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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "AutoscrollAnimation.h"
#include <cmath> // for sqrtf()
#include "AsyncPanZoomController.h"
#include "APZCTreeManager.h"
#include "FrameMetrics.h"
#include "mozilla/Telemetry.h" // for Telemetry
namespace mozilla {
namespace layers {
// Helper function for AutoscrollAnimation::DoSample().
// Basically copied as-is from toolkit/actors/AutoScrollChild.sys.mjs.
static float Accelerate(ScreenCoord curr, ScreenCoord start) {
static const int speed = 12;
float val = (curr - start) / speed;
if (val > 1) {
return val * sqrtf(val) - 1;
}
if (val < -1) {
return val * sqrtf(-val) + 1;
}
return 0;
}
AutoscrollAnimation::AutoscrollAnimation(AsyncPanZoomController& aApzc,
const ScreenPoint& aAnchorLocation)
: mApzc(aApzc), mAnchorLocation(aAnchorLocation) {}
bool AutoscrollAnimation::DoSample(FrameMetrics& aFrameMetrics,
const TimeDuration& aDelta) {
APZCTreeManager* treeManager = mApzc.GetApzcTreeManager();
if (!treeManager) {
return false;
}
ScreenPoint mouseLocation = treeManager->GetCurrentMousePosition();
// The implementation of this function closely mirrors that of its main-
// thread equivalent, the autoscrollLoop() function in
// toolkit/actors/AutoScrollChild.jsm.
// Avoid long jumps when the browser hangs for more than |maxTimeDelta| ms.
static const TimeDuration maxTimeDelta = TimeDuration::FromMilliseconds(100);
TimeDuration timeDelta = TimeDuration::Min(aDelta, maxTimeDelta);
float timeCompensation = timeDelta.ToMilliseconds() / 20;
// Notes:
// - The main-thread implementation rounds the scroll delta to an integer,
// and keeps track of the fractional part as an "error". It does this
// because it uses Window.scrollBy() or Element.scrollBy() to perform
// the scrolling, and those functions truncate the fractional part of
// the offset. APZ does no such truncation, so there's no need to keep
// track of the fractional part separately.
// - The Accelerate() function takes Screen coordinates as inputs, but
// its output is interpreted as CSS coordinates. This is intentional,
// insofar as autoscrollLoop() does the same thing.
CSSPoint scrollDelta{
Accelerate(mouseLocation.x, mAnchorLocation.x) * timeCompensation,
Accelerate(mouseLocation.y, mAnchorLocation.y) * timeCompensation};
mApzc.ScrollByAndClamp(scrollDelta);
// An autoscroll animation never ends of its own accord.
// It can be stopped in response to various input events, in which case
// AsyncPanZoomController::StopAutoscroll() will stop it via
// CancelAnimation().
return true;
}
void AutoscrollAnimation::Cancel(CancelAnimationFlags aFlags) {
// The cancellation was initiated by browser.js, so there's no need to
// notify it.
if (aFlags & TriggeredExternally) {
return;
}
if (RefPtr<GeckoContentController> controller =
mApzc.GetGeckoContentController()) {
controller->CancelAutoscroll(mApzc.GetGuid());
}
}
} // namespace layers
} // namespace mozilla
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