Handle insertFromPaste properly for wider ranging paste support

src/components/views/rooms/BasicMessageComposer.tsx

@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 import classNames from "classnames";
-import React, { createRef, ClipboardEvent } from "react";
+import React, { createRef, ClipboardEvent, SyntheticEvent } from "react";
 import { Room } from "matrix-js-sdk/src/models/room";
 import { MatrixEvent } from "matrix-js-sdk/src/models/event";
 import EMOTICON_REGEX from "emojibase-regex/emoticon";
@@ -108,7 +108,7 @@ interface IProps {
     disabled?: boolean;
 
     onChange?(selection: Caret, inputType?: string, diff?: IDiff): void;
-    onPaste?(event: ClipboardEvent<HTMLDivElement>, model: EditorModel): boolean;
+    onPaste?(event: Event | SyntheticEvent, data: DataTransfer, model: EditorModel): boolean;
 }
 
 interface IState {
@@ -355,18 +355,18 @@ export default class BasicMessageEditor extends React.Component<IProps, IState>
         this.onCutCopy(event, "cut");
     };
 
-    private onPaste = (event: ClipboardEvent<HTMLDivElement>): boolean | undefined => {
+    private onPasteHandler = (event: Event | SyntheticEvent, data: DataTransfer): boolean | undefined => {
         event.preventDefault(); // we always handle the paste ourselves
         if (!this.editorRef.current) return;
-        if (this.props.onPaste?.(event, this.props.model)) {
+        if (this.props.onPaste?.(event, data, this.props.model)) {
             // to prevent double handling, allow props.onPaste to skip internal onPaste
             return true;
         }
 
         const { model } = this.props;
         const { partCreator } = model;
-        const plainText = event.clipboardData.getData("text/plain");
-        const partsText = event.clipboardData.getData("application/x-element-composer");
+        const plainText = data.getData("text/plain");
+        const partsText = data.getData("application/x-element-composer");
 
         let parts: Part[];
         if (partsText) {
@@ -387,6 +387,21 @@ export default class BasicMessageEditor extends React.Component<IProps, IState>
         }
     };
 
+    private onPaste = (event: ClipboardEvent<HTMLDivElement>): boolean | undefined => {
+        return this.onPasteHandler(event, event.clipboardData);
+    };
+
+    private onBeforeInput = (event: InputEvent): void => {
+        // ignore any input while doing IME compositions
+        if (this.isIMEComposing) {
+            return;
+        }
+
+        if (event.inputType === "insertFromPaste" && event.dataTransfer) {
+            this.onPasteHandler(event, event.dataTransfer);
+        }
+    };
+
     private onInput = (event: Partial<InputEvent>): void => {
         if (!this.editorRef.current) return;
         // ignore any input while doing IME compositions
@@ -703,6 +718,7 @@ export default class BasicMessageEditor extends React.Component<IProps, IState>
 
     public componentWillUnmount(): void {
         document.removeEventListener("selectionchange", this.onSelectionChange);
+        this.editorRef.current?.removeEventListener("beforeinput", this.onBeforeInput, true);
         this.editorRef.current?.removeEventListener("input", this.onInput, true);
         this.editorRef.current?.removeEventListener("compositionstart", this.onCompositionStart, true);
         this.editorRef.current?.removeEventListener("compositionend", this.onCompositionEnd, true);
@@ -728,6 +744,7 @@ export default class BasicMessageEditor extends React.Component<IProps, IState>
         this.updateEditorState(this.getInitialCaretPosition());
         // attach input listener by hand so React doesn't proxy the events,
         // as the proxied event doesn't support inputType, which we need.
+        this.editorRef.current?.addEventListener("beforeinput", this.onBeforeInput, true);
         this.editorRef.current?.addEventListener("input", this.onInput, true);
         this.editorRef.current?.addEventListener("compositionstart", this.onCompositionStart, true);
         this.editorRef.current?.addEventListener("compositionend", this.onCompositionEnd, true);

src/components/views/rooms/SendMessageComposer.tsx

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { ClipboardEvent, createRef, KeyboardEvent } from "react";
+import React, { createRef, KeyboardEvent, SyntheticEvent } from "react";
 import EMOJI_REGEX from "emojibase-regex";
 import { IContent, MatrixEvent, IEventRelation, IMentions } from "matrix-js-sdk/src/models/event";
 import { DebouncedFunc, throttle } from "lodash";
@@ -666,15 +666,14 @@ export class SendMessageComposer extends React.Component<ISendMessageComposerPro
         }
     };
 
-    private onPaste = (event: ClipboardEvent<HTMLDivElement>): boolean => {
-        const { clipboardData } = event;
+    private onPaste = (event: Event | SyntheticEvent, data: DataTransfer): boolean => {
         // Prioritize text on the clipboard over files if RTF is present as Office on macOS puts a bitmap
         // in the clipboard as well as the content being copied. Modern versions of Office seem to not do this anymore.
         // We check text/rtf instead of text/plain as when copy+pasting a file from Finder or Gnome Image Viewer
         // it puts the filename in as text/plain which we want to ignore.
-        if (clipboardData.files.length && !clipboardData.types.includes("text/rtf")) {
+        if (data.files.length && !data.types.includes("text/rtf")) {
             ContentMessages.sharedInstance().sendContentListToRoom(
-                Array.from(clipboardData.files),
+                Array.from(data.files),
                 this.props.room.roomId,
                 this.props.relation,
                 this.props.mxClient,