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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/. */
/* A global table that tracks images referenced by CSS variables. */
#ifndef mozilla_CSSVariableImageTable_h
#define mozilla_CSSVariableImageTable_h
#include "nsClassHashtable.h"
#include "nsCSSPropertyID.h"
#include "nsCSSValue.h"
#include "nsStyleContext.h"
#include "nsTArray.h"
/**
* CSSVariableImageTable maintains a global mapping
* (nsStyleContext, nsCSSPropertyID) -> nsTArray<ImageValue>
* which allows us to track the relationship between CSS property values
* involving variables and any images they may reference.
*
* When properties like background-image contain a normal url(), the
* Declaration's data block will hold a reference to the ImageValue. When a
* token stream is used, the Declaration only holds on to an
* nsCSSValueTokenStream object, and the ImageValue would only exist for the
* duration of nsRuleNode::WalkRuleTree, in the AutoCSSValueArray. So instead
* when we re-parse a token stream and get an ImageValue, we record it in the
* CSSVariableImageTable to keep the ImageValue alive. Such ImageValues are
* eventually freed the next time the token stream is re-parsed, or when the
* associated style context is destroyed.
*
* To add ImageValues to the CSSVariableImageTable, callers should pass a lambda
* to CSSVariableImageTable::ReplaceAll() that calls
* CSSVariableImageTable::Add() for each ImageValue that needs to be added to
* the table. When callers are sure that the ImageValues for a given
* nsStyleContext won't be needed anymore, they can call
* CSSVariableImageTable::RemoveAll() to release them.
*/
namespace mozilla {
namespace CSSVariableImageTable {
namespace detail {
typedef nsTArray<RefPtr<css::ImageValue>> ImageValueArray;
typedef nsClassHashtable<nsGenericHashKey<nsCSSPropertyID>, ImageValueArray>
PerPropertyImageHashtable;
typedef nsClassHashtable<nsPtrHashKey<nsStyleContext>, PerPropertyImageHashtable>
CSSVariableImageHashtable;
inline CSSVariableImageHashtable& GetTable()
{
static CSSVariableImageHashtable imageTable;
return imageTable;
}
#ifdef DEBUG
inline bool& IsReplacing()
{
static bool isReplacing = false;
return isReplacing;
}
#endif
} // namespace detail
/**
* ReplaceAll() allows callers to replace the ImageValues associated with a
* (nsStyleContext, nsCSSPropertyID) pair. The memory used by the previous list of
* ImageValues is automatically released.
*
* @param aContext The style context the ImageValues are associated with.
* @param aProp The CSS property the ImageValues are associated with.
* @param aFunc A lambda that calls CSSVariableImageTable::Add() to add new
* ImageValues which will replace the old ones.
*/
template <typename Lambda>
inline void ReplaceAll(nsStyleContext* aContext,
nsCSSPropertyID aProp,
Lambda aFunc)
{
MOZ_ASSERT(aContext);
auto& imageTable = detail::GetTable();
// Clear the existing image array, if any, for this property.
{
auto* perPropertyImageTable = imageTable.Get(aContext);
auto* imageList = perPropertyImageTable ? perPropertyImageTable->Get(aProp)
: nullptr;
if (imageList) {
imageList->ClearAndRetainStorage();
}
}
#ifdef DEBUG
MOZ_ASSERT(!detail::IsReplacing());
detail::IsReplacing() = true;
#endif
aFunc();
#ifdef DEBUG
detail::IsReplacing() = false;
#endif
// Clean up.
auto* perPropertyImageTable = imageTable.Get(aContext);
auto* imageList = perPropertyImageTable ? perPropertyImageTable->Get(aProp)
: nullptr;
if (imageList) {
if (imageList->IsEmpty()) {
// We used to have an image array for this property, but now we don't.
// Remove the entry in the per-property image table for this property.
// That may then allow us to remove the entire per-property image table.
perPropertyImageTable->Remove(aProp);
if (perPropertyImageTable->Count() == 0) {
imageTable.Remove(aContext);
}
} else {
// We still have a non-empty image array for this property. Compact the
// storage it's using if possible.
imageList->Compact();
}
}
}
/**
* Adds a new ImageValue @aValue to the CSSVariableImageTable, which will be
* associated with @aContext and @aProp.
*
* It's illegal to call this function outside of a lambda passed to
* CSSVariableImageTable::ReplaceAll().
*/
inline void
Add(nsStyleContext* aContext, nsCSSPropertyID aProp, css::ImageValue* aValue)
{
MOZ_ASSERT(aValue);
MOZ_ASSERT(aContext);
MOZ_ASSERT(detail::IsReplacing());
auto& imageTable = detail::GetTable();
// Ensure there's a per-property image table for this style context.
auto* perPropertyImageTable = imageTable.Get(aContext);
if (!perPropertyImageTable) {
perPropertyImageTable = new detail::PerPropertyImageHashtable();
imageTable.Put(aContext, perPropertyImageTable);
}
// Ensure there's an image array for this property.
auto* imageList = perPropertyImageTable->Get(aProp);
if (!imageList) {
imageList = new detail::ImageValueArray();
perPropertyImageTable->Put(aProp, imageList);
}
// Append the provided ImageValue to the list.
imageList->AppendElement(aValue);
}
/**
* Removes all ImageValues stored in the CSSVariableImageTable for the provided
* @aContext.
*/
inline void
RemoveAll(nsStyleContext* aContext)
{
// Move all ImageValue references into removedImageList so that we can
// release them outside of any hashtable methods. (If we just call
// Remove(aContext) on the table then we can end up calling back
// re-entrantly into hashtable methods, as other style contexts
// are released.)
detail::ImageValueArray removedImages;
auto& imageTable = detail::GetTable();
auto* perPropertyImageTable = imageTable.Get(aContext);
if (perPropertyImageTable) {
for (auto it = perPropertyImageTable->Iter(); !it.Done(); it.Next()) {
auto* imageList = it.UserData();
removedImages.AppendElements(Move(*imageList));
}
}
imageTable.Remove(aContext);
}
} // namespace CSSVariableImageTable
} // namespace mozilla
#endif // mozilla_CSSVariableImageTable_h
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