section">
-                    <h3>{ _t("Rooms") }</h3>
-                    <TruncatedList
-                        truncateAt={truncateAt}
-                        createOverflowElement={overflowTile}
-                        getChildren={(start, end) => rooms.slice(start, end).map(room =>
-                            <Entry
-                                key={room.roomId}
-                                room={room}
-                                checked={selectedToAdd.has(room)}
-                                onChange={onChange ? (checked) => {
-                                    onChange(checked, room);
-                                } : null}
-                            />,
-                        )}
-                        getChildCount={() => rooms.length}
-                    />
-                </div>
+            { rooms.length > 0 && roomsRenderer ? (
+                roomsRenderer(rooms, selectedToAdd, onChange, truncateAt, overflowTile)
             ) : undefined }
 
-            { spaces.length > 0 ? (
-                <div className="mx_AddExistingToSpace_section mx_AddExistingToSpace_section_spaces">
-                    <h3>{ _t("Spaces") }</h3>
-                    <div className="mx_AddExistingToSpace_section_experimental">
-                        <div>{ _t("Feeling experimental?") }</div>
-                        <div>{ _t("You can add existing spaces to a space.") }</div>
-                    </div>
-                    { spaces.map(space => {
-                        return <Entry
-                            key={space.roomId}
-                            room={space}
-                            checked={selectedToAdd.has(space)}
-                            onChange={onChange ? (checked) => {
-                                onChange(checked, space);
-                            } : null}
-                        />;
-                    }) }
-                </div>
+            { spaces.length > 0 && spacesRenderer ? (
+                spacesRenderer(spaces, selectedToAdd, onChange)
             ) : null }
 
-            { dms.length > 0 ? (
-                <div className="mx_AddExistingToSpace_section">
-                    <h3>{ _t("Direct Messages") }</h3>
-                    { dms.map(room => {
-                        return <Entry
-                            key={room.roomId}
-                            room={room}
-                            checked={selectedToAdd.has(room)}
-                            onChange={onChange ? (checked) => {
-                                onChange(checked, room);
-                            } : null}
-                        />;
-                    }) }
-                </div>
+            { dms.length > 0 && dmsRenderer ? (
+                dmsRenderer(dms, selectedToAdd, onChange)
             ) : null }
 
-            { spaces.length + rooms.length + dms.length < 1 ? <span className="mx_AddExistingToSpace_noResults">
+            { noResults ? <span className="mx_AddExistingToSpace_noResults">
                 { _t("No results") }
             </span> : undefined }
         </AutoHideScrollbar>
@@ -293,50 +286,126 @@ export const AddExistingToSpace: React.FC<IAddExistingToSpaceProps> = ({
     </div>;
 };
 
-const AddExistingToSpaceDialog: React.FC<IProps> = ({ space, onCreateRoomClick, onFinished }) => {
-    const [selectedSpace, setSelectedSpace] = useState(space);
-    const existingSubspaces = SpaceStore.instance.getChildSpaces(space.roomId);
+export const defaultRoomsRenderer: IAddExistingToSpaceProps["roomsRenderer"] = (
+    rooms, selectedToAdd, onChange, truncateAt, overflowTile,
+) => (
+    <div className="mx_AddExistingToSpace_section">
+        <h3>{ _t("Rooms") }</h3>
+        <TruncatedList
+            truncateAt={truncateAt}
+            createOverflowElement={overflowTile}
+            getChildren={(start, end) => rooms.slice(start, end).map(room =>
+                <Entry
+                    key={room.roomId}
+                    room={room}
+                    checked={selectedToAdd.has(room)}
+                    onChange={onChange ? (checked: boolean) => {
+                        onChange(checked, room);
+                    } : null}
+                />,
+            )}
+            getChildCount={() => rooms.length}
+        />
+    </div>
+);
 
-    let spaceOptionSection;
-    if (existingSubspaces.length > 0) {
-        const options = [space, ...existingSubspaces].map((space) => {
-            const classes = classNames("mx_AddExistingToSpaceDialog_dropdownOption", {
-                mx_AddExistingToSpaceDialog_dropdownOptionActive: space === selectedSpace,
-            });
-            return <div key={space.roomId} className={classes}>
-                <RoomAvatar room={space} width={24} height={24} />
-                { space.name || getDisplayAliasForRoom(space) || space.roomId }
-            </div>;
-        });
+export const defaultSpacesRenderer: IAddExistingToSpaceProps["spacesRenderer"] = (spaces, selectedToAdd, onChange) => (
+    <div className="mx_AddExistingToSpace_section">
+        { spaces.map(space => {
+            return <Entry
+                key={space.roomId}
+                room={space}
+                checked={selectedToAdd.has(space)}
+                onChange={onChange ? (checked) => {
+                    onChange(checked, space);
+                } : null}
+            />;
+        }) }
+    </div>
+);
 
-        spaceOptionSection = (
+export const defaultDmsRenderer: IAddExistingToSpaceProps["dmsRenderer"] = (dms, selectedToAdd, onChange) => (
+    <div className="mx_AddExistingToSpace_section">
+        <h3>{ _t("Direct Messages") }</h3>
+        { dms.map(room => {
+            return <Entry
+                key={room.roomId}
+                room={room}
+                checked={selectedToAdd.has(room)}
+                onChange={onChange ? (checked: boolean) => {
+                    onChange(checked, room);
+                } : null}
+            />;
+        }) }
+    </div>
+);
+
+interface ISubspaceSelectorProps {
+    title: string;
+    space: Room;
+    value: Room;
+    onChange(space: Room): void;
+}
+
+export const SubspaceSelector = ({ title, space, value, onChange }: ISubspaceSelectorProps) => {
+    const options = useMemo(() => {
+        return [space, ...SpaceStore.instance.getChildSpaces(space.roomId).filter(space => {
+            return space.currentState.maySendStateEvent(EventType.SpaceChild, space.client.credentials.userId);
+        })];
+    }, [space]);
+
+    let body;
+    if (options.length > 1) {
+        body = (
             <Dropdown
                 id="mx_SpaceSelectDropdown"
+                className="mx_SpaceSelectDropdown"
                 onOptionChange={(key: string) => {
-                    setSelectedSpace(existingSubspaces.find(space => space.roomId === key) || space);
+                    onChange(options.find(space => space.roomId === key) || space);
                 }}
-                value={selectedSpace.roomId}
+                value={value.roomId}
                 label={_t("Space selection")}
             >
-                { options }
+                { options.map((space) => {
+                    const classes = classNames({
+                        mx_SubspaceSelector_dropdownOptionActive: space === value,
+                    });
+                    return <div key={space.roomId} className={classes}>
+                        <RoomAvatar room={space} width={24} height={24} />
+                        { space.name || getDisplayAliasForRoom(space) || space.roomId }
+                    </div>;
+                }) }
             </Dropdown>
         );
     } else {
-        spaceOptionSection = <div className="mx_AddExistingToSpaceDialog_onlySpace">
-            { space.name || getDisplayAliasForRoom(space) || space.roomId }
-        </div>;
+        body = (
+            <div className="mx_SubspaceSelector_onlySpace">
+                { space.name || getDisplayAliasForRoom(space) || space.roomId }
+            </div>
+        );
     }
 
-    const title = <React.Fragment>
-        <RoomAvatar room={selectedSpace} height={40} width={40} />
+    return <div className="mx_SubspaceSelector">
+        <RoomAvatar room={value} height={40} width={40} />
         <div>
-            <h1>{ _t("Add existing rooms") }</h1>
-            { spaceOptionSection }
+            <h1>{ title }</h1>
+            { body }
         </div>
-    </React.Fragment>;
+    </div>;
+};
+
+const AddExistingToSpaceDialog: React.FC<IProps> = ({ space, onCreateRoomClick, onAddSubspaceClick, onFinished }) => {
+    const [selectedSpace, setSelectedSpace] = useState(space);
 
     return <BaseDialog
-        title={title}
+        title={(
+            <SubspaceSelector
+                title={_t("Add existing rooms")}
+                space={space}
+                value={selectedSpace}
+                onChange={setSelectedSpace}
+            />
+        )}
         className="mx_AddExistingToSpaceDialog"
         contentId="mx_AddExistingToSpace"
         onFinished={onFinished}
@@ -348,10 +417,27 @@ const AddExistingToSpaceDialog: React.FC<IProps> = ({ space, onCreateRoomClick,
                 onFinished={onFinished}
                 footerPrompt={<>
                     <div>{ _t("Want to add a new room instead?") }</div>
-                    <AccessibleButton onClick={() => onCreateRoomClick(space)} kind="link">
+                    <AccessibleButton kind="link" onClick={() => {
+                        onCreateRoomClick();
+                        onFinished();
+                    }}>
                         { _t("Create a new room") }
                     </AccessibleButton>
                 </>}
+                filterPlaceholder={_t("Search for rooms")}
+                roomsRenderer={defaultRoomsRenderer}
+                spacesRenderer={() => (
+                    <div className="mx_AddExistingToSpace_section">
+                        <h3>{ _t("Spaces") }</h3>
+                        <AccessibleButton kind="link" onClick={() => {
+                            onAddSubspaceClick();
+                            onFinished();
+                        }}>
+                            { _t("Adding spaces has moved.") }
+                        </AccessibleButton>
+                    </div>
+                )}
+                dmsRenderer={defaultDmsRenderer}
             />
         </MatrixClientContext.Provider>
 

src/components/views/dialogs/CreateRoomDialog.tsx

@@ -32,8 +32,8 @@ import RoomAliasField from "../elements/RoomAliasField";
 import LabelledToggleSwitch from "../elements/LabelledToggleSwitch";
 import DialogButtons from "../elements/DialogButtons";
 import BaseDialog from "../dialogs/BaseDialog";
-import Dropdown from "../elements/Dropdown";
 import SpaceStore from "../../../stores/SpaceStore";
+import JoinRuleDropdown from "../elements/JoinRuleDropdown";
 
 interface IProps {
     defaultPublic?: boolean;
@@ -321,21 +321,6 @@ export default class CreateRoomDialog extends React.Component<IProps, IState> {
             title = this.state.joinRule === JoinRule.Public ? _t('Create a public room') : _t('Create a private room');
         }
 
-        const options = [
-            <div key={JoinRule.Invite} className="mx_CreateRoomDialog_dropdown_invite">
-                { _t("Private room (invite only)") }
-            </div>,
-            <div key={JoinRule.Public} className="mx_CreateRoomDialog_dropdown_public">
-                { _t("Public room") }
-            </div>,
-        ];
-
-        if (this.supportsRestricted) {
-            options.unshift(<div key={JoinRule.Restricted} className="mx_CreateRoomDialog_dropdown_restricted">
-                { _t("Visible to space members") }
-            </div>);
-        }
-
         return (
             <BaseDialog className="mx_CreateRoomDialog" onFinished={this.props.onFinished} title={title}>
                 <form onSubmit={this.onOk} onKeyDown={this.onKeyDown}>
@@ -355,16 +340,14 @@ export default class CreateRoomDialog extends React.Component<IProps, IState> {
                             className="mx_CreateRoomDialog_topic"
                         />
 
-                        <Dropdown
-                            id="mx_CreateRoomDialog_typeDropdown"
-                            className="mx_CreateRoomDialog_typeDropdown"
-                            onOptionChange={this.onJoinRuleChange}
-                            menuWidth={448}
-                            value={this.state.joinRule}
+                        <JoinRuleDropdown
                             label={_t("Room visibility")}
-                        >
-                            { options }
-                        </Dropdown>
+                            labelInvite={_t("Private room (invite only)")}
+                            labelPublic={_t("Public room")}
+                            labelRestricted={this.supportsRestricted ? _t("Visible to space members") : undefined}
+                            value={this.state.joinRule}
+                            onChange={this.onJoinRuleChange}
+                        />
 
                         { publicPrivateLabel }
                         { e2eeSection }

src/components/views/dialogs/CreateSubspaceDialog.tsx

@@ -0,0 +1,183 @@
+/*
+Copyright 2021 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 React, { useRef, useState } from "react";
+import { Room } from "matrix-js-sdk/src/models/room";
+import { JoinRule, Preset } from "matrix-js-sdk/src/@types/partials";
+import { RoomType } from "matrix-js-sdk/src/@types/event";
+
+import { _t } from '../../../languageHandler';
+import BaseDialog from "./BaseDialog";
+import AccessibleButton from "../elements/AccessibleButton";
+import MatrixClientContext from "../../../contexts/MatrixClientContext";
+import { BetaPill } from "../beta/BetaCard";
+import Field from "../elements/Field";
+import RoomAliasField from "../elements/RoomAliasField";
+import SpaceStore from "../../../stores/SpaceStore";
+import { SpaceCreateForm } from "../spaces/SpaceCreateMenu";
+import createRoom from "../../../createRoom";
+import { SubspaceSelector } from "./AddExistingToSpaceDialog";
+import JoinRuleDropdown from "../elements/JoinRuleDropdown";
+
+interface IProps {
+    space: Room;
+    onAddExistingSpaceClick(): void;
+    onFinished(added?: boolean): void;
+}
+
+const CreateSubspaceDialog: React.FC<IProps> = ({ space, onAddExistingSpaceClick, onFinished }) => {
+    const [parentSpace, setParentSpace] = useState(space);
+
+    const [busy, setBusy] = useState<boolean>(false);
+    const [name, setName] = useState("");
+    const spaceNameField = useRef<Field>();
+    const [alias, setAlias] = useState("");
+    const spaceAliasField = useRef<RoomAliasField>();
+    const [avatar, setAvatar] = useState<File>(null);
+    const [topic, setTopic] = useState<string>("");
+
+    const supportsRestricted = !!SpaceStore.instance.restrictedJoinRuleSupport?.preferred;
+
+    const spaceJoinRule = space.getJoinRule();
+    let defaultJoinRule = JoinRule.Invite;
+    if (spaceJoinRule === JoinRule.Public) {
+        defaultJoinRule = JoinRule.Public;
+    } else if (supportsRestricted) {
+        defaultJoinRule = JoinRule.Restricted;
+    }
+    const [joinRule, setJoinRule] = useState<JoinRule>(defaultJoinRule);
+
+    const onCreateSubspaceClick = async (e) => {
+        e.preventDefault();
+        if (busy) return;
+
+        setBusy(true);
+        // require & validate the space name field
+        if (!await spaceNameField.current.validate({ allowEmpty: false })) {
+            spaceNameField.current.focus();
+            spaceNameField.current.validate({ allowEmpty: false, focused: true });
+            setBusy(false);
+            return;
+        }
+        // validate the space name alias field but do not require it
+        if (joinRule === JoinRule.Public && !await spaceAliasField.current.validate({ allowEmpty: true })) {
+            spaceAliasField.current.focus();
+            spaceAliasField.current.validate({ allowEmpty: true, focused: true });
+            setBusy(false);
+            return;
+        }
+
+        try {
+            await createRoom({
+                createOpts: {
+                    preset: joinRule === JoinRule.Public ? Preset.PublicChat : Preset.PrivateChat,
+                    name,
+                    power_level_content_override: {
+                        // Only allow Admins to write to the timeline to prevent hidden sync spam
+                        events_default: 100,
+                        ...joinRule === JoinRule.Public ? { invite: 0 } : {},
+                    },
+                    room_alias_name: joinRule === JoinRule.Public && alias
+                        ? alias.substr(1, alias.indexOf(":") - 1)
+                        : undefined,
+                    topic,
+                },
+                avatar,
+                roomType: RoomType.Space,
+                parentSpace,
+                spinner: false,
+                encryption: false,
+                andView: true,
+                inlineErrors: true,
+            });
+
+            onFinished(true);
+        } catch (e) {
+            console.error(e);
+        }
+    };
+
+    return <BaseDialog
+        title={(
+            <SubspaceSelector
+                title={_t("Create a subspace")}
+                space={space}
+                value={parentSpace}
+                onChange={setParentSpace}
+            />
+        )}
+        className="mx_CreateSubspaceDialog"
+        contentId="mx_CreateSubspaceDialog"
+        onFinished={onFinished}
+        fixedWidth={false}
+    >
+        <MatrixClientContext.Provider value={space.client}>
+            <div className="mx_CreateSubspaceDialog_content">
+                <div className="mx_CreateSubspaceDialog_betaNotice">
+                    <BetaPill />
+                    { _t("Add a subspace to a space you manage.") }
+                </div>
+
+                <SpaceCreateForm
+                    busy={busy}
+                    onSubmit={onCreateSubspaceClick}
+                    setAvatar={setAvatar}
+                    name={name}
+                    setName={setName}
+                    nameFieldRef={spaceNameField}
+                    topic={topic}
+                    setTopic={setTopic}
+                    alias={alias}
+                    setAlias={setAlias}
+                    showAliasField={joinRule === JoinRule.Public}
+                    aliasFieldRef={spaceAliasField}
+                >
+                    <JoinRuleDropdown
+                        label={_t("Subspace visibility")}
+                        labelInvite={_t("Private subspace (invite only)")}
+                        labelPublic={_t("Public subspace")}
+                        labelRestricted={supportsRestricted ? _t("Visible to space members") : undefined}
+                        width={478}
+                        value={joinRule}
+                        onChange={setJoinRule}
+                    />
+                </SpaceCreateForm>
+            </div>
+
+            <div className="mx_CreateSubspaceDialog_footer">
+                <span>
+                    <div>{ _t("Want to add an existing space instead?") }</div>
+                    <AccessibleButton kind="link" onClick={() => {
+                        onAddExistingSpaceClick();
+                        onFinished();
+                    }}>
+                        { _t("Add existing space") }
+                    </AccessibleButton>
+                </span>
+
+                <AccessibleButton kind="primary_outline" disabled={busy} onClick={() => onFinished(false)}>
+                    { _t("Cancel") }
+                </AccessibleButton>
+                <AccessibleButton kind="primary" disabled={busy} onClick={onCreateSubspaceClick}>
+                    { busy ? _t("Adding...") : _t("Add") }
+                </AccessibleButton>
+            </div>
+        </MatrixClientContext.Provider>
+    </BaseDialog>;
+};
+
+export default CreateSubspaceDialog;
+

src/components/views/elements/JoinRuleDropdown.tsx

@@ -0,0 +1,68 @@
+/*
+Copyright 2021 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 React from 'react';
+import { JoinRule } from 'matrix-js-sdk/src/@types/partials';
+
+import Dropdown from "./Dropdown";
+
+interface IProps {
+    value: JoinRule;
+    label: string;
+    width?: number;
+    labelInvite: string;
+    labelPublic: string;
+    labelRestricted?: string; // if omitted then this option will be hidden, e.g if unsupported
+    onChange(value: JoinRule): void;
+}
+
+const JoinRuleDropdown = ({
+    label,
+    labelInvite,
+    labelPublic,
+    labelRestricted,
+    value,
+    width = 448,
+    onChange,
+}: IProps) => {
+    const options = [
+        <div key={JoinRule.Invite} className="mx_JoinRuleDropdown_invite">
+            { labelInvite }
+        </div>,
+        <div key={JoinRule.Public} className="mx_JoinRuleDropdown_public">
+            { labelPublic }
+        </div>,
+    ];
+
+    if (labelRestricted) {
+        options.unshift(<div key={JoinRule.Restricted} className="mx_JoinRuleDropdown_restricted">
+            { labelRestricted }
+        </div>);
+    }
+
+    return <Dropdown
+        id="mx_JoinRuleDropdown"
+        className="mx_JoinRuleDropdown"
+        onOptionChange={onChange}
+        menuWidth={width}
+        value={value}
+        label={label}
+    >
+        { options }
+    </Dropdown>;
+};
+
+export default JoinRuleDropdown;

src/components/views/spaces/SpaceCreateMenu.tsx

@@ -14,9 +14,9 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { useContext, useRef, useState } from "react";
+import React, { ComponentProps, RefObject, SyntheticEvent, useContext, useRef, useState } from "react";
 import classNames from "classnames";
-import { EventType, RoomType, RoomCreateTypeField } from "matrix-js-sdk/src/@types/event";
+import { RoomType } from "matrix-js-sdk/src/@types/event";
 import FocusLock from "react-focus-lock";
 
 import { _t } from "../../../languageHandler";
@@ -24,7 +24,7 @@ import AccessibleTooltipButton from "../elements/AccessibleTooltipButton";
 import { ChevronFace, ContextMenu } from "../../structures/ContextMenu";
 import createRoom from "../../../createRoom";
 import MatrixClientContext from "../../../contexts/MatrixClientContext";
-import { SpaceAvatar } from "./SpaceBasicSettings";
+import SpaceBasicSettings, { SpaceAvatar } from "./SpaceBasicSettings";
 import AccessibleButton from "../elements/AccessibleButton";
 import { BetaPill } from "../beta/BetaCard";
 import defaultDispatcher from "../../../dispatcher/dispatcher";
@@ -33,8 +33,7 @@ import { UserTab } from "../dialogs/UserSettingsDialog";
 import Field from "../elements/Field";
 import withValidation from "../elements/Validation";
 import { SpaceFeedbackPrompt } from "../../structures/SpaceRoomView";
-import { Preset } from "matrix-js-sdk/src/@types/partials";
-import { ICreateRoomStateEvent } from "matrix-js-sdk/src/@types/requests";
+import { HistoryVisibility, Preset } from "matrix-js-sdk/src/@types/partials";
 import RoomAliasField from "../elements/RoomAliasField";
 
 const SpaceCreateMenuType = ({ title, description, className, onClick }) => {
@@ -66,8 +65,83 @@ const nameToAlias = (name: string, domain: string): string => {
     return `#${localpart}:${domain}`;
 };
 
-const SpaceCreateMenu = ({ onFinished }) => {
+type BProps = Pick<ComponentProps<typeof SpaceBasicSettings>, "setAvatar" | "name" | "setName" | "topic" | "setTopic">;
+interface ISpaceCreateFormProps extends BProps {
+    busy: boolean;
+    alias: string;
+    nameFieldRef: RefObject<Field>;
+    aliasFieldRef: RefObject<RoomAliasField>;
+    showAliasField?: boolean;
+    onSubmit(e: SyntheticEvent): void;
+    setAlias(alias: string): void;
+}
+
+export const SpaceCreateForm: React.FC<ISpaceCreateFormProps> = ({
+    busy,
+    onSubmit,
+    setAvatar,
+    name,
+    setName,
+    nameFieldRef,
+    alias,
+    aliasFieldRef,
+    setAlias,
+    showAliasField,
+    topic,
+    setTopic,
+    children,
+}) => {
     const cli = useContext(MatrixClientContext);
+    const domain = cli.getDomain();
+
+    return <form className="mx_SpaceBasicSettings" onSubmit={onSubmit}>
+        <SpaceAvatar setAvatar={setAvatar} avatarDisabled={busy} />
+
+        <Field
+            name="spaceName"
+            label={_t("Name")}
+            autoFocus={true}
+            value={name}
+            onChange={ev => {
+                const newName = ev.target.value;
+                if (!alias || alias === nameToAlias(name, domain)) {
+                    setAlias(nameToAlias(newName, domain));
+                }
+                setName(newName);
+            }}
+            ref={nameFieldRef}
+            onValidate={spaceNameValidator}
+            disabled={busy}
+        />
+
+        { showAliasField
+            ? <RoomAliasField
+                ref={aliasFieldRef}
+                onChange={setAlias}
+                domain={domain}
+                value={alias}
+                placeholder={name ? nameToAlias(name, domain) : _t("e.g. my-space")}
+                label={_t("Address")}
+                disabled={busy}
+            />
+            : null
+        }
+
+        <Field
+            name="spaceTopic"
+            element="textarea"
+            label={_t("Description")}
+            value={topic}
+            onChange={ev => setTopic(ev.target.value)}
+            rows={3}
+            disabled={busy}
+        />
+
+        { children }
+    </form>;
+};
+
+const SpaceCreateMenu = ({ onFinished }) => {
     const [visibility, setVisibility] = useState<Visibility>(null);
     const [busy, setBusy] = useState<boolean>(false);
 
@@ -98,42 +172,26 @@ const SpaceCreateMenu = ({ onFinished }) => {
             return;
         }
 
-        const initialState: ICreateRoomStateEvent[] = [
-            {
-                type: EventType.RoomHistoryVisibility,
-                content: {
-                    "history_visibility": visibility === Visibility.Public ? "world_readable" : "invited",
-                },
-            },
-        ];
-        if (avatar) {
-            const url = await cli.uploadContent(avatar);
-
-            initialState.push({
-                type: EventType.RoomAvatar,
-                content: { url },
-            });
-        }
-
         try {
             await createRoom({
                 createOpts: {
                     preset: visibility === Visibility.Public ? Preset.PublicChat : Preset.PrivateChat,
                     name,
-                    creation_content: {
-                        [RoomCreateTypeField]: RoomType.Space,
-                    },
-                    initial_state: initialState,
                     power_level_content_override: {
                         // Only allow Admins to write to the timeline to prevent hidden sync spam
                         events_default: 100,
-                        ...Visibility.Public ? { invite: 0 } : {},
+                        ...visibility === Visibility.Public ? { invite: 0 } : {},
                     },
                     room_alias_name: visibility === Visibility.Public && alias
                         ? alias.substr(1, alias.indexOf(":") - 1)
                         : undefined,
                     topic,
                 },
+                avatar,
+                roomType: RoomType.Space,
+                historyVisibility: visibility === Visibility.Public
+                    ? HistoryVisibility.WorldReadable
+                    : HistoryVisibility.Invited,
                 spinner: false,
                 encryption: false,
                 andView: true,
@@ -171,7 +229,6 @@ const SpaceCreateMenu = ({ onFinished }) => {
             <SpaceFeedbackPrompt onClick={onFinished} />
         </React.Fragment>;
     } else {
-        const domain = cli.getDomain();
         body = <React.Fragment>
             <AccessibleTooltipButton
                 className="mx_SpaceCreateMenu_back"
@@ -192,49 +249,20 @@ const SpaceCreateMenu = ({ onFinished }) => {
                 }
             </p>
 
-            <form className="mx_SpaceBasicSettings" onSubmit={onSpaceCreateClick}>
-                <SpaceAvatar setAvatar={setAvatar} avatarDisabled={busy} />
-
-                <Field
-                    name="spaceName"
-                    label={_t("Name")}
-                    autoFocus={true}
-                    value={name}
-                    onChange={ev => {
-                        const newName = ev.target.value;
-                        if (!alias || alias === nameToAlias(name, domain)) {
-                            setAlias(nameToAlias(newName, domain));
-                        }
-                        setName(newName);
-                    }}
-                    ref={spaceNameField}
-                    onValidate={spaceNameValidator}
-                    disabled={busy}
-                />
-
-                { visibility === Visibility.Public
-                    ? <RoomAliasField
-                        ref={spaceAliasField}
-                        onChange={setAlias}
-                        domain={domain}
-                        value={alias}
-                        placeholder={name ? nameToAlias(name, domain) : _t("e.g. my-space")}
-                        label={_t("Address")}
-                        disabled={busy}
-                    />
-                    : null
-                }
-
-                <Field
-                    name="spaceTopic"
-                    element="textarea"
-                    label={_t("Description")}
-                    value={topic}
-                    onChange={ev => setTopic(ev.target.value)}
-                    rows={3}
-                    disabled={busy}
-                />
-            </form>
+            <SpaceCreateForm
+                busy={busy}
+                onSubmit={onSpaceCreateClick}
+                setAvatar={setAvatar}
+                name={name}
+                setName={setName}
+                nameFieldRef={spaceNameField}
+                topic={topic}
+                setTopic={setTopic}
+                alias={alias}
+                setAlias={setAlias}
+                showAliasField={visibility === Visibility.Public}
+                aliasFieldRef={spaceAliasField}
+            />
 
             <AccessibleButton kind="primary" onClick={onSpaceCreateClick} disabled={busy}>
                 { busy ? _t("Creating...") : _t("Create") }

src/components/views/spaces/SpaceTreeLevel.tsx

@@ -34,6 +34,7 @@ import {
     shouldShowSpaceSettings,
     showAddExistingRooms,
     showCreateNewRoom,
+    showCreateNewSubspace,
     showSpaceInvite,
     showSpaceSettings,
 } from "../../../utils/space";
@@ -48,6 +49,7 @@ import { EventType } from "matrix-js-sdk/src/@types/event";
 import { StaticNotificationState } from "../../../stores/notifications/StaticNotificationState";
 import { NotificationColor } from "../../../stores/notifications/NotificationColor";
 import { getKeyBindingsManager, RoomListAction } from "../../../KeyBindingsManager";
+import { BetaPill } from "../beta/BetaCard";
 
 interface IItemProps extends InputHTMLAttributes<HTMLLIElement> {
     space?: Room;
@@ -234,6 +236,14 @@ export class SpaceItem extends React.PureComponent<IItemProps, IItemState> {
         this.setState({ contextMenuPosition: null }); // also close the menu
     };
 
+    private onNewSubspaceClick = (ev: ButtonEvent) => {
+        ev.preventDefault();
+        ev.stopPropagation();
+
+        showCreateNewSubspace(this.props.space);
+        this.setState({ contextMenuPosition: null }); // also close the menu
+    };
+
     private onMembersClick = (ev: ButtonEvent) => {
         ev.preventDefault();
         ev.stopPropagation();
@@ -318,6 +328,13 @@ export class SpaceItem extends React.PureComponent<IItemProps, IItemState> {
                         label={_t("Add existing room")}
                         onClick={this.onAddExistingRoomClick}
                     />
+                    <IconizedContextMenuOption
+                        iconClassName="mx_SpacePanel_iconPlus"
+                        label={_t("Add subspace")}
+                        onClick={this.onNewSubspaceClick}
+                    >
+                        <BetaPill />
+                    </IconizedContextMenuOption>
                 </IconizedContextMenuOptionList>;
             }