Update visual style and sandbox properly

src/components/views/messages/DownloadActionButton.tsx

@@ -0,0 +1,110 @@
+/*
+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 { MatrixEvent } from "matrix-js-sdk/src";
+import { MediaEventHelper } from "../../../utils/MediaEventHelper";
+import React, { createRef } from "react";
+import { RovingAccessibleTooltipButton } from "../../../accessibility/RovingTabIndex";
+import Spinner from "../elements/Spinner";
+import classNames from "classnames";
+import { _t } from "../../../languageHandler";
+import { replaceableComponent } from "../../../utils/replaceableComponent";
+import { DOWNLOAD_ICON_URL } from "./MFileBody";
+
+interface IProps {
+    mxEvent: MatrixEvent;
+
+    // XXX: It can take a cycle or two for the MessageActionBar to have all the props/setup
+    // required to get us a MediaEventHelper, so we use a getter function instead to prod for
+    // one.
+    mediaEventHelperGet: () => MediaEventHelper;
+}
+
+interface IState {
+    loading: boolean;
+    blob?: Blob;
+}
+
+@replaceableComponent("views.messages.DownloadActionButton")
+export class DownloadActionButton extends React.PureComponent<IProps, IState> {
+    private iframe: React.RefObject<HTMLIFrameElement> = createRef();
+
+    public constructor(props: IProps) {
+        super(props);
+
+        this.state = {
+            loading: false,
+        };
+    }
+
+    private onDownloadClick = async () => {
+        if (this.state.loading) return;
+
+        this.setState({ loading: true });
+
+        if (this.state.blob) {
+            // Cheat and trigger a download, again.
+            return this.onFrameLoad();
+        }
+
+        const blob = await this.props.mediaEventHelperGet().sourceBlob.value;
+        this.setState({ blob });
+    };
+
+    private onFrameLoad = () => {
+        this.setState({ loading: false });
+
+        // we aren't showing the iframe, so we can send over the bare minimum styles and such.
+        this.iframe.current.contentWindow.postMessage({
+            imgSrc: DOWNLOAD_ICON_URL,
+            imgStyle: null,
+            style: "",
+            blob: this.state.blob,
+            download: this.props.mediaEventHelperGet().fileName,
+            textContent: "",
+            auto: true, // autodownload
+        }, '*');
+    };
+
+    public render() {
+        let spinner: JSX.Element;
+        if (this.state.loading) {
+            spinner = <Spinner w={18} h={18} />;
+        }
+
+        const classes = classNames({
+            'mx_MessageActionBar_maskButton': true,
+            'mx_MessageActionBar_downloadButton': true,
+            'mx_MessageActionBar_downloadSpinnerButton': !!spinner,
+        });
+
+        return <RovingAccessibleTooltipButton
+            className={classes}
+            title={_t("Download")}
+            onClick={this.onDownloadClick}
+            disabled={!!spinner}
+        >
+            { spinner }
+            { this.state.blob && <iframe
+                src={"usercontent/" /* XXX: Like MFileBody, this should come from the skin */}
+                ref={this.iframe}
+                onLoad={this.onFrameLoad}
+                sandbox="allow-scripts allow-downloads allow-downloads-without-user-activation"
+                style={{ display: "none" }}
+            /> }
+        </RovingAccessibleTooltipButton>;
+    }
+}