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::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;
}
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;
}