1 files changed, 95 insertions, 0 deletions
diff --git a/src/templates/assets/javascripts/browser/media/index.ts b/src/templates/assets/javascripts/browser/media/index.ts
new file mode 100644
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+++ b/src/templates/assets/javascripts/browser/media/index.ts
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+/*
+ * Copyright (c) 2016-2023 Martin Donath <martin.donath@squidfunk.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+import {
+  EMPTY,
+  Observable,
+  fromEvent,
+  fromEventPattern,
+  map,
+  merge,
+  startWith,
+  switchMap
+} from "rxjs"
+
+/* ----------------------------------------------------------------------------
+ * Functions
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Watch media query
+ *
+ * Note that although `MediaQueryList.addListener` is deprecated we have to
+ * use it, because it's the only way to ensure proper downward compatibility.
+ *
+ * @see https://bit.ly/3dUBH2m - GitHub issue
+ *
+ * @param query - Media query
+ *
+ * @returns Media observable
+ */
+export function watchMedia(query: string): Observable<boolean> {
+  const media = matchMedia(query)
+  return fromEventPattern<boolean>(next => (
+    media.addListener(() => next(media.matches))
+  ))
+    .pipe(
+      startWith(media.matches)
+    )
+}
+
+/**
+ * Watch print mode
+ *
+ * @returns Print observable
+ */
+export function watchPrint(): Observable<boolean> {
+  const media = matchMedia("print")
+  return merge(
+    fromEvent(window, "beforeprint").pipe(map(() => true)),
+    fromEvent(window, "afterprint").pipe(map(() => false))
+  )
+    .pipe(
+      startWith(media.matches)
+    )
+}
+
+/* ------------------------------------------------------------------------- */
+
+/**
+ * Toggle an observable with a media observable
+ *
+ * @template T - Data type
+ *
+ * @param query$ - Media observable
+ * @param factory - Observable factory
+ *
+ * @returns Toggled observable
+ */
+export function at<T>(
+  query$: Observable<boolean>, factory: () => Observable<T>
+): Observable<T> {
+  return query$
+    .pipe(
+      switchMap(active => active ? factory() : EMPTY)
+    )
+}