+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;
+}
+