gecko-dev/layout/painting/DisplayItemClipChain.h
Markus Stange b9c74f8bdc Bug 1298218 - Add DisplayItemClipChain. r=mattwoodrow,tnikkel
MozReview-Commit-ID: K9mg86VgK10

--HG--
extra : rebase_source : 3b234829ec7dbe0ad7dff8ca55f813b082b21b0c
2017-01-27 12:57:44 +01:00

59 lines
2.2 KiB
C++

/* -*- Mode: C++; tab-width: 20; 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 DISPLAYITEMCLIPCHAIN_H_
#define DISPLAYITEMCLIPCHAIN_H_
#include "mozilla/Assertions.h"
#include "DisplayItemClip.h"
#include "nsString.h"
class nsIScrollableFrame;
namespace mozilla {
struct ActiveScrolledRoot;
/**
* A DisplayItemClipChain is a linked list of DisplayItemClips where each clip
* is associated with an active scrolled root that describes what the clip
* moves with.
* We use a chain instead of just one intersected clip due to async scrolling:
* A clip that moves along with a display item can be fused to the item's
* contents when drawing the layer contents, but all other clips in the chain
* need to be kept separate so that they can be applied at composition time,
* after any async scroll offsets have been applied.
* The clip chain is created during display list construction by the builder's
* DisplayListClipState.
* The clip chain order is determined by the active scrolled root order.
* For every DisplayItemClipChain object |clipChain|, the following holds:
* !clipChain->mParent || ActiveScrolledRoot::IsAncestor(clipChain->mParent->mASR, clipChain->mASR).
* The clip chain can skip over active scrolled roots. That just means that
* there is no clip that moves with the skipped ASR in this chain.
*/
struct DisplayItemClipChain {
/**
* Get the display item clip in this chain that moves with aASR, or nullptr
* if no such clip exists. aClipChain can be null.
*/
static const DisplayItemClip* ClipForASR(const DisplayItemClipChain* aClipChain,
const ActiveScrolledRoot* aASR);
static bool Equal(const DisplayItemClipChain* aClip1, const DisplayItemClipChain* aClip2);
static nsCString ToString(const DisplayItemClipChain* aClipChain);
bool HasRoundedCorners() const;
DisplayItemClip mClip;
const ActiveScrolledRoot* mASR;
const DisplayItemClipChain* mParent;
};
} // namespace mozilla
#endif /* DISPLAYITEMCLIPCHAIN_H_ */