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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 19:33:14 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 19:33:14 +0000 |
commit | 36d22d82aa202bb199967e9512281e9a53db42c9 (patch) | |
tree | 105e8c98ddea1c1e4784a60a5a6410fa416be2de /gfx/layers/wr/ClipManager.h | |
parent | Initial commit. (diff) | |
download | firefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.tar.xz firefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.zip |
Adding upstream version 115.7.0esr.upstream/115.7.0esr
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'gfx/layers/wr/ClipManager.h')
-rw-r--r-- | gfx/layers/wr/ClipManager.h | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/gfx/layers/wr/ClipManager.h b/gfx/layers/wr/ClipManager.h new file mode 100644 index 0000000000..7253fec8bb --- /dev/null +++ b/gfx/layers/wr/ClipManager.h @@ -0,0 +1,150 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* 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_CLIPMANAGER_H +#define GFX_CLIPMANAGER_H + +#include <stack> +#include <unordered_map> + +#include "mozilla/Attributes.h" +#include "mozilla/webrender/WebRenderAPI.h" + +namespace mozilla { + +class nsDisplayItem; +struct ActiveScrolledRoot; +struct DisplayItemClipChain; + +namespace wr { +class DisplayListBuilder; +} + +namespace layers { + +class StackingContextHelper; +class WebRenderLayerManager; + +/** + * This class manages creating and assigning scroll layers and clips in + * WebRender based on the gecko display list. It has a few public functions that + * are intended to be invoked while traversing the Gecko display list, and it + * uses the ASR and clip information from the display list to create the + * necessary clip state in WebRender. + * + * The structure of the clip state in WebRender ends up quite similar to how + * it is in Gecko. For each ASR in Gecko, we create a scroll layer (i.e. a + * scrolling clip) in WebRender; these form a tree structure similar to the + * ASR tree structure. Ancestors of scroll layers are always other scroll + * layers, or the root scroll node. + * The DisplayItemClipChain list of clips from the gecko display list is + * converted to a WR clip chain and pushed on the stack prior to creating + * any WR commands for that item, and is popped afterwards. In addition, + * the WR clip chain has a parent pointer, which points to the clip chain for + * any enclosing stacking context. This again results in a strucuture very + * similar to that in Gecko, where the clips from container display items get + * applied to the contained display items. + */ +class ClipManager { + public: + ClipManager(); + + void BeginBuild(WebRenderLayerManager* aManager, + wr::DisplayListBuilder& aBuilder); + void EndBuild(); + + void BeginList(const StackingContextHelper& aStackingContext); + void EndList(const StackingContextHelper& aStackingContext); + + wr::WrSpaceAndClipChain SwitchItem(nsDisplayListBuilder* aBuilder, + nsDisplayItem* aItem); + ~ClipManager(); + + void PushOverrideForASR(const ActiveScrolledRoot* aASR, + const wr::WrSpatialId& aSpatialId); + void PopOverrideForASR(const ActiveScrolledRoot* aASR); + + private: + wr::WrSpatialId SpatialIdAfterOverride(const wr::WrSpatialId& aSpatialId); + wr::WrSpatialId GetScrollLayer(const ActiveScrolledRoot* aASR); + + Maybe<wr::WrSpatialId> DefineScrollLayers(const ActiveScrolledRoot* aASR, + nsDisplayItem* aItem); + + Maybe<wr::WrClipChainId> DefineClipChain(const DisplayItemClipChain* aChain, + int32_t aAppUnitsPerDevPixel); + + WebRenderLayerManager* MOZ_NON_OWNING_REF mManager; + wr::DisplayListBuilder* mBuilder; + + // Stack of clip caches. Each cache contains a map from gecko + // DisplayItemClipChain objects to webrender WrClipIds, which allows us to + // avoid redefining identical clips in WR. However, the gecko + // DisplayItemClipChain items get deduplicated quite aggressively, without + // regard to things like the enclosing reference frame or mask. On the WR + // side, we cannot deduplicate clips that aggressively. So what we do is + // any time we enter a new reference frame (for example) we create a new clip + // cache on mCacheStack. This ensures we continue caching stuff within a given + // reference frame, but disallow caching stuff across reference frames. In + // general we need to do this anytime PushOverrideForASR is called, as that is + // called for the same set of conditions for which we cannot deduplicate + // clips. + using ClipIdMap = std::unordered_map<const DisplayItemClipChain*, + AutoTArray<wr::WrClipId, 4>>; + std::stack<ClipIdMap> mCacheStack; + + // A map that holds the cache overrides created by (a) "out of band" clips, + // i.e. clips that are generated by display items but that ClipManager + // doesn't know about and (b) stacking contexts that affect clip positioning. + // These are called "cache overrides" because while we're inside these things, + // we cannot use the ASR from the gecko display list as-is. Fundamentally this + // results from a mismatch between the ASR+clip items on the gecko side and + // the ClipScrollTree on the WR side; the WR side incorporates things like + // transforms and stacking context origins while the gecko side manages those + // differently. + // Any time ClipManager wants to define a new clip as a child of ASR X, it + // should first check the cache overrides to see if there is a cache override + // item ((a) or (b) above) that is already a child of X, and then define that + // clip as a child of Y instead. This map stores X -> Y, which allows + // ClipManager to do the necessary lookup. Note that there theoretically might + // be multiple different "Y" clips (in case of nested cache overrides), which + // is why we need a stack. + std::unordered_map<wr::WrSpatialId, std::stack<wr::WrSpatialId>> mASROverride; + + // This holds some clip state for a single nsDisplayItem + struct ItemClips { + ItemClips(const ActiveScrolledRoot* aASR, + const DisplayItemClipChain* aChain, int32_t aAppUnitsPerDevPixel, + bool aSeparateLeaf); + + // These are the "inputs" - they come from the nsDisplayItem + const ActiveScrolledRoot* mASR; + const DisplayItemClipChain* mChain; + int32_t mAppUnitsPerDevPixel; + bool mSeparateLeaf; + + // These are the "outputs" - they are pushed to WR as needed + wr::WrSpatialId mScrollId; + Maybe<wr::WrClipChainId> mClipChainId; + + void UpdateSeparateLeaf(wr::DisplayListBuilder& aBuilder, + int32_t aAppUnitsPerDevPixel); + bool HasSameInputs(const ItemClips& aOther); + wr::WrSpaceAndClipChain GetSpaceAndClipChain() const; + }; + + // A stack of ItemClips corresponding to the nsDisplayItem ancestry. Each + // time we recurse into a nsDisplayItem's child list, this stack size + // increases by one. The topmost item on the stack is for the display item + // we are currently processing and items deeper on the stack are for that + // display item's ancestors. + std::stack<ItemClips> mItemClipStack; +}; + +} // namespace layers +} // namespace mozilla + +#endif |