- // Correct position if greater than extent of canvas minus
- // the visible portion of it or if below zero
- m_xScrollPosition = wxMin( m_xScrollLines-noPagePositions, m_xScrollPosition);
- m_xScrollPosition = wxMax( 0, m_xScrollPosition );
+ GetTargetSize(&w, 0);
+
+ // scroll lines per page: if 0, no scrolling is needed
+ int linesPerPage;
+
+ if ( m_xScrollPixelsPerLine == 0 )
+ {
+ // scrolling is disabled
+ m_xScrollLines = 0;
+ m_xScrollPosition = 0;
+ linesPerPage = 0;
+ }
+ else // might need scrolling
+ {
+ // Round up integer division to catch any "leftover" client space.
+ const int wVirt = m_targetWindow->GetVirtualSize().GetWidth();
+ m_xScrollLines = (wVirt + m_xScrollPixelsPerLine - 1) / m_xScrollPixelsPerLine;
+
+ // Calculate page size i.e. number of scroll units you get on the
+ // current client window.
+ linesPerPage = w / m_xScrollPixelsPerLine;
+
+ // Special case. When client and virtual size are very close but
+ // the client is big enough, kill scrollbar.
+ if ((linesPerPage < m_xScrollLines) && (w >= wVirt)) ++linesPerPage;
+
+ if (linesPerPage >= m_xScrollLines)
+ {
+ // we're big enough to not need scrolling
+ linesPerPage =
+ m_xScrollLines =
+ m_xScrollPosition = 0;
+ }
+ else // we do need a scrollbar
+ {
+ if ( linesPerPage < 1 )
+ linesPerPage = 1;
+
+ // Correct position if greater than extent of canvas minus
+ // the visible portion of it or if below zero
+ const int posMax = m_xScrollLines - linesPerPage;
+ if ( m_xScrollPosition > posMax )
+ m_xScrollPosition = posMax;
+ else if ( m_xScrollPosition < 0 )
+ m_xScrollPosition = 0;
+ }
+ }
+
+ m_win->SetScrollbar(wxHORIZONTAL, m_xScrollPosition,
+ linesPerPage, m_xScrollLines);