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