private ImmutableViewportMetrics getValidViewportMetrics(
ImmutableViewportMetrics viewportMetrics) {
/* First, we adjust the zoom factor so that we can make no overscrolled area visible. */
float zoomFactor = viewportMetrics.zoomFactor;
RectF pageRect = viewportMetrics.getPageRect();
RectF viewport = viewportMetrics.getViewport();
float focusX = viewport.width() / 2.0f;
float focusY = viewport.height() / 2.0f;
float minZoomFactor = 0.0f;
float maxZoomFactor = MAX_ZOOM;
ZoomConstraints constraints = mTarget.getZoomConstraints();
if (constraints.getMinZoom() > 0) minZoomFactor = constraints.getMinZoom();
if (constraints.getMaxZoom() > 0) maxZoomFactor = constraints.getMaxZoom();
if (!constraints.getAllowZoom()) {
// If allowZoom is false, clamp to the default zoom level.
maxZoomFactor = minZoomFactor = constraints.getDefaultZoom();
}
// Ensure minZoomFactor keeps the page at least as big as the viewport.
if (pageRect.width() > 0) {
float scaleFactor = viewport.width() / pageRect.width();
minZoomFactor = Math.max(minZoomFactor, zoomFactor * scaleFactor);
if (viewport.width() > pageRect.width()) focusX = 0.0f;
}
if (pageRect.height() > 0) {
float scaleFactor = viewport.height() / pageRect.height();
minZoomFactor = Math.max(minZoomFactor, zoomFactor * scaleFactor);
if (viewport.height() > pageRect.height()) focusY = 0.0f;
}
maxZoomFactor = Math.max(maxZoomFactor, minZoomFactor);
if (zoomFactor < minZoomFactor) {
// if one (or both) of the page dimensions is smaller than the viewport,
// zoom using the top/left as the focus on that axis. this prevents the
// scenario where, if both dimensions are smaller than the viewport, but
// by different scale factors, we end up scrolled to the end on one axis
// after applying the scale
PointF center = new PointF(focusX, focusY);
viewportMetrics = viewportMetrics.scaleTo(minZoomFactor, center);
} else if (zoomFactor > maxZoomFactor) {
PointF center = new PointF(viewport.width() / 2.0f, viewport.height() / 2.0f);
viewportMetrics = viewportMetrics.scaleTo(maxZoomFactor, center);
}
/* Now we pan to the right origin. */
viewportMetrics = viewportMetrics.clamp();
return viewportMetrics;
}
/**
* Zoom to a specified rect IN CSS PIXELS.
*
* <p>While we usually use device pixels, @zoomToRect must be specified in CSS pixels.
*/
private boolean animatedZoomTo(RectF zoomToRect) {
setState(PanZoomState.ANIMATED_ZOOM);
final float startZoom = getMetrics().zoomFactor;
RectF viewport = getMetrics().getViewport();
// 1. adjust the aspect ratio of zoomToRect to match that of the current viewport,
// enlarging as necessary (if it gets too big, it will get shrunk in the next step).
// while enlarging make sure we enlarge equally on both sides to keep the target rect
// centered.
float targetRatio = viewport.width() / viewport.height();
float rectRatio = zoomToRect.width() / zoomToRect.height();
if (FloatUtils.fuzzyEquals(targetRatio, rectRatio)) {
// all good, do nothing
} else if (targetRatio < rectRatio) {
// need to increase zoomToRect height
float newHeight = zoomToRect.width() / targetRatio;
zoomToRect.top -= (newHeight - zoomToRect.height()) / 2;
zoomToRect.bottom = zoomToRect.top + newHeight;
} else { // targetRatio > rectRatio) {
// need to increase zoomToRect width
float newWidth = targetRatio * zoomToRect.height();
zoomToRect.left -= (newWidth - zoomToRect.width()) / 2;
zoomToRect.right = zoomToRect.left + newWidth;
}
float finalZoom = viewport.width() / zoomToRect.width();
ImmutableViewportMetrics finalMetrics = getMetrics();
finalMetrics =
finalMetrics.setViewportOrigin(
zoomToRect.left * finalMetrics.zoomFactor, zoomToRect.top * finalMetrics.zoomFactor);
finalMetrics = finalMetrics.scaleTo(finalZoom, new PointF(0.0f, 0.0f));
// 2. now run getValidViewportMetrics on it, so that the target viewport is
// clamped down to prevent overscroll, over-zoom, and other bad conditions.
finalMetrics = getValidViewportMetrics(finalMetrics);
bounce(finalMetrics);
return true;
}
/**
* Scales the viewport, keeping the given focus point in the same place before and after the scale
* operation. You must hold the monitor while calling this.
*/
private void scaleWithFocus(float zoomFactor, PointF focus) {
ImmutableViewportMetrics viewportMetrics = getMetrics();
viewportMetrics = viewportMetrics.scaleTo(zoomFactor, focus);
mTarget.setViewportMetrics(viewportMetrics);
}