added new sections to the element-composite article.

docs/docs/building-ui/element-composite.md

@@ -7,58 +7,165 @@ slug: element_composite
 <DocChip chip='since' label='23.06' />
 <JavadocLink type="foundation" location="com/webforj/component/element/ElementComposite" top='true'/>
 
-The `ElementComposite` class serves as a versatile foundation for managing composite elements in webforJ applications. Its primary purpose is to facilitate the interaction with HTML elements, represented by the `Element` class, by providing a structured approach to handle properties, attributes, and event listeners. It allows for implementation and reuse of elements in an application. Use the `ElementComposite` class when implementing Web Components for use in webforJ applications.
+The `ElementComposite` class provides a structured base for building reusable web components in webforJ. It streamlines interaction with underlying HTML elements, enabling you to define properties, attributes, and event listeners in a type-safe, maintainable way. Use `ElementComposite` to encapsulate and integrate custom elements or third-party web components within your app.
 
 While using the `ElementComposite` class, using the `getElement()` method will give you access to the underlying `Element` component. Similarly, the `getNodeName()` method gives you the name of that node in the DOM. 
 
 :::tip
-It is possible to do everything with the `Element` class itself, without using `ElementComposite` class. However, the provided methods in the `ElementComposite` give users a way to reuse the work that's being done. 
+It's possible to do everything with the `Element` class itself, without using `ElementComposite` class. However, the provided methods in the `ElementComposite` give users a way to reuse the work that's being done. 
 :::
 
-Throughout this guide, we'll be implementing the [Shoelace QR code web component](https://shoelace.style/components/qr-code) using the `ElementComposite` class.
+
+## Annotations
+
+The `ElementComposite` class supports several annotations to simplify integration with web components:
+
+- **@NodeName**: Defines the custom HTML tag for your component. For example, `@NodeName("sl-qr-code")` will create a `<sl-qr-code>` element in the DOM.
+- **@JavaScript**: Loads external JavaScript resources (such as third-party web components). Example:
+  ```java
+  @JavaScript(value = "https://cdn.jsdelivr.net/npm/@shoelace-style/shoelace/dist/shoelace.js", attributes = {@Attribute(name = "type", value = "module")})
+  ```
+- **@StyleSheet**: Loads external CSS files for your component. Example:
+  ```java
+  @StyleSheet("https://cdn.example.com/library.css")
+  ```
+
+:::tip
+These annotations are typically placed on your `ElementComposite` subclass to make sure are loaded automatically when the component is used.
+:::
+
+This guide demonstrates integration of the [Shoelace QR code web component](https://shoelace.style/components/qr-code) using the `ElementComposite` class.
+
+## Concern Interfaces
+
+To add common behaviors to your custom element, implement the appropriate concern interfaces. For example:
+
+- **HasText**: Adds support for getting and setting text content.
+- **HasClassName**: Adds support for manipulating CSS class names.
+- **HasStyle**: Adds support for inline styles.
+
+You can implement multiple interfaces to compose the desired capability. Example:
+```java
+@NodeName("my-component")
+public final class MyComponent extends ElementComposite
+    implements HasText<MyComponent>, HasClassName<MyComponent>, HasStyle<MyComponent> {
+    // ...
+}
+```
+## `ElementCompositeContainer` for components with slots
+
+For components that need to manage child components in named slots (such as headers, footers, or content areas), extend `ElementCompositeContainer` instead of `ElementComposite`.
+
+`ElementCompositeContainer` provides a structured way to add, remove, and manage components in specific slots. For example:
+
+```java
+@NodeName("my-container")
+public final class MyContainer extends ElementCompositeContainer
+    implements HasClassName<MyContainer>, HasStyle<MyContainer> {
+    private static final String HEADER_SLOT = "header";
+    private static final String CONTENT_SLOT = "content";
+    private static final String FOOTER_SLOT = "footer";
+
+    public MyContainer() {
+        super();
+    }
+
+    public MyContainer addToHeader(Component... components) {
+        getElement().add(HEADER_SLOT, components);
+        return this;
+    }
+
+    public MyContainer addToContent(Component... components) {
+        add(components); // Default slot
+        return this;
+    }
+
+    public MyContainer addToFooter(Component... components) {
+        getElement().add(FOOTER_SLOT, components);
+        return this;
+    }
+}
+```
+
+Use `ElementCompositeContainer` whenever your component needs to support multiple content areas or slots, such as layouts, dialogs, or toolbars.
 
 <ComponentDemo 
 path='/webforj/qrdemo?' 
 javaE='https://raw.githubusercontent.com/webforj/webforj-documentation/refs/heads/main/src/main/java/com/webforj/samples/views/elementcomposite/QRDemoView.java'
 height='175px'
 />
 
+
 ## Property and attribute descriptors
 
-Properties and attributes in web components represent the state of the component. They are often used to manage data or configuration. The `ElementComposite` class provides a convenient way to work with properties and attributes.
+Properties and attributes in web components represent the state and configuration of a component. In webforJ, the `ElementComposite` class provides a structured way to define, set, and get properties and attributes using `PropertyDescriptor`.
 
-Properties and attributes can be declared and initialized as `PropertyDescriptor` members of the `ElementComposite` class being written, and then used in the code. To define properties and attributes, use the `set()` method to set the value of a property. For example, `set(PropertyDescriptor<V> property, V value)` sets a property to a specified value. 
+### Defining properties and attributes
 
-:::info
-Properties are accessed and manipulated internally within the component's code and do not reflect in the DOM. Attributes on the other hand are part of the component's external interface and can be used to pass information into a component from the outside, providing a way for external elements or scripts to configure the component.
-:::
+To define a property or attribute, declare a `PropertyDescriptor` as a field in your `ElementComposite` subclass. Use `PropertyDescriptor.property("name", defaultValue)` for properties and `PropertyDescriptor.attribute("name", defaultValue)` for attributes.
 
+**Syntax:**
+```java
+// For a property (not reflected in the DOM)
+private final PropertyDescriptor<Type> PROPERTY_NAME = PropertyDescriptor.property("property-name", defaultValue);
+
+// For an attribute (reflected in the DOM)
+private final PropertyDescriptor<Type> ATTRIBUTE_NAME = PropertyDescriptor.attribute("attribute-name", defaultValue);
+```
+
+### Defining the type of properties
+
+The generic type parameter `<Type>` specifies the Java type of the property or attribute. This guarantees type safety when setting or getting values.
+
+**Example:**
 ```java
-// Example property called TITLE in an ElementComposite class
 private final PropertyDescriptor<String> TITLE = PropertyDescriptor.property("title", "");
-// Example attribute called VALUE in an ElementComposite class
-private final PropertyDescriptor<String> VALUE = PropertyDescriptor.attribute("value", "");
-//...
+private final PropertyDescriptor<Integer> COUNT = PropertyDescriptor.attribute("count", 0);
+```
+
+### Setting and getting values
+
+Use the `set()` method to assign a value, and the `get()` method to retrieve it:
+```java
 set(TITLE, "My Title");
-set(VALUE, "My Value");
+String title = get(TITLE);
 ```
 
-In addition to setting a property, utilize the `get()` method in the `ElementComposite` class to access and read properties. The `get()` method can be passed an optional `boolean` value, which is false by default, to dictate whether the method should make a trip to the client to retrieve the value. This impacts performance, but might be necessary if the property can be modified purely in the client. 
+You can also use the overloaded `get()` method to specify whether to fetch the value from the client, and to cast to a specific type:
+```java
+String title = get(TITLE, false, String.class);
+```
 
-A `Type` can also be passed to the method, which dictates what to cast retrieved result to.
+### Best practices for validating properties
 
-:::tip
-This `Type` is not overtly necessary, and adds an extra layer of specification as the data is retrieved.
-:::
+To guarantee valid values, add validation logic in your setter methods or before calling `set()`. For example:
+```java
+public void setCount(int count) {
+    if (count < 0) {
+        throw new IllegalArgumentException("Count must be non-negative");
+    }
+    set(COUNT, count);
+}
+```
+This approach helps prevent invalid state.
+
+### Enum-style properties
+
+For properties that should only accept a fixed set of values, use Java enums. Define the enum, then use it as the type parameter for your `PropertyDescriptor`:
 
 ```java
-// Example property called TITLE in an ElementComposite class
-private final PropertyDescriptor<String> TITLE = PropertyDescriptor.property("title", "");
-//...
-String title = get(TITLE, false, String);
+public enum Status {
+    ACTIVE, INACTIVE, DISABLED
+}
+
+private final PropertyDescriptor<Status> STATUS = PropertyDescriptor.attribute("status", Status.ACTIVE);
+
+// Usage
+set(STATUS, Status.INACTIVE);
+Status status = get(STATUS);
 ```
 
-In the demo below, properties have been added for the QR code based on the documentation for the web component. Methods have then been implemented which allow users to get and set the various properties that have been implemented.
+This pattern guarantees valid values are used and improves code readability.
 
 <ComponentDemo 
 path='/webforj/qrproperties?' 
@@ -68,7 +175,7 @@ height='250px'
 
 ## Event registration
 
-Events are a crucial part of web components, allowing communication between different parts of an application. The `ElementComposite` class simplifies event registration and handling. To register an event listener, use the `addEventListener()` method to register event listeners for specific event types. Specify the event class, the listener, and optional event options.
+Events enable communication between parts of your app and are essential for interactive components. `ElementComposite` makes event handling straightforward: register listeners for specific event types using `addEventListener()` with the event class, your listener, and optional options.
 
 ```java
 // Example: Adding a click event listener
@@ -81,23 +188,23 @@ addEventListener(ClickEvent.class, event -> {
 The `ElementComposite` events are different than `Element` events, in that this doesn't allow any class, but only specified `Event` classes.
 :::
 
-In the demonstration below, a click event has been created and then added to the QR code component. This event, when fired, will display the "X" coordinate of the mouse at the time of clicking the component, which is provided to the Java event as data. A method is then implemented to allow the user to access this data, which is how it is displayed in the application.
+In the demonstration below, a click event has been created and then added to the QR code component. This event, when fired, will display the "X" coordinate of the mouse at the time of clicking the component, which is provided to the Java event as data. A method is then implemented to allow the user to access this data, which is how it's displayed in the app.
 <ComponentDemo 
 path='/webforj/qrevent?' 
 javaE='https://raw.githubusercontent.com/webforj/webforj-documentation/refs/heads/main/src/main/java/com/webforj/samples/views/elementcomposite/QREventView.java'
 height='300px'
 />
 
-## Interacting with Slots
+## Interacting with slots
 
 Web components often use slots to allow developers to define the structure of a component from the outside. A slot is a placeholder inside a web component that can be filled with content when using the component. In the context of the `ElementComposite` class, slots provide a way to customize the content within a component. The following methods are provided to allow developers to interact with and manipulate slots:
 
-1. **`findComponentSlot()`**: This method is used to search for a specific component across all slots in a component system. It returns the name of the slot where the component is located. If the component is not found in any slot, an empty string is returned.
+1. **`findComponentSlot()`**: This method is used to search for a specific component across all slots in a component system. It returns the name of the slot where the component is located. If the component isn't found in any slot, an empty string is returned.
 
 2. **`getComponentsInSlot()`**: This method retrieves the list of components assigned to a given slot in a component system. Optionally, pass a specific class type to filter the results of the method.
 
 3. **`getFirstComponentInSlot()`**: This method is designed to fetch the first component assigned to the slot. Optionally pass a specific class type to filter the results of this method.
 
-It is also possible to use the `add()` method with a `String` parameter to specify the desired slot in which to add the passed component.
+It's also possible to use the `add()` method with a `String` parameter to specify the desired slot in which to add the passed component.
 
 These interactions allow developers to harness the power of web components by providing a clean and straightforward API for manipulating slots, properties, and handling events within the `ElementComposite` class.