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///////////////////////////////////////////////////////////////////////////////
// Name: wx/private/rowheightcache.h
// Purpose: height cache of rows in a dataview
// Author: Jens Goepfert (mail@jensgoepfert.de)
// Created: 2018-03-06
// Copyright: (c) wxWidgets team
// Licence: wxWindows licence
///////////////////////////////////////////////////////////////////////////////
#ifndef _WX_PRIVATE_ROWHEIGHTCACHE_H_
#define _WX_PRIVATE_ROWHEIGHTCACHE_H_
#include "wx/hashmap.h"
#include "wx/vector.h"
// struct describing a range of rows which contains rows <from> .. <to-1>
struct RowRange
{
unsigned int from;
unsigned int to;
};
/**
A helper class that manages a set of RowRange objects.
It stores the indices that are members of a group in a memory
efficient way.
*/
class WXDLLIMPEXP_CORE RowRanges
{
public:
/**
Adds a row index to this group by adding it to an existing RowRange
or by creating a new one.
*/
void Add(unsigned int row);
/**
Removes a row index and all indices after idx from this group.
*/
void Remove(unsigned int row);
/**
Checks whether a row index is contained in this group.
*/
bool Has(unsigned int row) const;
/**
Returns the number of row indices that are contained in this group.
*/
unsigned int CountAll() const;
/**
Returns the number of rows that are in this group before the given row
index.
Not that this doesn't include the given row.
*/
unsigned int CountTo(unsigned int row) const;
/**
Returns the size of the range.
This is only used for testing and debugging.
*/
unsigned int GetSize() const { return m_ranges.size(); }
private:
wxVector<RowRange> m_ranges;
/**
If a new row index was inserted, Cleanup() checks if the neighbour
ranges of idx can includes the same row indices and discards
unnecessary RowRange objects.
*/
void CleanUp(unsigned int idx);
};
WX_DECLARE_HASH_MAP(unsigned int, RowRanges*, wxIntegerHash, wxIntegerEqual,
HeightToRowRangesMap);
/**
HeightCache implements a cache mechanism for wxDataViewCtrl.
It gives fast access to:
* the height of one line (GetLineHeight)
* the y-coordinate where a row starts (GetLineStart)
* and vice versa (GetLineAt)
The layout of the cache is a hashmap where the keys are all existing row
heights in pixels. The values are RowRange objects that represent all rows
having the specified height.
An example:
@code
{
22: RowRange([0..10], [15..17], [20..2000]),
42: RowRange([11..12], [18..18]),
62: RowRange([13..14], [19..19])
}
@endcode
Examples
========
GetLineStart
------------
To retrieve the y-coordinate of item 1000 it is necessary to look into
each key of the hashmap *m_heightToRowRange*. Get the row count of
indices lower than 1000 (RowRange::CountTo) and multiplies it which the
according height.
RowRange([0..10], [15..17], [20..2000]).CountTo(1000)
--> 0..10 are 11 items, 15..17 are 3 items and 20..1000 are 980 items (1000-20)
= 11 + 3 + 980 = 994 items
GetLineStart(1000) --> (22 * 994) + (42 * 3) + (62 * 3) = 22180
GetLineHeight
-------------
To retrieve the line height look into each key and check if row is
contained in RowRange (RowRange::Has)
GetLineAt
---------
To retrieve the row that starts at a specific y-coordinate.
Look into each key and count all rows.
Use bisect algorithm in combination with GetLineStart() to
find the appropriate item
*/
class WXDLLIMPEXP_CORE HeightCache
{
public:
~HeightCache();
bool GetLineStart(unsigned int row, int& start);
bool GetLineHeight(unsigned int row, int& height);
bool GetLineAt(int y, unsigned int& row);
bool GetLineInfo(unsigned int row, int &start, int &height);
void Put(unsigned int row, int height);
/**
Removes the stored height of the given row from the cache and
invalidates all cached rows (including the given one).
*/
void Remove(unsigned int row);
void Clear();
private:
HeightToRowRangesMap m_heightToRowRange;
};
#endif // _WX_PRIVATE_ROWHEIGHTCACHE_H_
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