private void PageUpDown(ScrollDirection direction)
{
if (direction == ScrollDirection.Up)
{
//If we scrolled a full page, then the bottom of the first fully visible line will be below
//the bottom of the view.
ITextViewLine firstVisibleLine = TextView.AdvancedTextView.TextViewLines.FirstVisibleLine;
SnapshotPoint oldFullyVisibleStart = (firstVisibleLine.VisibilityState == VisibilityState.FullyVisible)
? firstVisibleLine.Start
: firstVisibleLine.EndIncludingLineBreak; //Start of next line.
if (TextView.AdvancedTextView.ViewScroller.ScrollViewportVerticallyByPage(direction))
{
ITextViewLine newFirstLine = TextView.AdvancedTextView.TextViewLines.GetTextViewLineContainingBufferPosition(oldFullyVisibleStart);
//The old fully visible line should -- if we scrolled as much as we could -- be partially
//obscured. The shortfall between a full page and what we actually scrolled is the distance
//between the bottom of that line and the bottom of the screen.
if (TextView.AdvancedTextView.ViewportBottom > newFirstLine.Bottom)
{
AdvancedCaret.MoveTo(TextView.AdvancedTextView.TextViewLines.FirstVisibleLine);
}
else
{
AdvancedCaret.MoveToPreferredCoordinates();
}
}
}
else
{
//If we scroll a full page, the bottom of the last fully visible line will be
//positioned at 0.0.
ITextViewLine lastVisibleLine = TextView.AdvancedTextView.TextViewLines.LastVisibleLine;
// If the last line in the buffer is fully visible , then just move the caret to
// the last visible line
if ((lastVisibleLine.VisibilityState == VisibilityState.FullyVisible) &&
(lastVisibleLine.End == lastVisibleLine.Snapshot.Length))
{
AdvancedCaret.MoveTo(lastVisibleLine);
// No need to ensure the caret is visible since the line it just moved to is fully visible.
return;
}
SnapshotPoint oldFullyVisibleStart = ((lastVisibleLine.VisibilityState == VisibilityState.FullyVisible) || (lastVisibleLine.Start == 0))
? lastVisibleLine.Start
: (lastVisibleLine.Start - 1); //Actually just a point on the previous line.
if (TextView.AdvancedTextView.ViewScroller.ScrollViewportVerticallyByPage(direction))
{
ITextViewLine newLastLine = TextView.AdvancedTextView.TextViewLines.GetTextViewLineContainingBufferPosition(oldFullyVisibleStart);
if (newLastLine.Bottom > TextView.AdvancedTextView.ViewportTop)
{
AdvancedCaret.MoveTo(TextView.AdvancedTextView.TextViewLines.LastVisibleLine);
}
else
{
AdvancedCaret.MoveToPreferredCoordinates();
}
}
}
EnsureVisible();
}