Angular 2 does not display component styles for D3.js

I am working with Angular 2 and D3.js to display a red rectangle.

The issue arises when I attempt to define styles within the style.css file. You can view the problem on this plunkr

If I try to place my styles in the component using styles: [], it fails to render as expected. Take a look at the example on this plunkr

Is there a way to make it work when utilizing styles: [] within the component? Any suggestions would be appreciated.

UPDATE: @micronyks has offered a solution, but it essentially makes the component's styles global, which is similar to defining them in the style.css file. As shown in this plunkr, conflicting component styles prevent displaying both green and red rectangles simultaneously.

UPDATE 2: @Günter's method successfully resolves this issue!! It's worth noting that Günter's approach requires at least Angular beta 10 (while my previous examples were based on Angular beta 8). To see a functional demo showcasing both green and one red rectangle using Angular beta 12, visit here.

import {Component} from 'angular2/core'
@Component({
  selector: 'my-app',
  providers: [],
   styles: [`
    /*this does not work*/
    .bar {
      fill: red;
    }
  `],
  template: `
    <div>
      <svg class="chart"></svg>
    </div>
  `,
  directives: []
})
export class App {
  constructor() {}

  ngOnInit() {
    this.draw();
  }

  draw() {
    let data = [{name: 'A', value: 1}];
    let width = 400, height = 200;

    let x = d3.scale.ordinal().rangeRoundBands([0, width]);
    let y = d3.scale.linear().range([height, 0]);

    let chart = d3.select(".chart")
      .attr("width", width)
      .attr("height", height)
      .append("g");

    x.domain(data.map(function(d) { return d.name; }));
    y.domain([0, d3.max(data, function(d) { return d.value; })]);

    chart.selectAll(".bar")
      .data(data)
      .enter().append("rect")
      .attr("class", "bar")
      .attr("x", function(d) { return x(d.name); })
      .attr("y", function(d) { return y(d.value); })
      .attr("height", function(d) { return height - y(d.value); })
      .attr("width", x.rangeBand());
  }
}

Answer №1

Update

Angular and SASS have reached an agreement to back the use of ::ng-deep (instead of >>> or /deep/) for the time being, until ::slotted or similar methods are universally available in all browsers.

ViewEncapsulation.Emulated (default)

This is intentional. Angular incorporates unique class names for components and adjusts the added styles to only affect the specific components they were assigned to.

The issue arises when D3 dynamically generates HTML without notifying Angular, preventing it from applying the necessary classes for style implementation on the generated HTML.

If styles are included at the initial HTML entry point, Angular does not rewrite the styles, rendering the added helper classes ineffective.

ViewEncapsulation.None

When using

encapsulation: ViewEncapsulation.None
, Angular skips this rewriting process, resulting in a behavior akin to embedding the HTML directly within index.html.

"Shadow-piercing"

Alternatively, one can utilize the recently introduced shadow piercing CSS combinators such as >>>, /deep/, and ::shadow (::shadow being simply replaced by a space, thus with limited functionality). More information can be found at along with a Plunker

:host /deep/ div {
  color: red;
}

SASS

/deep/ functions well with SASS, however, the alias >>> does not.

The shadow-piercing CSS combinators get modified by Angular, eliminating the need for browser support. While Chrome previously backed them, they are now deprecated - but this becomes inconsequential as Angular reconfigures them to align with its encapsulation emulation.

ViewEncapsulation.Native

Angular lacks a method to style such components externally. Only if the browser extends support like CSS variables can they be utilized.

Answer №2

Solving your issue can be achieved by using ViewEncapsulation.

import {Component,ViewEncapsulation} from 'angular2/core'

@Component({
  selector: 'my-app',
  encapsulation: ViewEncapsulation.None,
  providers: [],
   styles: [`
     .bar {
       fill: red;
    }
  `],
  template: `
    <div>
      <svg class="chart"></svg>
    </div>
  `,
  directives: []
})

Answer №3

The Concept of View Encapsulation

Angular 2 employs view encapsulation to ensure that styles are only applied locally by default. This means that any CSS defined within a component will only affect elements within that specific component, rather than globally across the entire application.

h2 { color: red; }

For instance, applying the above style in your component's CSS file will exclusively change the appearance of h2 elements inside that particular component. To gain further insights into this feature, refer to the official Angular documentation on View Encapsulation.

Relevance of View Encapsulation

While Angular can influence your styles, it cannot yet manipulate HTML/SVG prior to the C3 graph being rendered. Hence, component styles might not align with elements inside the C3 graph.

Suggested Actions

Utilize External Stylesheets

External stylesheets remain unaffected by View Encapsulation, thereby enabling them to impact elements such as the C3 chart without hindrance.

If you are utilizing Angular CLI, integrating an external stylesheet is a straightforward process. Update your angular-cli.json file and add the desired stylesheet under the styles array within the apps section:

{
    …
    "apps": [
        {
            …
            "styles": [
                "styles.scss",
                "c3.scss" // <---- include this or another file
            ],
        }
    ],
    …
}

Alternatively, if you do not use Angular CLI, you can directly embed a <link …> tag within the <head> of your index.html file.

ViewEncapsulation.None Option

An alternate approach involves creating a dedicated component solely for the chart, toggling off View Encapsulation within that component. This practice also adheres to the Single Responsibility Principle. Disabling View Encapsulation is achieved by modifying the @Component decorator:

@Component({
    …
    encapsulation: ViewEncapsulation.None
})

/deep/ Selector in CSS

If disabling View Encapsulation is not preferable, consider utilizing the /deep/ selector within your CSS. This selector penetrates all child components' views, essentially breaking encapsulation and impacting the C3 chart. For example, this could be implemented as follows within your component's CSS file:

/deep/ .c3-chart-arc path {
    stroke: white;
}

Regardless of the method chosen, familiarizing yourself with the Angular 2 documentation on View Encapsulation is highly recommended. Understanding the underlying principles can aid in better code development, minimizing potential challenges. Further insights on this topic can be found in articles such as this one from blog.thoughtram.io.

Answer №5

When it comes to displaying one red and one green rectangle, I encounter a recurring issue.

I believe there might be an override causing this problem. While I cannot confirm the veracity of this information, I believe implementing the following solution may resolve your issue.

You can try adding child1-cmp and child1-cmp .bar like so:

@Component({
  encapsulation: ViewEncapsulation.None,
  selector: 'child1-cmp',
   styles: [`
    child1-cmp .bar {
      fill: red;
    }
  `],
  template: `
    <div>
      <svg class="chart1"></svg>
    </div>
  `,
  directives: []
})

Please note that in addition to

encapsulation: ViewEncapsulation.None
, as mentioned by micronyks.

Test

Plunker


Alternatively, you can also try the following approach:

@Component({
  selector: 'my-app',
  directives: [Child1Cmp, Child2Cmp],
   encapsulation: ViewEncapsulation.None,
   styles: [`
    child1-cmp .bar {
      fill: red;
    }
  
    child2-cmp .bar {
      fill: yellow;
    }
  `],
   ..//

@Component({
  //encapsulation: ViewEncapsulation.None,
  selector: 'child1-cmp',
  template: `
    <div>
      <svg class="chart1"></svg>
    </div>
  `,
  directives: []
})

@Component({
  //encapsulation: ViewEncapsulation.None,
  selector: 'child2-cmp',
  template: `
    <div>
      <svg class="chart2"></svg>
    </div>
  `,
  directives: []
})

Test

Plunker


Or, if you prefer, you can use class selectors such as .chart1 and .chart2:

@Component({
  selector: 'my-app',
  directives: [Child1Cmp, Child2Cmp],
   encapsulation: ViewEncapsulation.None,
   styles: [`
    .chart1 .bar {
      fill: red;
    }
  
    .chart2 .bar {
      fill: yellow;
    }
  `],
   ..//

Test

Plunker

Answer №6

After experimenting, I discovered that using * /deep/ .my-element-class does the trick. However, it seems to only work when the svg parent element is included in the html template (not when it's dynamically created by d3).

For example, the following setup would be successful:

mycomponent.component.html

<svg id="mygraph"></svg> <!-- It's crucial!! -->

mycomponent.component.css

* /deep/ .my-element-class {
  /* ... desired styles */
}

mycomponent.component.ts

d3.select("svg#mygraph").append("circle").classed("my-element-class", true)
 ...

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