Allow vertical scroll positioning with pixel accuracy #190

icsharpcode/AvalonEdit#190 (commented out)

Author: JamesLopte

src/AvaloniaEdit/TextEditor.cs

@@ -1119,57 +1119,77 @@ 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);
+        }
 
-            //TextView textView = textArea.TextView;
-            //TextDocument document = textView.Document;
-            //if (scrollViewer != null && document != null)
-            //{
-            //    if (line < 1)
-            //        line = 1;
-            //    if (line > document.LineCount)
-            //        line = document.LineCount;
-
-            //    IScrollInfo scrollInfo = textView;
-            //    if (!scrollInfo.CanHorizontallyScroll)
-            //    {
-            //        // Word wrap is enabled. Ensure that we have up-to-date info about line height so that we scroll
-            //        // 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.Viewport.Height / 2;
-            //        while (remainingHeight > 0)
-            //        {
-            //            DocumentLine prevLine = vl.FirstDocumentLine.PreviousLine;
-            //            if (prevLine == null)
-            //                break;
-            //            vl = textView.GetOrConstructVisualLine(prevLine);
-            //            remainingHeight -= vl.Height;
-            //        }
-            //    }
-
-            //    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)
-            //    {
-            //        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)
-            //            {
-            //                scrollViewer.ScrollToHorizontalOffset(horizontalPos);
-            //            }
-            //        }
-            //        else
-            //        {
-            //            scrollViewer.ScrollToHorizontalOffset(0);
-            //        }
-            //    }
-            //}
+        /// <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)
+            {
+                if (line < 1)
+                    line = 1;
+                if (line > document.LineCount)
+                    line = document.LineCount;
+
+                IScrollInfo scrollInfo = textView;
+                if (!scrollInfo.CanHorizontallyScroll)
+                {
+                    // Word wrap is enabled. Ensure that we have up-to-date info about line height so that we scroll
+                    // 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 = referencedVerticalViewPortOffset;
+
+                    while (remainingHeight > 0)
+                    {
+                        DocumentLine prevLine = vl.FirstDocumentLine.PreviousLine;
+                        if (prevLine == null)
+                            break;
+                        vl = textView.GetOrConstructVisualLine(prevLine);
+                        remainingHeight -= vl.Height;
+                    }
+                }
+
+                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) >
+                            minimumScrollFraction * scrollViewer.ViewportWidth)
+                        {
+                            scrollViewer.ScrollToHorizontalOffset(horizontalPos);
+                        }
+                    }
+                    else
+                    {
+                        scrollViewer.ScrollToHorizontalOffset(0);
+                    }
+                }
+            }*/
         }
     }
 }