Angular's default view encapsulation mechanism ensures that the styles defined in a component affect only that component and not other parts of the application. Here's how it works:

1. Unique Attribute Generation:

   • Angular assigns a unique attribute to each component during the compilation process. These attributes are in the form of _ngcontent-c0, _ngcontent-c1, _ngcontent-c2, etc.
   • This unique attribute is associated with the component and helps in scoping styles.

2. Stamping HTML Elements:

   • When Angular instantiates a component's template, it automatically adds this unique attribute to all the HTML elements within that template.
   • This stamping process ensures that every element in the component's template is marked with the component's unique attribute.

3. Scoped Styles Application:

   • Angular modifies the component's styles by appending the unique attribute to each CSS selector in the component's stylesheet.
   • This means the styles are transformed to target only elements that have the matching unique attribute.

4. Style Encapsulation:

   • As a result, the styles defined in a component's stylesheet apply only to the elements within that component's template.
   • This prevents styles from leaking out and affecting other components, ensuring style encapsulation and modularity.

Key Benefits:

• Style Isolation: Components have their own isolated styles, reducing the risk of style conflicts.
• Maintainability: Encapsulated styles make the application easier to maintain and reason about.
• Automatic Process: Angular handles the generation of unique attributes and the scoping of styles automatically during the build process.

Visual Representation:

• Before Compilation:

• Component Template:

<div class="my-element">
  Content here
</div>

Component Stylesheet:

.my-element {
  color: blue;
}

After Compilation:

• Modified Template

<div class="my-element" _ngcontent-c0>
  Content here
</div>

Modified Stylesheet:

.my-element[_ngcontent-c0] {
  color: blue;
}

In this way, Angular's view encapsulation ensures that each component's styles apply only to its own template elements, promoting a modular and maintainable codebase.

Angular View Encapsulation - the Host Selector

In Angular, the :host selector is used within component styles to target and style the host element—the element that encapsulates the component. 

1. Unique Host Attributes:

   • Angular assigns a unique attribute to each component's host element during compilation (e.g., _nghost-c1).
   • This unique attribute differentiates the host element from its child elements and other components.

2. Styling the Host Element:

• The :host selector allows you to apply styles directly to the host element from within the component's styles.
  

  :host {
    display: block;
    border: 1px solid #ccc;
  }

  
  
• This ensures that the styles apply specifically to the host element, not affecting child elements.

3. View Encapsulation:

• Angular uses view encapsulation to scope styles to a specific component.
• The host element receives a special property (e.g., _nghost-c1) that is unique to the component.

4. Child Elements:

   • Child elements inside the component do not have the host's unique attribute.
   • Styles defined with :host do not cascade to child elements, maintaining encapsulation.

5. Multiple Instances:

   • Multiple instances of a component share the same host selector but maintain encapsulation through unique attributes. That means all these instances will have same _nghost attribute.
     
     
   • Each instance's host element has the same _nghost attribute specific to that component.

6. Inspecting in HTML:

• In the rendered HTML, you can observe these unique attributes applied to host elements.
• Example:
  

  <app-image-card _nghost-c1>
    <!-- component content -->
  </app-image-card>

Key Points:

• The :host selector is crucial for applying styles to the component's host element.
• It ensures styles are encapsulated and do not leak to other components.
• Understanding :host helps in designing modular and maintainable Angular components.