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Allow vertical scroll positioning with pixel accuracy #158

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Allow vertical scroll positioning with pixel accuracy #158

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28 changes: 21 additions & 7 deletions ICSharpCode.AvalonEdit/TextEditor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1123,8 +1123,21 @@ public void ScrollToLine(int line)
/// </summary>
public void ScrollTo(int line, int column)
{
const double MinimumScrollPercentage = 0.3;

const double MinimumScrollFraction = 0.3;
ScrollTo(line, column, VisualYPosition.LineMiddle, null != scrollViewer ? scrollViewer.ViewportHeight / 2 : 0.0, MinimumScrollFraction);
}

/// <summary>
/// Scrolls to the specified line/column.
/// This method requires that the TextEditor was already assigned a size (WPF layout must have run prior).
/// </summary>
/// <param name="line">Line to scroll to.</param>
/// <param name="column">Column to scroll to (important if wrapping is 'on', and for the horizontal scroll position).</param>
/// <param name="yPositionMode">The mode how to reference the Y position of the line.</param>
/// <param name="referencedVerticalViewPortOffset">Offset from the top of the viewport to where the referenced line/column should be positioned.</param>
/// <param name="minimumScrollFraction">The minimum vertical and/or horizontal scroll offset, expressed as fraction of the height or width of the viewport window, respectively.</param>
public void ScrollTo(int line, int column, VisualYPosition yPositionMode, double referencedVerticalViewPortOffset, double minimumScrollFraction)
{
TextView textView = textArea.TextView;
TextDocument document = textView.Document;
if (scrollViewer != null && document != null) {
Expand All @@ -1139,7 +1152,8 @@ public void ScrollTo(int line, int column)
// to the correct position.
// This avoids that the user has to repeat the ScrollTo() call several times when there are very long lines.
VisualLine vl = textView.GetOrConstructVisualLine(document.GetLineByNumber(line));
double remainingHeight = scrollViewer.ViewportHeight / 2;
double remainingHeight = referencedVerticalViewPortOffset;

while (remainingHeight > 0) {
DocumentLine prevLine = vl.FirstDocumentLine.PreviousLine;
if (prevLine == null)
Expand All @@ -1149,15 +1163,15 @@ public void ScrollTo(int line, int column)
}
}

Point p = textArea.TextView.GetVisualPosition(new TextViewPosition(line, Math.Max(1, column)), VisualYPosition.LineMiddle);
double verticalPos = p.Y - scrollViewer.ViewportHeight / 2;
if (Math.Abs(verticalPos - scrollViewer.VerticalOffset) > MinimumScrollPercentage * scrollViewer.ViewportHeight) {
Point p = textArea.TextView.GetVisualPosition(new TextViewPosition(line, Math.Max(1, column)), yPositionMode);
double verticalPos = p.Y - referencedVerticalViewPortOffset;
if (Math.Abs(verticalPos - scrollViewer.VerticalOffset) > minimumScrollFraction * scrollViewer.ViewportHeight) {
scrollViewer.ScrollToVerticalOffset(Math.Max(0, verticalPos));
}
if (column > 0) {
if (p.X > scrollViewer.ViewportWidth - Caret.MinimumDistanceToViewBorder * 2) {
double horizontalPos = Math.Max(0, p.X - scrollViewer.ViewportWidth / 2);
if (Math.Abs(horizontalPos - scrollViewer.HorizontalOffset) > MinimumScrollPercentage * scrollViewer.ViewportWidth) {
if (Math.Abs(horizontalPos - scrollViewer.HorizontalOffset) > minimumScrollFraction * scrollViewer.ViewportWidth) {
scrollViewer.ScrollToHorizontalOffset(horizontalPos);
}
} else {
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