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;
}
@Override
public boolean onScale(SimpleScaleGestureDetector detector) {
if (GeckoApp.mAppContext == null || GeckoApp.mAppContext.mDOMFullScreen) return false;
if (mState != PanZoomState.PINCHING) return false;
float prevSpan = detector.getPreviousSpan();
if (FloatUtils.fuzzyEquals(prevSpan, 0.0f)) {
// let's eat this one to avoid setting the new zoom to infinity (bug 711453)
return true;
}
float spanRatio = detector.getCurrentSpan() / prevSpan;
/*
* Apply edge resistance if we're zoomed out smaller than the page size by scaling the zoom
* factor toward 1.0.
*/
float resistance = Math.min(mX.getEdgeResistance(true), mY.getEdgeResistance(true));
if (spanRatio > 1.0f) spanRatio = 1.0f + (spanRatio - 1.0f) * resistance;
else spanRatio = 1.0f - (1.0f - spanRatio) * resistance;
synchronized (mTarget.getLock()) {
float newZoomFactor = getMetrics().zoomFactor * spanRatio;
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 (newZoomFactor < minZoomFactor) {
// apply resistance when zooming past minZoomFactor,
// such that it asymptotically reaches minZoomFactor / 2.0
// but never exceeds that
final float rate = 0.5f; // controls how quickly we approach the limit
float excessZoom = minZoomFactor - newZoomFactor;
excessZoom = 1.0f - (float) Math.exp(-excessZoom * rate);
newZoomFactor = minZoomFactor * (1.0f - excessZoom / 2.0f);
}
if (newZoomFactor > maxZoomFactor) {
// apply resistance when zooming past maxZoomFactor,
// such that it asymptotically reaches maxZoomFactor + 1.0
// but never exceeds that
float excessZoom = newZoomFactor - maxZoomFactor;
excessZoom = 1.0f - (float) Math.exp(-excessZoom);
newZoomFactor = maxZoomFactor + excessZoom;
}
scrollBy(mLastZoomFocus.x - detector.getFocusX(), mLastZoomFocus.y - detector.getFocusY());
PointF focus = new PointF(detector.getFocusX(), detector.getFocusY());
scaleWithFocus(newZoomFactor, focus);
}
mLastZoomFocus.set(detector.getFocusX(), detector.getFocusY());
GeckoEvent event =
GeckoEvent.createNativeGestureEvent(
GeckoEvent.ACTION_MAGNIFY, mLastZoomFocus, getMetrics().zoomFactor);
GeckoAppShell.sendEventToGecko(event);
return true;
}