diff options
Diffstat (limited to 'content_scripts')
| -rw-r--r-- | content_scripts/scroller.coffee | 43 |
1 files changed, 21 insertions, 22 deletions
diff --git a/content_scripts/scroller.coffee b/content_scripts/scroller.coffee index fc4b922e..03be9694 100644 --- a/content_scripts/scroller.coffee +++ b/content_scripts/scroller.coffee @@ -77,37 +77,38 @@ performScroll = (element, axisName, amount, checkVisibility = true) -> # Return the amount by which the scroll position has changed. 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. +# - 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. + # Scroll by a relative amount (a number) in some direction, possibly smoothly. doScrollBy = do -> time = 0 - lastActivationId = -1 - keyupHandler = null - - # When the keyboard is repeating and then the key is released, sometimes the last key event is delivered - # *after* the keyup event. This could cause indefinite scrolling with no key pressed, because no further - # keyup event is delivered (so we behave as if the key is still pressed). To get around this, we briefly - # hold a lock; this prevents a new smooth scrolling event from starting too soon after the end of the - # previous one. - smoothScrollLock = false + mostRecentActivationId = -1 + lastEvent = null + keyHandler = null (element, direction, amount, wantSmooth) -> + if not keyHandler + keyHandler = root.handlerStack.push + keydown: (event) -> lastEvent = event + keyup: -> time += 1 + axisName = scrollProperties[direction].axisName unless wantSmooth and settings.get "smoothScroll" return performScroll element, axisName, amount - if lastActivationId == time or smoothScrollLock - # This is a keyboard repeat (and the most-recently activated animator -- which is still active -- will - # keep going), or it's too soon to begin smooth scrolling again. + if mostRecentActivationId == 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). return - if not keyupHandler - keyupHandler = root.handlerStack.push keyup: -> - time += 1 - setTimeout((-> smoothScrollLock = false), 50) - smoothScrollLock = true # Hereby also returning true, so allowing further propagation of the event. - - lastActivationId = activationId = ++time + mostRecentActivationId = activationId = ++time duration = 100 # Duration in ms. fudgeFactor = 25 @@ -126,7 +127,7 @@ doScrollBy = do -> shouldStopScrolling = (progress) -> if activationId == time - # This is the most recent animator and the key is still pressed, so keep going. + # This is the most recently-activated animator and we haven't yet seen its keyup event, so keep going. false else duration <= progress @@ -142,8 +143,6 @@ doScrollBy = do -> # One final call of performScroll to check the visibility of the activated element. performScroll(element, axisName, 0, true) window.cancelAnimationFrame(animatorId) - # Advance time if this is the most-recently activated animator and time hasn't otherwise advanced. - time += 1 if activationId == time else animatorId = window.requestAnimationFrame(animate) |