gecko-dev/layout/base/FramePropertyTable.h

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/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Corporation code.
*
* The Initial Developer of the Original Code is Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2010
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Robert O'Callahan <robert@ocallahan.org>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef FRAMEPROPERTYTABLE_H_
#define FRAMEPROPERTYTABLE_H_
#include "nsTHashtable.h"
#include "nsHashKeys.h"
class nsIFrame;
namespace mozilla {
struct FramePropertyDescriptor;
typedef void (*FramePropertyDestructor)(void* aPropertyValue);
typedef void (*FramePropertyDestructorWithFrame)(nsIFrame* aFrame,
void* aPropertyValue);
/**
* A pointer to a FramePropertyDescriptor serves as a unique property ID.
* The FramePropertyDescriptor stores metadata about the property.
* Currently the only metadata is a destructor function. The destructor
* function is called on property values when they are overwritten or
* deleted.
*
* To use this class, declare a global (i.e., file, class or function-scope
* static member) FramePropertyDescriptor and pass its address as
* aProperty in the FramePropertyTable methods.
*/
struct FramePropertyDescriptor {
/**
* mDestructor will be called if it's non-null.
*/
FramePropertyDestructor mDestructor;
/**
* mDestructorWithFrame will be called if it's non-null and mDestructor
* is null. WARNING: The frame passed to mDestructorWithFrame may
* be a dangling frame pointer, if this is being called during
* presshell teardown. Do not use it except to compare against
* other frame pointers. No frame will have been allocated with
* the same address yet.
*/
FramePropertyDestructorWithFrame mDestructorWithFrame;
/**
* mDestructor and mDestructorWithFrame may both be null, in which case
* no value destruction is a no-op.
*/
};
/**
* The FramePropertyTable is optimized for storing 0 or 1 properties on
* a given frame. Storing very large numbers of properties on a single
* frame will not be efficient.
*
* Property values are passed as void* but do not actually have to be
* valid pointers. You can use NS_INT32_TO_PTR/NS_PTR_TO_INT32 to
* store PRInt32 values. Null/zero values can be stored and retrieved.
* Of course, the destructor function (if any) must handle such values
* correctly.
*/
class FramePropertyTable {
public:
FramePropertyTable() : mLastFrame(nsnull), mLastEntry(nsnull)
{
mEntries.Init();
}
~FramePropertyTable()
{
DeleteAll();
}
/**
* Set a property value on a frame. This requires one hashtable
* lookup (using the frame as the key) and a linear search through
* the properties of that frame. Any existing value for the property
* is destroyed.
*/
void Set(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
void* aValue);
/**
* Get a property value for a frame. This requires one hashtable
* lookup (using the frame as the key) and a linear search through
* the properties of that frame. If the frame has no such property,
* returns null.
* @param aFoundResult if non-null, receives a value 'true' iff
* the frame has a value for the property. This lets callers
* disambiguate a null result, which can mean 'no such property' or
* 'property value is null'.
*/
void* Get(const nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
PRBool* aFoundResult = nsnull);
/**
* Remove a property value for a frame. This requires one hashtable
* lookup (using the frame as the key) and a linear search through
* the properties of that frame. The old property value is returned
* (and not destroyed). If the frame has no such property,
* returns null.
* @param aFoundResult if non-null, receives a value 'true' iff
* the frame had a value for the property. This lets callers
* disambiguate a null result, which can mean 'no such property' or
* 'property value is null'.
*/
void* Remove(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
PRBool* aFoundResult = nsnull);
/**
* Remove and destroy a property value for a frame. This requires one
* hashtable lookup (using the frame as the key) and a linear search
* through the properties of that frame. If the frame has no such
* property, nothing happens.
*/
void Delete(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty);
/**
* Remove and destroy all property values for a frame. This requires one
* hashtable lookup (using the frame as the key).
*/
void DeleteAllFor(nsIFrame* aFrame);
/**
* Remove and destroy all property values for all frames.
*/
void DeleteAll();
protected:
/**
* Stores a property descriptor/value pair. It can also be used to
* store an nsTArray of PropertyValues.
*/
struct PropertyValue {
PropertyValue() : mProperty(nsnull), mValue(nsnull) {}
PropertyValue(const FramePropertyDescriptor* aProperty, void* aValue)
: mProperty(aProperty), mValue(aValue) {}
PRBool IsArray() { return !mProperty && mValue; }
nsTArray<PropertyValue>* ToArray()
{
NS_ASSERTION(IsArray(), "Must be array");
return reinterpret_cast<nsTArray<PropertyValue>*>(&mValue);
}
void DestroyValueFor(nsIFrame* aFrame) {
if (mProperty->mDestructor) {
mProperty->mDestructor(mValue);
} else if (mProperty->mDestructorWithFrame) {
mProperty->mDestructorWithFrame(aFrame, mValue);
}
}
const FramePropertyDescriptor* mProperty;
void* mValue;
};
/**
* Used with an array of PropertyValues to allow lookups that compare
* only on the FramePropertyDescriptor.
*/
class PropertyComparator {
public:
PRBool Equals(const PropertyValue& a, const PropertyValue& b) const {
return a.mProperty == b.mProperty;
}
PRBool Equals(const FramePropertyDescriptor* a, const PropertyValue& b) const {
return a == b.mProperty;
}
PRBool Equals(const PropertyValue& a, const FramePropertyDescriptor* b) const {
return a.mProperty == b;
}
};
/**
* Our hashtable entry. The key is an nsIFrame*, the value is a
* PropertyValue representing one or more property/value pairs.
*/
class Entry : public nsPtrHashKey<nsIFrame>
{
public:
Entry(KeyTypePointer aKey) : nsPtrHashKey<nsIFrame>(aKey) {}
Entry(const Entry &toCopy) :
nsPtrHashKey<nsIFrame>(toCopy), mProp(toCopy.mProp) {}
PropertyValue mProp;
};
static void DeleteAllForEntry(Entry* aEntry);
static PLDHashOperator DeleteEnumerator(Entry* aEntry, void* aArg);
nsTHashtable<Entry> mEntries;
nsIFrame* mLastFrame;
Entry* mLastEntry;
};
/**
* This class encapsulates the properties of a frame.
*/
class FrameProperties {
public:
FrameProperties(FramePropertyTable* aTable, nsIFrame* aFrame)
: mTable(aTable), mFrame(aFrame) {}
FrameProperties(FramePropertyTable* aTable, const nsIFrame* aFrame)
: mTable(aTable), mFrame(const_cast<nsIFrame*>(aFrame)) {}
void Set(const FramePropertyDescriptor* aProperty, void* aValue) const
{
mTable->Set(mFrame, aProperty, aValue);
}
void* Get(const FramePropertyDescriptor* aProperty,
PRBool* aFoundResult = nsnull) const
{
return mTable->Get(mFrame, aProperty, aFoundResult);
}
void* Remove(const FramePropertyDescriptor* aProperty,
PRBool* aFoundResult = nsnull) const
{
return mTable->Remove(mFrame, aProperty, aFoundResult);
}
void Delete(const FramePropertyDescriptor* aProperty)
{
mTable->Delete(mFrame, aProperty);
}
private:
FramePropertyTable* mTable;
nsIFrame* mFrame;
};
}
#endif /* FRAMEPROPERTYTABLE_H_ */