Rework backdrop to draw one image with two different level of blur

res/css/structures/_LeftPanel.scss

@@ -18,7 +18,6 @@ $groupFilterPanelWidth: 56px; // only applies in this file, used for calculation
 $roomListCollapsedWidth: 68px;
 
 .mx_LeftPanel {
-    background-color: $roomlist-bg-color;
     // TODO decrease this once Spaces launches as it'll no longer need to include the 56px Community Panel
     min-width: 206px;
     max-width: 50%;

res/css/structures/_MatrixChat.scss

@@ -39,10 +39,10 @@ limitations under the License.
     position: absolute;
     top: 0;
     left: 0;
-    width: 100%;
     min-height: 100%;
     z-index: 0;
     pointer-events: none;
+    overflow: hidden;
 }
 
 .mx_MatrixToolbar {
@@ -76,7 +76,7 @@ limitations under the License.
 }
 
 /* not the left panel, and not the resize handle, so the roomview/groupview/... */
-.mx_MatrixChat > :not(.mx_LeftPanel):not(.mx_SpacePanel):not(.mx_ResizeHandle) {
+.mx_MatrixChat > :not(.mx_LeftPanel):not(.mx_SpacePanel):not(.mx_ResizeHandle):not(canvas) {
     background-color: $primary-bg-color;
 
     flex: 1 1 0;

res/css/structures/_SpacePanel.scss

@@ -24,7 +24,6 @@ $activeBorderColor: $secondary-fg-color;
 
 .mx_SpacePanel {
     flex: 0 0 auto;
-    background-color: $groupFilterPanel-bg-color;
     padding: 0;
     margin: 0;
     position: relative;

src/components/structures/BackdropPanel.tsx

@@ -17,25 +17,44 @@ limitations under the License.
 import React, { createRef } from "react";
 import "context-filter-polyfill";
 
+import UIStore from "../../stores/UIStore";
+
 interface IProps {
-    width?: number;
-    height?: number;
     backgroundImage?: CanvasImageSource;
-    blur?: string;
-    opacity?: number;
 }
 
-export default class BackdropPanel extends React.PureComponent<IProps> {
+interface IState {
-    private canvasRef = createRef<HTMLCanvasElement>();
+    spacePanelWidth: number;
-    private ctx: CanvasRenderingContext2D;
+    roomListWidth: number;
+    viewportHeight: number;
+}
 
-    static defaultProps = {
+export default class BackdropPanel extends React.PureComponent<IProps, IState> {
-        blur: "60px",
+    private spacesCanvasRef = createRef<HTMLCanvasElement>();
-        opacity: .15,
+    private roomListCanvasRef = createRef<HTMLCanvasElement>();
+
+    private spacesCtx: CanvasRenderingContext2D;
+    private roomListCtx: CanvasRenderingContext2D;
+
+    constructor(props: IProps) {
+        super(props);
+        this.state = {
+            spacePanelWidth: 0,
+            roomListWidth: 0,
+            viewportHeight: UIStore.instance.windowHeight,
         };
+    }
 
     public componentDidMount() {
-        this.ctx = this.canvasRef.current.getContext("2d");
+        this.spacesCtx = this.spacesCanvasRef.current.getContext("2d");
+        this.roomListCtx = this.roomListCanvasRef.current.getContext("2d");
+        UIStore.instance.on("SpacePanel", this.onResize);
+        UIStore.instance.on("LeftPanel", this.onResize);
+    }
+
+    public componentWillUnmount() {
+        UIStore.instance.off("SpacePanel", this.onResize);
+        UIStore.instance.off("LeftPanel", this.onResize);
     }
 
     public componentDidUpdate() {
@@ -44,10 +63,20 @@ export default class BackdropPanel extends React.PureComponent<IProps> {
         }
     }
 
+    private onResize = () => {
+        const spacePanelDimensions = UIStore.instance.getElementDimensions("SpacePanel");
+        const roomListDimensions = UIStore.instance.getElementDimensions("LeftPanel");
+        this.setState({
+            spacePanelWidth: spacePanelDimensions ? spacePanelDimensions.width : 0,
+            roomListWidth: roomListDimensions ? roomListDimensions.width : 0,
+            viewportHeight: UIStore.instance.windowHeight,
+        });
+    };
+
     private refreshBackdropImage = (): void => {
-        const { width, height, backgroundImage } = this.props;
+        const width = this.state.spacePanelWidth + this.state.roomListWidth;
-        this.canvasRef.current.width = width;
+        const height = this.state.viewportHeight;
-        this.canvasRef.current.height = height;
+        const { backgroundImage } = this.props;
 
         const imageWidth = (backgroundImage as ImageBitmap).width
         || (backgroundImage as HTMLImageElement).naturalWidth;
@@ -69,23 +98,48 @@ export default class BackdropPanel extends React.PureComponent<IProps> {
         const x = (width - resultWidth) / 2;
         const y = (height - resultHeight) / 2;
 
-        this.ctx.filter = `blur(${this.props.blur})`;
+        this.spacesCanvasRef.current.width = this.state.spacePanelWidth;
-        this.ctx.drawImage(
+        this.spacesCanvasRef.current.height = this.state.viewportHeight;
+        this.roomListCanvasRef.current.width = this.state.roomListWidth;
+        this.roomListCanvasRef.current.height = this.state.viewportHeight;
+
+        this.spacesCtx.filter = `blur(30px)`;
+        this.roomListCtx.filter = `blur(60px)`;
+        this.spacesCtx.drawImage(
             backgroundImage,
             x,
             y,
             resultWidth,
             resultHeight,
         );
+        this.roomListCtx.drawImage(
+            backgroundImage,
+            0, 0,
+            imageWidth, imageHeight,
+            x - this.state.spacePanelWidth,
+            y,
+            resultWidth,
+            resultHeight,
+        );
     };
 
     public render() {
-        return <canvas
+        return <>
-            ref={this.canvasRef}
+            <canvas
+                ref={this.spacesCanvasRef}
                 className="mx_BackdropPanel"
                 style={{
-                opacity: this.props.opacity,
+                    opacity: .15,
                 }}
-        />;
+            />
+            <canvas
+                style={{
+                    transform: `translateX(${this.state.spacePanelWidth}px)`,
+                    opacity: .1,
+                }}
+                ref={this.roomListCanvasRef}
+                className="mx_BackdropPanel"
+            />
+        </>;
     }
 }

src/components/structures/GroupFilterPanel.js

@@ -30,7 +30,6 @@ import AutoHideScrollbar from "./AutoHideScrollbar";
 import SettingsStore from "../../settings/SettingsStore";
 import UserTagTile from "../views/elements/UserTagTile";
 import { replaceableComponent } from "../../utils/replaceableComponent";
-import BackdropPanel from "./BackdropPanel";
 import UIStore from "../../stores/UIStore";
 
 @replaceableComponent("structures.GroupFilterPanel")
@@ -153,14 +152,7 @@ class GroupFilterPanel extends React.Component {
             );
         }
 
-        const panelDimensions = UIStore.instance.getElementDimensions("GroupPanel");
-
         return <div className={classes} onClick={this.onClearFilterClick} ref={this.ref}>
-            <BackdropPanel
-                backgroundImage={this.props.backgroundImage}
-                width={panelDimensions?.width}
-                height={panelDimensions?.height}
-            />
             <AutoHideScrollbar
                 className="mx_GroupFilterPanel_scroller"
                 onClick={this.onClick}

src/components/structures/LeftPanel.tsx

@@ -43,12 +43,10 @@ import { replaceableComponent } from "../../utils/replaceableComponent";
 import SpaceStore, { UPDATE_SELECTED_SPACE } from "../../stores/SpaceStore";
 import { getKeyBindingsManager, RoomListAction } from "../../KeyBindingsManager";
 import UIStore from "../../stores/UIStore";
-import BackdropPanel from "./BackdropPanel";
 
 interface IProps {
     isMinimized: boolean;
     resizeNotifier: ResizeNotifier;
-    backgroundImage?: CanvasImageSource;
 }
 
 interface IState {
@@ -426,7 +424,7 @@ export default class LeftPanel extends React.Component<IProps, IState> {
         if (this.state.showGroupFilterPanel) {
             leftLeftPanel = (
                 <div className="mx_LeftPanel_GroupFilterPanelContainer">
-                    <GroupFilterPanel backgroundImage={this.props.backgroundImage} />
+                    <GroupFilterPanel />
                     {SettingsStore.getValue("feature_custom_tags") ? <CustomRoomTagPanel /> : null}
                 </div>
             );
@@ -453,15 +451,8 @@ export default class LeftPanel extends React.Component<IProps, IState> {
             "mx_AutoHideScrollbar",
         );
 
-        const panelDimensions = UIStore.instance.getElementDimensions("LeftPanel");
-
         return (
             <div className={containerClasses} ref={this.ref}>
-                <BackdropPanel
-                    backgroundImage={this.props.backgroundImage}
-                    width={panelDimensions?.width}
-                    height={panelDimensions?.height}
-                />
                 {leftLeftPanel}
                 <aside className="mx_LeftPanel_roomListContainer">
                     {this.renderHeader()}

src/components/structures/LoggedInView.tsx

@@ -65,6 +65,7 @@ import ToastContainer from './ToastContainer';
 import MyGroups from "./MyGroups";
 import UserView from "./UserView";
 import GroupView from "./GroupView";
+import BackdropPanel from "./BackdropPanel";
 
 // We need to fetch each pinned message individually (if we don't already have it)
 // so each pinned message may trigger a request. Limit the number per room for sanity.
@@ -643,13 +644,15 @@ class LoggedInView extends React.Component<IProps, IState> {
                 >
                     <ToastContainer />
                     <div ref={this._resizeContainer} className={bodyClasses}>
+                        <BackdropPanel
+                            backgroundImage={this.state.backgroundImage}
+                        />
                         { SettingsStore.getValue("feature_spaces")
-                            ? <SpacePanel backgroundImage={this.state.backgroundImage} />
+                            ? <SpacePanel />
                             : null }
                         <LeftPanel
                             isMinimized={this.props.collapseLhs || false}
                             resizeNotifier={this.props.resizeNotifier}
-                            backgroundImage={this.state.backgroundImage}
                         />
                         <ResizeHandle />
                         { pageElement }

src/components/views/spaces/SpacePanel.tsx

@@ -43,7 +43,6 @@ import { Key } from "../../../Keyboard";
 import { RoomNotificationStateStore } from "../../../stores/notifications/RoomNotificationStateStore";
 import { NotificationState } from "../../../stores/notifications/NotificationState";
 import SettingsStore from "../../../settings/SettingsStore";
-import BackdropPanel from "../../structures/BackdropPanel";
 import UIStore from "../../../stores/UIStore";
 
 interface IButtonProps {
@@ -180,9 +179,7 @@ const InnerSpacePanel = React.memo<IInnerSpacePanelProps>(({ children, isPanelCo
     </div>;
 });
 
-interface IProps {
+interface IProps {}
-    backgroundImage?: CanvasImageSource;
-}
 
 const SpacePanel = (props: IProps) => {
     // We don't need the handle as we position the menu in a constant location
@@ -274,7 +271,6 @@ const SpacePanel = (props: IProps) => {
             UIStore.instance.stopTrackingElementDimensions("SpacePanel");
         };
     }, []);
-    const panelDimensions = UIStore.instance.getElementDimensions("SpacePanel");
 
     return (
         <DragDropContext onDragEnd={result => {
@@ -288,12 +284,6 @@ const SpacePanel = (props: IProps) => {
                         onKeyDown={onKeyDownHandler}
                         ref={ref}
                     >
-                        <BackdropPanel
-                            backgroundImage={props.backgroundImage}
-                            width={panelDimensions?.width}
-                            height={panelDimensions?.height}
-                            opacity={.3}
-                        />
                         <Droppable droppableId="top-level-spaces">
                             {(provided, snapshot) => (
                                 <AutoHideScrollbar