void
AsyncCompositionManager::TransformScrollableLayer(Layer* aLayer, const LayoutDeviceToLayerScale& aResolution)
{
LayerComposite* layerComposite = aLayer->AsLayerComposite();
ContainerLayer* container = aLayer->AsContainerLayer();
const FrameMetrics& metrics = container->GetFrameMetrics();
// We must apply the resolution scale before a pan/zoom transform, so we call
// GetTransform here.
const gfx3DMatrix& currentTransform = aLayer->GetTransform();
gfx3DMatrix oldTransform = currentTransform;
gfx3DMatrix treeTransform;
CSSToLayerScale geckoZoom = metrics.mDevPixelsPerCSSPixel * aResolution;
LayerIntPoint scrollOffsetLayerPixels = RoundedToInt(metrics.mScrollOffset * geckoZoom);
if (mIsFirstPaint) {
mContentRect = metrics.mScrollableRect;
SetFirstPaintViewport(scrollOffsetLayerPixels,
geckoZoom,
mContentRect);
mIsFirstPaint = false;
} else if (!metrics.mScrollableRect.IsEqualEdges(mContentRect)) {
mContentRect = metrics.mScrollableRect;
SetPageRect(mContentRect);
}
// We synchronise the viewport information with Java after sending the above
// notifications, so that Java can take these into account in its response.
// Calculate the absolute display port to send to Java
LayerIntRect displayPort = RoundedToInt(
(metrics.mCriticalDisplayPort.IsEmpty()
? metrics.mDisplayPort
: metrics.mCriticalDisplayPort
) * geckoZoom);
displayPort += scrollOffsetLayerPixels;
LayerMargin fixedLayerMargins(0, 0, 0, 0);
ScreenPoint offset(0, 0);
// Ideally we would initialize userZoom to AsyncPanZoomController::CalculateResolution(metrics)
// but this causes a reftest-ipc test to fail (see bug 883646 comment 27). The reason for this
// appears to be that metrics.mZoom is poorly initialized in some scenarios. In these scenarios,
// however, we can assume there is no async zooming in progress and so the following statement
// works fine.
CSSToScreenScale userZoom(metrics.mDevPixelsPerCSSPixel.scale * metrics.mResolution.scale);
ScreenPoint userScroll = metrics.mScrollOffset * userZoom;
SyncViewportInfo(displayPort, geckoZoom, mLayersUpdated,
userScroll, userZoom, fixedLayerMargins,
offset);
mLayersUpdated = false;
// Apply the render offset
mLayerManager->GetCompositor()->SetScreenRenderOffset(offset);
// Handle transformations for asynchronous panning and zooming. We determine the
// zoom used by Gecko from the transformation set on the root layer, and we
// determine the scroll offset used by Gecko from the frame metrics of the
// primary scrollable layer. We compare this to the user zoom and scroll
// offset in the view transform we obtained from Java in order to compute the
// transformation we need to apply.
LayerToScreenScale zoomAdjust = userZoom / geckoZoom;
LayerIntPoint geckoScroll(0, 0);
if (metrics.IsScrollable()) {
geckoScroll = scrollOffsetLayerPixels;
}
LayerPoint translation = (userScroll / zoomAdjust) - geckoScroll;
treeTransform = gfx3DMatrix(ViewTransform(-translation, userZoom / metrics.mDevPixelsPerCSSPixel));
// The transform already takes the resolution scale into account. Since we
// will apply the resolution scale again when computing the effective
// transform, we must apply the inverse resolution scale here.
gfx3DMatrix computedTransform = treeTransform * currentTransform;
computedTransform.Scale(1.0f/container->GetPreXScale(),
1.0f/container->GetPreYScale(),
1);
computedTransform.ScalePost(1.0f/container->GetPostXScale(),
1.0f/container->GetPostYScale(),
1);
layerComposite->SetShadowTransform(computedTransform);
NS_ASSERTION(!layerComposite->GetShadowTransformSetByAnimation(),
"overwriting animated transform!");
// Apply resolution scaling to the old transform - the layer tree as it is
// doesn't have the necessary transform to display correctly.
oldTransform.Scale(aResolution.scale, aResolution.scale, 1);
// Make sure that overscroll and under-zoom are represented in the old
// transform so that fixed position content moves and scales accordingly.
// These calculations will effectively scale and offset fixed position layers
// in screen space when the compensatory transform is performed in
// AlignFixedLayersForAnchorPoint.
ScreenRect contentScreenRect = mContentRect * userZoom;
gfxPoint3D overscrollTranslation;
if (userScroll.x < contentScreenRect.x) {
overscrollTranslation.x = contentScreenRect.x - userScroll.x;
} else if (userScroll.x + metrics.mCompositionBounds.width > contentScreenRect.XMost()) {
overscrollTranslation.x = contentScreenRect.XMost() -
(userScroll.x + metrics.mCompositionBounds.width);
}
if (userScroll.y < contentScreenRect.y) {
overscrollTranslation.y = contentScreenRect.y - userScroll.y;
} else if (userScroll.y + metrics.mCompositionBounds.height > contentScreenRect.YMost()) {
overscrollTranslation.y = contentScreenRect.YMost() -
(userScroll.y + metrics.mCompositionBounds.height);
}
oldTransform.Translate(overscrollTranslation);
gfxSize underZoomScale(1.0f, 1.0f);
if (mContentRect.width * userZoom.scale < metrics.mCompositionBounds.width) {
underZoomScale.width = (mContentRect.width * userZoom.scale) /
metrics.mCompositionBounds.width;
}
if (mContentRect.height * userZoom.scale < metrics.mCompositionBounds.height) {
underZoomScale.height = (mContentRect.height * userZoom.scale) /
metrics.mCompositionBounds.height;
}
oldTransform.Scale(underZoomScale.width, underZoomScale.height, 1);
// Make sure fixed position layers don't move away from their anchor points
// when we're asynchronously panning or zooming
AlignFixedLayersForAnchorPoint(aLayer, aLayer, oldTransform, fixedLayerMargins);
}
