gecko-dev/gfx/layers/FrameMetrics.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef GFX_FRAMEMETRICS_H
#define GFX_FRAMEMETRICS_H
#include "gfxPoint.h"
#include "gfxTypes.h"
#include "nsRect.h"
#include "mozilla/gfx/Rect.h"
namespace mozilla {
namespace layers {
/**
* The viewport and displayport metrics for the painted frame at the
* time of a layer-tree transaction. These metrics are especially
* useful for shadow layers, because the metrics values are updated
* atomically with new pixels.
*/
struct THEBES_API FrameMetrics {
public:
// We use IDs to identify frames across processes.
typedef uint64_t ViewID;
static const ViewID NULL_SCROLL_ID; // This container layer does not scroll.
static const ViewID ROOT_SCROLL_ID; // This is the root scroll frame.
static const ViewID START_SCROLL_ID; // This is the ID that scrolling subframes
// will begin at.
FrameMetrics()
: mCompositionBounds(0, 0, 0, 0)
, mContentRect(0, 0, 0, 0)
, mDisplayPort(0, 0, 0, 0)
, mCriticalDisplayPort(0, 0, 0, 0)
, mViewport(0, 0, 0, 0)
, mScrollOffset(0, 0)
, mScrollId(NULL_SCROLL_ID)
, mScrollableRect(0, 0, 0, 0)
, mResolution(1, 1)
, mZoom(1, 1)
, mDevPixelsPerCSSPixel(1)
, mMayHaveTouchListeners(false)
{}
// Default copy ctor and operator= are fine
bool operator==(const FrameMetrics& aOther) const
{
return mCompositionBounds.IsEqualEdges(aOther.mCompositionBounds) &&
mContentRect.IsEqualEdges(aOther.mContentRect) &&
mDisplayPort.IsEqualEdges(aOther.mDisplayPort) &&
mCriticalDisplayPort.IsEqualEdges(aOther.mCriticalDisplayPort) &&
mViewport.IsEqualEdges(aOther.mViewport) &&
mScrollOffset == aOther.mScrollOffset &&
mScrollId == aOther.mScrollId &&
mScrollableRect.IsEqualEdges(aOther.mScrollableRect) &&
mResolution == aOther.mResolution &&
mDevPixelsPerCSSPixel == aOther.mDevPixelsPerCSSPixel &&
mMayHaveTouchListeners == aOther.mMayHaveTouchListeners;
}
bool operator!=(const FrameMetrics& aOther) const
{
return !operator==(aOther);
}
bool IsDefault() const
{
return (FrameMetrics() == *this);
}
bool IsRootScrollable() const
{
return mScrollId == ROOT_SCROLL_ID;
}
bool IsScrollable() const
{
return mScrollId != NULL_SCROLL_ID;
}
gfxSize LayersPixelsPerCSSPixel() const
{
return mResolution * mDevPixelsPerCSSPixel;
}
gfxPoint GetScrollOffsetInLayerPixels() const
{
return gfxPoint(
static_cast<gfx::Float>(
mScrollOffset.x * LayersPixelsPerCSSPixel().width),
static_cast<gfx::Float>(
mScrollOffset.y * LayersPixelsPerCSSPixel().height));
}
// ---------------------------------------------------------------------------
// 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 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
// 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.
nsIntRect mCompositionBounds;
// |mScrollableRect|, stored in device pixels. DECPRECATED, DO NOT USE.
//
// This is valid on any layer where |mScrollableRect| is, though it may be
// more lazily maintained than |mScrollableRect|. That is, when
// |mScrollableRect| is updated, this may lag. For this reason, it's better to
// use |mScrollableRect| for any control logic.
//
// FIXME/bug 785929: Is this really necessary? Can it not be calculated from
// |mScrollableRect| whenever it's needed?
nsIntRect mContentRect;
// ---------------------------------------------------------------------------
// The following metrics are all in CSS pixels. They are not in any uniform
// space, so each is explained separately.
//
// The area of a frame's contents that has been painted, relative to the
// viewport. It is in the same coordinate space as |mViewport|. For example,
// if it is at 0,0, then it's at the same place at the viewport, which is at
// the top-left in the layer, and at the same place as the scroll offset of
// the document.
//
// Note that this is structured in such a way that it doesn't depend on the
// method layout uses to scroll content.
//
// May be larger or smaller than |mScrollableRect|.
//
// To pre-render a margin of 100 CSS pixels around the window,
// { x = -100, y = - 100,
// width = window.innerWidth + 100, height = window.innerHeight + 100 }
//
// This is only valid on the root layer. Nested iframes do not have a
// displayport set on them. See bug 775452.
gfx::Rect mDisplayPort;
// If non-empty, the area of a frame's contents that is considered critical
// to paint. Area outside of this area (i.e. area inside mDisplayPort, but
// outside of mCriticalDisplayPort) is considered low-priority, and may be
// painted with lower precision, or not painted at all.
//
// The same restrictions for mDisplayPort apply here.
gfx::Rect mCriticalDisplayPort;
// The CSS viewport, which is the dimensions we're using to constrain the
// <html> element of this frame, relative to the top-left of the layer. Note
// that its offset is structured in such a way that it doesn't depend on the
// method layout uses to scroll content.
//
// This is mainly useful on the root layer, however nested iframes can have
// their own viewport, which will just be the size of the window of the
// iframe. For layers that don't correspond to a document, this metric is
// meaningless and invalid.
gfx::Rect mViewport;
// The position of the top-left of the CSS viewport, relative to the document
// (or the document relative to the viewport, if that helps understand it).
//
// Thus it is relative to the document. It is in the same coordinate space as
// |mScrollableRect|, but a different coordinate space than |mViewport| and
// |mDisplayPort|.
//
// It is required that the rect:
// { x = mScrollOffset.x, y = mScrollOffset.y,
// width = mCompositionBounds.x / mResolution.width,
// height = mCompositionBounds.y / mResolution.height }
// Be within |mScrollableRect|.
//
// This is valid for any layer, but is always relative to this frame and
// not any parents, regardless of parent transforms.
gfx::Point mScrollOffset;
// A unique ID assigned to each scrollable frame (unless this is
// ROOT_SCROLL_ID, in which case it is not unique).
ViewID mScrollId;
// The scrollable bounds of a frame. This is determined by reflow.
// For the top-level |window|,
// { x = window.scrollX, y = window.scrollY, // could be 0, 0
// width = window.innerWidth, height = window.innerHeight }
//
// This is relative to the document. It is in the same coordinate space as
// |mScrollOffset|, but a different coordinate space than |mViewport| and
// |mDisplayPort|. Note also that this coordinate system is understood by
// window.scrollTo().
//
// This is valid on any layer unless it has no content.
gfx::Rect mScrollableRect;
// ---------------------------------------------------------------------------
// The following metrics are dimensionless.
//
// The resolution, along both axes, that the current frame has been painted
// at.
//
// Every time this frame is composited and the compositor samples its
// transform, this metric is used to create a transform which is
// post-multiplied into the parent's transform. Since this only happens when
// we walk the layer tree, the resulting transform isn't stored here. Thus the
// resolution of parent layers is opaque to this metric.
gfxSize mResolution;
// The resolution-independent "user zoom". For example, if a page
// configures the viewport to a zoom value of 2x, then this member
// will always be 2.0 no matter what the viewport or composition
// bounds.
//
// In the steady state (no animations), and ignoring DPI, then the
// following is usually true
//
// intrinsicScale = (mCompositionBounds / mViewport)
// mResolution = mZoom * intrinsicScale
//
// When this is not true, we're probably asynchronously sampling a
// zoom animation for content.
gfxSize mZoom;
// The conversion factor between CSS pixels and device pixels for this frame.
// This can vary based on a variety of things, such as reflowing-zoom. The
// conversion factor for device pixels to layers pixels is just the
// resolution.
float mDevPixelsPerCSSPixel;
// Whether or not this frame may have touch listeners.
bool mMayHaveTouchListeners;
};
}
}
#endif /* GFX_FRAMEMETRICS_H */