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added EstimateTotalHeight

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@21426 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
2003-06-26 15:39:24 +00:00
parent ae500232a4
commit 1e0af0bcda
3 changed files with 63 additions and 27 deletions
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61
src/generic/vscroll.cpp
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@@ -53,6 +53,38 @@ void wxVScrolledWindow::Init()
// various helpers
// ----------------------------------------------------------------------------
wxCoord wxVScrolledWindow::EstimateTotalHeight() const
{
// estimate the total height: it is impossible to call
// OnGetLineHeight() for every line because there may be too many of
// them, so we just make a guess using some lines in the beginning,
// some in the end and some in the middle
static const size_t NUM_LINES_TO_SAMPLE = 10;
wxCoord heightTotal;
if ( m_lineMax < 3*NUM_LINES_TO_SAMPLE )
{
// in this case calculating exactly is faster and more correct than
// guessing
heightTotal = GetLinesHeight(0, m_lineMax);
}
else // too many lines to calculate exactly
{
// look at some lines in the beginning/middle/end
heightTotal =
GetLinesHeight(0, NUM_LINES_TO_SAMPLE) +
GetLinesHeight(m_lineMax - NUM_LINES_TO_SAMPLE, m_lineMax) +
GetLinesHeight(m_lineMax/2 - NUM_LINES_TO_SAMPLE/2,
m_lineMax/2 + NUM_LINES_TO_SAMPLE/2);
// use the height of the lines we looked as the average
heightTotal = (wxCoord)
(((float)m_heightTotal / (3*NUM_LINES_TO_SAMPLE)) * m_lineMax);
}
return heightTotal;
}
wxCoord wxVScrolledWindow::GetLinesHeight(size_t lineMin, size_t lineMax) const
{
if ( lineMin == lineMax )
@@ -147,33 +179,8 @@ void wxVScrolledWindow::SetLineCount(size_t count)
// save the number of lines
m_lineMax = count;
// estimate the total height: it is impossible to call
// OnGetLineHeight() for every line because there may be too many of
// them, so we just make a guess using some lines in the beginning,
// some in the end and some in the middle
static const size_t NUM_LINES_TO_SAMPLE = 10;
if ( count < 3*NUM_LINES_TO_SAMPLE )
{
// in this case calculating exactly is faster and more correct than
// guessing
m_heightTotal = GetLinesHeight(0, m_lineMax);
}
else // too many lines to calculate exactly
{
// look at some lines in the beginning/middle/end
m_heightTotal =
GetLinesHeight(0, NUM_LINES_TO_SAMPLE) +
GetLinesHeight(count - NUM_LINES_TO_SAMPLE, count) +
GetLinesHeight(count/2 - NUM_LINES_TO_SAMPLE/2,
count/2 + NUM_LINES_TO_SAMPLE/2);
// use the height of the lines we looked as the average
m_heightTotal = (wxCoord)
(((float)m_heightTotal / (3*NUM_LINES_TO_SAMPLE)) * m_lineMax);
}
// and our estimate for their total height
m_heightTotal = EstimateTotalHeight();
// recalculate the scrollbars parameters
m_lineFirst = 1; // make sure it is != 0