Bug 924407 - Update FrameMetrics::mCompositionBounds documentation. r=botond

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Kartikaya Gupta 2013-10-08 17:13:11 -04:00
Родитель c8822d5aa7
Коммит c7fbacefb1
1 изменённых файлов: 6 добавлений и 8 удалений

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@ -129,22 +129,20 @@ public:
// The following metrics are all in widget space/device pixels.
//
// This is the area within the widget that we're compositing to, which means
// that it is the visible region of this frame. It is not relative to
// anything.
// So { 0, 0, [compositeArea.width], [compositeArea.height] }.
// This is the area within the widget that we're compositing to. It is relative
// to the layer tree origin.
//
// This is useful because, on mobile, the viewport and composition dimensions
// are not always the same. In this case, we calculate the displayport using
// an area bigger than the region we're compositing to. If we used the
// viewport dimensions to calculate the displayport, we'd run into situations
// where we're prerendering the wrong regions and the content may be clipped,
// or too much of it prerendered. If the displayport is the same as the
// viewport, there is no need for this and we can just use the viewport
// or too much of it prerendered. If the composition dimensions are the same as the
// viewport dimensions, there is no need for this and we can just use the viewport
// instead.
//
// This is only valid on the root layer. Nested iframes do not need this
// metric as they do not have a displayport set. See bug 775452.
// This value is valid for nested scrollable layers as well, and is still
// relative to the layer tree origin.
ScreenIntRect mCompositionBounds;
// ---------------------------------------------------------------------------