Move all the ContextMenu semantic helper (ARIA) components out to separate modules

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/accessibility/context_menu/StyledMenuItemCheckbox.tsx

@@ -0,0 +1,64 @@
+/*
+Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2018 New Vector Ltd
+Copyright 2019 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 {Key} from "../../Keyboard";
+import StyledCheckbox from "../../components/views/elements/StyledCheckbox";
+
+interface IProps extends React.ComponentProps<typeof StyledCheckbox> {
+    label?: string;
+    onChange();
+    onClose(): void; // gets called after onChange on Key.ENTER
+}
+
+// Semantic component for representing a styled role=menuitemcheckbox
+export const StyledMenuItemCheckbox: React.FC<IProps> = ({children, label, onChange, onClose, ...props}) => {
+    const onKeyDown = (e: React.KeyboardEvent) => {
+        if (e.key === Key.ENTER || e.key === Key.SPACE) {
+            e.stopPropagation();
+            e.preventDefault();
+            onChange();
+            // Implements https://www.w3.org/TR/wai-aria-practices/#keyboard-interaction-12
+            if (e.key === Key.ENTER) {
+                onClose();
+            }
+        }
+    };
+    const onKeyUp = (e: React.KeyboardEvent) => {
+        // prevent the input default handler as we handle it on keydown to match
+        // https://www.w3.org/TR/wai-aria-practices/examples/menubar/menubar-2/menubar-2.html
+        if (e.key === Key.SPACE || e.key === Key.ENTER) {
+            e.stopPropagation();
+            e.preventDefault();
+        }
+    };
+    return (
+        <StyledCheckbox
+            {...props}
+            role="menuitemcheckbox"
+            tabIndex={-1}
+            aria-label={label}
+            onChange={onChange}
+            onKeyDown={onKeyDown}
+            onKeyUp={onKeyUp}
+        >
+            { children }
+        </StyledCheckbox>
+    );
+};