I have css class which needs to be added to three different component(for example) which might not require for other components of our application.
which one would be the best approach.
add that css class to style.css (global css)and use it or
add it to three different component specific style sheet as it is not used anywhere in the application(is this considered as code duplicate ?)
Thanks!
I would say that adding it to the global styles is just fine for this purpose. View encapsulation is cool, but the cascading part of CSS is still something that we're supposed to take advantage of...just as long as you're still cognizant of keeping styles organized and not too high of specificity.
Conversely, if you knew all three components would share parent component, you could turn off view encapsulation for that component and add the class there, which is essentially the same as adding to global styles with the difference being the style would only be loaded when the component is loaded.
You could also use ::ng-deepon a parent component to target its children. Sass brings other solutions, but it doesn't look like you're using .scss files.
Related
A lot of our site is structured as such:
component
component CSS
component template
child component
We often need to style the child component differently based on which parent component it was in. This is annoying, of course, but was manageable when we were using global CSS as we could simply target the specific instance with unique ID and class CSS selectors.
We're trying to now stop using global styles and encapsulating our CSS within each component. The problem with this is that, from what I see, encapsulate angular CSS will scope your CSS so that it only applies to that component...which means it also will not apply to any child components.
One solution appears to be to use ::ng-deep selectors in our component CSS to target the child. This is meeting some resistance, though, as I'm being told this also breaks encapsulation in general and could affect other parts of the site in different components.
This is where I'm confused. Some questions:
Does any style targeted with ::ng-deep become descoped so that it is global application-wide? Or is it simply 'global' within that one parent component?
If it's the former, would it be an OK practice to still use ::ng-deep, but also make sure you are using additional unique css selectors so it only applies to the child component you are targeting?
Or is there a more proper way to add styles to a particular child component instance?
:ng-deep is global. No matter where you put it, it applies to all components. Not just children.
If you use :host :ng-deep, then it will work from that component down (Into the children, grand children etc).
The main issue working with ng-deep is that styles in Angular are lazy loaded. So in some cases, you can be viewing the site perfectly fine, then you view a particular page that uses ng-deep, then you can go back to previous pages that were fine that are now broken because the ng-deep style is applied site wide. e.x. https://tutorialsforangular.com/2020/04/13/the-dangers-of-ng-deep-bleeding/
Generally speaking, if I need to style a child component slightly differently depending on where it's placed, then I create an input variable for the child, make the parent set it, then make it a class somewhere in the child component HTML. The child component can then style that class how it see's fit and you haven't had to break encapsulation.
::ng-deep by itself does make the style global, but when combined with :host may do what you need, but as #eldar alluded to with this link, ::ng-deep is deprecated (and has been for some time).
We've two options to keep styles in an Angular 9 app; global styles in styles.css or individual component level styles in the component css file.
If looked at the project from performance perspective;
what should be the preferred way?
Should we keep all styles in a single global style.css file or keep each component related styles in their component.css file?
To answer this question we have to refer to the Angular official doc.
By using Using component styles you will have a better modular design.
Angular can bundle component styles with components, enabling a more
modular design than regular stylesheets.
But, if there are some styles that are common between more than one component it's better to have a shared css and e.g. if you use pre-processor such as .SCSS, LESS, SASS, ..., you can have some _var.scss to define general styles such as base color, fonts, ... and then #import in other component styles or just register global style files in the styles section which, by default, is pre-configured with the global styles.css file.
So, using component styles provide scoping restriction and View encapsulation for your app. This scoping restriction is a styling modularity feature:
You can use the CSS class names and selectors that make the most sense
in the context of each component.
Class names and selectors are local to the component and don't collide with classes and selectors used elsewhere in the application.
Changes to styles elsewhere in the
application don't affect the component's styles.
You can co-locate the
CSS code of each component with the Typescript and HTML code of the
component, which leads to a neat and tidy project structure.
You can
change or remove component CSS code without searching through the
whole application to find where else the code is used.
There are several ways to add Global (Application wide styles) styles to the Angular application. The styles can be added inline, imported in index.html or added via angular-cli.json. The angular allow us to add the component specific styles in individual components, which will override the global styles.
I don't think there is much (if any at all) significant difference in performance. The global or component style distinction is all about the scope of those styles and maintainability of your codebase. Generally its good idea to keep everything in components as they are scoped to themselves and will not accidentally override other same styles from anywhere else. And global styles should stay mostly to theming, utility, helpers etc.
Besides you have an option to make component style global as well, if for some reason you need to do that.
step to define/preferable way for global style
Create _base.scss file in the css folder (first create css folder).
import other helping scss file in _base.scss file
add the entry of _base scss file in style.scss file (style.scss available when we create the folder).
In my app.component.html I have the following, working class assignment.
<body>
<span class="test">SHABOO</span>
<div class="container">
<router-outlet></router-outlet>
</div>
</body>
In the outlet, a component is rendered and it contains the following.
<span class="test">HAZAA</span>
I expected it to get the same style as the first one but it seems that the style doesn't cascade down to the component. It made me uncertain if I'm mistaken about how the styles are supposed to behave between parent and child components in Angular.
I made sure that the name of the class isn't overriden (to exclude the risk of collision). At the moment, I'm putting similar chunks of SCSS code in each component and that's obviously bad practice.
If I #import "../app.component.scss", the styles kicks in. But I was under the impression that even without the import, the style is supposed to cascade.
Angular components use view encapsulation. This is by design so that components are reusable across applications. To treat a component's styles as global, set the view encapsulation mode to none (not recommended).
Instead of using none, register global style files in the Angular CLI styles section, which is pre-configured with the styles.css file.
Component CSS styles are encapsulated into the component's view and don't affect the rest of the application.
To control how this encapsulation happens on a per component basis, you can set the view encapsulation mode in the component metadata. Choose from the following modes:
ShadowDom view encapsulation uses the browser's native shadow DOM implementation (see Shadow DOM on the MDN site) to attach a shadow DOM to the component's host element, and then puts the component view inside that shadow DOM. The component's styles are included within the shadow DOM.
Native view encapsulation uses a now deprecated version of the browser's native shadow DOM implementation - learn about the changes.
Emulated view encapsulation (the default) emulates the behavior of shadow DOM by preprocessing (and renaming) the CSS code to effectively scope the CSS to the component's view. For details, see Appendix 1.
None means that Angular does no view encapsulation. Angular adds the CSS to the global styles. The scoping rules, isolations, and protections discussed earlier don't apply. This is essentially the same as pasting the component's styles into the HTML.
To set the components encapsulation mode, use the encapsulation property in the component metadata:
src/app/quest-summary.component.ts
// warning: few browsers support shadow DOM encapsulation at this time
encapsulation: ViewEncapsulation.Native
ShadowDom view encapsulation only works on browsers that have native support for shadow DOM (see Shadow DOM v1 on the Can I use site). The support is still limited, which is why Emulated view encapsulation is the default mode and recommended in most cases.
External and global style files
When building with the CLI, you must configure the angular.json to include all external assets, including external style files.
Register global style files in the styles section which, by default, is pre-configured with the global styles.css file.
See the CLI wiki to learn more.
This is how angular works. Every component is separated with it's CSS, even if it is child component of a parent. They can't inherit their parent CSS.
Haza span component is child of your app component, but it is separated component. So, you can't get those Shaboo styling to Haza.
Solution:
if you want to maintain same CSS, there are multiple ways.
Recommended way:
a) if it is only for onle class, copy the class to the child component.
b) if it is for huge number of classes, create a css file for them and import them in both parent and child component css.
Example:
#import '../span.css';
you can add this css to styles.css. then you will get it anywhere in the app. if you want this style many places, you can do it.
As #Christopher Peisert mentioned, by using
encapsulation: ViewEncapsulation.Native
end of the #component decorator in child.component.ts. It is not recommended way
The global CSS files are those that are listed in angular.json. All others CSS files are encapsulated by default (this can be removed but is not recommended.)
Keeping your global CSS organised is important as your application grows. What I like to do is create a global styles folder and then add new files for different widgets that I might be altering. Since removal of ::ng-deep these types of changes have to be done in the global scope.
It works like that. If you are in need of having a common style then add it in the global styles.scss file.
If you want a global style put it in the global file styles.css or styles.[Your css preprocessor]
See this example https://stackblitz.com/edit/angular-a5ntm6?file=src%2Fstyles.css
I put test class at the end
.test{
color:red;
}
I'd like to change the styles of a component outside the scope of my current component. The markup in my app.component.html is as follows:
<app-nav></app-nav>
<div id='content-container'>
<router-outlet></router-outlet>
</div>
I'm looking to change the styles of a class main-nav in the app-nav component from the 'home-component' which is loaded from a route. I use routerLink's in the nav and I've found if I add encapsulation: ViewEncapsulation.None to the home.component.ts I can alter the styles of the the class in the app-nav component however the changes are only applied once and if I go to other routes using the routerLink's I cannot revert the changes (seems like the css is only loaded/applied once - when the component is initialized/comes into view)
Special selectors are designed to access and apply css outside the encapsulation without having to change encapsulation scope. In your case I think :host or :host-context will help.
See https://angular.io/guide/component-styles#special-selectors
Use the :host pseudo-class selector to target styles in the element
that hosts the component (as opposed to targeting elements inside the
component's template).
and
Sometimes it's useful to apply styles based on some condition outside
of a component's view. For example, a CSS theme class could be applied
to the document element, and you want to change how your
component looks based on that.
Use the :host-context() pseudo-class selector, which works just like
the function form of :host(). The :host-context() selector looks for a
CSS class in any ancestor of the component host element, up to the
document root. The :host-context() selector is useful when combined
with another selector.
change the styles of a component outside the scope of my current component
Before I say anything else, this is highly discouraged. Components are supposed to be self-contained entities, which can be reusable across your project, or even other projects. By creating a component that changes something else in the system only through CSS, you're creating a tight coupling which is difficult to see immediately from code, leading to difficult-to-debug bugs and other errors.
If you want to change your app-nav (or main-nav as you refer to it later, I'm not sure if this is my mistake) based on the current route, you should do so by injecting the ActivatedRoute and querying it to determine the specific version of header which you want.
Another option is to simply move the header below the router outlet, so you always direct access to it from the component which rests across the whole page.
the changes are only applied once and if I go to other routes using the routerLink's
This is expected, since the styles are injected into DOM only when you visit the actual component, no need for them to appear before there's need for it. Angular expects that the styles you define for a component and used only on that component. You're breaking this rule of thumb.
I cannot revert the changes (seems like the css is only loaded/applied once - when the component is initialized/comes into view)
Your observation is correct.
I have 2 jsps for 2 cq components that have the same html structure but the css is different.
What are the best practices for refactoring in this case?
One scenario would be to have a single component and set the css classes based on some input provided by the author in the dialog (component type 1, component type 2), but this gets messy cause I need to do the if checks and set different values for the css classes. It becomes even more complicated if I add a 3rd component with the same html structure and different css.
I would suggest to use one of next approaches:
Create base component with html structure and for each design create components which have sling:resourceSuperType of base component. And in child components you can override css file with specific one.
Base component should be made of (at least) 2 jsp files:
container with some class (unique among different designs) which contains include of actual component content. This class then should be used in you selectors in css file. Like .container-design-1 .title {}. This container also can be overwritten in child components.
jsp with content.
Also you can still use component dialogue, but populate dropdown menu with available designs dynamically. For example, you can have some servlet+service which looks into repository and collects available clientlib categories for this component. And during rendering you will include selected clientlib category, set unique class for your container and use it in css selectors (like in previous approach).
Also in both cases html and id/class names of elements should be the same, and only styles implementation is different.