124 lines
4.2 KiB
C++
124 lines
4.2 KiB
C++
/////////////////////////////////////////////////////////////////////////////
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// Name: wx/generic/private/widthcalc.h
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// Purpose: wxMaxWidthCalculatorBase helper class.
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// Author: Václav Slavík, Kinaou Hervé
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// Copyright: (c) 2015 wxWidgets team
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// Licence: wxWindows licence
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/////////////////////////////////////////////////////////////////////////////
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#ifndef _WX_GENERIC_PRIVATE_WIDTHCALC_H_
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#define _WX_GENERIC_PRIVATE_WIDTHCALC_H_
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#include "wx/defs.h"
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#if wxUSE_DATAVIEWCTRL || wxUSE_LISTCTRL
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#include "wx/log.h"
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#include "wx/timer.h"
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// ----------------------------------------------------------------------------
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// wxMaxWidthCalculatorBase: base class for calculating max column width
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// ----------------------------------------------------------------------------
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class wxMaxWidthCalculatorBase
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{
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public:
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// column of which calculate the width
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explicit wxMaxWidthCalculatorBase(size_t column)
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: m_column(column),
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m_width(0)
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{
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}
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void UpdateWithWidth(int width)
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{
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m_width = wxMax(m_width, width);
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}
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// Update the max with for the expected row
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virtual void UpdateWithRow(int row) = 0;
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int GetMaxWidth() const { return m_width; }
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size_t GetColumn() const { return m_column; }
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void
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ComputeBestColumnWidth(size_t count,
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size_t first_visible,
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size_t last_visible)
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{
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// The code below deserves some explanation. For very large controls, we
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// simply can't afford to calculate sizes for all items, it takes too
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// long. So the best we can do is to check the first and the last N/2
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// items in the control for some sufficiently large N and calculate best
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// sizes from that. That can result in the calculated best width being too
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// small for some outliers, but it's better to get slightly imperfect
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// result than to wait several seconds after every update. To avoid highly
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// visible miscalculations, we also include all currently visible items
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// no matter what. Finally, the value of N is determined dynamically by
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// measuring how much time we spent on the determining item widths so far.
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#if wxUSE_STOPWATCH
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size_t top_part_end = count;
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static const long CALC_TIMEOUT = 20/*ms*/;
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// don't call wxStopWatch::Time() too often
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static const unsigned CALC_CHECK_FREQ = 100;
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wxStopWatch timer;
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#else
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// use some hard-coded limit, that's the best we can do without timer
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size_t top_part_end = wxMin(500, count);
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#endif // wxUSE_STOPWATCH/!wxUSE_STOPWATCH
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size_t row = 0;
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for ( row = 0; row < top_part_end; row++ )
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{
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#if wxUSE_STOPWATCH
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if ( row % CALC_CHECK_FREQ == CALC_CHECK_FREQ-1 &&
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timer.Time() > CALC_TIMEOUT )
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break;
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#endif // wxUSE_STOPWATCH
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UpdateWithRow(row);
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}
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// row is the first unmeasured item now; that's our value of N/2
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if ( row < count )
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{
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top_part_end = row;
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// add bottom N/2 items now:
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const size_t bottom_part_start = wxMax(row, count - row);
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for ( row = bottom_part_start; row < count; row++ )
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{
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UpdateWithRow(row);
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}
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// finally, include currently visible items in the calculation:
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first_visible = wxMax(first_visible, top_part_end);
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last_visible = wxMin(bottom_part_start, last_visible);
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for ( row = first_visible; row < last_visible; row++ )
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{
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UpdateWithRow(row);
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}
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wxLogTrace("items container",
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"determined best size from %zu top, %zu bottom "
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"plus %zu more visible items out of %zu total",
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top_part_end,
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count - bottom_part_start,
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wxMax(0, last_visible - first_visible),
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count);
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}
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}
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private:
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const size_t m_column;
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int m_width;
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wxDECLARE_NO_COPY_CLASS(wxMaxWidthCalculatorBase);
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};
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#endif // wxUSE_DATAVIEWCTRL || wxUSE_LISTCTRL
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#endif // _WX_GENERIC_PRIVATE_WIDTHCALC_H_
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