documentation/api.md

   1 <!--
   2 This is part of the VimFx documentation.
   3 Copyright Simon Lydell 2015, 2016.
   4 See the file README.md for copying conditions.
   5 -->
   6
   7 # API
   8
   9 This file documents VimFx’s [config file] API.
  10
  11 Both `config.js` and `frame.js` have access to a variable called `vimfx`. Note
  12 that while the variables have the same name, they are different and provide
  13 different API methods.
  14
  15
  16 ## `config.js` API
  17
  18 In `config.js`, the following API is available as the variable `vimfx`.
  19
  20 ### `vimfx.get(...)`, `vimfx.getDefault(...)` and `vimfx.set(...)`
  21
  22 Gets or sets the (default) value of a VimFx pref.
  23
  24 You can see all prefs in [defaults.coffee], or by opening [about:config] and
  25 filtering by `extensions.vimfx`. Note that you can also access the [special
  26 options], which may not be accessed in [about:config], using `vimfx.get(...)`
  27 and `vimfx.set(...)`—in fact, this is the _only_ way of accessing those options.
  28
  29 #### `vimfx.get(pref)`
  30
  31 Gets the value of the VimFx pref `pref`.
  32
  33 ```js
  34 // Get the value of the Hint chars option:
  35 vimfx.get('hint_chars')
  36 // Get all keyboard shortcuts (as a string) for the `f` command:
  37 vimfx.get('mode.normal.follow')
  38 ```
  39
  40 #### `vimfx.getDefault(pref)`
  41
  42 Gets the default value of the VimFx pref `pref`.
  43
  44 Useful when you wish to extend a default, rather than replacing it. See below.
  45
  46 #### `vimfx.set(pref, value)`
  47
  48 Sets the value of the VimFx pref `pref` to `value`.
  49
  50 ```js
  51 // Set the value of the Hint chars option:
  52 vimfx.set('hint_chars', 'abcdefghijklmnopqrstuvwxyz')
  53 // Add yet a keyboard shortcut for the `f` command:
  54 vimfx.set('mode.normal.follow', vimfx.getDefault('mode.normal.follow') + '  ee')
  55 ```
  56
  57 When extending a pref (as in the second example above), be sure to use
  58 `vimfx.getDefault` rather than `vimfx.get`. Otherwise you get a multiplying
  59 effect. In the above example, after starting Firefox a few times the pref would
  60 be `f  e  e  e  e`. Also, if you find that example very verbose: Remember that
  61 you’re using a programming language! Write a small helper function that suits
  62 your needs.
  63
  64 Note: If you produce conflicting keyboard shortcuts, the order of your code does
  65 not matter. The command that comes first in VimFx’s settings page in the Add-ons
  66 Manager (and in the Keyboard Shortcuts help dialog) gets the shortcut; the other
  67 one(s) do(es) not. See the notes about order in [mode object], [category object]
  68 and [command object] for more information about order.
  69
  70 ```js
  71 // Even though we set the shortcut for focusing the search bar last, the command
  72 // for focusing the location bar “wins”, because it comes first in VimFx’s
  73 // settings page in the Add-ons Manager.
  74 vimfx.set('mode.normal.focus_location_bar', 'ö')
  75 vimfx.set('mode.normal.focus_search_bar', 'ö')
  76
  77 // Swapping their orders also swaps the “winner”.
  78 let {commands} = vimfx.modes.normal
  79 ;[commands.focus_location_bar.order, commands.focus_search_bar.order] =
  80   [commands.focus_search_bar.order, commands.focus_location_bar.order]
  81 ```
  82
  83 ### `vimfx.addCommand(options, fn)`
  84
  85 Creates a new command.
  86
  87 `options`:
  88
  89 - name: `String`. The name used when accessing the command via
  90   `vimfx.modes[options.mode].commands[options.name]`. It is also used for the
  91   pref used to store the shortcuts for the command:
  92   `` `custom.mode.${options.mode}.${options.name}` ``.
  93 - description: `String`. Shown in the Keyboard Shortcuts help dialog and VimFx’s
  94   settings page in the Add-ons Manager.
  95 - mode: `String`. Defaults to `'normal'`. The mode to add the command to. The
  96   value has to be one of the keys of [`vimfx.modes`].
  97 - category: `String`. Defaults to `'misc'` for Normal mode and `''`
  98   (uncategorized) otherwise. The category to add the command to. The
  99   value has to be one of the keys of [`vimfx.get('categories')`][categories].
 100 - order: `Number`. Defaults to putting the command at the end of the category.
 101   The first of the default commands has the order `100` and then they increase
 102   by `100` per command. This allows to put new commands between two already
 103   existing ones.
 104
 105 `fn` is called when the command is activated. See the [onInput] documentation
 106 below for more information.
 107
 108 <strong id="custom-command-shortcuts">Note</strong> that you have to give the
 109 new command a shortcut in VimFx’s settings page in the Add-ons Manager or set
 110 one using `vimfx.set(...)` to able to use the new command.
 111
 112 ```js
 113 vimfx.addCommand({
 114   name: 'hello',
 115   description: 'Log Hello World',
 116 }, () => {
 117   console.log('Hello World!')
 118 })
 119 // Optional:
 120 vimfx.set('custom.mode.normal.hello', 'gö')
 121 ```
 122
 123 ### `vimfx.addOptionOverrides(...)` and `vimfx.addKeyOverrides(...)`
 124
 125 These methods take any number of arguments. Each argument is a rule. The rules
 126 are added in order. The methods may be run multiple times.
 127
 128 A rule is an `Array` of length 2:
 129
 130 1. The first item is a function that returns `true` if the rule should be
 131    applied and `false` if not. This is called the matching function.
 132 2. The second item is the value that should be used if the rule is applied. This
 133    is called the override.
 134
 135 The rules are tried in the same order they were added. When a matching rule is
 136 found it is applied. No more rules will be applied.
 137
 138 #### `vimfx.addOptionOverrides(...rules)`
 139
 140 The rules are matched any time the value of a VimFx pref is needed.
 141
 142 The matching function receives a [location object].
 143
 144 The override is an object whose keys are VimFx pref names and whose values
 145 override the pref in question. The values should be formatted as in an [options
 146 object].
 147
 148 ```js
 149 vimfx.addOptionOverrides(
 150   [ ({hostname, pathname, hash}) =>
 151     `${hostname}${pathname}${hash}` === 'google.com/',
 152     {prevent_autofocus: false}
 153   ]
 154 )
 155
 156 vimfx.addOptionOverrides(
 157   [ ({hostname}) => hostname === 'imgur.com',
 158     {
 159       pattern_attrs: ['class'],
 160       pattern_selector: 'div.next-prev .btn',
 161       prev_patterns: [/\bnavPrev\b/],
 162       next_patterns: [/\bnavNext\b/],
 163     }
 164   ]
 165 )
 166 ```
 167
 168 #### `vimfx.addKeyOverrides(...rules)`
 169
 170 The rules are matched any time you press a key that is not part of the tail of a
 171 multi-key shortcut.
 172
 173 The matching function receives a [location object] as well as the current
 174 mode name (one of the keys of [`vimfx.modes`]).
 175
 176 The override is an array of keys which should not activate VimFx commands but be
 177 sent to the page.
 178
 179 This allows to disable commands on specific sites. To _add_ commands on specific
 180 sites, add them globally and then disable them on all _other_ sites.
 181
 182 ```js
 183 vimfx.addKeyOverrides(
 184   [ location => location.hostname === 'facebook.com',
 185     ['j', 'k']
 186   ]
 187 )
 188 ```
 189
 190 ### `vimfx.send(vim, message, data = null, callback = null)`
 191
 192 Send `message` (a string) to the instance of `frame.js` in the tab managed by
 193 [`vim`][vim object], and pass it `data`. If provided, `callback` must be a
 194 function that takes a single argument, which is the data that `frame.js`
 195 responds with. `frame.js` uses its [`vimfx.listen(...)`] method to listen for
 196 (and optionally respond to) `message`.
 197
 198 Here is an example:
 199
 200 ```js
 201 // config.js
 202 // You get a `vim` instance by using `vimfx.addCommand(...)` or `vimfx.on(...)`.
 203 vimfx.send(vim, 'getSelection', {example: 5}, selection => {
 204   console.log('Currently selected text:', selection)
 205 })
 206 ```
 207
 208 ```js
 209 // frame.js
 210 vimfx.listen('getSelection', ({example}, callback) => {
 211   console.log('`example` should be 5:', example)
 212   let selection = content.getSelection().toString()
 213   callback(selection)
 214 })
 215 ```
 216
 217 What if you want to do it the other way around: Send a message _from_ `frame.js`
 218 and listen for it in `config.js`? That’s not the common use case, so VimFx does
 219 not provide convenience functions for it. Yes, `vimfx.send(...)`, and
 220 `vimfx.listen(...)` in `frame.js`, are just light wrappers around the standard
 221 Firefox [Message Manager] to make it easier to create custom commands that ask
 222 `frame.js` for information about the current web page (as in the above example).
 223 If you want to send messages any other way, you’ll need to use the Message
 224 Manager directly. See [the `shutdown` event] for an example.
 225
 226 (While it would have made sense to provide `vim.send(message, data, callback)`
 227 instead of `vimfx.send(vim, message, data, callback)`, the latter was chosen for
 228 symmetry between `config.js` and `frame.js`. Use `vimfx.send()` to send
 229 messages, and `vimfx.listen()` to listen for them.)
 230
 231 ### `vimfx.on(eventName, listener)` and `vimfx.off(eventName, listener)`
 232
 233 After calling `vimfx.on(eventName, listener)`, `listener(data)` will be called
 234 when `eventName` is fired, where `data` is an object. Which properties `data`
 235 has is specific to each event.
 236
 237 You may use `vimfx.off(eventName, listener)` if you’d like to remove your
 238 added listener for some reason.
 239
 240 While [`vimfx.send(...)`] and [`vimfx.listen(...)`] are all about passing
 241 messages between `config.js` and `frame.js`, `vimfx.on(...)` is all about doing
 242 something whenever VimFx emits internal events.
 243
 244 #### The `locationChange` event
 245
 246 Occurs when opening a new tab, navigating to a new URL or refreshing the page,
 247 causing a full page load.
 248
 249 `data`:
 250
 251 - vim: The current [vim object].
 252 - location: A [location object].
 253
 254 This event can be used to enter a different mode by default on some pages (which
 255 can be used to replace the blacklist option).
 256
 257 ```js
 258 vimfx.on('locationChange', ({vim, location}) => {
 259   if (location.hostname === 'example.com') {
 260     vimfx.modes.normal.commands.enter_mode_ignore.run({vim, blacklist: true})
 261   }
 262 })
 263 ```
 264
 265 #### The `notification` and `hideNotification` events
 266
 267 The `notification` event occurs when `vim.notify(message)` is called, and means
 268 that `message` should be displayed to the user.
 269
 270 The `hideNotification` event occurs when the `vim.hideNotification()` is called,
 271 and means that the current notification is requested to be hidden.
 272
 273 `data`:
 274
 275 - vim: The current [vim object].
 276 - message: The message that should be notified. Only for the `notification`
 277   event.
 278
 279 Both of these events are emitted even if the [`notifications_enabled`] option is
 280 disabled, allowing you to display notifications in any way you want.
 281
 282 #### The `modeChange` event
 283
 284 Occurs whenever the current mode in any tab changes. The initial entering of the
 285 default mode in new tabs also counts as a mode change.
 286
 287 `data`:
 288
 289 - vim: The current [vim object].
 290
 291 ```js
 292 vimfx.on('modeChange', ({vim}) => {
 293   let mode = vimfx.modes[vim.mode].name
 294   vim.notify(`Entering mode: ${mode}`)
 295 })
 296 ```
 297
 298 #### The `TabSelect` event
 299
 300 Occurs whenever any tab in any window is selected. This is also fired when
 301 Firefox starts for the currently selected tab.
 302
 303 `data`:
 304
 305 - event: The `event` object passed to the standard Firefox [TabSelect] event.
 306
 307 #### The `modeDisplayChange` event
 308
 309 This is basically a combination of the `modeChange` and the `TabSelect` events.
 310 The event is useful for knowing when to update UI showing the current mode.
 311
 312 `data`:
 313
 314 - vim: The current [vim object].
 315
 316 (VimFx itself uses this event to update the toolbar [button], by setting
 317 `#main-window[vimfx-mode]` to the current mode. You may use this with custom
 318 [styling].)
 319
 320 #### The `focusTypeChange` event
 321
 322 Occurs when focusing or blurring any element. See also the [`blur_timeout`]
 323 pref.
 324
 325 `data`:
 326
 327 - vim: The current [vim object].
 328
 329 `data.vim.focusType` has been updated just before this event fires.
 330
 331 (VimFx itself uses this event to update the toolbar [button], by setting
 332 `#main-window[vimfx-focus-type]` to the current focus type. You may use this
 333 with custom [styling].)
 334
 335 #### The `shutdown` event
 336
 337 Occurs when:
 338
 339 - VimFx shuts down: When Firefox shuts down, when VimFx is disabled or when
 340   VimFx is updated.
 341 - When the config file is reloaded using the `gC` command.
 342
 343 `data`: No data at all is passed.
 344
 345 If you care about that things you do in `config.js` and `frame.js` are undone
 346 when any of the above happens, read on.
 347
 348 If all you do is using the methods of the `vimfx` object, you shouldn’t need to
 349 care about this event.
 350
 351 The following methods don’t need any undoing:
 352
 353 - `vimfx.get(...)`
 354 - `vimfx.getDefault(...)`
 355 - `vimfx.send(...)`
 356 - `vimfx.off(...)`
 357
 358 The following methods are automatically undone when the `shutdown` event fires.
 359 This means that if you, for example, add a custom command in `config.js` but
 360 then remove it from `config.js` and hit `gC`, the custom command will be gone in
 361 VimFx.
 362
 363 - `vimfx.set(...)`
 364 - `vimfx.addCommand(...)`
 365 - `vimfx.addOptionOverrides(...)`
 366 - `vimfx.addKeyOverrides(...)`
 367 - `vimfx.on(...)`
 368
 369 The following require manual undoing:
 370
 371 - `vimfx.mode`. Any changes you do here must be manually undone.
 372
 373 If you add event listeners in `frame.js`, here’s an example of how to remove
 374 them on `shutdown`:
 375
 376 ```js
 377 // config.js
 378 vimfx.on('shutdown', () => {
 379   Components.classes['@mozilla.org/globalmessagemanager;1']
 380     .getService(Components.interfaces.nsIMessageListenerManager)
 381     // Send this message to _all_ frame scripts.
 382     .broadcastAsyncMessage('VimFx-config:shutdown')
 383 })
 384 ```
 385
 386 ```js
 387 // frame.js
 388 let listeners = []
 389 function listen(eventName, listener) {
 390   addEventListener(eventName, listener, true)
 391   listeners.push([eventName, listener])
 392 }
 393
 394 listen('focus', event => {
 395   console.log('focused element', event.target)
 396 })
 397
 398 addMessageListener('VimFx-config:shutdown', () => {
 399   listeners.forEach(([eventName, listener]) => {
 400     removeMessageListener(eventName, listener, true)
 401   })
 402 })
 403 ```
 404
 405 ### `vimfx.modes`
 406
 407 An object whose keys are mode names and whose values are [mode object]s.
 408
 409 This is a very low-level part of the API. It allows to:
 410
 411 - Access all commands and run them. This is the most common thing that a config
 412   file user needs it for.
 413
 414   ```js
 415     let {commands} = vimfx.modes.normal
 416     // Inside a custom command:
 417     commands.tab_new.run(args)
 418   ```
 419
 420 - Adding new commands. It is recommended to use the `vimfx.addCommand(...)`
 421   helper instead. It’s easier.
 422
 423   ```js
 424   vimfx.modes.normal.commands.new_command = {
 425     pref: 'extensions.my_extension.mode.normal.new_command',
 426     category: 'misc',
 427     order: 10000,
 428     description: translate('mode.normal.new_command'),
 429     run: args => console.log('New command! args:', args)
 430   }
 431   ```
 432
 433 - Adding new modes. This is the most advanced customization you can do to VimFx.
 434   Expect having to read VimFx’s source code to figure it all out.
 435
 436   ```js
 437   vimfx.modes.new_mode = {
 438     name: translate('mode.new_mode'),
 439     order: 10000,
 440     commands: {},
 441     onEnter(args) {},
 442     onLeave(args) {},
 443     onInput(args, match) {
 444       if (match.type === 'full') {
 445         match.command.run(args)
 446       }
 447       return (match.type !== 'none')
 448     },
 449   }
 450   ```
 451
 452 Have a look at [modes.coffee] and [commands.coffee] for more information.
 453
 454 ### `vimfx.get('categories')`
 455
 456 An object whose keys are category names and whose values are [category object]s.
 457
 458 ```js
 459 let categories = vimfx.get('categories')
 460
 461 // Add a new category.
 462 categories.custom = {
 463   name: 'Custom commands',
 464   order: 10000,
 465 }
 466
 467 // Swap the order of the Location and Tabs categories.
 468 ;[commands.focus_location_bar.order, categories.tabs.order] =
 469   [categories.tabs.order, commands.focus_location_bar.order]
 470 ```
 471
 472 ### Custom hint commands
 473
 474 Apart from the standard hint commands, you can create your own.
 475
 476 You may run any VimFx command by using the following pattern:
 477
 478 ```js
 479 // config.js
 480 vimfx.addCommand({
 481   name: 'run_other_command_example',
 482   description: 'Run other command example',
 483 }, (args) => {
 484   // Replace 'follow' with any command name here:
 485   vimfx.modes.normal.commands.follow.run(args)
 486 })
 487 ```
 488
 489 All hint commands (except `eb`) also support `args.callbackOverride`:
 490
 491 ```js
 492 // config.js
 493 vimfx.addCommand({
 494   name: 'custom_hint_command_example',
 495   description: 'Custom hint command example',
 496 }, (args) => {
 497   vimfx.modes.normal.commands.follow.run(Object.assign({}, args, {
 498     callbackOverride({type, href, id, timesLeft}) {
 499       console.log('Marker data:', {type, href, id, timesLeft})
 500       return (timesLeft > 1)
 501     },
 502   }))
 503 })
 504 ```
 505
 506 This lets you piggy-back on one of the existing hint commands by getting the
 507 same hints on screen as that command, but then doing something different with
 508 the matched hint marker.
 509
 510 `callbackOverride` is called with an object with the following properties:
 511
 512 - type: `String`. The type of the element of the matched hint marker. See
 513   [`vimfx.setHintMatcher(...)`] for all possible values.
 514
 515 - href: `String` or `null`. If `type` is `'link'`, then this is the `href`
 516   attribute of the element of the matched hint marker.
 517
 518 - id: An id that you can pass to [`vimfx.getMarkerElement(...)`] to get the
 519   element of the matched hint marker.
 520
 521 - timesLeft: `Number`. Calling a hint command with a count means that you want
 522   to run it _count_ times in a row. This number tells how many times there are
 523   left to run. If you don’t provide a count, the number is `1`.
 524
 525 `callbackOverride` should return `true` if you want the hint markers to
 526 re-appear on screen after you’ve matched one of them (as in the `af` command),
 527 and `false` if you wish to exit Hints mode. If your command ignores counts,
 528 simply always return `false`. Otherwise you most likely want to return
 529 `timesLeft > 1`.
 530
 531 Here’s an example which adds a silly command for marking links with
 532 color—`http://` links with red and all other links with green.
 533
 534 ```js
 535 // config.js
 536 let {commands} = vimfx.modes.normal
 537
 538 vimfx.addCommand({
 539   name: 'mark_link',
 540   category: 'browsing',
 541   description: 'Mark link with red or green',
 542 }, (args) => {
 543   let {vim} = args
 544   commands.follow_in_tab.run(Object.assign({}, args, {
 545     callbackOverride({type, href, id, timesLeft}) {
 546       if (href) {
 547         let color = href.startsWith('http://') ? 'red' : 'green'
 548         vimfx.send(vim, 'highlight_marker_element', {id, color})
 549       }
 550       return false
 551     },
 552   }))
 553 })
 554 ```
 555
 556 ```js
 557 // frame.js
 558 vimfx.listen('highlight_marker_element', ({id, color}) => {
 559   let element = vimfx.getMarkerElement(id)
 560   if (element) {
 561     element.style.backgroundColor = color
 562   }
 563 })
 564 ```
 565
 566 ### Mode object
 567
 568 A mode is an object with the following properties:
 569
 570 - name: `String`. A human readable name of the mode used in the Keyboard
 571   Shortcuts help dialog and VimFx’s settings page in the Add-ons Manager. Config
 572   file users adding custom modes could simply use a hard-coded string; extension
 573   authors are encouraged to look up the name from a locale file.
 574 - order: `Number`. The first of the default modes has the order `100` and then
 575   they increase by `100` per mode. This allows to put new modes between two
 576   already existing ones.
 577 - commands: `Object`. The keys are command names and the values are [command
 578   object]s.
 579 - onEnter(data, ...args): `Function`. Called when the mode is entered.
 580 - onLeave(data): `Function`. Called when the mode is left.
 581 - onInput(data, match): `Function`. Called when a key is pressed.
 582
 583 #### onEnter, onLeave and onInput
 584
 585 These methods are called with an object (called `data` above) with the following
 586 properties:
 587
 588 - vim: The current [vim object].
 589 - storage: An object unique to the current [vim object] and to the current mode.
 590   Allows to share things between commands of the same mode by getting and
 591   setting keys on it.
 592
 593 ##### onEnter
 594
 595 This method is called with an object as mentioned above, and after that there
 596 may be any number of arguments that the mode is free to do whatever it wants
 597 with.
 598
 599 ##### onInput
 600
 601 The object passed to this method (see above) also has the following properties:
 602
 603 - uiEvent: `Event` or `false`. The keydown event object if the event occurred in
 604   the browser UI, `false` otherwise (if the event occurred in web page content).
 605 - count: `Number`. The count for the command. `undefined` if no count. (This is
 606   simply a copy of `match.count`. `match` is defined below.)
 607
 608 The above object should be passed to commands when running them. The mode is
 609 free to do whatever it wants with the return value (if any) of the commands it
 610 runs.
 611
 612 It also receives a [match object] as the second argument.
 613
 614 `onInput` should return `true` if the current keypress should not be passed on
 615 to the browser and web pages, and `false` otherwise.
 616
 617 ### Category object
 618
 619 A category is an object with the following properties:
 620
 621 - name: `String`. A human readable name of the category used in the Keyboard
 622   Shortcuts help dialog and VimFx’s settings page in the Add-ons Manager. Config
 623   file users adding custom categories could simply a use hard-coded string;
 624   extension authors are encouraged to look up the name from a locale file.
 625 - order: `Number`. The first of the default categories is the “uncategorized”
 626   category. It has the order `100` and then they increase by `100` per category.
 627   This allows to put new categories between two already existing ones.
 628
 629 ### Command object
 630
 631 A command is an object with the following properties:
 632
 633 - pref: `String`. The pref used to store the shortcuts for the command.
 634 - run(args): `Function`. Called when the command is activated.
 635 - description: `String`. A description of the command, shown in the Keyboard
 636   Shortcuts help dialog and VimFx’s settings page in the Add-ons Manager. Config
 637   file users adding custom commands could simply use a hard-coded string;
 638   extension authors are encouraged to look up the name from a locale file.
 639 - category: `String`. The category to add the command to. The value has to be
 640   one of the keys of [`vimfx.get('categories')`][categories].
 641 - order: `Number`. The first of the default commands has the order `100` and
 642   then they increase by `100` per command. This allows to put new commands
 643   between two already existing ones.
 644
 645 ### Match object
 646
 647 A `match` object has the following properties:
 648
 649 - type: `String`. It has one of the following values:
 650
 651   - `'full'`: The current keypress, together with previous keypresses, fully
 652     matches a command shortcut.
 653   - `'partial'`: The current keypress, together with previous keypresses,
 654     partially matches a command shortcut.
 655   - `'count'`: The current keypress is not part of a command shortcut, but is a
 656     digit and contributes to the count of a future matched command.
 657   - `'none'`: The current keypress is not part of a command shortcut and does
 658     not contribute to a count.
 659
 660 - likelyConflict: `Boolean`. This is `true` if the current keypress is likely to
 661   cause conflicts with default Firefox behavior of that key, and `false`
 662   otherwise. A mode might not want to run commands and suppress the event if
 663   this value is `true`. VimFx uses the current keypress and `vim.focusType` of
 664   the current [vim object] to decide if the current keypress is a likely
 665   conflict:
 666
 667   1. If the key is part of the tail of a shortcut, it is never a conflict.
 668   2. If `vim.focusType` is `'activatable'` or `'adjustable'` and the key is
 669      present in [`activatable_element_keys`] or [`adjustable_element_keys`]
 670      (respectively), then it is a likely conflict.
 671   3. Finally, unless `vim.focusType` is `'none'`, then it is a likely conflict.
 672      This most commonly means that a text input is focused.
 673
 674   Note that any VimFx shortcut starting with a keypress involving a modifier is
 675   _very_ likely to conflict with either a Firefox default shortcut or a shortcut
 676   from some other add-on. This is _not_ attempted to be detected in any way.
 677   Instead, VimFx uses no modifiers in any default Normal mode shortcuts, leaving
 678   it up to you to choose modifier-shortcuts that work out for you if you want
 679   such shortcuts. In other words, for modifier-shortcuts the point of VimFx _is_
 680   to conflict (overriding default shortcuts).
 681
 682 - command: `null` unless `type` is `'full'`. Then it is the matched command (a
 683   [command object]).
 684
 685   The matched command should usually be run at this point. It is suitable to
 686   pass on the object passed to [onInput] to the command. Some modes might choose
 687   to add extra properties to the object first. (That is favored over passing
 688   several arguments, since it makes it easier for the command to in turn pass
 689   the same data it got on to another command, if needed.)
 690
 691   Usually the return value of the command isn’t used, but that’s up to the mode.
 692
 693 - count: `Number`. The count for the command. `undefined` if no count.
 694
 695 - specialKeys: `Object`. The keys may be any of the following:
 696
 697   - `<force>`
 698   - `<late>`
 699
 700   If a key exists, its value is always `true`. The keys that exist indicate the
 701   [special keys] for the sequence used for the matched command (if any).
 702
 703 - keyStr: `String`. The current keypress represented as a string.
 704
 705 - unmodifiedKey: `String`. `keyStr` without modifiers.
 706
 707 - toplevel: `Boolean`. Whether or not the match was a toplevel match in the
 708   shortcut key tree. This is `true` unless the match is part of the tail of a
 709   multi-key shortcut.
 710
 711 - discard(): `Function`. Discards keys pressed so far: If `type` is `'partial'`
 712   or `'count'`. For example, if you have typed `12g`, run `match.discard()` and
 713   then press `$`, the `$` command will be run instead of `12g$`.
 714
 715 ### Vim object
 716
 717 There is one `vim` object per tab.
 718
 719 A `vim` object has the following properties:
 720
 721 - window: [`Window`]. The current Firefox window object. Most commands
 722   interacting with Firefox’s UI use this.
 723
 724 - browser: [`Browser`]. The `browser` that this vim object handles.
 725
 726 - options: `Object`. Provides access to all of VimFx’s options. It is an
 727   [options object].
 728
 729 - mode: `String`. The current mode name.
 730
 731 - focusType: `String`. The type of currently focused element. VimFx decides the
 732   type based on how it responds to keystorkes. It has one of the following
 733   values:
 734
 735   - `'ignore'`: Some kind of Vim-style editor. VimFx automatically
 736     enters Ignore mode when this focus type is encountered.
 737   - `'editable'`: Some kind of text input, a `<select>` element or a
 738     “contenteditable” element.
 739   - `'activatable'`: An “activatable” element (link or button).
 740     (See also the [`activatable_element_keys`] option.)
 741   - `'adjustable'`: An “adjustable” element (form control or video
 742     player). (See also the [`adjustable_element_keys`] option.)
 743   - `'findbar'`: The findbar text input is focused.
 744   - `'none'`: The currently focused element does not appear to respond to
 745     keystrokes in any special way.
 746
 747   [The `focusTypeChange` event] is fired whenever `focusType` is updated.
 748
 749   `match.likelyConflict` of [match object]s depend on `focusType`.
 750
 751 - isUIEvent(event): `Function`. Returns `true` if `event` occurred in the
 752   browser UI, and `false` otherwise (if it occurred in web page content).
 753
 754 - notify(message): `Function`. Display a notification with the text `message`.
 755
 756 - hideNotification(): `Function`. Hide the current notification (if any).
 757
 758 - markPageInteraction(value=true): `Function`. When `value` is `true` (as it is
 759   by default when the argument is omitted), marks that the user has interacted
 760   with the page. After that [autofocus prevention] is not done anymore. Commands
 761   interacting with web page content might want to do this. If `value` is
 762   `false`, the state is reset and autofocus prevention _will_ be done again.
 763
 764 **Warning:** There are also properties starting with an underscore on `vim`
 765 objects. They are private, and not supposed to be used outside of VimFx’s own
 766 source code. They may change at any time.
 767
 768 ### Options object
 769
 770 An `options` object provides access to all of VimFx’s options. It is an object
 771 whose keys are VimFx pref names.
 772
 773 Note that the values are not just simply `vimfx.get(pref)` for the `pref` in
 774 question; they are _parsed_ (`parse(vimfx.get(pref))`):
 775
 776 - Space-separated prefs are parsed into arrays of strings. For example,
 777   `pattern_attrs: ['class']`.
 778
 779 - `blacklist`, `prev_patterns` and `next_patterns` are parsed into arrays of
 780   regular expressions. For example, `prev_patterns: [/\bnavPrev\b/]`.
 781
 782 (See [parse-prefs.coffee] for all details.)
 783
 784 Any [option overrides] are automatically taken into account when getting an
 785 option value.
 786
 787 The [special options] are also available on this object.
 788
 789
 790 ### Location object
 791
 792 A location object is very similar to [`window.location`] in web pages.
 793 Technically, it is a [`URL`] instance. You can experiment with the current
 794 location object by opening the [web console] and entering `location`.
 795
 796
 797 ## `frame.js` API
 798
 799 In `frame.js`, the following API is available as the variable `vimfx`.
 800
 801 ### `vimfx.listen(message, listener)`
 802
 803 Listen for `message` (a string) from `config.js`. `listener` will be called with
 804 the data sent from `config.js` (if any), and optionally a callback function if
 805 `config.js` wants you to respond. If so, call the callback function, optionally
 806 with some data to send back to `config.js.` `config.js` uses its
 807 [`vimfx.send(...)`] method to send  `message` (and optionally some data along
 808 with it).
 809
 810 See the [`vimfx.send(...)`] method in `config.js` for more information and
 811 examples.
 812
 813 ### `vimfx.setHintMatcher(hintMatcher)`
 814
 815 `hintMatcher` is a function that lets you customize which elements do and don’t
 816 get hints. It might help to read about [the hint commands] first.
 817
 818 If you call `vimfx.setHintMatcher(hintMatcher)` more than once, only the
 819 `hintMatcher` provided the last time will be used.
 820
 821 ```js
 822 vimfx.setHintMatcher((id, element, type) => {
 823   // Inspect `element` and return a different `type` if needed.
 824   return type
 825 })
 826 ```
 827
 828 The arguments passed to the `hintMatcher` function are:
 829
 830 - id: `String`. A string identifying which command is used:
 831
 832   - `'normal'`: `f` or `af`.
 833   - `'tab'`: `F`, `et`, `ew` or `ep`.
 834   - `'copy'`: `yf`.
 835   - `'focus'`: `ef`.
 836   - `'context'`: `ec`.
 837   - `'select'`: `v`, `av` or `yv`.
 838
 839 - element: `Element`. One out of all elements currently inside the viewport.
 840
 841 - type: `String` or `null`. If a string, it means that `element` should get a
 842   hint. If `null`, it won’t. See the available strings below. When a marker
 843   is matched, `type` decides what happens to `element`.
 844
 845   This parameter tells how VimFx has matched `element`. You have the opportunity
 846   to change that.
 847
 848 The available type strings depend on `id`:
 849
 850 - normal:
 851
 852   - link: A “proper” link (not used as a button with the help of JavaScript),
 853     with an `href` attribute.
 854   - text: An element that can you can type in, such as text inputs.
 855   - clickable: Some clickable element not falling into another category.
 856   - clickable-special: Like “clickable,” but uses a different technique to
 857     simulate a click on the element. If “clickable” doesn’t work, try this one.
 858   - scrollable: A scrollable element.
 859
 860 - tab:
 861
 862   - link: Like “link” when `id` is “normal” (see above).
 863
 864 - copy:
 865
 866   - link: Like “link” when `id` is “normal” (see above).
 867   - text: Like “text” when `id` is “normal” (see above), except that in this
 868     case “contenteditable” elements are not included.
 869   - contenteditable: Elements with “contenteditable” turned on.
 870
 871 - focus:
 872
 873   - focusable: Any focusable element not falling into another category.
 874   - scrollable: Like “scrollable” when `id` is “normal” (see above).
 875
 876 - context:
 877
 878   - context: An element that can have a context menu opened.
 879
 880 - select:
 881
 882   - selectable: An element with selectable text (but not text inputs).
 883
 884 The function must return `null` or a string like the `type` parameter.
 885
 886 ### `vimfx.getMarkerElement(id)`
 887
 888 Takes an id that has been given to you when creating [custom hint commands] and
 889 returns the DOM element associated with that id. If no element can be found,
 890 `null` is returned.
 891
 892
 893 ## Stability
 894
 895 The API is currently **experimental** and therefore **unstable.** Things might
 896 break with new VimFx versions. However, no breaking changes are planned, and
 897 will be avoided if feasible.
 898
 899 As soon as VimFx 1.0.0 (which does not seem to be too far away) is released
 900 backwards compatibility will be a priority and won’t be broken until VimFx
 901 2.0.0.
 902
 903 [option overrides]: #vimfxaddoptionoverridesrules
 904 [`vimfx.send(...)`]: #vimfxsendvim-message-data--null-callback--null
 905 [`vimfx.listen(...)`]: #vimfxlistenmessage-listener
 906 [categories]: #vimfxgetcategories
 907 [custom hint commands]: #custom-hints-commands
 908 [`vimfx.modes`]: #vimfxmodes
 909 [onInput]: #oninput
 910 [mode object]: #mode-object
 911 [category object]: #category-object
 912 [command object]: #command-object
 913 [match object]: #match-object
 914 [vim object]: #vim-object
 915 [options object]: #options-object
 916 [location object]: #location-object
 917 [The `focusTypeChange` event]: #the-focustypechange-event
 918 [the `shutdown` event]: #the-shutdown-event
 919 [`vimfx.setHintMatcher(...)`]: #vimfxsethintmatcherhintmatcher
 920 [`vimfx.getMarkerElement(...)`]: #vimfxgetmarkerelementid
 921
 922 [blacklisted]: options.md#blacklist
 923 [special options]: options.md#special-options
 924 [config file]: config-file.md
 925 [bootstrap.js]: config-file.md#bootstrapjs
 926 [autofocus prevention]: options.md#prevent-autofocus
 927 [`activatable_element_keys`]: options.md#activatable_element_keys
 928 [`adjustable_element_keys`]: options.md#adjustable_element_keys
 929 [`blur_timeout`]: options.md#blur_timeout
 930 [`notifications_enabled`]: options.md#notifications_enabled
 931
 932 [button]: button.md
 933 [the hint commands]: commands.md#the-hint-commands--hints-mode
 934 [special keys]: shortcuts.md#special-keys
 935 [styling]: styling.md
 936
 937 [defaults.coffee]: ../extension/lib/defaults.coffee
 938 [parse-prefs.coffee]: ../extension/lib/parse-prefs.coffee
 939 [modes.coffee]: ../extension/lib/modes.coffee
 940 [commands.coffee]: ../extension/lib/commands.coffee
 941 [vim.coffee]: ../extension/lib/vim.coffee
 942
 943 [`Window`]: https://developer.mozilla.org/en-US/docs/Web/API/Window
 944 [`Browser`]: https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/browser
 945 [`window.location`]: https://developer.mozilla.org/en-US/docs/Web/API/Location
 946 [`URL`]: https://developer.mozilla.org/en-US/docs/Web/API/URL
 947 [Message Manager]: https://developer.mozilla.org/en-US/Firefox/Multiprocess_Firefox/Message_Manager
 948 [TabSelect]: https://developer.mozilla.org/en-US/docs/Web/Events/TabSelect
 949 [web console]: https://developer.mozilla.org/en-US/docs/Tools/Web_Console
 950 [about:config]: http://kb.mozillazine.org/About:config