extension/lib/markable-elements.coffee

   1 # This file contains functions for getting markable elements and related data.
   2
   3 utils = require('./utils')
   4 viewportUtils = require('./viewport')
   5
   6 {devtools} = Cu.import('resource://devtools/shared/Loader.jsm', {})
   7
   8 _Element = Ci.nsIDOMElement
   9 if _Element
  10   isElementInstance = (el) -> el instanceof _Element
  11 else
  12   Cu.importGlobalProperties(['Element'])
  13   isElementInstance = (el) -> Element.isInstance(el)
  14
  15 MIN_TEXTNODE_SIZE = 4
  16
  17 find = (window, filter, selector = '*') ->
  18   viewport = viewportUtils.getWindowViewport(window)
  19   wrappers = []
  20   getMarkableElements(window, viewport, wrappers, filter, selector)
  21   return wrappers
  22
  23 # `filter` is a function that is given every element in every frame of the page.
  24 # It should return wrapper objects for markable elements and a falsy value for
  25 # all other elements. All returned wrappers are added to `wrappers`. `wrappers`
  26 # is modified instead of using return values to avoid array concatenation for
  27 # each frame. It might sound expensive to go through _every_ element, but that’s
  28 # actually what other methods like using XPath or CSS selectors would need to do
  29 # anyway behind the scenes. However, it is possible to pass in a CSS selector,
  30 # which allows getting markable elements in several passes with different sets
  31 # of candidates.
  32 getMarkableElements = (
  33   window, viewport, wrappers, filter, selector, parents = []
  34 ) ->
  35   {document} = window
  36
  37   for element in getAllElements(document, selector)
  38     continue unless isElementInstance(element)
  39     # `getRects` is fast and filters out most elements, so run it first of all.
  40     rects = getRects(element, viewport)
  41     continue unless rects.insideViewport.length > 0
  42     continue unless wrapper = filter(
  43       element, (elementArg, tryRight = 1) ->
  44         return getElementShape(
  45           {window, viewport, parents, element: elementArg}, tryRight,
  46           if elementArg == element then rects else null
  47         )
  48     )
  49     wrappers.push(wrapper)
  50
  51   for frame in window.frames when frame.frameElement
  52     continue unless result = viewportUtils.getFrameViewport(
  53       frame.frameElement, viewport
  54     )
  55     {viewport: frameViewport, offset} = result
  56     getMarkableElements(
  57       frame, frameViewport, wrappers, filter, selector,
  58       parents.concat({window, offset})
  59     )
  60
  61   return
  62
  63 findAllDOMs = (dom) ->
  64   return [dom].concat(
  65     Array.from(dom.querySelectorAll('*'))
  66       .filter((e) -> e.shadowRoot?)
  67       .map((e) -> findAllDOMs(e.shadowRoot))...
  68   )
  69
  70 getAllElements = (document, selector) ->
  71   return [].concat(
  72     findAllDOMs(document).map((d) ->
  73       Array.from(d.querySelectorAll(selector))
  74     )...
  75   )
  76
  77 getRects = (element, viewport) ->
  78   # `element.getClientRects()` returns a list of rectangles, usually just one,
  79   # which is identical to the one returned by `element.getBoundingClientRect()`.
  80   # However, if `element` is inline and line-wrapped, then it returns one
  81   # rectangle for each line, since each line may be of different length, for
  82   # example. That allows us to properly add hints to line-wrapped links.
  83   rects = element.getClientRects?() or []
  84   return {
  85     all: rects,
  86     insideViewport: Array.prototype.filter.call(
  87       rects,
  88       (rect) -> viewportUtils.isInsideViewport(rect, viewport)
  89     )
  90   }
  91
  92 # Returns the “shape” of an element:
  93 #
  94 # - `nonCoveredPoint`: The coordinates of the first point of the element that
  95 #   isn’t covered by another element (except children of the element). It also
  96 #   contains the offset needed to make those coordinates relative to the top
  97 #   frame, as well as the rectangle that the coordinates occur in. It is `null`
  98 #   if the element is outside `viewport` or entirely covered by other elements.
  99 # - `area`: The area of the part of the element that is inside the viewport.
 100 # - `width`: The width of the visible rect at `nonCoveredPoint`.
 101 # - `textOffset`: The distance between the left edge of the element and the left
 102 #   edge of its text vertically near `nonCoveredPoint`. Might be `null`. The
 103 #   calculation might stop early if `isBlock`.
 104 # - `isBlock`: `true` if the element is a block and has several lines of text
 105 #   (which is the case for “cards” with an image to the left and a title as well
 106 #   as some text to the right (where the entire “card” is a link)). This is used
 107 #   to place the the marker at the edge of the block.
 108 getElementShape = (elementData, tryRight, rects = null) ->
 109   {viewport, element} = elementData
 110   result =
 111     {nonCoveredPoint: null, area: 0, width: 0, textOffset: null, isBlock: false}
 112
 113   rects ?= getRects(element, viewport)
 114   totalArea = 0
 115   visibleRects = []
 116   for rect, index in rects.insideViewport
 117     visibleRect = viewportUtils.adjustRectToViewport(rect, viewport)
 118     continue if visibleRect.area == 0
 119     visibleRect.index = index
 120     totalArea += visibleRect.area
 121     visibleRects.push(visibleRect)
 122
 123   if visibleRects.length == 0
 124     if rects.all.length == 1 and totalArea == 0
 125       [rect] = rects.all
 126       if rect.width > 0 or rect.height > 0
 127         # If we get here, it means that everything inside `element` is floated
 128         # and/or absolutely positioned (and that `element` hasn’t been made to
 129         # “contain” the floats). For example, a link in a menu could contain a
 130         # span of text floated to the left and an icon floated to the right.
 131         # Those are still clickable. Therefore we return the shape of the first
 132         # visible child instead. At least in that example, that’s the best bet.
 133         for child in element.children
 134           childData = Object.assign({}, elementData, {element: child})
 135           shape = getElementShape(childData, tryRight)
 136           return shape if shape
 137     return result
 138
 139   result.area = totalArea
 140
 141   # Even if `element` has a visible rect, it might be covered by other elements.
 142   nonCoveredPoint = null
 143   nonCoveredPointRect = null
 144   for visibleRect in visibleRects
 145     nonCoveredPoint = getFirstNonCoveredPoint(
 146       elementData, visibleRect, tryRight
 147     )
 148     if nonCoveredPoint
 149       nonCoveredPointRect = visibleRect
 150       break
 151
 152   return result unless nonCoveredPoint
 153   result.nonCoveredPoint = nonCoveredPoint
 154
 155   result.width = nonCoveredPointRect.width
 156
 157   lefts = []
 158   smallestBottom = Infinity
 159   hasSingleRect = (rects.all.length == 1)
 160
 161   utils.walkTextNodes(element, (node) ->
 162     unless node.data.trim() == ''
 163       for quads in node.getBoxQuads()
 164         bounds = quads.getBounds()
 165         if bounds.width < MIN_TEXTNODE_SIZE or bounds.height < MIN_TEXTNODE_SIZE
 166           continue
 167
 168         if utils.overlaps(bounds, nonCoveredPointRect)
 169           lefts.push(bounds.left)
 170
 171         if hasSingleRect
 172           # The element is likely a block and has several lines of text; ignore
 173           # the `textOffset` (see the description of `textOffset` at the
 174           # beginning of the function).
 175           if bounds.top > smallestBottom
 176             result.isBlock = true
 177             return true
 178
 179           if bounds.bottom < smallestBottom
 180             smallestBottom = bounds.bottom
 181
 182     return false
 183   )
 184
 185   if lefts.length > 0
 186     result.textOffset =
 187       Math.round(Math.min(lefts...) - nonCoveredPointRect.left)
 188
 189   return result
 190
 191 getFirstNonCoveredPoint = (elementData, elementRect, tryRight) ->
 192   # Try the left-middle point, or immediately to the right of a covering element
 193   # at that point (when `tryRight == 1`). If both of those are covered the whole
 194   # element is considered to be covered. The reasoning is:
 195   #
 196   # - A marker should show up as near the left edge of its visible area as
 197   #   possible. Having it appear to the far right (for example) is confusing.
 198   # - We can’t try too many times because of performance.
 199   # - We used to try left-top first, but if the element has `border-radius`, the
 200   #   corners won’t belong to the element, so `document.elementFromPoint()` will
 201   #   return whatever is behind. One _could_ temporarily add a CSS class that
 202   #   removes `border-radius`, but that turned out to be too slow. Trying
 203   #   left-middle instead avoids the problem, and looks quite nice, actually.
 204   # - We used to try left-bottom as well, but that is so rare that it’s not
 205   #   worth it.
 206   #
 207   # It is safer to try points at least one pixel into the element from the
 208   # edges, hence the `+1`.
 209   {left, top, bottom, height} = elementRect
 210   return tryPoint(
 211     elementData, elementRect,
 212     left, +1, Math.round(top + height / 2), 0, tryRight
 213   )
 214
 215 # Tries a point `(x + dx, y + dy)`. Returns `(x, y)` (and the frame offset) if
 216 # the element passes the tests. Otherwise it tries to the right of whatever is
 217 # at `(x, y)`, `tryRight` times . If nothing succeeds, `false` is returned. `dx`
 218 # and `dy` are used to offset the wanted point `(x, y)` while trying.
 219 tryPoint = (elementData, elementRect, x, dx, y, dy, tryRight = 0) ->
 220   {window, viewport, parents, element} = elementData
 221   elementAtPoint = window.document.elementFromPoint(x + dx, y + dy)
 222   offset = {left: 0, top: 0}
 223   found = false
 224   firstLevel = true
 225
 226   # Ensure that `element`, or a child of `element` (anything inside an `<a>` is
 227   # clickable too), really is present at (x,y). Note that this is not 100%
 228   # bullet proof: Combinations of CSS can cause this check to fail, even though
 229   # `element` isn’t covered. We don’t try to temporarily reset such CSS because
 230   # of performance. (See further down for the special value `-1` of `tryRight`.)
 231   if contains(element, elementAtPoint) or tryRight == -1
 232     found = true
 233     # If we’re currently in a frame, there might be something on top of the
 234     # frame that covers `element`. Therefore we ensure that the frame really is
 235     # present at the point for each parent in `parents`.
 236     currentWindow = window
 237     for parent in parents by -1
 238       # If leaving the devtools container take the devtools zoom into account.
 239       if utils.isDevtoolsWindow(currentWindow)
 240         docShell = currentWindow
 241           .getInterface(Ci.nsIWebNavigation)
 242           .QueryInterface(Ci.nsIDocShell)
 243         if docShell
 244           devtoolsZoom = docShell.contentViewer.fullZoom
 245           offset.left *= devtoolsZoom
 246           offset.top  *= devtoolsZoom
 247           x  *= devtoolsZoom
 248           y  *= devtoolsZoom
 249           dx *= devtoolsZoom
 250           dy *= devtoolsZoom
 251
 252       offset.left += parent.offset.left
 253       offset.top  += parent.offset.top
 254       elementAtPoint = parent.window.document.elementFromPoint(
 255         offset.left + x + dx, offset.top + y + dy
 256       )
 257       firstLevel = false
 258       unless contains(currentWindow.frameElement, elementAtPoint)
 259         found = false
 260         break
 261       currentWindow = parent.window
 262
 263   return {x, y, offset} if found
 264
 265   return false if elementAtPoint == null or tryRight <= 0
 266   rect = elementAtPoint.getBoundingClientRect()
 267
 268   # `.getBoundingClientRect()` does not include pseudo-elements that are
 269   # absolutely positioned so that they go outside of the element (which is
 270   # common for `/###\`-looking tabs), but calling `.elementAtPoint()` on the
 271   # pseudo-element _does_ return the element. This means that the covering
 272   # element’s _rect_ won’t cover the element we’re looking for. If so, it’s
 273   # better to try again, forcing the element to be considered located at this
 274   # point. That’s what `-1` for the `tryRight` argument means. This is also used
 275   # in the 'complementary' pass, to include elements considered covered in
 276   # earlier passes (which might have been false positives).
 277   if firstLevel and rect.right <= x + offset.left
 278     return tryPoint(elementData, elementRect, x, dx, y, dy, -1)
 279
 280   # If `elementAtPoint` is a parent to `element`, it most likely means that
 281   # `element` is hidden some way. It can also mean that a pseudo-element of
 282   # `elementAtPoint` covers `element` partly. Therefore, try once at the most
 283   # likely point: The center of the part of the rect to the right of `x`.
 284   if elementRect.right > x and contains(elementAtPoint, element)
 285     return tryPoint(
 286       elementData, elementRect,
 287       (x + elementRect.right) / 2, 0, y, 0, 0
 288     )
 289
 290   newX = rect.right - offset.left + 1
 291   return false if newX > viewport.right or newX > elementRect.right
 292   return tryPoint(elementData, elementRect, newX, 0, y, 0, tryRight - 1)
 293
 294 # In XUL documents there are “anonymous” elements. These are never returned by
 295 # `document.elementFromPoint` but their closest non-anonymous parents are.
 296 # The same is true for Web Components (where their hosts are returned), with
 297 # the further caveat that they might be nested.
 298 # Note: getBindingParent() has been removed from fx72.
 299 normalize = (element) ->
 300   element = e while (e = element.ownerDocument.getBindingParent?(element))?
 301   element = e while (e = element.containingShadowRoot?.host)? # >=fx72
 302   element = element.parentNode while element.prefix?
 303   return element
 304
 305 # Returns whether `element` corresponds to `elementAtPoint`. This is only
 306 # complicated for browser elements in the web page content area.
 307 # `.elementAtPoint()` always returns `<tabbrowser#content>` then. The element
 308 # might be in another tab and thus invisible, but `<tabbrowser#content>` is the
 309 # same and visible in _all_ tabs, so we have to check that the element really
 310 # belongs to the current tab.
 311 contains = (element, elementAtPoint) ->
 312   return false unless elementAtPoint
 313   container = normalize(element)
 314   if elementAtPoint.localName == 'tabbrowser' and elementAtPoint.id == 'content'
 315     {gBrowser} = element.ownerGlobal.top
 316     tabpanel = gBrowser.getNotificationBox(gBrowser.selectedBrowser)
 317     return tabpanel.contains(element)
 318   else
 319     # Note that `a.contains(a)` is supposed to be true, but strangely aren’t for
 320     # `<menulist>`s in the Add-ons Manager, so do a direct comparison as well.
 321     return container == elementAtPoint or container.contains(elementAtPoint)
 322
 323 module.exports = {
 324   find
 325 }