CSSCoord Axis::ClampOriginToScrollableRect(CSSCoord aOrigin) const
{
CSSToParentLayerScale zoom = GetScaleForAxis(GetFrameMetrics().GetZoom());
ParentLayerCoord origin = aOrigin * zoom;
ParentLayerCoord result;
if (origin < GetPageStart()) {
result = GetPageStart();
} else if (origin + GetCompositionLength() > GetPageEnd()) {
result = GetPageEnd() - GetCompositionLength();
} else {
return aOrigin;
}
return result / zoom;
}
float Axis::ScaleWillOverscrollAmount(float aScale, int32_t aFocus) {
float originAfterScale = (GetOrigin() + aFocus) * aScale - aFocus;
switch (ScaleWillOverscroll(aScale, aFocus)) {
case OVERSCROLL_MINUS: return originAfterScale - GetPageStart() * aScale;
case OVERSCROLL_PLUS: return (originAfterScale + GetCompositionLength()) -
NS_lround(GetPageEnd() * aScale);
// Don't handle OVERSCROLL_BOTH. Client code is expected to deal with it.
default: return 0;
}
}
CSSCoord Axis::ApplyResistance(CSSCoord aRequestedOverscroll) const {
// 'resistanceFactor' is a value between 0 and 1, which:
// - tends to 1 as the existing overscroll tends to 0
// - tends to 0 as the existing overscroll tends to the composition length
// The actual overscroll is the requested overscroll multiplied by this
// factor; this should prevent overscrolling by more than the composition
// length.
float resistanceFactor = 1 - fabsf(mOverscroll) / GetCompositionLength();
return resistanceFactor < 0 ? CSSCoord(0) : aRequestedOverscroll * resistanceFactor;
}
float Axis::ScaleWillOverscrollAmount(float aScale, float aFocus) {
float originAfterScale = (GetOrigin() + aFocus) - (aFocus / aScale);
bool both = ScaleWillOverscrollBothSides(aScale);
bool minus = originAfterScale < GetPageStart();
bool plus = (originAfterScale + (GetCompositionLength() / aScale)) > GetPageEnd();
if ((minus && plus) || both) {
// If we ever reach here it's a bug in the client code.
MOZ_ASSERT(false, "In an OVERSCROLL_BOTH condition in ScaleWillOverscrollAmount");
return 0;
}
if (minus) {
return originAfterScale - GetPageStart();
}
if (plus) {
return originAfterScale + (GetCompositionLength() / aScale) - GetPageEnd();
}
return 0;
}
ParentLayerCoord Axis::ApplyResistance(ParentLayerCoord aRequestedOverscroll) const {
// 'resistanceFactor' is a value between 0 and 1/16, which:
// - tends to 1/16 as the existing overscroll tends to 0
// - tends to 0 as the existing overscroll tends to the composition length
// The actual overscroll is the requested overscroll multiplied by this
// factor.
float resistanceFactor = (1 - fabsf(GetOverscroll()) / GetCompositionLength()) / 16;
float result = resistanceFactor < 0 ? ParentLayerCoord(0) : aRequestedOverscroll * resistanceFactor;
result = clamped(result, -8.0f, 8.0f);
return result;
}
CSSCoord Axis::ScaleWillOverscrollAmount(float aScale, CSSCoord aFocus) const {
// Internally, do computations in ParentLayer coordinates *before* the scale
// is applied.
CSSToParentLayerScale zoom = GetFrameMetrics().GetZoom().ToScaleFactor();
ParentLayerCoord focus = aFocus * zoom;
ParentLayerCoord originAfterScale = (GetOrigin() + focus) - (focus / aScale);
bool both = ScaleWillOverscrollBothSides(aScale);
bool minus = GetPageStart() - originAfterScale > COORDINATE_EPSILON;
bool plus = (originAfterScale + (GetCompositionLength() / aScale)) - GetPageEnd() > COORDINATE_EPSILON;
if ((minus && plus) || both) {
// If we ever reach here it's a bug in the client code.
MOZ_ASSERT(false, "In an OVERSCROLL_BOTH condition in ScaleWillOverscrollAmount");
return 0;
}
if (minus) {
return (originAfterScale - GetPageStart()) / zoom;
}
if (plus) {
return (originAfterScale + (GetCompositionLength() / aScale) - GetPageEnd()) / zoom;
}
return 0;
}
Axis::Overscroll Axis::ScaleWillOverscroll(float aScale, int32_t aFocus) {
float originAfterScale = (GetOrigin() + aFocus) * aScale - aFocus;
bool both = ScaleWillOverscrollBothSides(aScale);
bool minus = originAfterScale < GetPageStart() * aScale;
bool plus = (originAfterScale + GetCompositionLength()) > GetPageEnd() * aScale;
if ((minus && plus) || both) {
return OVERSCROLL_BOTH;
}
if (minus) {
return OVERSCROLL_MINUS;
}
if (plus) {
return OVERSCROLL_PLUS;
}
return OVERSCROLL_NONE;
}
float Axis::GetCompositionEnd() {
return GetOrigin() + GetCompositionLength();
}
bool Axis::Scrollable() {
if (mAxisLocked) {
return false;
}
return GetCompositionLength() < GetPageLength();
}
CSSCoord Axis::GetCompositionEnd() const {
return GetOrigin() + GetCompositionLength();
}
bool Axis::CanScroll() const {
return GetPageLength() - GetCompositionLength() > COORDINATE_EPSILON;
}
ParentLayerCoord Axis::GetScrollRangeEnd() const {
return GetPageEnd() - GetCompositionLength();
}