diff options
| -rw-r--r-- | content_scripts/scroller.coffee | 38 |
1 files changed, 19 insertions, 19 deletions
diff --git a/content_scripts/scroller.coffee b/content_scripts/scroller.coffee index 33deb5cf..8ce87253 100644 --- a/content_scripts/scroller.coffee +++ b/content_scripts/scroller.coffee @@ -35,7 +35,7 @@ shouldScroll = (element, direction) -> # Elements with `overflow: hidden` should not be scrolled. return false if computedStyle.getPropertyValue("overflow-#{direction}") == "hidden" # Non-visible elements should not be scrolled. - return false if ["hidden", "collapse"].indexOf(computedStyle.getPropertyValue("visibility")) != -1 + return false if computedStyle.getPropertyValue("visibility") in ["hidden", "collapse"] return false if computedStyle.getPropertyValue("display") == "none" true @@ -73,25 +73,28 @@ performScroll = (element, axisName, amount, checkVisibility = true) -> # if the activated element has been scrolled completely offscreen, subsequent changes in its scroll # position will not provide any more visual feedback to the user. therefore we deactivate it so that # subsequent scrolls only move the parent element. + # TODO(smblott) Refactor this out of here. rect = activatedElement.getBoundingClientRect() if (rect.bottom < 0 || rect.top > window.innerHeight || rect.right < 0 || rect.left > window.innerWidth) activatedElement = element - # Return the amount by which the scroll position has changed. - element[axisName] - before + # Return true if we successfully scrolled by the requested amount, false otherwise. + amount == element[axisName] - before # How scrolling is handled: # - For non-smooth scrolling, the entire scroll happens immediately. # - For smooth scrolling with distinct key presses, a separate animator is initiated for each key press. # Therefore, several animators may be active at the same time. This ensures that two quick taps on `j` -# scroll to (roughly) the same position as two slower taps. +# scroll to the same position as two slower taps (modulo rounding errors). # - For smooth scrolling with keyboard repeat, the most recently-activated animator continues scrolling -# until its corresponding keyup event is received. We never initiate a new animator on keyboard repeat. +# at least until its corresponding keyup event is received. We never initiate a new animator on keyboard +# repeat. # Scroll by a relative amount (a number) in some direction, possibly smoothly. doScrollBy = do -> - time = 0 # Logical time. - mostRecentActivationId = -1 + # This is logical time. Time is advanced each time an animator is activated, and on each keyup event. + time = 0 + mostRecentActivationTime = -1 lastEvent = null keyHandler = null @@ -108,22 +111,19 @@ doScrollBy = do -> unless settings.get "smoothScroll" return performScroll element, axisName, amount - if mostRecentActivationId == time or lastEvent?.repeat + if mostRecentActivationTime == time or lastEvent?.repeat # Either the most-recently activated animator has not yet received its keyup event (so it's still # scrolling), or this is a keyboard repeat (for which we don't initiate a new animator). We need both # of these checks because sometimes (perhaps one time in twenty) the last keyboard repeat arrives # *after* the corresponding keyup. return - mostRecentActivationId = activationId = ++time + mostRecentActivationTime = activationTime = ++time - duration = 100 # Duration in ms. - fudgeFactor = 25 + # Duration in ms. Allow a bit longer for longer scrolls. + duration = 100 + 25 * Math.log Math.abs amount - # Allow a bit longer for longer scrolls. - duration += fudgeFactor * Math.log Math.abs amount - - # Round away from 0, so that we don't leave any scroll amount unscrolled. + # Round away from 0, so that we don't leave any requested scroll amount unscrolled. roundOut = if 0 <= amount then Math.ceil else Math.floor delta = roundOut(amount / duration) @@ -132,9 +132,9 @@ doScrollBy = do -> scrolledAmount = 0 shouldStopScrolling = (progress) -> - # If activationId == time, then this is the most recently-activated animator and we haven't yet seen its - # keyup event, so keep going. - if activationId == time then false else duration <= progress + # If activationTime == time, then this is the most recently-activated animator and we haven't yet seen + # its keyup event, so keep going; otherwise, check progress and duration. + if activationTime == time then false else duration <= progress animate = (timestamp) -> start ?= timestamp @@ -143,7 +143,7 @@ doScrollBy = do -> scrollDelta = roundOut(delta * progress) - scrolledAmount scrolledAmount += scrollDelta - if performScroll(element, axisName, scrollDelta, false) != scrollDelta or shouldStopScrolling progress + if not performScroll(element, axisName, scrollDelta, false) or shouldStopScrolling progress # One final call of performScroll to check the visibility of the activated element. performScroll(element, axisName, 0, true) window.cancelAnimationFrame(animatorId) |