static bool
IsRectZoomedIn(const CSSRect& aRect, const CSSRect& aCompositedArea)
{
// This functions checks to see if the area of the rect visible in the
// composition bounds (i.e. the overlapArea variable below) is approximately
// the max area of the rect we can show.
CSSRect overlap = aCompositedArea.Intersect(aRect);
float overlapArea = overlap.width * overlap.height;
float availHeight = std::min(aRect.width * aCompositedArea.height / aCompositedArea.width,
aRect.height);
float showing = overlapArea / (aRect.width * availHeight);
float ratioW = aRect.width / aCompositedArea.width;
float ratioH = aRect.height / aCompositedArea.height;
return showing > 0.9 && (ratioW > 0.9 || ratioH > 0.9);
}
static void
MaybeAlignAndClampDisplayPort(mozilla::layers::FrameMetrics& aFrameMetrics,
const CSSPoint& aActualScrollOffset)
{
// Correct the display-port by the difference between the requested scroll
// offset and the resulting scroll offset after setting the requested value.
CSSRect& displayPort = aFrameMetrics.mDisplayPort;
displayPort += aFrameMetrics.mScrollOffset - aActualScrollOffset;
// Expand the display port to the next tile boundaries, if tiled thebes layers
// are enabled.
if (gfxPlatform::GetPrefLayersEnableTiles()) {
displayPort =
ExpandDisplayPortToTileBoundaries(displayPort + aActualScrollOffset,
aFrameMetrics.LayersPixelsPerCSSPixel())
- aActualScrollOffset;
}
// Finally, clamp the display port to the expanded scrollable rect.
CSSRect scrollableRect = aFrameMetrics.GetExpandedScrollableRect();
displayPort = scrollableRect.Intersect(displayPort + aActualScrollOffset)
- aActualScrollOffset;
}