feat: new InjectStyleFeature feature to inject style elements

Author: jsamr

packages/webshell/etc/webshell.api.md

@@ -275,6 +275,14 @@ export interface HTMLDimensions {
 // @public
 export type HTMLDimensionsImplementation = 'resize' | 'mutation' | 'polling';
 
+// @public
+export const InjectStyleFeature: FeatureClass<InjectStyleFeatureOptions>;
+
+// @public
+export interface InjectStyleFeatureOptions {
+    css: string;
+}
+
 // @public
 export interface LinkPressOptions {
     ignoreHashChange?: boolean;

packages/webshell/src/features/InjectStyleFeature.ts

@@ -0,0 +1,28 @@
+import injectStyleScript from './InjectStyleFeature.webjs';
+import FeatureBuilder from '../FeatureBuilder';
+import type { FeatureClass } from '../Feature';
+
+/**
+ * An object describing options for the inject style feature.
+ *
+ * @public
+ */
+export interface InjectStyleFeatureOptions {
+  /**
+   * CSS markup to inject in a `<style>` element.
+   */
+  css: string;
+}
+
+/**
+ * This feature injects a `<style>` element in the header of the page.
+ *
+ * @public
+ */
+export const InjectStyleFeature: FeatureClass<InjectStyleFeatureOptions> = new FeatureBuilder<InjectStyleFeatureOptions>(
+  {
+    defaultOptions: { css: '' },
+    identifier: '@native-html/iframe-strip-body-spacing',
+    script: injectStyleScript
+  }
+).build();

packages/webshell/src/features/InjectStyleFeature.webjs

@@ -0,0 +1,9 @@
+function InjectStyleFeature(context) {
+  var options = context.options || {},
+    css = options.css || '',
+    head = document.head || document.getElementsByTagName('head')[0],
+    style = document.createElement('style');
+  style.type = 'text/css';
+  style.appendChild(document.createTextNode(css));
+  head.appendChild(style);
+}

packages/webshell/src/features/index.ts

@@ -5,3 +5,4 @@ export * from './HandleHashChangeFeature';
 export * from './HandleVisualViewportFeature';
 export * from './ForceResponsiveViewportFeature';
 export * from './ForceElementSizeFeature';
+export * from './InjectStyleFeature';