private void computeCoverAndKeepRect(final Rect visibleRect, Rect coverRect, Rect keepRect) {
visibleRect.copyTo(coverRect);
visibleRect.copyTo(keepRect);
// If we cover more that the actual viewport we can be smart about which tiles we choose to
// render.
if (mCoverAreaMultiplier > 1) {
// The initial cover area covers equally in each direction, according to the
// coverAreaMultiplier.
coverRect.inflate(
(int) (visibleRect.getWidth() * (mCoverAreaMultiplier - 1) / 2),
(int) (visibleRect.getHeight() * (mCoverAreaMultiplier - 1) / 2));
coverRect.copyTo(keepRect);
if (mPendingTrajectoryVector.getX() != 0 || mPendingTrajectoryVector.getY() != 0) {
// A null trajectory vector (no motion) means that tiles for the coverArea will be created.
// A non-null trajectory vector will shrink the covered rect to visibleRect plus its
// expansion from its
// center toward the cover area edges in the direction of the given vector.
// E.g. if visibleRect == (10,10)5x5 and coverAreaMultiplier == 3.0:
// a (0,0) trajectory vector will create tiles intersecting (5,5)15x15,
// a (1,0) trajectory vector will create tiles intersecting (10,10)10x5,
// and a (1,1) trajectory vector will create tiles intersecting (10,10)10x10.
// Multiply the vector by the distance to the edge of the cover area.
float trajectoryVectorMultiplier = (mCoverAreaMultiplier - 1) / 2;
// Unite the visible rect with a "ghost" of the visible rect moved in the direction of the
// trajectory vector.
visibleRect.copyTo(coverRect);
coverRect.offset(
(int) (coverRect.getWidth() * mTrajectoryVector.getX() * trajectoryVectorMultiplier),
(int) (coverRect.getHeight() * mTrajectoryVector.getY() * trajectoryVectorMultiplier));
coverRect.composite(visibleRect);
}
assert (keepRect.contains(coverRect));
}
adjustForContentsRect(coverRect);
// The keep rect is an inflated version of the cover rect, inflated in tile dimensions.
keepRect.composite(coverRect);
keepRect.inflate(mTileSize.getWidth() / 2, mTileSize.getHeight() / 2);
keepRect.intersect(mRect);
assert (coverRect.isEmpty() || keepRect.contains(coverRect));
}
private void adjustForContentsRect(Rect rect) {
Rect bounds = mRect;
Size candidateSize = new Size(rect.getWidth(), rect.getHeight());
rect.intersect(bounds);
if (rect.getWidth() == candidateSize.getWidth()
&& rect.getHeight() == candidateSize.getHeight()) return;
/*
* In the following case, there is no intersection of the contents rect and the cover rect.
* Thus the latter should not be inflated.
*
* +---------------+
* | m_rect |
* +---------------+
*
* +-------------------------------+
* | cover rect |
* | +---------+ |
* | | visible | |
* | | rect | |
* | +---------+ |
* +-------------------------------+
*/
if (rect.isEmpty()) return;
// Try to create a cover rect of the same size as the candidate, but within content bounds.
int pixelsCovered = candidateSize.getWidth() * candidateSize.getHeight();
if (rect.getWidth() < candidateSize.getWidth())
rect.inflate(0, ((pixelsCovered / rect.getWidth()) - rect.getHeight()) / 2);
if (rect.getHeight() < candidateSize.getHeight())
rect.inflate(((pixelsCovered / rect.getHeight()) - rect.getWidth()) / 2, 0);
rect.intersect(bounds);
}