status_t
Butterfly::StartSaver(BView* view, bool preview)
{
view->SetLowColor(0, 0, 0);
view->FillRect(view->Bounds(), B_SOLID_LOW);
view->SetDrawingMode(B_OP_ALPHA);
view->SetBlendingMode(B_CONSTANT_ALPHA, B_ALPHA_OVERLAY);
view->SetLineMode(B_ROUND_CAP, B_ROUND_JOIN);
if (!preview)
view->SetPenSize(2.0);
SetTickSize(20000);
// Set fBase to a random radian value scaled by 1000. The scaling produces
// more interesting results.
srand48(system_time());
fBase = drand48() * 2 * M_PI * 1000;
// calculate transformation
BRect bounds = view->Bounds();
fScale = MIN(bounds.Width(), bounds.Height()) * 0.1f;
fTrans.Set(bounds.Width() * 0.5f, bounds.Height() * 0.5f);
fBounds = bounds;
fLast[0] = _Iterate();
fLast[1] = _Iterate();
fLast[2] = _Iterate();
return B_OK;
}
void
Butterfly::Draw(BView* view, int32 frame)
{
if (frame == 1024) {
// calculate bounding box ( (-5.92,-5.92) to (5.92, 5.92) )
fBounds.Set(-5.92f * fScale + fTrans.x, -5.92f * fScale + fTrans.y,
5.92f * fScale + fTrans.x, 5.92f * fScale + fTrans.y);
}
if ((frame & 3) == 0) {
// fade out
view->SetHighColor(0, 0, 0, 4);
view->FillRect(fBounds);
}
// create a color from a hue of (fBase * 15) degrees
view->SetHighColor(_HueToColor(fBase * 15));
BPoint p = _Iterate();
// cubic Hermite interpolation from fLast[1] to fLast[2]
// calculate tangents for a Catmull-Rom spline
//(these values need to be halved)
BPoint m1 = fLast[2] - fLast[0]; // tangent for fLast[1]
BPoint m2 = p - fLast[1]; // tangent for fLast[2]
// draw Bezier from fLast[1] to fLast[2] with control points
// fLast[1] + m1/3, fLast[2] - m2/3
m1.x /= 6;
m1.y /= 6;
m2.x /= 6;
m2.y /= 6;
BPoint control[4] = { fLast[1], fLast[1] + m1, fLast[2] - m2, fLast[2] };
view->StrokeBezier(control);
fLast[0] = fLast[1];
fLast[1] = fLast[2];
fLast[2] = p;
}
void
TraceCollection::ReverseIterate(Visitor& visitor) const {
_Iterate(visitor, true);
}
void
TraceCollection::Iterate(Visitor& visitor) const {
_Iterate(visitor, false);
}
