Added anchor list implementation

src/assets/javascripts/actions/anchor/index.ts

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2016-2019 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.
+ */
+
+/* ----------------------------------------------------------------------------
+ * Functions
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Set anchor blur
+ *
+ * @param el - Anchor element
+ * @param value - Whether the anchor is blurred
+ */
+export function setAnchorBlur(
+  el: HTMLElement, value: boolean
+): void {
+  el.setAttribute("data-md-state", value ? "blur" : "")
+}
+
+/**
+ * Reset anchor blur
+ *
+ * @param el - Anchor element
+ */
+export function resetAnchorBlur(
+  el: HTMLElement
+): void {
+  el.removeAttribute("data-md-state")
+}
+
+/* ------------------------------------------------------------------------- */
+
+/**
+ * Set anchor active
+ *
+ * @param el - Anchor element
+ * @param value - Whether the anchor is active
+ */
+export function setAnchorActive(
+  el: HTMLElement, value: boolean
+): void {
+  el.classList.toggle("md-nav__link--active", value)
+}
+
+/**
+ * Reset anchor active
+ *
+ * @param el - Anchor element
+ */
+export function resetAnchorActive(
+  el: HTMLElement
+): void {
+  el.classList.remove("md-nav__link--active")
+}

src/assets/javascripts/actions/index.ts

@@ -20,6 +20,7 @@
  * IN THE SOFTWARE.
  */
 
+export * from "./anchor"
 export * from "./header"
 export * from "./hidden"
 export * from "./search"

src/assets/javascripts/components/anchor/index.ts

@@ -0,0 +1,246 @@
+/*
+ * Copyright (c) 2016-2019 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 { difference, reverse } from "ramda"
+import {
+  MonoTypeOperatorFunction,
+  Observable,
+  animationFrameScheduler,
+  combineLatest,
+  pipe
+} from "rxjs"
+import {
+  distinctUntilChanged,
+  finalize,
+  map,
+  observeOn,
+  scan,
+  shareReplay,
+  switchMap,
+  tap
+} from "rxjs/operators"
+
+import {
+  resetAnchorActive,
+  resetAnchorBlur,
+  setAnchorActive,
+  setAnchorBlur
+} from "actions"
+import {
+  ViewportOffset,
+  ViewportSize,
+  getElement
+} from "utilities"
+
+import { Header } from "../header"
+
+/* ----------------------------------------------------------------------------
+ * Types
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Anchor list
+ */
+export interface AnchorList {
+  prev: HTMLAnchorElement[][]          /* Anchors (previous) */
+  next: HTMLAnchorElement[][]          /* Anchors (next) */
+}
+
+/* ----------------------------------------------------------------------------
+ * Helper types
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Options
+ */
+interface Options {
+  size$: Observable<ViewportSize>      /* Viewport size observable */
+  offset$: Observable<ViewportOffset>  /* Viewport offset observable */
+  header$: Observable<Header>          /* Header observable */
+}
+
+/* ----------------------------------------------------------------------------
+ * Functions
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Watch anchor list
+ *
+ * This is effectively a scroll-spy implementation which will account for the
+ * fixed header and automatically re-calculate anchor offsets when the viewport
+ * is resized. The returned observable will only emit if the anchor list needs
+ * to be repainted.
+ *
+ * This implementation tracks an anchor element's entire path starting from its
+ * level up to the top-most anchor element, e.g. `[h3, h2, h1]`. Although the
+ * Material theme currently doesn't make use of this information, it enables
+ * the styling of the entire hierarchy through customization.
+ *
+ * Note that the current anchor is the last item of the `prev` anchor list.
+ *
+ * @param els - Anchor elements
+ * @param options - Options
+ *
+ * @return Anchor list observable
+ */
+export function watchAnchorList(
+  els: HTMLAnchorElement[], { size$, offset$, header$ }: Options
+): Observable<AnchorList> {
+  const table = new Map<HTMLAnchorElement, HTMLElement>()
+  for (const el of els) {
+    const id = decodeURIComponent(el.hash.substring(1))
+    const target = getElement(`[id="${id}"]`)
+    if (typeof target !== "undefined")
+      table.set(el, target)
+  }
+
+  /* Compute necessary adjustment for header */
+  const adjust$ = header$
+    .pipe(
+      map(header => 18 + header.height)
+    )
+
+  /* Compute partition of previous and next anchors */
+  const partition$ = size$
+    .pipe(
+
+      /* Build index to map anchor paths to vertical offsets */
+      map(() => {
+        let path: HTMLAnchorElement[] = []
+        return [...table].reduce((index, [anchor, target]) => {
+          while (path.length) {
+            const last = table.get(path[path.length - 1])!
+            if (last.tagName >= target.tagName) {
+              path.pop()
+            } else {
+              break
+            }
+          }
+          return index.set(
+            reverse(path = [...path, anchor]),
+            target.offsetTop
+          )
+        }, new Map<HTMLAnchorElement[], number>())
+      }),
+
+      /* Re-compute partition when viewport offset changes */
+      switchMap(index => combineLatest(offset$, adjust$)
+        .pipe(
+          scan(([prev, next], [{ y }, adjust]) => {
+
+            /* Look forward */
+            while (next.length) {
+              const [, offset] = next[0]
+              if (offset - adjust < y) {
+                prev = [...prev, next.shift()!]
+              } else {
+                break
+              }
+            }
+
+            /* Look backward */
+            while (prev.length) {
+              const [, offset] = prev[prev.length - 1]
+              if (offset - adjust >= y) {
+                next = [prev.pop()!, ...next]
+              } else {
+                break
+              }
+            }
+
+            /* Return partition */
+            return [prev, next]
+          }, [[], [...index]]),
+          distinctUntilChanged((a, b) => {
+            return a[0] === b[0]
+                && a[1] === b[1]
+          })
+        )
+      )
+    )
+
+  /* Compute anchor list migrations */
+  const migration$ = partition$
+    .pipe(
+      map(([prev, next]) => ({
+        prev: prev.map(([path]) => path),
+        next: next.map(([path]) => path)
+      })),
+
+      /* Extract anchor list migrations */
+      scan<AnchorList>((a, b) => {
+        const begin = Math.max(0, Math.min(b.prev.length, a.prev.length) - 1)
+        const end   = Math.max(b.prev.length, a.prev.length)
+        return {
+          prev: b.prev.slice(begin, end + 1),
+          next: difference(b.next, a.next)
+        }
+      }, { prev: [], next: [] })
+    )
+
+  /* Return anchor list migrations as hot observable */
+  return migration$
+    .pipe(
+      shareReplay(1)
+    )
+}
+
+/* ------------------------------------------------------------------------- */
+
+/**
+ * Paint anchor list from source observable
+ *
+ * @param els - Anchor elements
+ *
+ * @return Operator function
+ */
+export function paintAnchorList(
+  els: HTMLAnchorElement[]
+): MonoTypeOperatorFunction<AnchorList> {
+  return pipe(
+
+    /* Defer repaint to next animation frame */
+    observeOn(animationFrameScheduler),
+    tap(({ prev, next }) => {
+
+      /* Look forward */
+      for (const [el] of next) {
+        resetAnchorActive(el)
+        resetAnchorBlur(el)
+      }
+
+      /* Look backward */
+      for (const [index, [el]] of prev.entries()) {
+        setAnchorActive(el, index === prev.length - 1)
+        setAnchorBlur(el, true)
+      }
+    }),
+
+    /* Reset on complete or error */
+    finalize(() => {
+      for (const el of els) {
+        resetAnchorActive(el)
+        resetAnchorBlur(el)
+      }
+    })
+  )
+}

src/assets/javascripts/components/index.ts

@@ -21,6 +21,7 @@
  */
 
 export * from "./_"
+export * from "./anchor"
 export * from "./header"
 export * from "./hidden"
 export * from "./main"