/**
* Returns true if this client is fine with performing a redraw operation or false if it would
* prefer that the action didn't take place.
*/
private boolean getRedrawHint() {
if (mForceRedraw) {
mForceRedraw = false;
return true;
}
if (!mPanZoomController.getRedrawHint()) {
return false;
}
return DisplayPortCalculator.aboutToCheckerboard(
mViewportMetrics, mPanZoomController.getVelocityVector(), mDisplayPort);
}
// This is called on the Gecko thread to determine if we're still interested
// in the update of this display-port to continue. We can return true here
// to abort the current update and continue with any subsequent ones. This
// is useful for slow-to-render pages when the display-port starts lagging
// behind enough that continuing to draw it is wasted effort.
public ProgressiveUpdateData progressiveUpdateCallback(
boolean aHasPendingNewThebesContent,
float x,
float y,
float width,
float height,
float resolution,
boolean lowPrecision) {
// Skip all low precision draws until we're at risk of checkerboarding
if (lowPrecision && !mProgressiveUpdateWasInDanger) {
mProgressiveUpdateData.abort = true;
return mProgressiveUpdateData;
}
// Reset the checkerboard risk flag
if (!lowPrecision && mLastProgressiveUpdateWasLowPrecision) {
mProgressiveUpdateWasInDanger = false;
}
mLastProgressiveUpdateWasLowPrecision = lowPrecision;
// Grab a local copy of the last display-port sent to Gecko and the
// current viewport metrics to avoid races when accessing them.
DisplayPortMetrics displayPort = mDisplayPort;
ImmutableViewportMetrics viewportMetrics = mViewportMetrics;
mProgressiveUpdateData.setViewport(viewportMetrics);
mProgressiveUpdateData.abort = false;
// Always abort updates if the resolution has changed. There's no use
// in drawing at the incorrect resolution.
if (!FloatUtils.fuzzyEquals(resolution, viewportMetrics.zoomFactor)) {
Log.d(LOGTAG, "Aborting draw due to resolution change");
mProgressiveUpdateData.abort = true;
return mProgressiveUpdateData;
}
// Store the high precision displayport for comparison when doing low
// precision updates.
if (!lowPrecision) {
if (!FloatUtils.fuzzyEquals(resolution, mProgressiveUpdateDisplayPort.resolution)
|| !FloatUtils.fuzzyEquals(x, mProgressiveUpdateDisplayPort.getLeft())
|| !FloatUtils.fuzzyEquals(y, mProgressiveUpdateDisplayPort.getTop())
|| !FloatUtils.fuzzyEquals(x + width, mProgressiveUpdateDisplayPort.getRight())
|| !FloatUtils.fuzzyEquals(y + height, mProgressiveUpdateDisplayPort.getBottom())) {
mProgressiveUpdateDisplayPort =
new DisplayPortMetrics(x, y, x + width, y + height, resolution);
}
}
// XXX All sorts of rounding happens inside Gecko that becomes hard to
// account exactly for. Given we align the display-port to tile
// boundaries (and so they rarely vary by sub-pixel amounts), just
// check that values are within a couple of pixels of the
// display-port bounds.
// Never abort drawing if we can't be sure we've sent a more recent
// display-port. If we abort updating when we shouldn't, we can end up
// with blank regions on the screen and we open up the risk of entering
// an endless updating cycle.
if (Math.abs(displayPort.getLeft() - mProgressiveUpdateDisplayPort.getLeft()) <= 2
&& Math.abs(displayPort.getTop() - mProgressiveUpdateDisplayPort.getTop()) <= 2
&& Math.abs(displayPort.getBottom() - mProgressiveUpdateDisplayPort.getBottom()) <= 2
&& Math.abs(displayPort.getRight() - mProgressiveUpdateDisplayPort.getRight()) <= 2) {
return mProgressiveUpdateData;
}
if (!lowPrecision && !mProgressiveUpdateWasInDanger) {
// If we're not doing low precision draws and we're about to
// checkerboard, give up and move onto low precision drawing.
if (DisplayPortCalculator.aboutToCheckerboard(
viewportMetrics, mPanZoomController.getVelocityVector(), mProgressiveUpdateDisplayPort)) {
mProgressiveUpdateWasInDanger = true;
}
}
// Abort updates when the display-port no longer contains the visible
// area of the page (that is, the viewport cropped by the page
// boundaries).
// XXX This makes the assumption that we never let the visible area of
// the page fall outside of the display-port.
if (Math.max(viewportMetrics.viewportRectLeft, viewportMetrics.pageRectLeft) + 1 < x
|| Math.max(viewportMetrics.viewportRectTop, viewportMetrics.pageRectTop) + 1 < y
|| Math.min(viewportMetrics.viewportRectRight, viewportMetrics.pageRectRight) - 1
> x + width
|| Math.min(viewportMetrics.viewportRectBottom, viewportMetrics.pageRectBottom) - 1
> y + height) {
Log.d(LOGTAG, "Aborting update due to viewport not in display-port");
mProgressiveUpdateData.abort = true;
return mProgressiveUpdateData;
}
// Abort drawing stale low-precision content if there's a more recent
// display-port in the pipeline.
if (lowPrecision && !aHasPendingNewThebesContent) {
mProgressiveUpdateData.abort = true;
}
return mProgressiveUpdateData;
}