diff options
| -rw-r--r-- | content_scripts/scroller.coffee | 38 |
1 files changed, 20 insertions, 18 deletions
diff --git a/content_scripts/scroller.coffee b/content_scripts/scroller.coffee index e418a930..1e5bac65 100644 --- a/content_scripts/scroller.coffee +++ b/content_scripts/scroller.coffee @@ -33,7 +33,7 @@ performScroll = (element, direction, amount) -> axisName = scrollProperties[direction].axisName before = element[axisName] element[axisName] += amount - amount == element[axisName] - before + element[axisName] == amount + before # Test whether element should be scrolled. shouldScroll = (element, direction) -> @@ -88,6 +88,7 @@ CoreScroller = @time = 0 @lastEvent = null @keyIsDown = false + handlerStack.push keydown: (event) => @keyIsDown = true @@ -96,6 +97,14 @@ CoreScroller = @keyIsDown = false @time += 1 + # Calibration fudge factors for continuous scrolling. The calibration value starts at 1.0. We then + # increase it (until it exceeds @maxCalibration) if we guess that the scroll is too slow, or decrease it + # (until it is less than @minCalibration) if we guess that the scroll is too fast. The cutoff point for + # which guess we make is @calibrationBoundary. We require: 0 < @minCalibration <= 1 <= @maxCalibration. + @minCalibration = 0.5 # Controls how much we're willing to slow scrolls down; smaller => more slow down. + @maxCalibration = 1.6 # Controls how much we're willing to speed scrolls up; bigger => more speed up. + @calibrationBoundary = 150 # Boundary between scrolls which are considered too slow, and those too fast. + # Scroll element by a relative amount (a number) in some direction. scroll: (element, direction, amount) -> return unless amount @@ -110,9 +119,7 @@ CoreScroller = return if @lastEvent?.repeat activationTime = ++@time - - isMyKeyStillDown = => - @time == activationTime and @keyIsDown + isMyKeyStillDown = => @time == activationTime and @keyIsDown # Store amount's sign and make amount positive; the logic is clearer when amount is positive. sign = Math.sign amount @@ -127,17 +134,12 @@ CoreScroller = previousTimestamp = null animatorId = null - advanceAnimation = -> - animatorId = requestAnimationFrame animate + advanceAnimation = -> animatorId = requestAnimationFrame animate + cancelAnimation = -> cancelAnimationFrame animatorId - cancelAnimation = -> - cancelAnimationFrame animatorId - - animate = (timestamp) -> + animate = (timestamp) => previousTimestamp ?= timestamp - - if timestamp == previousTimestamp - return advanceAnimation() + return advanceAnimation() if timestamp == previousTimestamp # The elapsed time is typically about 16ms. elapsed = timestamp - previousTimestamp @@ -145,11 +147,11 @@ CoreScroller = previousTimestamp = timestamp # The constants in the duration calculation, above, are chosen to provide reasonable scroll speeds for - # scrolls resulting from distinct keypresses. For continuous scrolls (where the key remains depressed), - # some scrolls are too slow, and others too fast. Here, we compensate a bit. - if isMyKeyStillDown() and 50 <= totalElapsed and 0.5 <= calibration <= 1.6 - calibration *= 1.05 if 1.05 * calibration * amount <= 150 # Speed up slow scrolls. - calibration *= 0.95 if 150 <= 0.95 * calibration * amount # Slow down fast scrolls. + # distinct keypresses. For continuous scrolls, some scrolls are too slow, and others too fast. Here, we + # speed up the slower scrolls, and slow down the faster scrolls. + if isMyKeyStillDown() and 50 <= totalElapsed and @minCalibration <= calibration <= @maxCalibration + calibration *= 1.05 if 1.05 * calibration * amount <= @calibrationBoundary # Speed up slow scrolls. + calibration *= 0.95 if @calibrationBoundary <= 0.95 * calibration * amount # Slow down fast scrolls. # Calculate the initial delta, rounding up to ensure progress. Then, adjust delta to account for the # current scroll state. |