OverrideList Class Reference

An override list contains items that can override each other. More...

#include <overlist.h>

Inheritance diagram for OverrideList:

List of all members.

Public Member Functions
	OverrideList ()
	Default constructor.
virtual void	AddHead (OverrideListItem *)
	Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them.
virtual void	AddTail (OverrideListItem *)
	Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them.
virtual LISTPOS	InsertBefore (LISTPOS here, OverrideListItem *item)
	Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them.
virtual ListItem *	InsertBefore (OverrideListItem *here, OverrideListItem *item)
	Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them.
virtual LISTPOS	InsertAfter (LISTPOS here, OverrideListItem *item)
	Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them.
virtual ListItem *	InsertAfter (OverrideListItem *here, OverrideListItem *item)
	Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them.
Protected Member Functions
virtual BOOL	CompareWithItemsAbove (OverrideListItem *pliStartPos, OverrideListItem *pliToInsert)
	Compares this list item with all the items above pliStartPos, inclusive.
virtual BOOL	CompareWithItemsBelow (OverrideListItem *pliStartPos, OverrideListItem *pliToInsert)
	Compares this list item with all the items below pliStartPos, inclusive.

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Detailed Description

An override list contains items that can override each other.

Author:

Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com>

Date:

21/4/97

For example, imagine we are building a list of clickable areas in an imagemap. Our list of clickable areas already contains a rectangle with bottom left corner (0,0) and top right corner (200, 200), that links to the URL "http://www.xara.com".

Now we add another clickable rectangle to the imagemap. This rectangle has bottom left corner (50,50) and top right corner (100,100) and also links to "http://www.xara.com".

But our first rectangle is contained within our second rectangle! There is no need for the second rectangle at all.

It is clear that the first rectangle overrides the second, so the second rectangle should not be added to the list.

Now imagine the small rectangle is already in the list and the large rectangle is added.

Again, the large rectangle overrides the small one. So the large rectangle should be added to the list and the smaller rectangle should be deleted.

So, this class works as follows.

When an OverrideListItem is added to this list, this function compares the item with every other item in the list.

It does this by calling either the function OverrideListItem::OverrideFromAbove (if the item in the list is before the item being added) or OverrideListItem::OverrideFromBelow(if the item in the list is below the item being added).

Then:

a. If an item in the list overrides the item being added, then the new item is not added to the list.

b. If the item being added overrides an item in the list, then the new item is added and the item in the list is deleted.

Definition at line 156 of file overlist.h.

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Constructor & Destructor Documentation

OverrideList::OverrideList (   )

Default constructor. OverrideList::OverrideList() Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Definition at line 118 of file overlist.cpp. : List() { }

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Member Function Documentation

void OverrideList::AddHead (  OverrideListItem *  poliToAdd  )  [virtual]

Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them. virtual void OverrideList::AddHead( OverrideListItem* poliToAdd) Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Parameters: poliToAdd  The item to add [INPUTS] Returns: - If this list item overrides any items already present in the list, the items in the list are deleted and this list item is added. If any item in the list overrides this list item, this list item is not added to the list. This function simply calls the InsertBefore function. See also: OverrideList::InsertBefore() Definition at line 149 of file overlist.cpp. { if (poliToAdd==NULL) { ERROR2RAW("OverrideList::AddHead - NULL parameter"); return; } //Get the first item in the list OverrideListItem* pliFirst=(OverrideListItem*) GetHead(); //Was there anything in the list? if (pliFirst!=NULL) { //Yes. So call our InsertBefore function InsertBefore(pliFirst, poliToAdd); } else { //No. So we need do no special checking - simply insert //the list item List::AddHead(poliToAdd); } }

void OverrideList::AddTail (  OverrideListItem *  poliToAdd  )  [virtual]

Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them. virtual void OverrideList::AddTail( OverrideListItem* poliToAdd) Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Parameters: poliToAdd  The item to add [INPUTS] Returns: - If this list item overrides any items already present in the list, the items in the list are deleted and this list item is added. If any item in the list overrides this list item, this list item is not added to the list. This function simply calls the InsertAfter function. See also: OverrideList::InsertAfter() Definition at line 202 of file overlist.cpp. { if (poliToAdd==NULL) { ERROR2RAW("OverrideList::AddTail - NULL parameter"); return; } //Get the last item in the list OverrideListItem* pliLast=(OverrideListItem*) GetTail(); //Was there anything in the list? if (pliLast!=NULL) { //Yes. So call our InsertAfter function InsertAfter(pliLast, poliToAdd); } else { //No. So we need do no special checking - simply insert //the list item List::AddTail(poliToAdd); } //And add our item after it InsertAfter(pliLast, poliToAdd); }

BOOL OverrideList::CompareWithItemsAbove (  OverrideListItem *  pliStartPos, OverrideListItem *  pliToInsert )  [protected, virtual]

Compares this list item with all the items above pliStartPos, inclusive. virtual BOOL OverrideList::CompareWithItemsAbove(OverrideListItem* pliStartPos, OverrideListItem* pliToInsert); Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Parameters: pliStartPos  The position to start searching from [INPUTS] pliToAdd The list items to add Returns: FALSE if pliToAdd was overridden by another item in the list TRUE if pliToAdd was not overridden Note that, if pliToAdd overrides another item in the list, this does not affect the result returned. See also: OverrideList::InsertBefore(), OverrideList::After() Definition at line 479 of file overlist.cpp. { //This pointer will show the item we are looking at OverrideListItem* pliLook=pliStartPos; //While we are still looking at a valid item while (pliLook!=NULL) { //This will be the next item we look at //It's important to do this now - because we may delete pliLook in a moment OverrideListItem* pliNext=(OverrideListItem*) GetPrev(pliLook); //Does the item we are looking at override the item //we are about to insert? if (pliLook->OverrideFromAbove(pliToInsert)) { //Yes. So return to say that we're not going to insert the //item return FALSE; } //Does the item we are about to insert override the item //we are looking at? if (pliToInsert->OverrideFromBelow(pliLook)) { //Yes. So delete the item we are looking at. RemoveItem(pliLook); delete pliLook; } //And move on to the next item pliLook=pliNext; } //ANd return to say that pliToInsert has not been overridden return TRUE; }

BOOL OverrideList::CompareWithItemsBelow (  OverrideListItem *  pliStartPos, OverrideListItem *  pliToInsert )  [protected, virtual]

Compares this list item with all the items below pliStartPos, inclusive. virtual BOOL OverrideList::CompareWithItemsBelow(OverrideListItem* pliStartPos, OverrideListItem* pliToInsert) Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Parameters: pliStartPos  The position to start searching from [INPUTS] pliToAdd The list items to add Returns: FALSE if pliToAdd was overridden by another item in the list TRUE if pliToAdd was not overridden Note that, if pliToAdd overrides another item in the list, this does not affect the result returned. See also: OverrideList::InsertBefore(), OverrideList::After() Definition at line 541 of file overlist.cpp. { //This pointer will show the item we are looking at OverrideListItem* pliLook=pliStartPos; //While we are still looking at a valid item while (pliLook!=NULL) { //This will be the next item we look at //It's important to do this now - because we may delete pliLook in a moment OverrideListItem* pliNext=(OverrideListItem*) GetNext(pliLook); //Does the item we are looking at override the item //we are about to insert? if (pliLook->OverrideFromBelow(pliToInsert)) { //Yes. So return to say that we're not going to insert the //item return FALSE; } //Does the item we are about to insert override the item //we are looking at? if (pliToInsert->OverrideFromAbove(pliLook)) { //Yes. So delete the item we are looking at. RemoveItem(pliLook); delete pliLook; } //And move on to the next item pliLook=pliNext; } //And return to say that pliToInsert has not been overridden return TRUE; }

ListItem * OverrideList::InsertAfter (  OverrideListItem *  pliInsertPoint, OverrideListItem *  pliToInsert )  [virtual]

Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them. virtual ListItem* OverrideList::InsertAfter(OverrideListItem* here, OverrideListItem* item); Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Parameters: poliToAdd  The item to add [INPUTS] Returns: - It does this by calling the function MergeListItem::OverrideFromBelow on all items below the insertion position, and MergeListItem::OverrideFromAbove on all items above the insertion position. If this list item overrides any items already present in the list, the items in the list are deleted and this list item is added. If any item in the list overrides this list item, this list item is not added to the list. This function simply calls the InsertBefore function. See also: OverrideList::InsertBefore() Definition at line 372 of file overlist.cpp. { ERROR2IF(pliToInsert==NULL, NULL, "OverrideList::InsertAfter - NULL parameter"); //This variable will tell us whether to insert pliToInsert //into the list BOOL fInsert=TRUE; //First compare pliToInsert with everything above pliInsertPoint in the list fInsert=CompareWithItemsAbove(pliInsertPoint, pliToInsert); //Now get the list item after pliInsertPoint OverrideListItem* pliTest=(OverrideListItem*) GetNext(pliInsertPoint); //If there is anything before pliInsertPoint if (fInsert && pliTest!=NULL) { //Then test everything before pliInsertPoint fInsert=CompareWithItemsBelow(pliInsertPoint, pliToInsert); } //So, should we insert pliToInsert? if (fInsert) //Yes. So do it. return List::InsertAfter(pliInsertPoint, pliToInsert); else //No. So return an error value. return NULL; }

LISTPOS OverrideList::InsertAfter (  LISTPOS  here, OverrideListItem *  item )  [virtual]

Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them. virtual ListItem* OverrideList::InsertAfter(OverrideListItem* here, OverrideListItem* item); Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Parameters: poliToAdd  The item to add [INPUTS] Returns: - This function simply calls the other InsertAfter override. See also: OverrideList::InsertAfter() Definition at line 425 of file overlist.cpp. { ERROR2IF(item==NULL, 0, "OverrideList::InsertAfter - NULL parameter"); //First find the list item at the position we have been given OverrideListItem* pliInsertionPoint=(OverrideListItem*) FindItem(here); //If we have not found it, return -1 if (pliInsertionPoint==NULL) return -1; //Otherwise, call our other function to do the insertion OverrideListItem* pliResult=(OverrideListItem*) InsertAfter(pliInsertionPoint, item); //If we have been returned NULL, then return an error value if (pliResult==NULL) return -1; //Otherwise, find our newly returned list item in the list //and return it return FindPosition(pliResult); }

ListItem * OverrideList::InsertBefore (  OverrideListItem *  pliInsertPoint, OverrideListItem *  pliToInsert )  [virtual]

Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them. virtual ListItem* OverrideList::InsertBefore(OverrideListItem* here, OverrideListItem* item); Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Parameters: poliToAdd  The item to add [INPUTS] Returns: - It does this by calling the function OverrideListItem::OverrideFromBelow on all items below the insertion position, and MergeListItem::OverrideFromAbove on all items above the insertion position. If this list item overrides any items already present in the list, the items in the list are deleted and this list item is added. If any item in the list overrides this list item, this list item is not added to the list. This function simply calls the InsertBefore function. See also: OverrideList::InsertBefore() Definition at line 263 of file overlist.cpp. { ERROR2IF(pliToInsert==NULL, NULL, "OverrideList::InsertBefore - NULL parameter"); //This variable will tell us whether to insert pliToInsert //into the list BOOL fInsert=TRUE; //First compare pliToInsert with everything below pliInsertPoint in the list fInsert=CompareWithItemsBelow(pliInsertPoint, pliToInsert); //Now get the list item above pliInsertPoint OverrideListItem* pliTest=(OverrideListItem*) GetPrev(pliInsertPoint); //If there is anything above pliInsertPoint if (fInsert && pliTest!=NULL) { //Then test everything above pliInsertPoint fInsert=CompareWithItemsAbove(pliInsertPoint, pliToInsert); } //So, should we insert pliToInsert? if (fInsert) //Yes. So do it. return List::InsertBefore(pliInsertPoint, pliToInsert); else //No. So return an error value. return NULL; }

LISTPOS OverrideList::InsertBefore (  LISTPOS  here, OverrideListItem *  item )  [virtual]

Compares this list item with all the items in the list, to find out whether they override this list item or whether this list item overrides them. virtual ListItem* OverrideList::InsertBefore(OverrideListItem* here, OverrideListItem* item); Author: Graham_Walmsley (Xara Group Ltd) <camelotdev@xara.com> Date: 22/4/97 Parameters: poliToAdd  The item to add [INPUTS] Returns: - This function simply calls the other InsertBefore override. See also: OverrideList::InsertBefore() Definition at line 314 of file overlist.cpp. { ERROR2IF(item==NULL, NULL, "OverrideList::InsertBefore - NULL parameter"); //First find the list item at the position we have been given OverrideListItem* pliInsertionPoint=(OverrideListItem*) FindItem(here); //If we have not found it, return -1 if (pliInsertionPoint==NULL) return -1; //Otherwise, call our other function to do the insertion OverrideListItem* pliResult=(OverrideListItem*) InsertBefore(pliInsertionPoint, item); //If we have been returned NULL, then return an error value if (pliResult==NULL) return -1; //Otherwise, find our newly returned list item in the list //and return it return FindPosition(pliResult); }

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The documentation for this class was generated from the following files:

• Kernel/overlist.h (r1785/r1282)
• Kernel/overlist.cpp (r1785/r1282)

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