make login view enabled again if load view is not busy anymore

src/domain/LoginViewModel.js

@@ -8,13 +8,26 @@ export class LoginViewModel extends ViewModel {
         this._sessionCallback = sessionCallback;
         this._defaultHomeServer = defaultHomeServer;
         this._loadViewModel = null;
+        this._loadViewModelSubscription = null;
     }
 
     get defaultHomeServer() { return this._defaultHomeServer; }
 
     get loadViewModel() {return this._loadViewModel; }
 
+    get isBusy() {
+        if (!this._loadViewModel) {
+            return false;
+        } else {
+            return this._loadViewModel.loading;
+        }
+    }
+
     async login(username, password, homeserver) {
+        this._loadViewModelSubscription = this.disposeTracked(this._loadViewModelSubscription);
+        if (this._loadViewModel) {
+            this._loadViewModel.cancel();
+        }
         this._loadViewModel = new SessionLoadViewModel({
             createAndStartSessionContainer: () => {
                 const sessionContainer = this._createSessionContainer();
@@ -36,10 +49,16 @@ export class LoginViewModel extends ViewModel {
         });
         this._loadViewModel.start();
         this.emitChange("loadViewModel");
+        this._loadViewModelSubscription = this.track(this._loadViewModel.disposableOn("change", () => {
+            if (!this._loadViewModel.loading) {
+                this._loadViewModelSubscription = this.disposeTracked(this._loadViewModelSubscription);
+            }
+            this.emitChange("isBusy");
+        }));
     }
 
     cancel() {
-        if (!this._loadViewModel) {
+        if (!this.isBusy) {
             this._sessionCallback();
         }
     }

src/ui/web/general/TemplateView.js

@@ -276,10 +276,9 @@ class TemplateBuilder {
         return vm => new TemplateView(vm, render);
     }
 
-    // creates a conditional subtemplate
-    if(fn, viewCreator) {
-        const boolFn = value => !!fn(value);
-        return this._addReplaceNodeBinding(boolFn, (prevNode) => {
+    // map a value to a view, every time the value changes
+    mapView(mapFn, viewCreator) {
+        return this._addReplaceNodeBinding(mapFn, (prevNode) => {
             if (prevNode && prevNode.nodeType !== Node.COMMENT_NODE) {
                 const subViews = this._templateView._subViews;
                 const viewIdx = subViews.findIndex(v => v.root() === prevNode);
@@ -288,14 +287,22 @@ class TemplateBuilder {
                     view.unmount();
                 }
             }
-            if (boolFn(this._value)) {
-                const view = viewCreator(this._value);
+            const view = viewCreator(mapFn(this._value));
+            if (view) {
                 return this.view(view);
             } else {
-                return document.createComment("if placeholder");
+                return document.createComment("node binding placeholder");
             }
         });
     }
+
+    // creates a conditional subtemplate
+    if(fn, viewCreator) {
+        return this.mapView(
+            value => !!fn(value),
+            enabled => enabled ? viewCreator(this._value) : null
+        );
+    }
 }
 
 

src/ui/web/login/LoginView.js

@@ -4,7 +4,7 @@ import {SessionLoadView} from "./SessionLoadView.js";
 
 export class LoginView extends TemplateView {
     render(t, vm) {
-        const disabled = vm => !!vm.loadViewModel;
+        const disabled = vm => !!vm.isBusy;
         const username = t.input({type: "text", placeholder: vm.i18n`Username`, disabled});
         const password = t.input({type: "password", placeholder: vm.i18n`Password`, disabled});
         const homeserver = t.input({type: "text", placeholder: vm.i18n`Your matrix homeserver`, value: vm.defaultHomeServer, disabled});
@@ -18,8 +18,8 @@ export class LoginView extends TemplateView {
                 onClick: () => vm.login(username.value, password.value, homeserver.value),
                 disabled
             }, vm.i18n`Log In`)),
-            t.div(t.button({onClick: () => vm.goBack(), disabled}, [vm.i18n`Pick an existing session`])),
-            t.if(vm => vm.loadViewModel, vm => new SessionLoadView(vm.loadViewModel)),
+            t.div(t.button({onClick: () => vm.cancel(), disabled}, [vm.i18n`Pick an existing session`])),
+            t.mapView(vm => vm.loadViewModel, loadViewModel => loadViewModel ? new SessionLoadView(loadViewModel) : null),
             t.p(brawlGithubLink(t))
         ]);
     }

src/utils/EventEmitter.js

@@ -12,6 +12,13 @@ export class EventEmitter {
         }
     }
 
+    disposableOn(name, callback) {
+        this.on(name, callback);
+        return () => {
+            this.off(name, callback);
+        }
+    }
+
     on(name, callback) {
         let handlers = this._handlersByName[name];
         if (!handlers) {