Adds option to specify an header height (#1045)

* Adds option to specify an header height

When using a template that has a sticky-header, clicking on the sidebar will
scroll the page under the header.

I added the option `headerHeight` (default = `0`) so that the content div will
be scrolled down that amount of pixels.

* updates documentation and renames variable

Author: leorossi

docs/configuration.md

@@ -575,3 +575,16 @@ window.$docsify = {
 ```
 
 > Note: The options with fallbackLanguages didn't work with the `notFoundPage` options.
+
+## topMargin
+
+- type: `Number`
+- default: `0`
+
+Adds a space on top when scrolling content page to reach the selected section. This is useful in case you have a _sticky-header_ layout and you want to align anchors to the end of your header.
+
+```js
+window.$docsify = {
+  topMargin: 90, // default: 0
+};
+```

packages/docsify-server-renderer/index.js

@@ -1,13 +1,13 @@
 import { readFileSync } from 'fs';
 import { resolve, basename } from 'path';
+import resolvePathname from 'resolve-pathname';
+import debug from 'debug';
+import fetch from 'node-fetch';
 import { AbstractHistory } from '../../src/core/router/history/abstract';
 import { Compiler } from '../../src/core/render/compiler';
 import { isAbsolutePath } from '../../src/core/router/util';
 import * as tpl from '../../src/core/render/tpl';
 import { prerenderEmbed } from '../../src/core/render/embed';
-import resolvePathname from 'resolve-pathname';
-import debug from 'debug';
-import fetch from 'node-fetch';
 
 function cwd(...args) {
   return resolve(process.cwd(), ...args);

src/core/config.js

@@ -33,6 +33,7 @@ export default function() {
       routerMode: 'hash',
       noCompileLinks: [],
       relativePath: false,
+      topMargin: 0,
     },
     window.$docsify
   );

src/core/event/scroll.js

@@ -1,23 +1,24 @@
-import { isMobile } from '../util/env';
-import * as dom from '../util/dom';
 import Tweezer from 'tweezer.js';
 import cssEscape from 'css.escape';
+import { isMobile } from '../util/env';
+import * as dom from '../util/dom';
+import config from '../config';
 
 const nav = {};
 let hoverOver = false;
 let scroller = null;
 let enableScrollEvent = true;
 let coverHeight = 0;
 
-function scrollTo(el) {
+function scrollTo(el, offset = 0) {
   if (scroller) {
     scroller.stop();
   }
 
   enableScrollEvent = false;
   scroller = new Tweezer({
     start: window.pageYOffset,
-    end: el.getBoundingClientRect().top + window.pageYOffset,
+    end: el.getBoundingClientRect().top + window.pageYOffset - offset,
     duration: 500,
   })
     .on('tick', v => window.scrollTo(0, v))
@@ -142,9 +143,9 @@ export function scrollIntoView(path, id) {
   if (!id) {
     return;
   }
-
+  const topMargin = config().topMargin;
   const section = dom.find('#' + cssEscape(id));
-  section && scrollTo(section);
+  section && scrollTo(section, topMargin);
 
   const li = nav[getNavKey(path, id)];
   const sidebar = dom.getNode('.sidebar');

src/core/global-api.js

@@ -1,10 +1,10 @@
+import marked from 'marked';
+import prism from 'prismjs';
 import * as util from './util';
 import * as dom from './util/dom';
 import { Compiler } from './render/compiler';
 import { slugify } from './render/slugify';
 import { get } from './fetch/ajax';
-import marked from 'marked';
-import prism from 'prismjs';
 
 export default function() {
   window.Docsify = {

src/core/render/compiler.js

@@ -1,3 +1,4 @@
+import marked from 'marked';
 import { isAbsolutePath, getPath, getParentPath } from '../router/util';
 import { isFn, merge, cached, isPrimitive } from '../util/core';
 import { tree as treeTpl } from './tpl';
@@ -10,7 +11,6 @@ import { paragraphCompiler } from './compiler/paragraph';
 import { taskListCompiler } from './compiler/taskList';
 import { taskListItemCompiler } from './compiler/taskListItem';
 import { linkCompiler } from './compiler/link';
-import marked from 'marked';
 
 const cachedLinks = {};
 

src/core/render/embed.js

@@ -1,6 +1,6 @@
+import stripIndent from 'strip-indent';
 import { get } from '../fetch/ajax';
 import { merge } from '../util/core';
-import stripIndent from 'strip-indent';
 
 const cached = {};
 

src/core/render/index.js

@@ -1,4 +1,5 @@
 /* eslint-disable no-unused-vars */
+import tinydate from 'tinydate';
 import * as dom from '../util/dom';
 import cssVars from '../util/polyfill/css-vars';
 import { callHook } from '../init/lifecycle';
@@ -10,7 +11,6 @@ import { scrollActiveSidebar, scroll2Top } from '../event/scroll';
 import { Compiler } from './compiler';
 import * as tpl from './tpl';
 import { prerenderEmbed } from './embed';
-import tinydate from 'tinydate';
 
 function executeScript() {
   const script = dom

test/unit/base.test.js

@@ -2,8 +2,8 @@
 require = require('esm')(
   module /* , options */
 ); /* eslint-disable-line no-global-assign */
-const { History } = require('../../src/core/router/history/base');
 const { expect } = require('chai');
+const { History } = require('../../src/core/router/history/base');
 
 class MockHistory extends History {
   parse(path) {

test/unit/render.test.js

@@ -1,5 +1,5 @@
-const { init, expectSameDom } = require('../_helper');
 const { expect } = require('chai');
+const { init, expectSameDom } = require('../_helper');
 
 describe('render', function() {
   it('important content (tips)', async function() {