feat: add signal bind methods to app-layout component

vaadin-app-layout-flow-parent/vaadin-app-layout-flow/pom.xml

@@ -39,6 +39,12 @@
             <artifactId>vaadin-flow-components-base</artifactId>
             <version>${project.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.vaadin</groupId>
+            <artifactId>vaadin-flow-components-test-util</artifactId>
+            <version>${project.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>com.vaadin</groupId>
             <artifactId>vaadin-icons-flow</artifactId>

vaadin-app-layout-flow-parent/vaadin-app-layout-flow/src/main/java/com/vaadin/flow/component/applayout/AppLayout.java

@@ -30,8 +30,10 @@
 import com.vaadin.flow.component.dependency.JsModule;
 import com.vaadin.flow.component.dependency.NpmPackage;
 import com.vaadin.flow.component.shared.SlotUtils;
+import com.vaadin.flow.function.SerializableConsumer;
 import com.vaadin.flow.internal.JacksonUtils;
 import com.vaadin.flow.router.RouterLayout;
+import com.vaadin.flow.signals.Signal;
 
 /**
  * App Layout is a component for building common application layouts.
@@ -145,6 +147,28 @@ public void setDrawerOpened(boolean drawerOpened) {
         getElement().setProperty("drawerOpened", drawerOpened);
     }
 
+    /**
+     * Binds the drawer opened state to the given signal. The binding is
+     * two-way: signal changes push to the DOM property, and client-side
+     * property changes invoke the write callback.
+     * <p>
+     * While a signal is bound, any attempt to set the drawer opened state
+     * manually throws {@link com.vaadin.flow.signals.BindingActiveException}.
+     *
+     * @param signal
+     *            the signal to bind, not {@code null}
+     * @param writeCallback
+     *            the callback to propagate value changes back, or {@code null}
+     *            for one-way binding
+     * @since 25.1
+     */
+    public void bindDrawerOpened(Signal<Boolean> signal,
+            SerializableConsumer<Boolean> writeCallback) {
+        Objects.requireNonNull(signal, "Signal cannot be null");
+        getElement().bindProperty("drawerOpened",
+                signal.map(v -> v == null ? Boolean.TRUE : v), writeCallback);
+    }
+
     /**
      * <strong>Note:</strong> This property is controlled via CSS and can not be
      * changed directly.

vaadin-app-layout-flow-parent/vaadin-app-layout-flow/src/test/java/com/vaadin/flow/component/applayout/AppLayoutSignalTest.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright 2000-2026 Vaadin Ltd.
+ *
+ * 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.
+ */
+package com.vaadin.flow.component.applayout;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.vaadin.flow.component.UI;
+import com.vaadin.flow.signals.BindingActiveException;
+import com.vaadin.flow.signals.local.ValueSignal;
+import com.vaadin.tests.AbstractSignalsUnitTest;
+
+public class AppLayoutSignalTest extends AbstractSignalsUnitTest {
+
+    private AppLayout appLayout;
+    private ValueSignal<Boolean> signal;
+
+    @Before
+    public void setup() {
+        appLayout = new AppLayout();
+        signal = new ValueSignal<>(true);
+    }
+
+    @After
+    public void tearDown() {
+        if (appLayout != null && appLayout.isAttached()) {
+            appLayout.removeFromParent();
+        }
+    }
+
+    @Test
+    public void bindDrawerOpened_signalBound_propertySync() {
+        appLayout.bindDrawerOpened(signal, signal::set);
+        UI.getCurrent().add(appLayout);
+
+        Assert.assertTrue(appLayout.isDrawerOpened());
+
+        signal.set(false);
+        Assert.assertFalse(appLayout.isDrawerOpened());
+
+        signal.set(true);
+        Assert.assertTrue(appLayout.isDrawerOpened());
+    }
+
+    @Test
+    public void bindDrawerOpened_notAttached_noEffect() {
+        appLayout.bindDrawerOpened(signal, signal::set);
+
+        boolean initial = appLayout.getElement().getProperty("drawerOpened",
+                true);
+        signal.set(false);
+        Assert.assertEquals(initial,
+                appLayout.getElement().getProperty("drawerOpened", true));
+    }
+
+    @Test
+    public void bindDrawerOpened_detachAndReattach() {
+        appLayout.bindDrawerOpened(signal, signal::set);
+        UI.getCurrent().add(appLayout);
+
+        signal.set(false);
+        Assert.assertFalse(appLayout.isDrawerOpened());
+
+        appLayout.removeFromParent();
+        signal.set(true);
+        Assert.assertFalse(appLayout.isDrawerOpened());
+
+        UI.getCurrent().add(appLayout);
+        Assert.assertTrue(appLayout.isDrawerOpened());
+    }
+
+    @Test(expected = BindingActiveException.class)
+    public void bindDrawerOpened_setWhileBound_throws() {
+        appLayout.bindDrawerOpened(signal, signal::set);
+        UI.getCurrent().add(appLayout);
+
+        appLayout.setDrawerOpened(false);
+    }
+
+    @Test(expected = BindingActiveException.class)
+    public void bindDrawerOpened_doubleBind_throws() {
+        appLayout.bindDrawerOpened(signal, signal::set);
+        var other = new ValueSignal<>(false);
+        appLayout.bindDrawerOpened(other, other::set);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void bindDrawerOpened_nullSignal_throwsNPE() {
+        appLayout.bindDrawerOpened(null, null);
+    }
+
+    @Test
+    public void bindDrawerOpened_nullDefault_defaultsToTrue() {
+        ValueSignal<Boolean> nullSignal = new ValueSignal<>(null);
+        appLayout.bindDrawerOpened(nullSignal, nullSignal::set);
+        UI.getCurrent().add(appLayout);
+
+        Assert.assertTrue(appLayout.isDrawerOpened());
+    }
+}