Bug 1349828 Smooth scroller of <scrollbox> should not try to scroll to outside of the range r?mstange
The scroll destination of the smooth scroller of <scrollbox> can be outside of the actual scrollable range. Therefore, it doesn't make scroll slower even when the end appears.
This patch makes the destination always in the scrollable range.
MozReview-Commit-ID: CfEGzhG7Jh7
--- a/toolkit/content/widgets/scrollbox.xml
+++ b/toolkit/content/widgets/scrollbox.xml
@@ -335,34 +335,39 @@
// a part of continous scroll, for example, it's caused by turning mosue wheel.
start: function scrollAnim_start(distance, isContinuousScroll) {
// When it's a continous scroll and the scroll was started, this needs to
// respect preceding scroll requests. For example, 1.5px scroll occurs 2 times,
// 3px should be scrolled. So, fractional values shouldn't be discarded.
if (isContinuousScroll && this.distance) {
// |this.startPos| is integer due to cache of |.scrollPosition|. Therefore,
// we need to manage actual destination with |this.destination|.
- this.destination += distance;
+ var oldDestination = this.destination;
+ this.destination = this._clampPosition(this.destination + distance);
+
+ // If scroll position has already reached the ends, we need to do nothing.
+ if (oldDestination == this.destination)
+ return;
// If the integer part of the destination isn't changed, we need to do
// nothing now, wait next event.
if (Math.trunc(this.destination) == Math.trunc(this.destination - distance))
return;
// Let's restart animation from current position to the new destination.
if (this.requestHandle) {
this.stop();
this.startPos = this.scrollbox.scrollPosition;
// The call of |.stop()| causes clearing |this.distance| but let's recover it
// for keeping continuous scroll.
this.distance = this.destination - this.startPos;
}
} else {
this.startPos = this.scrollbox.scrollPosition;
- this.destination = this.startPos + distance;
+ this.destination = this._clampPosition(this.startPos + distance);
this.distance = this.destination - this.startPos;
// If absolute value of |this.distance| is less than 1px and this call is
// start of a continous scroll, should wait to scroll until accumulated
// scroll amount becomes 1px or greater.
if (isContinuousScroll && Math.abs(this.distance) < 1)
return;
}
@@ -389,16 +394,27 @@
1 - Math.pow(1 - timePassed / this.duration, 4);
this.scrollbox.scrollPosition = this.startPos + (this.distance * pos);
if (pos == 1)
this.scrollbox._stopSmoothScroll();
else
this.requestHandle = window.requestAnimationFrame(this.sample.bind(this));
+ },
+
+ _clampPosition: function scrollAnim_clampPosition(aScrollPosition) {
+ if (aScrollPosition < 0) {
+ return 0;
+ }
+ var maxPos = this.scrollbox.scrollSize - this.scrollbox.scrollClientSize;
+ if (aScrollPosition > maxPos) {
+ return maxPos;
+ }
+ return aScrollPosition;
}
})]]></field>
<method name="scrollByIndex">
<parameter name="index"/>
<parameter name="aSmoothScroll"/>
<body><