mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-10-31 22:25:30 +00:00
740 lines
26 KiB
HTML
740 lines
26 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
<html>
|
|
<head>
|
|
|
|
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
|
|
<title>Detailed Design Template</title>
|
|
</head>
|
|
<body>
|
|
|
|
<h1><font color="#cc0000">Gecko Layout Detailed Design Document</font></h1>
|
|
|
|
<h1>Space Manager Detailed Design</h1>
|
|
|
|
<h2>Overview</h2>
|
|
<p>
|
|
The Space Manager and related classes and structures are an important of
|
|
the Gecko Layout system, specifically Block Layout. See the High Level
|
|
Design document for an overview of the Space Manager, and as an introduction
|
|
to the classes, structures and algorithms container in this, the Detailed
|
|
Design Document.
|
|
</p>
|
|
|
|
|
|
|
|
<hr width="100%" size="2">
|
|
<h2>nsSpaceManager</h2>
|
|
<p>
|
|
The Space Manager is the central class is a group of classes that manage
|
|
the occupied and available space that exists in horizontal bands across
|
|
a canvas. The primary goal of the Space Manager is to provide information
|
|
about those bands of space to support the CSS notion of floated elements.
|
|
</p>
|
|
|
|
<p>
|
|
There are three important parts to the Space Manager API: the parts that
|
|
deal with the coordinate space of the Space Manager, the parts that deal with
|
|
the regions managed by the Space Manager, and the parts that manage float
|
|
impact intervals.
|
|
</p>
|
|
|
|
<p>
|
|
The class nsSpaceManager is declared in the file <a href="http://lxr.mozilla.org/seamonkey/source/layout/base/src/nsSpaceManager.h">
|
|
nsSpaceManger.h</a>
|
|
. The class is only used in the layout module and cannot be exported
|
|
outside of that module (nor does it need to be). It is not a general
|
|
purpose class, and is not intended to be subclasses<font color="#cc0000">
|
|
.</font>
|
|
</p>
|
|
|
|
<p>
|
|
Here is the class declaration, taken from the source file as of 01.08.02
|
|
</p>
|
|
|
|
|
|
|
|
<pre>/**
|
|
* Class for dealing with bands of available space. The space manager
|
|
* defines a coordinate space with an origin at (0, 0) that grows down
|
|
* and to the right.
|
|
*/
|
|
class nsSpaceManager {
|
|
public:
|
|
nsSpaceManager(nsIPresShell* aPresShell, nsIFrame* aFrame);
|
|
~nsSpaceManager();
|
|
|
|
void* operator new(size_t aSize);
|
|
void operator delete(void* aPtr, size_t aSize);
|
|
|
|
static void Shutdown();
|
|
|
|
/*
|
|
* Get the frame that's associated with the space manager. This frame
|
|
* created the space manager, and the world coordinate space is
|
|
* relative to this frame.
|
|
*
|
|
* You can use QueryInterface() on this frame to get any additional
|
|
* interfaces.
|
|
*/
|
|
nsIFrame* GetFrame() const { return mFrame; }
|
|
|
|
/**
|
|
* Translate the current origin by the specified (dx, dy). This
|
|
* creates a new local coordinate space relative to the current
|
|
* coordinate space.
|
|
*/
|
|
void Translate(nscoord aDx, nscoord aDy) { mX += aDx; mY += aDy; }
|
|
|
|
/**
|
|
* Returns the current translation from local coordinate space to
|
|
* world coordinate space. This represents the accumulated calls to
|
|
* Translate().
|
|
*/
|
|
void GetTranslation(nscoord& aX, nscoord& aY) const { aX = mX; aY = mY; }
|
|
|
|
/**
|
|
* Returns the y-most of the bottommost band or 0 if there are no bands.
|
|
*
|
|
* @return PR_TRUE if there are bands and PR_FALSE if there are no bands
|
|
*/
|
|
PRBool YMost(nscoord& aYMost) const;
|
|
|
|
/**
|
|
* Returns a band starting at the specified y-offset. The band data
|
|
* indicates which parts of the band are available, and which parts
|
|
* are unavailable
|
|
*
|
|
* The band data that is returned is in the coordinate space of the
|
|
* local coordinate system.
|
|
*
|
|
* The local coordinate space origin, the y-offset, and the max size
|
|
* describe a rectangle that's used to clip the underlying band of
|
|
* available space, i.e.
|
|
* {0, aYOffset, aMaxSize.width, aMaxSize.height} in the local
|
|
* coordinate space
|
|
*
|
|
* @param aYOffset the y-offset of where the band begins. The coordinate is
|
|
* relative to the upper-left corner of the local coordinate space
|
|
* @param aMaxSize the size to use to constrain the band data
|
|
* @param aBandData [in,out] used to return the list of trapezoids that
|
|
* describe the available space and the unavailable space
|
|
* @return NS_OK if successful and NS_ERROR_FAILURE if the band data is not
|
|
* not large enough. The 'count' member of the band data struct
|
|
* indicates how large the array of trapezoids needs to be
|
|
*/
|
|
nsresult GetBandData(nscoord aYOffset,
|
|
const nsSize& aMaxSize,
|
|
nsBandData& aBandData) const;
|
|
|
|
/**
|
|
* Add a rectangular region of unavailable space. The space is
|
|
* relative to the local coordinate system.
|
|
*
|
|
* The region is tagged with a frame
|
|
*
|
|
* @param aFrame the frame used to identify the region. Must not be NULL
|
|
* @param aUnavailableSpace the bounding rect of the unavailable space
|
|
* @return NS_OK if successful
|
|
* NS_ERROR_FAILURE if there is already a region tagged with aFrame
|
|
*/
|
|
nsresult AddRectRegion(nsIFrame* aFrame,
|
|
const nsRect& aUnavailableSpace);
|
|
|
|
/**
|
|
* Resize the rectangular region associated with aFrame by the specified
|
|
* deltas. The height change always applies to the bottom edge or the existing
|
|
* rect. You specify whether the width change applies to the left or right edge
|
|
*
|
|
* Returns NS_OK if successful, NS_ERROR_INVALID_ARG if there is no region
|
|
* tagged with aFrame
|
|
*/
|
|
enum AffectedEdge {LeftEdge, RightEdge};
|
|
nsresult ResizeRectRegion(nsIFrame* aFrame,
|
|
nscoord aDeltaWidth,
|
|
nscoord aDeltaHeight,
|
|
AffectedEdge aEdge = RightEdge);
|
|
|
|
/**
|
|
* Offset the region associated with aFrame by the specified amount.
|
|
*
|
|
* Returns NS_OK if successful, NS_ERROR_INVALID_ARG if there is no region
|
|
* tagged with aFrame
|
|
*/
|
|
nsresult OffsetRegion(nsIFrame* aFrame, nscoord dx, nscoord dy);
|
|
|
|
/**
|
|
* Remove the region associated with aFrane.
|
|
*
|
|
* Returns NS_OK if successful and NS_ERROR_INVALID_ARG if there is no region
|
|
* tagged with aFrame
|
|
*/
|
|
nsresult RemoveRegion(nsIFrame* aFrame);
|
|
|
|
/**
|
|
* Clears the list of regions representing the unavailable space.
|
|
*/
|
|
void ClearRegions();
|
|
|
|
/**
|
|
* Methods for dealing with the propagation of float damage during
|
|
* reflow.
|
|
*/
|
|
PRBool HasFloatDamage()
|
|
{
|
|
return !mFloatDamage.IsEmpty();
|
|
}
|
|
|
|
void IncludeInDamage(nscoord aIntervalBegin, nscoord aIntervalEnd)
|
|
{
|
|
mFloatDamage.IncludeInterval(aIntervalBegin + mY, aIntervalEnd + mY);
|
|
}
|
|
|
|
PRBool IntersectsDamage(nscoord aIntervalBegin, nscoord aIntervalEnd)
|
|
{
|
|
return mFloatDamage.Intersects(aIntervalBegin + mY, aIntervalEnd + mY);
|
|
}
|
|
|
|
#ifdef DEBUG
|
|
/**
|
|
* Dump the state of the spacemanager out to a file
|
|
*/
|
|
nsresult List(FILE* out);
|
|
|
|
void SizeOf(nsISizeOfHandler* aHandler, PRUint32* aResult) const;
|
|
#endif
|
|
|
|
private:
|
|
// Structure that maintains information about the region associated
|
|
// with a particular frame
|
|
struct FrameInfo {
|
|
nsIFrame* const mFrame;
|
|
nsRect mRect; // rectangular region
|
|
FrameInfo* mNext;
|
|
|
|
FrameInfo(nsIFrame* aFrame, const nsRect& aRect);
|
|
#ifdef NS_BUILD_REFCNT_LOGGING
|
|
~FrameInfo();
|
|
#endif
|
|
};
|
|
|
|
// Doubly linked list of band rects
|
|
struct BandRect : PRCListStr {
|
|
nscoord mLeft, mTop;
|
|
nscoord mRight, mBottom;
|
|
PRIntn mNumFrames; // number of frames occupying this rect
|
|
union {
|
|
nsIFrame* mFrame; // single frame occupying the space
|
|
nsVoidArray* mFrames; // list of frames occupying the space
|
|
};
|
|
|
|
BandRect(nscoord aLeft, nscoord aTop,
|
|
nscoord aRight, nscoord aBottom,
|
|
nsIFrame*);
|
|
BandRect(nscoord aLeft, nscoord aTop,
|
|
nscoord aRight, nscoord aBottom,
|
|
nsVoidArray*);
|
|
~BandRect();
|
|
|
|
// List operations
|
|
BandRect* Next() const {return (BandRect*)PR_NEXT_LINK(this);}
|
|
BandRect* Prev() const {return (BandRect*)PR_PREV_LINK(this);}
|
|
void InsertBefore(BandRect* aBandRect) {PR_INSERT_BEFORE(aBandRect, this);}
|
|
void InsertAfter(BandRect* aBandRect) {PR_INSERT_AFTER(aBandRect, this);}
|
|
void Remove() {PR_REMOVE_LINK(this);}
|
|
|
|
// Split the band rect into two vertically, with this band rect becoming
|
|
// the top part, and a new band rect being allocated and returned for the
|
|
// bottom part
|
|
//
|
|
// Does not insert the new band rect into the linked list
|
|
BandRect* SplitVertically(nscoord aBottom);
|
|
|
|
// Split the band rect into two horizontally, with this band rect becoming
|
|
// the left part, and a new band rect being allocated and returned for the
|
|
// right part
|
|
//
|
|
// Does not insert the new band rect into the linked list
|
|
BandRect* SplitHorizontally(nscoord aRight);
|
|
|
|
// Accessor functions
|
|
PRBool IsOccupiedBy(const nsIFrame*) const;
|
|
void AddFrame(const nsIFrame*);
|
|
void RemoveFrame(const nsIFrame*);
|
|
PRBool HasSameFrameList(const BandRect* aBandRect) const;
|
|
PRInt32 Length() const;
|
|
};
|
|
|
|
// Circular linked list of band rects
|
|
struct BandList : BandRect {
|
|
BandList();
|
|
|
|
// Accessors
|
|
PRBool IsEmpty() const {return PR_CLIST_IS_EMPTY((PRCListStr*)this);}
|
|
BandRect* Head() const {return (BandRect*)PR_LIST_HEAD(this);}
|
|
BandRect* Tail() const {return (BandRect*)PR_LIST_TAIL(this);}
|
|
|
|
// Operations
|
|
void Append(BandRect* aBandRect) {PR_APPEND_LINK(aBandRect, this);}
|
|
|
|
// Remove and delete all the band rects in the list
|
|
void Clear();
|
|
};
|
|
|
|
|
|
FrameInfo* GetFrameInfoFor(nsIFrame* aFrame);
|
|
FrameInfo* CreateFrameInfo(nsIFrame* aFrame, const nsRect& aRect);
|
|
void DestroyFrameInfo(FrameInfo*);
|
|
|
|
void ClearFrameInfo();
|
|
void ClearBandRects();
|
|
|
|
BandRect* GetNextBand(const BandRect* aBandRect) const;
|
|
void DivideBand(BandRect* aBand, nscoord aBottom);
|
|
PRBool CanJoinBands(BandRect* aBand, BandRect* aPrevBand);
|
|
PRBool JoinBands(BandRect* aBand, BandRect* aPrevBand);
|
|
void AddRectToBand(BandRect* aBand, BandRect* aBandRect);
|
|
void InsertBandRect(BandRect* aBandRect);
|
|
|
|
nsresult GetBandAvailableSpace(const BandRect* aBand,
|
|
nscoord aY,
|
|
const nsSize& aMaxSize,
|
|
nsBandData& aAvailableSpace) const;
|
|
|
|
nsIFrame* const mFrame; // frame associated with the space manager
|
|
nscoord mX, mY; // translation from local to global coordinate space
|
|
BandList mBandList; // header/sentinel for circular linked list of band rects
|
|
FrameInfo* mFrameInfoMap;
|
|
nsIntervalSet mFloatDamage;
|
|
|
|
static PRInt32 sCachedSpaceManagerCount;
|
|
static void* sCachedSpaceManagers[NS_SPACE_MANAGER_CACHE_SIZE];
|
|
|
|
nsSpaceManager(const nsSpaceManager&); // no implementation
|
|
void operator=(const nsSpaceManager&); // no implementation
|
|
};
|
|
|
|
</pre>
|
|
|
|
<h3>Public API</h3>
|
|
|
|
<h4>Life Cycle:</h4>
|
|
<p>
|
|
The Constructor requires a Presentation Shell, used for arena allocations
|
|
mostly, and a frame that this Space Manager is rooted on. The coordinate
|
|
space of this Space Manager is relative to the frame passed in to the constructor.
|
|
</p>
|
|
|
|
<pre> nsSpaceManager(nsIPresShell* aPresShell, nsIFrame* aFrame);
|
|
~nsSpaceManager();
|
|
</pre>
|
|
<p>
|
|
Operators 'new' and 'delete' are overridden to support a recycler. Space
|
|
Manager instances come and go pretty frequently, and this recycler prevents
|
|
excessive heap allocations and the performance penalties associated with
|
|
it. The #define NS_SPACE_MANAGER_CACHE_SIZE is used to control the number
|
|
of Space Manager instances that can be present in the recycler, currently
|
|
4. If more than NS_SPACE_MANAGER_CACHE_SIZE are allocated at a time,
|
|
then standard allocation is used.
|
|
</p>
|
|
|
|
<pre>
|
|
void* operator new(size_t aSize);
|
|
void operator delete(void* aPtr, size_t aSize);
|
|
|
|
</pre>
|
|
<p>
|
|
A Static method is used to shutdown the Space Manager recycling. This
|
|
method deletes all of the Space Mangers inthe recycler,and prevents further
|
|
recycling. It is meant to be called only when the layout module is being
|
|
terminated.
|
|
</p>
|
|
|
|
<pre> static void Shutdown();
|
|
|
|
</pre>
|
|
|
|
<h4>Origin / Coordinate Space Translation</h4>
|
|
|
|
<pre> /**
|
|
* Translate the current origin by the specified (dx, dy). This
|
|
* creates a new local coordinate space relative to the current
|
|
* coordinate space.
|
|
*/
|
|
void Translate(nscoord aDx, nscoord aDy) { mX += aDx; mY += aDy; }
|
|
|
|
/**
|
|
* Returns the current translation from local coordinate space to
|
|
* world coordinate space. This represents the accumulated calls to
|
|
* Translate().
|
|
*/
|
|
void GetTranslation(nscoord& aX, nscoord& aY) const { aX = mX; aY = mY; }
|
|
|
|
/**
|
|
* Returns the y-most of the bottommost band or 0 if there are no bands.
|
|
*
|
|
* @return PR_TRUE if there are bands and PR_FALSE if there are no bands
|
|
*/
|
|
PRBool YMost(nscoord& aYMost) const;
|
|
</pre>
|
|
|
|
<h4>Region Management</h4>
|
|
|
|
<pre> /**
|
|
* Returns a band starting at the specified y-offset. The band data
|
|
* indicates which parts of the band are available, and which parts
|
|
* are unavailable
|
|
*
|
|
* The band data that is returned is in the coordinate space of the
|
|
* local coordinate system.
|
|
*
|
|
* The local coordinate space origin, the y-offset, and the max size
|
|
* describe a rectangle that's used to clip the underlying band of
|
|
* available space, i.e.
|
|
* {0, aYOffset, aMaxSize.width, aMaxSize.height} in the local
|
|
* coordinate space
|
|
*
|
|
* @param aYOffset the y-offset of where the band begins. The coordinate is
|
|
* relative to the upper-left corner of the local coordinate space
|
|
* @param aMaxSize the size to use to constrain the band data
|
|
* @param aBandData [in,out] used to return the list of trapezoids that
|
|
* describe the available space and the unavailable space
|
|
* @return NS_OK if successful and NS_ERROR_FAILURE if the band data is not
|
|
* not large enough. The 'count' member of the band data struct
|
|
* indicates how large the array of trapezoids needs to be
|
|
*/
|
|
nsresult GetBandData(nscoord aYOffset,
|
|
const nsSize& aMaxSize,
|
|
nsBandData& aBandData) const;
|
|
|
|
/**
|
|
* Add a rectangular region of unavailable space. The space is
|
|
* relative to the local coordinate system.
|
|
*
|
|
* The region is tagged with a frame
|
|
*
|
|
* @param aFrame the frame used to identify the region. Must not be NULL
|
|
* @param aUnavailableSpace the bounding rect of the unavailable space
|
|
* @return NS_OK if successful
|
|
* NS_ERROR_FAILURE if there is already a region tagged with aFrame
|
|
*/
|
|
nsresult AddRectRegion(nsIFrame* aFrame,
|
|
const nsRect& aUnavailableSpace);
|
|
|
|
/**
|
|
* Resize the rectangular region associated with aFrame by the specified
|
|
* deltas. The height change always applies to the bottom edge or the existing
|
|
* rect. You specify whether the width change applies to the left or right edge
|
|
*
|
|
* Returns NS_OK if successful, NS_ERROR_INVALID_ARG if there is no region
|
|
* tagged with aFrame
|
|
*/
|
|
enum AffectedEdge {LeftEdge, RightEdge};
|
|
nsresult ResizeRectRegion(nsIFrame* aFrame,
|
|
nscoord aDeltaWidth,
|
|
nscoord aDeltaHeight,
|
|
AffectedEdge aEdge = RightEdge);
|
|
|
|
/**
|
|
* Offset the region associated with aFrame by the specified amount.
|
|
*
|
|
* Returns NS_OK if successful, NS_ERROR_INVALID_ARG if there is no region
|
|
* tagged with aFrame
|
|
*/
|
|
nsresult OffsetRegion(nsIFrame* aFrame, nscoord dx, nscoord dy);
|
|
|
|
/**
|
|
* Remove the region associated with aFrane.
|
|
*
|
|
* Returns NS_OK if successful and NS_ERROR_INVALID_ARG if there is no region
|
|
* tagged with aFrame
|
|
*/
|
|
nsresult RemoveRegion(nsIFrame* aFrame);
|
|
|
|
/**
|
|
* Clears the list of regions representing the unavailable space.
|
|
*/
|
|
void ClearRegions();
|
|
</pre>
|
|
|
|
<h4>Float Impact</h4>
|
|
|
|
<pre> /**
|
|
* Methods for dealing with the propagation of float damage during
|
|
* reflow.
|
|
*/
|
|
PRBool HasFloatDamage()
|
|
{
|
|
return !mFloatDamage.IsEmpty();
|
|
}
|
|
|
|
void IncludeInDamage(nscoord aIntervalBegin, nscoord aIntervalEnd)
|
|
{
|
|
mFloatDamage.IncludeInterval(aIntervalBegin + mY, aIntervalEnd + mY);
|
|
}
|
|
|
|
PRBool IntersectsDamage(nscoord aIntervalBegin, nscoord aIntervalEnd)
|
|
{
|
|
return mFloatDamage.Intersects(aIntervalBegin + mY, aIntervalEnd + mY);
|
|
}
|
|
</pre>
|
|
|
|
<h4>Debug Only Methods</h4>
|
|
|
|
<pre> /**
|
|
* Dump the state of the spacemanager out to a file
|
|
*/
|
|
nsresult List(FILE* out);
|
|
|
|
void SizeOf(nsISizeOfHandler* aHandler, PRUint32* aResult) const;
|
|
|
|
</pre>
|
|
|
|
<h4>Unused / Obsolete Methods</h4>
|
|
|
|
<pre> /*
|
|
* Get the frame that's associated with the space manager. This frame
|
|
* created the space manager, and the world coordinate space is
|
|
* relative to this frame.
|
|
*
|
|
* You can use QueryInterface() on this frame to get any additional
|
|
* interfaces.
|
|
*/
|
|
nsIFrame* GetFrame() const { return mFrame; }
|
|
|
|
</pre>
|
|
|
|
<h3>Implementation Notes</h3>
|
|
|
|
<h4></h4>
|
|
|
|
<h4>Algorithm 1: GetBandData</h4>
|
|
<p>
|
|
GetBandData is used to provide information to clients about what space if
|
|
available and unavailable in a band of space. The client provides a
|
|
vertical offset, the yOffset, that corresponds to the band that is of interest.
|
|
This will be the y offset of the frame that is being reflowed. The
|
|
caller also provides a collection of BandData objects (an array) and the
|
|
number of items that the collection can handle. If the collection is
|
|
too small, then an error is returned and the count is updated to indicate
|
|
the size required.
|
|
</p>
|
|
|
|
<p>
|
|
The algorithm to provide the band data is as follows:
|
|
</p>
|
|
<ul>
|
|
<li>Get a vertical offset in world coordinates (instead of frame-relative
|
|
coordinates) by adding the y-origin of the SpaceManager to the y offset passed
|
|
in</li>
|
|
<li>If the (adjusted) y value passed in is greater than the greatest band
|
|
being managed, then all space is available so a single trapezoid is returned,
|
|
marked as available and sized to the maximum size value (passed in).</li>
|
|
<li>If the (adjusted) y offset intersects a band, then gather the band
|
|
data:</li>
|
|
<ul>
|
|
<li>walk the internal bandData list from head to tail</li>
|
|
<li>for each band data entry, see if the top of the band is greater than
|
|
the (adjusted) y offset requested</li>
|
|
<li>if it is, then band is below the offset requested, so the area between
|
|
the band and the y offset is available - create a trapezoid with that region
|
|
and return it.</li>
|
|
<li>if the (adjusted) y offset is between the band top and bottom, then
|
|
get the available space for the band by calling GetBandAvailableSpace</li>
|
|
<li>otherwise, move to the next band</li>
|
|
</ul>
|
|
</ul>
|
|
<h5>GetBandAvailableSpace:</h5>
|
|
This method is called from GetBandData only. It walks all of the bands in
|
|
the space manager and determines which bands intersect with the band passed
|
|
in, and if within those bands there are regions that are available or occupied.
|
|
|
|
<ul>
|
|
<li>First, walk all of the bands until a band that is to the right of the
|
|
desired offset is located</li>
|
|
<li>Starting at that band, walk the remaining bands:</li>
|
|
<ul>
|
|
<li>if the current band is to the right of the requested band, then there
|
|
is available space. </li>
|
|
<ul>
|
|
<li>if there is more room in the bandData collection, then add a trapezoid
|
|
to the bandData collection such that it is marked as available and has a
|
|
rect that represents the space between the reference band tna dht band being
|
|
examined</li>
|
|
<li>if there is no more room in the BandData collection, estimate the
|
|
number of entries requires as the current count + twice the number of bands
|
|
below the reference band, plus two. Return an error code so the caller
|
|
can reallocate the collection and try again.</li>
|
|
</ul>
|
|
<li>check the size of the collection again, if there is no room left
|
|
then estimate the number of items requires as the current count + twice the
|
|
number of bands below the band in question plus one. </li>
|
|
<li>create a new trapezoid in the band collection that has a region corresponding
|
|
to the reference band rect, marked as occupied by either a single or multiple
|
|
frames.</li>
|
|
<li>move to the next band</li>
|
|
</ul>
|
|
<li>after walking all of the band data, se if we have reached the right
|
|
edge of the band. </li>
|
|
<ul>
|
|
<li>If not, then check for space in the band collection</li>
|
|
<ul>
|
|
<li>if there is no room left, then set the count to the current count
|
|
plus 1 and return an error.</li>
|
|
<li>otherwise, create another entry in the band collection, marked
|
|
as available, and with a rect corresponding to the area remainin in the band
|
|
(eg. from the right edge of the last band rect to the right edge of the band).</li>
|
|
</ul>
|
|
</ul>
|
|
</ul>
|
|
|
|
<h4>Algorithm 2: AddRectRegion</h4>
|
|
Clients call into this method to notify the Space Manager that a new frame
|
|
is occupying some space.
|
|
|
|
<ul>
|
|
<li>First, try to get frame info for the frame. If it is found, return
|
|
an error since the frame is already associated with a region in the Space
|
|
Manager.</li>
|
|
<li>Next, create a rect from the occupied space passed in by the caller,
|
|
transforming it first to world-coordinates by adding the Space Manager's
|
|
offset to the occupied space rect passed in.</li>
|
|
<li>Create a new Frame Info instance for the frame and rect, returning
|
|
an error if allocation fails.</li>
|
|
<li>Check if the occupied space rect (adjusted) is empty, if so, return
|
|
an error (<font color="#cc0000">NOTE: this could be done earlier, or
|
|
prevented by the caller</font>)</li>
|
|
<li>Allocate a new BandRect instance with the rect and frame as constructor
|
|
arguments, and insert it into the collection via InsertBandRect</li>
|
|
</ul>
|
|
<h5>InsertBandRect:</h5>
|
|
Internal method to insert a band rect into the BandList in the correct location.
|
|
There are several cases it has to handle, as specified in the source file
|
|
comments:
|
|
|
|
<pre>// When comparing a rect to a band there are seven cases to consider.
|
|
// 'R' is the rect and 'B' is the band.
|
|
//
|
|
// Case 1 Case 2 Case 3 Case 4
|
|
// ------ ------ ------ ------
|
|
// +-----+ +-----+ +-----+ +-----+
|
|
// | R | | R | +-----+ +-----+ | | | |
|
|
// +-----+ +-----+ | | | R | | B | | B |
|
|
// +-----+ | B | +-----+ | | +-----+ | |
|
|
// | | | | +-----+ | R | +-----+
|
|
// | B | +-----+ +-----+
|
|
// | |
|
|
// +-----+
|
|
//
|
|
//
|
|
//
|
|
// Case 5 Case 6 Case 7
|
|
// ------ ------ ------
|
|
// +-----+ +-----+ +-----+ +-----+
|
|
// | | | R | | B | | | +-----+
|
|
// | B | +-----+ +-----+ | R | | B |
|
|
// | | | | +-----+
|
|
// +-----+ +-----+
|
|
// +-----+
|
|
// | R |
|
|
// +-----+
|
|
//
|
|
</pre>
|
|
<ul>
|
|
<li>First, check for the easiest case, where there are no existing band
|
|
rects, or the band rect passed in is below the bottommost rect. In this case,
|
|
just append the band rect and return.</li>
|
|
<li>Starting at the head of the list of bandRects, check for intersection
|
|
with the rect passed in:</li>
|
|
<ul>
|
|
<li>case #1: the rect is totally above the current band rect, so insert
|
|
a new band rect before the current bandRect</li>
|
|
<li>cases #2 and #7: the rect is partially above the band rect, so it
|
|
is divided into two bandRects, one entirely above the band, and one containing
|
|
the remainder of the rect. Insert the part that is totally above the
|
|
bandRect before the current bandRect, as in case #1 above, and adjust the
|
|
other band rect to exclude the part already added.</li>
|
|
<li>case #5: the rect is totally below the current bandRect, so just
|
|
skip to the next band</li>
|
|
<li>case #3 and #4: rect is at least partially intersection with the
|
|
bandRect, so divide the current band into two parts, where the top part is
|
|
above the current rect. Move to the new band just created, which is
|
|
the next band.</li>
|
|
<li>case #6: the rect shares the bottom and height with the bandRect,
|
|
so just add the rect to the band.</li>
|
|
<li>case #4 and #7: create a new rect for the part that overlaps the
|
|
bandRect, and add it to the current bandRect (similar to case #6) and then
|
|
move on to the next band, removing that part from the rect passed in. If
|
|
no more bands, append the rect passed in to the end of the bandRect list.</li>
|
|
</ul>
|
|
</ul>
|
|
<i>This algorithm is pretty confusing - basically what needs to happen is
|
|
that rects and bands need to be divided up so that complicated cases like
|
|
#2, #4, and #7, are reduced to simpler cases where the rects is totally above,
|
|
below, or between a band rect. From the current implementation, it
|
|
might be worth verifying that the final result of the inserts is a correctly
|
|
ordered liest of bandRects (debug mode only).</i>
|
|
|
|
|
|
<h4>Algorithm 3: RemoveRegion</h4>
|
|
When a float is removed, the Space Manager is notified by a call to RemoveRegion,
|
|
passing in the frame that is being removed.
|
|
|
|
<ul>
|
|
<li>Get the FrameInfo for the frame passed in. If not found, an error is
|
|
returned.</li>
|
|
<li>If the rect for the frame is not empty, then visit each band in the
|
|
bandList:</li>
|
|
<ul>
|
|
<li>for each rect in the band:
|
|
|
|
</li>
|
|
</ul>
|
|
<ul>
|
|
<ul>
|
|
<li>if the bandRect is occupied by the frame, either remove the frame
|
|
from the bandRect (if there are other frames sharing it) and remember that
|
|
it was shared</li>
|
|
<li>otherwise simply remove the bandRect (no other frames share it).</li>
|
|
<li>if the bandRect was shared, then try to coalesce adjacent bandRects</li>
|
|
<ul>
|
|
<li>if the previous bandRect is directly next to the current bandRect,
|
|
and they have the same frame list, then make the current bandRect cover the
|
|
previous bandRect's full region (adjust the left edge to be that of the previous
|
|
bandRect) and remove the previous bandRect.</li>
|
|
</ul>
|
|
</ul>
|
|
</ul>
|
|
<ul>
|
|
<li>if the current band or prior band had a rect occupied byu the frame,
|
|
then try to join the two bands via JoinBands</li>
|
|
</ul>
|
|
<li>Finally, destroy the frameInfo for the frame.
|
|
|
|
</li>
|
|
</ul>
|
|
|
|
<br>
|
|
|
|
<hr width="100%" size="2">
|
|
<h2>Cross-Component Algorithms</h2>
|
|
|
|
<br>
|
|
|
|
|
|
|
|
<hr width="100%" size="2">
|
|
<h2>Tech Notes</h2>
|
|
<ul>
|
|
<li>
|
|
|
|
</li>
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|