gecko/gfx/layers/FrameMetrics.h

264 lines
9.9 KiB
C++

/* -*- 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 <stdint.h> // for uint32_t, uint64_t
#include "Units.h" // for CSSRect, CSSPixel, etc
#include "mozilla/gfx/BasePoint.h" // for BasePoint
#include "mozilla/gfx/Rect.h" // for RoundedIn
#include "mozilla/gfx/ScaleFactor.h" // for ScaleFactor
namespace mozilla {
namespace layers {
// The layer coordinates of the parent layer. Like the layer coordinates
// of the current layer (LayerPixel) but doesn't include the current layer's
// resolution.
struct ParentLayerPixel {};
typedef gfx::ScaleFactor<LayoutDevicePixel, ParentLayerPixel> LayoutDeviceToParentLayerScale;
typedef gfx::ScaleFactor<ParentLayerPixel, LayerPixel> ParentLayerToLayerScale;
typedef gfx::ScaleFactor<ParentLayerPixel, ScreenPixel> ParentLayerToScreenScale;
/**
* 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 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)
, 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)
, mCumulativeResolution(1)
, mZoom(1)
, mDevPixelsPerCSSPixel(1)
, mMayHaveTouchListeners(false)
, mPresShellId(-1)
{}
// Default copy ctor and operator= are fine
bool operator==(const FrameMetrics& aOther) const
{
return mCompositionBounds.IsEqualEdges(aOther.mCompositionBounds) &&
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 &&
mCumulativeResolution == aOther.mCumulativeResolution &&
mDevPixelsPerCSSPixel == aOther.mDevPixelsPerCSSPixel &&
mMayHaveTouchListeners == aOther.mMayHaveTouchListeners &&
mPresShellId == aOther.mPresShellId;
}
bool operator!=(const FrameMetrics& aOther) const
{
return !operator==(aOther);
}
bool IsDefault() const
{
FrameMetrics def;
def.mPresShellId = mPresShellId;
return (def == *this);
}
bool IsRootScrollable() const
{
return mScrollId == ROOT_SCROLL_ID;
}
bool IsScrollable() const
{
return mScrollId != NULL_SCROLL_ID;
}
CSSToLayerScale LayersPixelsPerCSSPixel() const
{
return mCumulativeResolution * mDevPixelsPerCSSPixel;
}
LayerPoint GetScrollOffsetInLayerPixels() const
{
return mScrollOffset * LayersPixelsPerCSSPixel();
}
LayoutDeviceToParentLayerScale GetParentResolution() const
{
return mCumulativeResolution / mResolution;
}
/**
* Return the scale factor needed to fit the viewport
* into its composition bounds.
*/
CSSToScreenScale CalculateIntrinsicScale() const
{
return CSSToScreenScale(float(mCompositionBounds.width) / float(mViewport.width));
}
CSSRect CalculateCompositedRectInCssPixels() const
{
return CSSRect(gfx::RoundedIn(mCompositionBounds / mZoom));
}
// ---------------------------------------------------------------------------
// The following metrics are all in widget space/device pixels.
//
// 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 composition dimensions are the same as the
// viewport dimensions, there is no need for this and we can just use the viewport
// instead.
//
// This value is valid for nested scrollable layers as well, and is still
// relative to the layer tree origin.
ScreenIntRect mCompositionBounds;
// ---------------------------------------------------------------------------
// 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 + 200, height = window.innerHeight + 200 }
//
// This is only valid on the root layer. Nested iframes do not have a
// displayport set on them. See bug 775452.
CSSRect 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.
CSSRect 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.
CSSRect 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.scale,
// height = mCompositionBounds.y / mResolution.scale }
// Be within |mScrollableRect|.
//
// This is valid for any layer, but is always relative to this frame and
// not any parents, regardless of parent transforms.
CSSPoint 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.
// Ordinarily the x and y will be 0 and the width and height will be the
// size of the element being scrolled. However for RTL pages or elements
// the x value may be negative.
//
// 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.
CSSRect mScrollableRect;
// ---------------------------------------------------------------------------
// The following metrics are dimensionless.
//
// The resolution 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.
ParentLayerToLayerScale mResolution;
// The cumulative resolution that the current frame has been painted at.
// This is the product of our mResolution and the mResolutions of our parent frames.
LayoutDeviceToLayerScale mCumulativeResolution;
// The "user zoom". Content is painted by gecko at mResolution * mDevPixelsPerCSSPixel,
// but will be drawn to the screen at mZoom. In the steady state, the
// two will be the same, but during an async zoom action the two may
// diverge.
CSSToScreenScale 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.
CSSToLayoutDeviceScale mDevPixelsPerCSSPixel;
// Whether or not this frame may have touch listeners.
bool mMayHaveTouchListeners;
uint32_t mPresShellId;
};
}
}
#endif /* GFX_FRAMEMETRICS_H */