Add preference for custom web instances, use it for Element

src/open/ClientViewModel.js

@@ -59,11 +59,11 @@ export class ClientViewModel extends ViewModel {
             if (this._proposedPlatform === this._nativePlatform) {
                 deepLinkLabel = "Open in app";
             } else {
-                deepLinkLabel = `Open on ${this._client.getPreferredWebInstance(this._link)}`;
+                deepLinkLabel = `Open on ${this.preferredWebInstance}`;
             }
         }
         const actions = [];
-        const proposedDeepLink = this._client.getDeepLink(this._proposedPlatform, this._link);
+        const proposedDeepLink = this._client.getDeepLink(this._proposedPlatform, this._link, this.preferredWebInstance);
         if (proposedDeepLink) {
             actions.push({
                 label: deepLinkLabel,
@@ -83,8 +83,8 @@ export class ClientViewModel extends ViewModel {
         // show only if there is a preferred instance, and if we don't already link to it in the first button
         if (hasPreferredWebInstance && this._webPlatform && this._proposedPlatform !== this._webPlatform) {
             actions.push({
-                label: `Open on ${this._client.getPreferredWebInstance(this._link)}`,
-                url: this._client.getDeepLink(this._webPlatform, this._link),
+                label: `Open on ${this.preferredWebInstance}`,
+                url: this._client.getDeepLink(this._webPlatform, this._link, this.preferredWebInstance),
                 kind: "open-in-web",
                 activated: () => {} // don't persist this choice as we don't persist the preferred web instance, it's in the url
             });
@@ -108,10 +108,10 @@ export class ClientViewModel extends ViewModel {
             actions.push(...nativeActions);
         }
         if (this._webPlatform) {
-            const webDeepLink = this._client.getDeepLink(this._webPlatform, this._link);
+            const webDeepLink = this._client.getDeepLink(this._webPlatform, this._link, this.preferredWebInstance);
             if (webDeepLink) {
                 const webLabel = this.hasPreferredWebInstance ?
-                    `Open on ${this._client.getPreferredWebInstance(this._link)}` :
+                    `Open on ${this.preferredWebInstance}` :
                     `Continue in your browser`;
                 actions.push({
                     label: webLabel,
@@ -128,14 +128,22 @@ export class ClientViewModel extends ViewModel {
         return actions;
     }
 
-    get hasPreferredWebInstance() {
+    get preferredWebInstance() {
         // also check there is a web platform that matches the platforms the user is on (mobile or desktop web)
-        return this._webPlatform && typeof this._client.getPreferredWebInstance(this._link) === "string";
+        if (!this._webPlatform) return undefined;
+        return (
+            this.preferences.getPreferredWebInstance(this._client.id)
+            || this._client.getPreferredWebInstance(this._link)
+        );
+    }
+
+    get hasPreferredWebInstance() {
+        return typeof this.preferredWebInstance === "string";
     }
 
     get hostedByBannerLabel() {
-        const preferredWebInstance = this._client.getPreferredWebInstance(this._link);
-        if (this._webPlatform && preferredWebInstance) {
+        if (this.hasPreferredWebInstance) {
+            const preferredWebInstance = this.preferredWebInstance;
             let label = preferredWebInstance;
             const subDomainIdx = preferredWebInstance.lastIndexOf(".", preferredWebInstance.lastIndexOf(".") - 1);
             if (subDomainIdx !== -1) {
@@ -188,7 +196,7 @@ export class ClientViewModel extends ViewModel {
 
     get showDeepLinkInInstall() {
         // we can assume this._nativePlatform as this._clientCanIntercept already checks it
-        return this._clientCanIntercept && !!this._client.getDeepLink(this._nativePlatform, this._link);
+        return this._clientCanIntercept && !!this._client.getDeepLink(this._nativePlatform, this._link, this.preferredWebInstance);
     }
 
     get availableOnPlatformNames() {

src/open/clients/Element.js

@@ -55,8 +55,9 @@ export class Element {
     get homepage() { return "https://element.io"; }
     get author() { return "Element"; }
     getMaturity(platform) { return Maturity.Stable; }
+    get supportsCustomInstances() { return true; }
 
-    getDeepLink(platform, link) {
+    getDeepLink(platform, link, preferredWebInstance) {
         let fragmentPath;
         switch (link.kind) {
             case LinkKind.User:
@@ -82,8 +83,8 @@ export class Element {
             let instanceHost = trustedWebInstances[0];
             // we use app.element.io which iOS will intercept, but it likely won't intercept any other trusted instances
             // so only use a preferred web instance for true web links.
-            if (isWebPlatform && trustedWebInstances.includes(link.webInstances[this.id])) {
-                instanceHost = link.webInstances[this.id];
+            if (isWebPlatform && preferredWebInstance) {
+                instanceHost = preferredWebInstance;
             }
             return `https://${instanceHost}/#/${fragmentPath}`;
         } else if (platform === Platform.Linux || platform === Platform.Windows || platform === Platform.macOS) {